latest research papers on solar cell

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals

Solar cells articles from across Nature Portfolio

Solar cells are devices for converting sunlight into electricity. Their primary element is often a semiconductor which absorbs light to produce carriers of electrical charge. An applied electric field can then sweep these carriers out of the semiconductor, thus producing an electrical current.

Breaking the reaction chain

Wide band gap perovskite solar cells suffer from halide segregation, which hampers their use in tandem solar cells. Now, researchers develop an additive with redox and defect passivating capabilities to suppress halide migration, enabling perovskite–organic tandems with over 25% efficiency.

• Aleksandra B. Djurišić

Latest Research and Reviews

Increase in the efficiency and stability of large-area flexible organic photovoltaic modules via improved electrical contact

Organic solar modules suffer from poor electrical contacts. Lu et al. embed the silver electrode into a polymer matrix and add chromium to enhance its electrical contact, achieving improved stability and a 14.04% efficiency on flexible modules with an active area of 41 cm 2 .

• Yinhua Zhou

Flexible quasi-2D perovskite solar cells with high specific power and improved stability for energy-autonomous drones

Demonstration of high performance, upscaling and integration of ultra-lightweight perovskite solar cells are still rare. Hailegnaw et al. develop 2D perovskite solar cells based on methylbenzyl ammonium iodide with improved specific power and stability, showing scalability and integration in drones.

• Bekele Hailegnaw
• Stepan Demchyshyn
• Martin Kaltenbrunner

On the role of asymmetric molecular geometry in high-performance organic solar cells

The correlation between asymmetric molecular geometry of non-fullerene acceptors and their optoelectronic properties was unclear. Here, the authors found asymmetric ones exhibit increased open-circuit voltage compared to their symmetric counterparts due to reduced non-radiative charge recombination.

• Jinfeng Huang
• Tianyi Chen

Deuteration-enhanced neutron contrasts to probe amorphous domain sizes in organic photovoltaic bulk heterojunction films

The use of conventional X-ray scattering techniques is challenging to detect donor-acceptor contrast within amorphous intermixing regions. Here, the authors apply neutron scattering and targeted deuteration to enhance the contrast by one order of magnitude and reveal short-range aggregations of d -Y6.

• Guilong Cai

Harnessing strong aromatic conjugation in low-dimensional perovskite heterojunctions for high-performance photovoltaic devices

The large organic cations in low-dimensional perovskite often introduces carrier mobility anisotropy and impedes charge transport. Here, authors report perovskite heterojunction with strong aromatic conjugated perovskites, realizing certified efficiency of over 25% in stable perovskite solar cells.

• Zonglong Zhu

Suppression of phase segregation in wide-bandgap perovskites with thiocyanate ions for perovskite/organic tandems with 25.06% efficiency

Wide-bandgap perovskite solar cells suffer from phase segregation. Zhang et al. show that thiocyanate ions overcome the issue by occupying iodide vacancies while regulating crystallization, enabling perovskite/organic tandem cells with 25.06% efficiency.

• Zhichao Zhang
• Weijie Chen
• Yongfang Li

News and Comment

Hybrid perovskites unlocking the development of light-emitting solar cells

Light-emitting perovskite solar cells are emerging optoelectronic devices that integrate light-emitting and electricity-generating functions in one device. This type of device unlocks new possibilities for applications as outdoor light sources, in multifunctional architecture, smart automobiles, self-powered displays and portable power floodlights.

• Alexey Tarasov

Tolerance testing

• Giulia Tregnago

Pump up the ultrasound

Semiconducting polymers require narrow molecular weight distributions for optimal efficiency. Synthesizing such polymers is no easy task, however a combined ultrasonication-assisted Stille polymerization reaction could be the solution to this problem.

• Alexander Rosu-Finsen

Getting the microstructure right

Carrier concentration resolved

Inhomogeneities in the optoelectronic properties of polycrystalline Cu(In,Ga)Se 2 absorbers can limit solar cell performance. Now, researchers quantify the spatial distribution of charge carrier concentration with nanometre resolution and show how different alkali-metal post-deposition treatments reduce the grain-to-grain fluctuations.

• Alex Redinger

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

MIT Technology Review

• Newsletters

Super-efficient solar cells: 10 Breakthrough Technologies 2024

Solar cells that combine traditional silicon with cutting-edge perovskites could push the efficiency of solar panels to new heights.

• Emma Foehringer Merchant archive page

Beyond Silicon, Caelux, First Solar, Hanwha Q Cells, Oxford PV, Swift Solar, Tandem PV

3 to 5 years

In November 2023, a buzzy solar technology broke yet another world record for efficiency. The previous record had existed for only about five months—and it likely won’t be long before it too is obsolete. This astonishing acceleration in efficiency gains comes from a special breed of next-­generation solar technology: perovskite tandem solar cells. These cells layer the traditional silicon with materials that share a unique crystal structure.

In the decade that scientists have been toying with perovskite solar technology , it has continued to best its own efficiency records, which measure how much of the sunlight that hits the cell is converted into electricity. Perovskites absorb different wavelengths of light from those absorbed by silicon cells, which account for 95% of the solar market today. When silicon and perovskites work together in tandem solar cells, they can utilize more of the solar spectrum, producing more electricity per cell. 

Technical efficiency levels for silicon-­based cells top out below 30%, while perovskite-only cells have reached experimental efficiencies of around 26%. But perovskite tandem cells have already exceeded 33% efficiency in the lab. That is the technology’s tantalizing promise: if deployed on a significant scale, perovskite tandem cells could produce more electricity than the legacy solar cells at a lower cost. 

But perovskites have stumbled when it comes to actual deployment. Silicon solar cells can last for decades. Few perovskite tandem panels have even been tested outside. 

The electrochemical makeup of perovskites means they’re sensitive to sucking up water and degrading in heat, though researchers have been working to create better barriers around panels and shifting to more stable perovskite compounds. 

In May, UK-based Oxford PV said it had reached an efficiency of 28.6% for a commercial-size perovskite tandem cell, which is significantly larger than those used to test the materials in the lab, and it plans to deliver its first panels and ramp up manufacturing in 2024. Other companies could unveil products later this decade. 

Climate change and energy

The problem with plug-in hybrids their drivers..

Plug-in hybrids are often sold as a transition to EVs, but new data from Europe shows we’re still underestimating the emissions they produce.

• Casey Crownhart archive page

Harvard has halted its long-planned atmospheric geoengineering experiment

The decision follows years of controversy and the departure of one of the program’s key researchers.

• James Temple archive page

Why hydrogen is losing the race to power cleaner cars

Batteries are dominating zero-emissions vehicles, and the fuel has better uses elsewhere.

Decarbonizing production of energy is a quick win 

Clean technologies, including carbon management platforms, enable the global energy industry to play a crucial role in the transition to net zero.

• ADNOC archive page

Stay connected

Get the latest updates from mit technology review.

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at [email protected] with a list of newsletters you’d like to receive.

The recent process and future of perovskite solar cells materials

• Review Article
• Published: 07 January 2022
• Volume 102 , pages 235–249, ( 2022 )

Cite this article

• Liguo Jin 1 ,
• Chaoying Su 1 ,
• Yuwen Wang 1 &
• Limin Dong 1  

1412 Accesses

Explore all metrics

Perovskite solar cells (PSCs) provide attractive prospects for the photovoltaic industry, but the harsh preparation conditions and stability of perovskite materials are still the biggest obstacles to the industrialization of PSCs. This review paper compares the differences in composition and working principle between dye-sensitized solar cells and PSC. It also reviews the optimization and development of electron transport layer, perovskite absorbers and hole transport layer in recent years. By analyzing the crystal morphology, grain size, internal and surface defects of each layer, it also highlights that surface/bulk passivation, composition and interface engineering are used to improve the photoelectric conversion efficiency and the stability of devices. At the same time, the research and development direction of PSC is prospected. It is believed that the industrialization of PSC will be accelerated through the efforts of scientists.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price includes VAT (Russian Federation)

Instant access to the full article PDF.

Rent this article via DeepDyve

Institutional subscriptions

Similar content being viewed by others

Recent Progress in Perovskite Solar Cell: Fabrication, Efficiency, and Stability

Potentials and challenges towards application of perovskite solar cells

Jing Wei, Chenglong Shi, … Qing Zhao

High Efficiency Perovskite Solar Cells: Materials and Devices Engineering

Nam-Gyu Park

Lee, M.M., Teuscher, J., Miyasaka, T., Murakami, T.N., Snaith, H.J.: Efficient hybrid solar cells based on meso-superstructured organometal halide perovskites. Science 338 , 643–647 (2012). https://doi.org/10.1126/science.1228604

Article   CAS   PubMed   Google Scholar  

Liu, Z., Wang, L., Han, J., Zeng, F., Liu, G., Xie, X.: Improving the performance of lead-acetate-based perovskite solar cells using solvent controlled crystallization process. Org. Electron. (2020). https://doi.org/10.1016/j.orgel.2019.105552

Article   Google Scholar  

Xu, T., Zou, K., Sun, X., Wan, Z., Tang, H., Zhang, Y., Chen, L., Qiao, Q., Huang, W.: Effect of antisolvent treatment on PbI 2 films for high performance carbon-based perovskite solar cells. Mater. Lett. (2020). https://doi.org/10.1016/j.matlet.2020.128157

Wu, F., Pathak, R., Qiao, Q.: Origin and alleviation of J–V hysteresis in perovskite solar cells: a short review. Catal. Today 374 , 86–101 (2021). https://doi.org/10.1016/j.cattod.2020.12.025

Article   CAS   Google Scholar  

Kojima, A., Teshima, K., Shirai, Y., Miyasaka, T.: Organometal halide perovskites as visible-light sensitizers for photovoltaic cells. J. Am. Chem. Soc. 131 , 6050–6051 (2009). https://doi.org/10.1021/ja809598r

Etgar, L., Gao, P., Xue, Z., Peng, Q., Chandiran, A.K., Liu, B., Nazeeruddin, Md.K., Grätzel, M.: Mesoscopic CH 3 NH 3 PbI 3 /TiO 2 heterojunction solar cells. J. Am. Chem. Soc. 134 , 17396–17399 (2012). https://doi.org/10.1021/ja307789s

Laban, W.A., Etgar, L.: Depleted hole conductor-free lead halide iodide heterojunction solar cells. Energy Environ. Sci. 6 , 3249–3253 (2013). https://doi.org/10.1039/C3EE42282H

Jeong, M., Choi, I.W., Go, E.M., Cho, Y., Kim, M., Lee, B., Jeong, S., Jo, Y., Choi, H.W., Lee, J., Bae, J.-H., Kwak, S.K., Kim, D.S., Yang, C.: Stable perovskite solar cells with efficiency exceeding 24.8% and 0.3-V voltage loss. Science 369 , 1615–1620 (2020). https://doi.org/10.1126/science.abb7167

Meng, F., Zhou, Y., Gao, L., Li, Y., Liu, A., Li, Y., Zhang, C., Fan, M., Wei, G., Ma, T.: Environmental risks and strategies for the long-term stability of carbon-based perovskite solar cells. Mater. Today Energy (2021). https://doi.org/10.1016/j.mtener.2020.100590

Li, J., Xia, R., Qi, W., Zhou, X., Cheng, J., Chen, Y., Hou, G., Ding, Y., Li, Y., Zhao, Y., Zhang, X.: Encapsulation of perovskite solar cells for enhanced stability: Structures, materials and characterization. J. Power Sources (2021). https://doi.org/10.1016/j.jpowsour.2020.229313

Naveen, K., Rani, J., Kurchania, R.: Advancement in CsPbBr 3 inorganic perovskite solar cells: fabrication, efficiency and stability. Sol. Energy 221 , 197–205 (2021). https://doi.org/10.1016/j.solener.2021.04.042

Matondo, J.T., Maurice, D.M., Chen, Q., Bai, L., Guli, M.: Inorganic copper-based hole transport materials for perovskite photovoltaics: challenges in normally structured cells, advances in photovoltaic performance and device stability. Sol. Energy Mater. Sol. Cells. (2021). https://doi.org/10.1016/j.solmat.2021.111011

Zhou, Q., Ma, W., Zhang, Z., Liu, Y., Zhang, H., Mao, Y.: Double-layered hole transport material of CuInS 2 /Spiro for highly efficient and stable perovskite solar cells. Org. Electron. (2021). https://doi.org/10.1016/j.orgel.2021.106249

Hu, J., Xiong, X., Guan, W., Long, H.: Recent advances in carbon nanomaterial-optimized perovskite solar cells. Mater. Today Energy (2021). https://doi.org/10.1016/j.mtener.2021.100769

Yang, Q., Dettori, R., Yuan, G., Anderson, L.R.: A perovskite solar cell owing very high stabilities and power conversion efficiencies. Sol. Energy 201 , 541–546 (2020). https://doi.org/10.1016/j.solener.2020.02.085

Mohseni, H.R., Dehghanipour, M., Dehghan, N., Tamaddon, F., Ahmadi, M., Sabet, M., Behjat, A.: Enhancement of the photovoltaic performance and the stability of perovskite solar cells via the modification of electron transport layers with reduced graphene oxide/polyaniline composite. Sol. Energy 213 , 59–66 (2021). https://doi.org/10.1016/j.solener.2020.11.017

Liu, W., Ma, H., Walsh, A.: Advance in photonic crystal solar cells. Renew. Sustain. Energy Rev. 116 , 109436 (2019). https://doi.org/10.1016/j.rser.2019.109436

Yang, X., Zhao, L., Wang, S., Li, J., Chi, B.: Recent progress of g-C3N 4 applied in solar cells. J. Materiomics 7 , 728–741 (2021). https://doi.org/10.1016/j.jmat.2021.01.004

Xiang, H., Liu, P., Wang, W., Ran, R., Zhou, W., Shao, Z.: Towards highly stable and efficient planar perovskite solar cells: Materials development, defect control and interfacial engineering. Chem. Eng. J. 420 , 127599 (2021). https://doi.org/10.1016/j.cej.2020.127599

Olaleru, S.A., Kirui, J.K., Wamwangi, D., Roro, K.T., Mwakikunga, B.: Perovskite solar cells: the new epoch in photovoltaics. Sol. Energy 196 , 295–309 (2020). https://doi.org/10.1016/j.solener.2019.12.025

Hardin, B.E., Snaith, H.J., McGehee, M.D.: The renaissance of dye-sensitized solar cells. Nat. Photonics 6 , 162–169 (2012). https://doi.org/10.1038/nphoton.2012.22

Wei, J., Zhao, Q., Li, H., Shi, C., Tian, J., Cao, G., Yu, D.: Perovskite solar cells: Promise of photovoltaics. Sci. Sin. Technol. 44 , 801–821 (2014). https://doi.org/10.1360/N092014-00135

Liu, M., Johnston, M.B., Snaith, H.J.: Efficient planar heterojunction perovskite solar cells by vapour deposition. Nature 501 , 395–398 (2013). https://doi.org/10.1038/nature12509

Jin, L., Zhai, J., Heng, L., Wei, T., Wen, L., Jiang, L., Zhao, X., Zhang, X.: Bio-inspired multi-scale structures in dye-sensitized solar cell. J. Photochem. Photobiol. C 10 , 149–158 (2009). https://doi.org/10.1016/j.jphotochemrev.2009.10.002

Pelicano, C.M., Yanagi, H.: Effect of rubrene: P3HT bilayer on photovoltaic performance of perovskite solar cells with electrodeposited ZnO nanorods, Journal of Energy. Chemistry 27 , 455–462 (2018). https://doi.org/10.1016/j.jechem.2017.11.018

Chunlin, F., Xing, S., He, Y., He, J., Li, J.: Current status of electron transport layer in perovskite solar cells. J. Synth. Crystals 50 , 959–966 (2021). https://doi.org/10.16553/j.cnki.issn1000-985x.20210427.001

Guo, X., Yang, Y., Luo, Y., Ma, S., Zhu, C., Zhu, L.: Advances of electron transport materials in perovskite solar cells: synthesis and application. Prog. Chem. 33 , 281–302 (2021). https://doi.org/10.7536/PC200515

Li, R., Huo, X., Han, X., Wang, Z., Zhang, M., Guo, M.: Facile synthesis of ordered Nb 2 O 5 coated TiO 2 nanorod arrays for efficient perovskite solar cells. Appl. Surf. Sci. 542 , 148728 (2021). https://doi.org/10.1016/j.apsusc.2020.148728

Jin, J., Li, H., Bi, W., Chen, C., Zhang, B., Xu, L., Dong, B., Song, H., Dai, Q.: Efficient and stable perovskite solar cells through e-beam preparation of cerium doped TiO 2 electron transport layer, ultraviolet conversion layer CsPbBr 3 and the encapsulation layer Al 2 O 3 . Sol. Energy 198 , 187–193 (2020). https://doi.org/10.1016/j.solener.2020.01.048

Wang, S., Liu, B., Zhu, Y., Ma, Z., Liu, B., Miao, X., Ma, R., Wang, C.: Enhanced performance of TiO 2 -based perovskite solar cells with Ru-doped TiO 2 electron transport layer. Sol. Energy 169 , 335–342 (2018). https://doi.org/10.1016/j.solener.2018.05.005

Xia, G., Liu, H., Zhao, X., Dong, X., Wang, S., Li, X.: Seeding-method-processed anatase TiO 2 film at low temperature for efficient planar perovskite solar cell. Chem. Eng. J. 370 , 1111–1118 (2019). https://doi.org/10.1016/j.cej.2019.03.257

Khan, J., Ur Rahman, N., Khan, W.U., Hayat, A., Yang, Z., Ahmed, G., Akhtar, M.N., Tong, S., Chi, Z., Wu, M.: Multi-dimensional anatase TiO 2 materials: Synthesis and their application as efficient charge transporter in perovskite solar cells. Sol. Energy. 184 , 323–330 (2019). https://doi.org/10.1016/j.solener.2019.04.020

Liao, Y.-H., Chang, Y.-H., Lin, T.-H., Chan, S.-H., Lee, K.-M., Hsu, K.-H., Hsu, J.-F., Wu, M.-C.: Boosting the power conversion efficiency of perovskite solar cells based on Sn doped TiO 2 electron extraction layer via modification the TiO 2 phase junction. Sol. Energy 205 , 390–398 (2020). https://doi.org/10.1016/j.solener.2020.05.039

Lifeng, Z., Jiangjian, S., Dongmei, L., Qingbo, M.: Effect of mesoporous TiO 2 layer thickness on the cell performance of perovskite solar cells. Acta Chim. Sinica. 73 , 261 (2015). https://doi.org/10.6023/A14110823

el Haimeur, A., Makha, M., Bakkali, H., González-Leal, J.M., Blanco, E., Dominguez, M., Voitenko, Z.V.: Enhanced performance of planar perovskite solar cells using dip-coated TiO2 as electron transporting layer. Sol. Energy 195 , 475–482 (2020). https://doi.org/10.1016/j.solener.2019.11.094

Abdi-Jalebi, M., Dar, M.I., Sadhanala, A., Senanayak, S.P., Giordano, F., Zakeeruddin, S.M., Grätzel, M., Friend, R.H.: Impact of a mesoporous titania–perovskite interface on the performance of hybrid organic–inorganic perovskite solar cells. J. Phys. Chem. Lett. 7 , 3264–3269 (2016). https://doi.org/10.1021/acs.jpclett.6b01617

Mei, Y., Liu, H., Li, X., Wang, S.: Hollow TiO 2 spheres as mesoporous layer for better efficiency and stability of perovskite solar cells. J. Alloys Compd. 866 , 158079 (2021). https://doi.org/10.1016/j.jallcom.2020.158079

Quy, H.V., Truyen, D.H., Kim, S., Bark, C.W.: Facile synthesis of spherical TiO 2 hollow nanospheres with a diameter of 150 nm for high-performance mesoporous perovskite solar cells. Materials (2021). https://doi.org/10.3390/ma14030629

Article   PubMed   PubMed Central   Google Scholar  

Seyed-Talebi, S.M., Kazeminezhad, I.: Performance improvement of fully ambient air fabricated perovskite solar cells in an anti-solvent process using TiO 2 hollow spheres. J. Colloid Interfaces Sci. 562 , 125–132 (2020). https://doi.org/10.1016/j.jcis.2019.12.004

Kanjana, N., Maiaugree, W., Poolcharuansin, P., Laokul, P.: Size controllable synthesis and photocatalytic performance of mesoporous TiO 2 hollow spheres. J. Mater. Sci. Technol. 48 , 105–113 (2020). https://doi.org/10.1016/j.jmst.2020.03.013

Jiang, Q., Sheng, X., Li, Y., Feng, X., Xu, T.: Rutile TiO 2 nanowire-based perovskite solar cells. Chem. Commun. 50 , 14720–14723 (2014). https://doi.org/10.1039/C4CC07367C

Wang, W., He, Y., Qi, L.: High-efficiency colorful perovskite solar cells using TiO 2 nanobowl arrays as a structured electron transport layer. Sci. China Mater. 63 , 35–46 (2020). https://doi.org/10.1007/s40843-019-9452-1

Chavan, R.D., Yadav, P., Nimbalkar, A., Bhoite, S.P., Bhosale, P.N., Kook Hong, C.: Ruthenium doped mesoporous titanium dioxide for highly efficient, hysteresis-free and stable perovskite solar cells. Sol. Energy 186 , 156–165 (2019). https://doi.org/10.1016/j.solener.2019.04.098

Duan, Y., Zhao, G., Liu, X., Ma, J., Chen, S., Song, Y., Pi, X., Yu, X., Yang, D., Zhang, Y., Guo, F.: Low-temperature processed tantalum/niobium co-doped TiO 2 electron transport layer for high-performance planar perovskite solar cells. Nanotechnology 32 , 1–11 (2021). https://doi.org/10.1088/1361-6528/abeb37

Ding, B., Zhao, X., Wang, S., Shan, X., Chen, Z., Deng, Z., Tao, R., Shao, J., Meng, G., Fang, X.: Mechanism of improving the performance of perovskite solar cells through alkali metal bis(trifluoromethanesulfonyl)imide modifying mesoporous titania electron transport layer. J. Power Sources 484 , 229275 (2021). https://doi.org/10.1016/j.jpowsour.2020.229275

Meng, X., Chi, K., Li, Q., Cao, Y., Song, G., Liu, B., Yang, H., Fu, W.: Interfacial modification of mesoporous TiO2 films with PbI2-ethanolamine-dimethyl sulfoxide solution for CsPbIBr 2 perovskite solar cells. Nanomaterials (2020). https://doi.org/10.3390/nano10050962

Bao, W., Ichimura, M.: Band offsets at the ZnO/Cu 2 ZnSnS 4 interface based on the first principles calculation. Jpn. J. Appl. Phys. 52 , 61203 (2013). https://doi.org/10.7567/jjap.52.061203

Wang, B., Li, N., Yang, L., Dall’Agnese, C., Jena, A.K., Sasaki, S., Miyasaka, T., Tamiaki, H., Wang, X.-F.: Chlorophyll derivative-sensitized TiO 2 electron transport layer for record efficiency of Cs 2 AgBiBr 6 double perovskite solar cells. J. Am. Chem. Soc. 143 , 2207–2211 (2021). https://doi.org/10.1021/jacs.0c12786

Luo, Q., Zhang, C., Deng, X., Zhu, H., Li, Z., Wang, Z., Chen, X., Huang, S.: Plasmonic effects of metallic nanoparticles on enhancing performance of perovskite solar cells. ACS Appl. Mater. Interfaces. 9 , 34821–34832 (2017). https://doi.org/10.1021/acsami.7b08489

Jiang, W.-L., Zhou, W., Ying, J.-F., Yang, T.-Y., Gao, Y.-M.: Thermal stable perovskite solar cells improved by ZnO/graphene oxide as electron transfer layers. J. Inorg. Mater. 32 (1), 96–100 (2017)

Hossain, M.I., Yumnam, N., Qarony, W., Salleo, A., Wagner, V., Knipp, D., Tsang, Y.H.: Non-resonant metal-oxide metasurfaces for efficient perovskite solar cells. Sol. Energy 198 , 570–577 (2020). https://doi.org/10.1016/j.solener.2020.01.082

Kang, J., Han, K., Sun, X., Zhang, L., Huang, R., Ismail, I., Wang, Z., Ding, C., Zha, W., Li, F., Luo, Q., Li, Y., Lin, J., Ma, C.-Q.: Suppression of Ag migration by low-temperature sol-gel zinc oxide in the Ag nanowires transparent electrode-based flexible perovskite solar cells. Org. Electron. 82 , 105714 (2020). https://doi.org/10.1016/j.orgel.2020.105714

Sharda, P., Chawla, K., Yadav, D.K., Singh, V., Jain, I.P., Lal, C.: Electronic structure and surface morphology of P3HT/MAPbI 2 Cl/GO-ZnO np’s thin films for PSCs. Mater. Today Proc. 42 , 1682–1684 (2021). https://doi.org/10.1016/j.matpr.2020.08.047

Khan, U., Iqbal, T., Khan, M., Wu, R.: SnO 2 /ZnO as double electron transport layer for halide perovskite solar cells. Sol. Energy 223 , 346–350 (2021). https://doi.org/10.1016/j.solener.2021.05.059

Ouslimane, T., Et-taya, L., Elmaimouni, L., Benami, A.: Impact of absorber layer thickness, defect density, and operating temperature on the performance of MAPbI 3 solar cells based on ZnO electron transporting material. Heliyon 7 , e06379 (2021). https://doi.org/10.1016/j.heliyon.2021.e06379

Khan, F., Kim, J.H.: Enhanced charge-transportation properties of low-temperature processed Al-doped ZnO and its impact on PV cell parameters of organic-inorganic perovskite solar cells. Solid-State Electron. 164 , 107714 (2020). https://doi.org/10.1016/j.sse.2019.107714

Kumar, A.M., Peter, I.J., Ramachandran, K., Mayandi, J., Jayakumar, K.: Influence of Al-Cu doping on the efficiency of BiFeO 3 based perovskite solar cell (PSC). Mater. Today Proc. 35 , 62–65 (2021). https://doi.org/10.1016/j.matpr.2019.05.454

Kang, J.H., Park, Y.J., Khan, Y., Ahn, Y., Seo, J.H., Walker, B.: Cationic polyelectrolytes as convenient electron extraction layers in perovskite solar cells. Dyes Pigm. 182 , 108634 (2020). https://doi.org/10.1016/j.dyepig.2020.108634

Lee, J.H., Jin, I.S., Jung, J.W.: Binary-mixed organic electron transport layers for planar heterojunction perovskite solar cells with high efficiency and thermal reliability. Chem. Eng. J. 420 , 129678 (2021). https://doi.org/10.1016/j.cej.2021.129678

Chen, X., Shi, Z., Pan, G., Zhu, J., Hu, J., Wu, Y., Tian, Y., Li, X., Xu, W.: Boosting interfacial charge transfer by constructing rare earth–doped WO x nanorods/SnO 2 hybrid electron transport layer for efficient perovskite solar cells. Mater. Today Energy 21 , 100724 (2021). https://doi.org/10.1016/j.mtener.2021.100724

Pylnev, M., Su, T.-S., Wei, T.C.: Titania augmented with TiI4 as electron transporting layer for perovskite solar cells. Appl. Surf. Sci. 549 , 149224 (2021). https://doi.org/10.1016/j.apsusc.2021.149224

Chen, J., Zhang, J., Huang, C., Bi, Z., Xu, X., Yu, H.: SnO 2 /2D-Bi 2 O 2 Se new hybrid electron transporting layer for efficient and stable perovskite solar cells. Chem. Eng. J. 410 , 128436 (2021). https://doi.org/10.1016/j.cej.2021.128436

Zaky, A.A., Christopoulos, E., Gkini, K., Arfanis, M.K., Sygellou, L., Kaltzoglou, A., Stergiou, A., Tagmatarchis, N., Balis, N., Falaras, P.: Enhancing efficiency and decreasing photocatalytic degradation of perovskite solar cells using a hydrophobic copper-modified titania electron transport layer. Appl. Catal. B 284 , 119714 (2021). https://doi.org/10.1016/j.apcatb.2020.119714

Yuan, W.S.C., Qi, Y., Jin, J., Dong, B.: Study on the performance of planar perovskite solar cells with interface modified SnO 2 by NH 4 I. Chin. J. Colloid Polym. 39 , 26–29 (2021). https://doi.org/10.13909/j.cnki.1009-1815.2021.01.007

Lee, J.-H., Lee, D.G., Jung, H.S., Lee, H.H., Kim, H.-K.: ITO and electron transport layer-free planar perovskite solar cells on transparent Nb-doped anatase TiO 2-x electrodes. J. Alloys Compd. 845 , 155531 (2020). https://doi.org/10.1016/j.jallcom.2020.155531

de Roo, J., Ibáñez, M., Geiregat, P., Nedelcu, G., Walravens, W., Maes, J., Martins, J.C., van Driessche, I., Kovalenko, M.V., Hens, Z.: Highly dynamic ligand binding and light absorption coefficient of cesium lead bromide perovskite nanocrystals. ACS Nano 10 , 2071–2081 (2016). https://doi.org/10.1021/acsnano.5b06295

Zhang, M., Ye, M., Wang, W., Ma, C., Wang, S., Liu, Q., Lian, T., Huang, J., Lin, Z.: Synergistic cascade carrier extraction via dual interfacial positioning of ambipolar black phosphorene for high-efficiency perovskite solar cells. Adv. Mater. (2020). https://doi.org/10.1002/adma.202000999

Ding, X.K., Li, X.M., Gao, X.D., de Zhang, S., di Huang, Y., Li, H.R.: Optical and electrical properties of CH 3 NH 3 PbI 3 perovskite thin films transformed from PbO-PbI 2 hybrid films. Acta Physico-Chim. Sin. 31 , 576–582 (2015). https://doi.org/10.3866/PKU.WHXB201501201

Green, M.A., Ho-Baillie, A., Snaith, H.J.: The emergence of perovskite solar cells. Nat. Photonics 8 , 506–514 (2014). https://doi.org/10.1038/nphoton.2014.134

Suresh Kumar, N., Chandra Babu Naidu, K.: A review on perovskite solar cells (PSCs), materials and applications. J. Materiomics 7 (5), 940–956 (2021). https://doi.org/10.1016/j.jmat.2021.04.002

Si, H., Xu, C., Ou, Y., Zhang, G., Fan, W., Xiong, Z., Kausar, A., Liao, Q., Zhang, Z., Sattar, A., Kang, Z., Zhang, Y.: Dual-passivation of ionic defects for highly crystalline perovskite. Nano Energy (2020). https://doi.org/10.1016/j.nanoen.2019.104320

Aydin, E., de Bastiani, M., de Wolf, S.: Defect and contact passivation for perovskite solar cells. Adv. Mater. 31 , 1900428 (2019). https://doi.org/10.1002/adma.201900428

Liu, C., Huang, L., Zhou, X., Wang, X., Yao, J., Liu, Z., Liu, S.F., Ma, W., Xu, B.: An in-situ defect passivation through a green anti-solvent approach for high-efficiency and stable perovskite solar cells. Sci. Bull. (2021). https://doi.org/10.1016/j.scib.2021.03.018

Godding, J.S.W., Ramadan, A.J., Lin, Y.-H., Schutt, K., Snaith, H.J., Wenger, B.: Oxidative passivation of metal halide perovskites. Joule 3 , 2716–2731 (2019). https://doi.org/10.1016/j.joule.2019.08.006

Srivastava, M., Singh, P.K., Singh, R.C.: Comparative study of PSCs formed by one step and sequential deposition of CH 3 NH 3 PbI 3 using PEDOT: PSS as HTM. Mater. TodayProc. (2021). https://doi.org/10.1016/j.matpr.2021.01.338

Yang, L., Han, G., Chang, Y., Zhang, Y., Xiao, Y.: Enhanced efficiency and stability of perovskite solar cells by synergistic effect of magnesium acetate introducing into CH 3 NH 3 PbI 3 . Mater. Sci. Semicond. Process. 104 , 104671 (2019). https://doi.org/10.1016/j.mssp.2019.104671

Mohanty, I., Mangal, S., Jana, S., Singh, U.P.: Stability factors of perovskite (CH 3 NH 3 PbI 3 ) thin films for solar cell applications: a study. Mater. Today Proc. 39 , 1829–1832 (2021). https://doi.org/10.1016/j.matpr.2020.06.183

Qi, X., Liu, G., Wang, D., Zhu, N., Zhang, Y., Zhang, Z., Wu, C., Li, X., Luo, W., Li, Y., Hu, H., Chen, Z., Xiao, L., Wang, S., Qu, B.: Stable power output (PCE > 19%) of planar perovskite solar cells with PbCl 2 modification at the interface of SnO 2 /CH 3 NH 3 PbI 3 . Org. Electron. 74 , 52–58 (2019). https://doi.org/10.1016/j.orgel.2019.06.048

Torres, J., Sanchez-Diaz, J., Rivas, J.M., de la Torre, J., Zarazua, I., Esparza, D.: Electrical properties and J–V modeling of perovskite (CH 3 NH 3 PbI 3 ) solar cells after external thermal exposure. Sol. Energy 222 , 95–102 (2021). https://doi.org/10.1016/j.solener.2021.05.014

Wu, C., Li, H., Yan, Y., Chi, B., Pu, J., Li, J., Sanghadasa, M., Priya, S.: Cost-effective sustainable-engineering of CH 3 NH 3 PbI 3 perovskite solar cells through slicing and restacking of 2D layers. Nano Energy 36 , 295–302 (2017). https://doi.org/10.1016/j.nanoen.2017.04.034

Rafieh, A.I., Ekanayake, P., Wakamiya, A., Nakajima, H., Lim, C.M.: Enhanced performance of CH 3 NH 3 PbI 3 -based perovskite solar cells by tuning the electrical and structural properties of mesoporous TiO 2 layer via Al and Mg doping. Sol. Energy 177 , 374–381 (2019). https://doi.org/10.1016/j.solener.2018.11.024

Liu, C., Li, W., Zhang, C., Ma, Y., Fan, J., Ma, Y.: All-inorganic CsPbI 2 Br perovskite solar cells with high efficiency exceeding 13%. J. Am. Chem. Soc. 140 (11), 3825–3828 (2018)

Zeng, Z., Zhang, J., Gan, X., Sun, H., Shang, M., Hou, D., Lu, C., Chen, R., Zhu, Y., Han, L.: In situ grain boundary functionalization for stable and efficient inorganic CsPbI 2 Br perovskite solar cells. Adv. Energy Mater. 1801050 , 1–8 (2018). https://doi.org/10.1002/aenm.201801050

Wang, Y., Zhang, T., Kan, M., Zhao, Y.: Bifunctional stabilization of all-inorganic α-CsPbI 3 perovskite for 17% efficiency photovoltaics. J. Am. Chem. Soc. (2018). https://doi.org/10.1021/jacs.8b07927

Yan, L., Xue, Q., Liu, M., Zhu, Z., Tian, J., Li, Z., Chen, Z.: Interface engineering for all-inorganic CsPbI 2 Br perovskite solar cells with efficiency over 14%. Adv. Mater. 30 (33), 1802509 (2018). https://doi.org/10.1002/adma.201802509

Stern, A., Aharon, S., Binyamin, T., Karmi, A., Rotem, D., Etgar, L., Porath, D.: Electrical characterization of individual cesium lead halide perovskite nanowires using conductive AFM. Adv. Mater. 32 , 1907812 (2020). https://doi.org/10.1002/adma.201907812

Aharon, S., Etgar, L.: Two dimensional organometal halide perovskite nanorods with tunable optical properties. Nano Lett. 16 , 3230–3235 (2016). https://doi.org/10.1021/acs.nanolett.6b00665

Im, J.-H., Jang, I.-H., Pellet, N., Grätzel, M., Park, N.-G.: Growth of CH 3 NH 3 PbI 3 cuboids with controlled size for high-efficiency perovskite solar cells. Nat. Nanotechnol. 9 , 927–932 (2014). https://doi.org/10.1038/nnano.2014.181

Ding, X.K., Li, X.M., Gao, X.D., de Zhang, S., di Huang, Y., Li, H.R.: Optical and electrical properties of CH 3 NH 3 PbI 3 perovskite thin films transformed from PbO-PbI 2 hybrid films. Wuli Huaxue Xuebao (Acta Physico-Chim. Sin.) 31 , 576–582 (2015). https://doi.org/10.3866/PKU.WHXB201501201

Givalou, L., Antoniadou, M., Kaltzoglou, A., Falaras, P.: High performance solid state solar cells incorporating CdS quantum dots and CH 3 NH 3 PbI 3 perovskite. Mater. Today Proc. 19 , 79–85 (2019). https://doi.org/10.1016/j.matpr.2019.07.661

Jarwal, D.K., Kumar, A., Mishra, A.K., Ratan, S., Upadhyay, R.K., Kumar, C., Mukherjee, B., Jit, S.: Fabrication and TCAD validation of ambient air-processed ZnO NRs/CH 3 NH 3 PbI 3 /spiro-OMeTAD solar cells. Superlattices Microstruct. 143 , 106540 (2020). https://doi.org/10.1016/j.spmi.2020.106540

Abdulrahman, S., Wang, C., Cao, C., Zhang, C., Yang, J., Jiang, L.: Improvement of CH 3 NH 3 PbI 3 thin film using the additive 1,8-diiodooctane for planar heterojunction perovskite cells. Physica B 522 , 43–47 (2017). https://doi.org/10.1016/j.physb.2017.07.065

Wang, K., Liu, C., Du, P., Chen, L., Zhu, J., Karim, A., Gong, X.: Efficiencies of perovskite hybrid solar cells influenced by film thickness and morphology of CH 3 NH 3 PbI 3-x Cl x layer. Org. Electron. 21 , 19–26 (2015). https://doi.org/10.1016/j.orgel.2015.02.023

Liu, D., Li, Y., Shi, B., Yao, X., Fan, L., Zhao, S., Liang, J., Ding, Y., Wei, C., Zhang, D., Zhao, Y., Zhang, X.: Tailoring morphology and thickness of perovskite layer for flexible perovskite solar cells on plastics: The role of CH 3 NH 3 I concentration. Sol. Energy 147 , 222–227 (2017). https://doi.org/10.1016/j.solener.2017.03.035

Li, D.: Preparation of organolead halide perovskite films and studies on photoelectric properties (2020)***

Li, N., Shi, C., Li, L., Zhang, Z., Ma, C.: Tunable Br-doping CH 3 NH 3 PbI 3−x Br x thin films for efficient planar perovskite solar cells. Superlattices Microstruct. 104 , 445–450 (2017). https://doi.org/10.1016/j.spmi.2017.03.011

Ni, X., Lei, L., Yu, Y., Xie, J., Li, M., Yang, S., Wang, M., Liu, J., Zhang, H., Ye, B.: Effect of Br content on phase stability and performance of H 2 N=CHNH 2 Pb(I 1−x Br x ) 3 perovskite thin films. Nanotechnology (2019). https://doi.org/10.1088/1361-6528/aafeb6

Article   PubMed   Google Scholar  

Binyamin, T., Pedesseau, L., Remennik, S., Sawahreh, A., Even, J., Etgar, L.: Fully inorganic mixed cation lead halide perovskite nanoparticles: a study at the atomic level. Chem. Mater. 32 , 1467–1474 (2020). https://doi.org/10.1021/acs.chemmater.9b04426

Tan, X., Liu, X., Liu, Z., Sun, B., Li, J., Xi, S., Shi, T., Tang, Z., Liao, G.: Enhancing the optical, morphological and electronic properties of the solution-processed CsPbIBr 2 films by Li doping for efficient carbon-based perovskite solar cells. Appl. Surf. Sci. 499 , 143990 (2020). https://doi.org/10.1016/j.apsusc.2019.143990

Wu, Y.-H., Ding, Y., Liu, X.-Y., Ding, X.-H., Liu, X.-P., Pan, X., Dai, S.-Y.: Ambient stable FAPbI 3 -based perovskite solar cells with a 2D-EDAPbI 4 thin capping layer. Sci. China Mater. 63 , 47–54 (2020). https://doi.org/10.1007/s40843-019-1174-3

Duan, J., Wei, J., Tang, Q., Li, Q.: Unveiling the interfacial charge extraction kinetics in inorganic perovskite solar cells with formamidinium lead halide (FAPbX 3 ) nanocrystals. Sol. Energy 195 , 644–650 (2020). https://doi.org/10.1016/j.solener.2019.12.001

Wang, X., Rakstys, K., Jack, K., Jin, H., Lai, J., Li, H., Ranasinghe, C.S.K., Saghaei, J., Zhang, G., Burn, P.L., Gentle, I.R., Shaw, P.E.: Engineering fluorinated-cation containing inverted perovskite solar cells with an efficiency of >21% and improved stability towards humidity. Nat. Commun. 12 , 52 (2021). https://doi.org/10.1038/s41467-020-20272-3

Article   CAS   PubMed   PubMed Central   Google Scholar  

Snaith, H.J.: Present status and future prospects of perovskite photovoltaics. Nat. Mater. (2018). https://doi.org/10.1038/s41563-018-0071-z

Sun, Q.Y., Kong, W.Y., Zhang, C.Y., Yang, X.D.: Phase transition stability of formamidine (FA)-based perovskite films. Sci. Sin. Phys. Mech. Astron. (2021). https://doi.org/10.1360/SSPMA-2020-0490

Shan, L., Ding, J., Sun, W., Han, Z., Jin, L.: Core-shell heterostructured BiVO 4 /BiVO 4 :Eu 3+ with improved photocatalytic activity. J. Inorg. Organomet. Polym Mater. 27 , 1750–1759 (2017). https://doi.org/10.1007/s10904-017-0638-1

Hui, W., Chao, L., Lu, H., Xia, F., Wei, Q., Su, Z., Niu, T., Tao, L., Du, B., Li, D., Wang, Y., Dong, H., Zuo, S., Li, B., Shi, W., Ran, X., Li, P., Zhang, H., Wu, Z., Ran, C., Song, L., Xing, G., Gao, X., Zhang, J., Xia, Y., Chen, Y., Huang, W.: Stabilizing black-phase formamidinium perovskite formation at room temperature and high humidity. Science 371 , 1359 (2021). https://doi.org/10.1126/science.abf7652

Liu, Z., Liu, F., Duan, C., Yuan, L., Zhu, H., Li, J., Wen, Q., Waterhouse, G.I.N., Yang, X., Yan, K.: Polymerization stabilized black-phase FAPbI 3 perovskite solar cells retain 100% of initial efficiency over 100 days. Chem. Eng. J. 419 , 129482 (2021). https://doi.org/10.1016/j.cej.2021.129482

Wang, J., Ye, X., Wang, Y., Wang, Z., Wong, W., Li, C.: Halide perovskite based on hydrophobic ionic liquid for stability improving and its application in high-efficient photovoltaic cell. Electrochim. Acta 303 , 133–139 (2019). https://doi.org/10.1016/j.electacta.2019.02.071

Isikgor, F.H., Subbiah, A.S., Eswaran, M.K., Howells, C.T., Babayigit, A., de Bastiani, M., Yengel, E., Liu, J., Furlan, F., Harrison, G.T., Zhumagali, S., Khan, J.I., Laquai, F., Anthopoulos, T.D., McCulloch, I., Schwingenschlögl, U., de Wolf, S.: Scaling-up perovskite solar cells on hydrophobic surfaces. Nano Energy (2021). https://doi.org/10.1016/j.nanoen.2020.105633

Li, J., Bu, T., Lin, Z., Mo, Y., Chai, N., Gao, X., Ji, M., Zhang, X.L., Cheng, Y.B., Huang, F.: Efficient and stable perovskite solar cells via surface passivation of an ultrathin hydrophobic organic molecular layer. Chem. Eng. J. (2021). https://doi.org/10.1016/j.cej.2020.126712

Zhou, Q., Liang, L., Hu, J., Cao, B., Yang, L., Wu, T., Li, X., Zhang, B., Gao, P.: High-performance perovskite solar cells with enhanced environmental stability based on a (p-FC 6 H 4 C 2 H 4 NH 3 ) 2 [PbI 4 ] capping layer. Adv. Energy Mater. (2019). https://doi.org/10.1002/aenm.201802595

Zhu, H., Liu, Y., Eickemeyer, F.T., Pan, L., Ren, D., Ruiz-Preciado, M.A., Carlsen, B., Yang, B., Dong, X., Wang, Z., Liu, H., Wang, S., Zakeeruddin, S.M., Hagfeldt, A., Dar, M.I., Li, X., Grätzel, M.: Tailored amphiphilic molecular mitigators for stable perovskite solar cells with 23.5% efficiency. Adv. Mater. (2020). https://doi.org/10.1002/ADMA.201907757

Boyd, C.C., Cheacharoen, R., Leijtens, T., McGehee, M.D.: Understanding degradation mechanisms and improving stability of perovskite photovoltaics. Chem. Rev. (2019). https://doi.org/10.1021/acs.chemrev.8b00336

Jin, L., Liu, T., Wang, C.: Ionic gel electrolytes composite with SiO 2 nanoparticles for quasi-solid-state dye-sensitized solar cells. Appl. Phys. A (2016). https://doi.org/10.1007/s00339-016-0131-7

Boonmongkolras, P., Naqvi, S.D.H., Kim, D., Pae, S.R., Kim, M.K., Ahn, S., Shin, B.: Universal passivation strategy for the hole transport layer/perovskite interface via an alkali treatment for high-efficiency perovskite solar cells. Solar RRL. 5 , 2000793 (2021). https://doi.org/10.1002/solr.202000793

Li, S., Lu, H., Kan, Z., Zhu, L., Wu, F.: Engineering of P3CT-Na through diprophylline treatment to realize efficient and stable inverted perovskite solar cells. Chem. Eng. J. 419 , 129581 (2021). https://doi.org/10.1016/j.cej.2021.129581

Li, M., Ma, S., Mateen, M., Liu, X., Ding, Y., Gao, J., Yang, Y., Zhang, X., Wu, Y., Dai, S.: Facile donor (D)-π-D triphenylamine-based hole transporting materials with different π-linker for perovskite solar cells. Sol. Energy 195 , 618–625 (2020). https://doi.org/10.1016/j.solener.2019.11.071

Min, C.D.Z., He, F., Wang, D., Yang, C., Fan, G.: Efficient carbon-based inorganic CsPbIBr 2 perovskite solar cells with P3HT hole transport layers. Aerosp. Shanghai. 37 , 98–103 (2020). https://doi.org/10.19328/j.cnki.1006

Jin, J., Yang, M., Deng, W., Xin, J., Tai, Q., Qian, J., Dong, B., Li, W., Wang, J., Li, J.: Highly efficient and stable carbon-based perovskite solar cells with the polymer hole transport layer. Sol. Energy 220 , 491–497 (2021). https://doi.org/10.1016/j.solener.2021.03.081

Ouyang, D., Chen, C., Huang, Z., Zhu, L., Yan, Y., Choy, W.C.H.: Hybrid 3D nanostructure-based hole transport layer for highly efficient inverted perovskite solar cells. ACS Appl. Mater. Interfaces 13 , 16611–16619 (2021). https://doi.org/10.1021/acsami.0c21064

Saranin, D., Komaricheva, T., Luchnikov, L., Muratov, D.S., Le, T.S., Karpov, Y., Gostishchev, P., Yurchuk, S., Kuznetsov, D., Didenko, S., di Carlo, A.: Hysteresis-free perovskite solar cells with compact and nanoparticle NiO for indoor application. Sol. Energy Mater. Sol. Cells 227 , 111095 (2021). https://doi.org/10.1016/j.solmat.2021.111095

Schloemer, T.H., Raiford, J.A., Gehan, T.S., Moot, T., Nanayakkara, S., Harvey, S.P., Bramante, R.C., Dunfield, S., Louks, A.E., Maughan, A.E., Bliss, L., McGehee, M.D., van Hest, M.F.A.M., Reese, M.O., Bent, S.F., Berry, J.J., Luther, J.M., Sellinger, A.: The molybdenum oxide interface limits the high-temperature operational stability of unencapsulated perovskite solar cells. ACS Energy Lett. 5 , 2349–2360 (2020). https://doi.org/10.1021/acsenergylett.0c01023

Download references

Author information

Authors and affiliations.

The School of Material Science & Chemical Engineering, Harbin University of Science and Technology, Harbin, 150040, People’s Republic of China

Liguo Jin, Chaoying Su, Yuwen Wang & Limin Dong

You can also search for this author in PubMed   Google Scholar

Corresponding author

Correspondence to Liguo Jin .

Additional information

Publisher's note.

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and permissions

About this article

Jin, L., Su, C., Wang, Y. et al. The recent process and future of perovskite solar cells materials. J Incl Phenom Macrocycl Chem 102 , 235–249 (2022). https://doi.org/10.1007/s10847-021-01126-x

Download citation

Received : 23 September 2021

Accepted : 03 December 2021

Published : 07 January 2022

Issue Date : April 2022

DOI : https://doi.org/10.1007/s10847-021-01126-x

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

• Perovskite solar cells
• Electron transport materials
• Hole transport materials
• Perovskite materials
• Power conversion efficiency
• Find a journal
• Publish with us
• Track your research

New solar cell breaks records for efficiency and voltage

• Nanotechnology
• Weinberg College

In the race to make solar energy more practical amidst soaring gas prices and threats of climate catastrophe, a team of researchers is taking steps toward a more efficient, higher-voltage solar cell.

Now, a Northwestern University, University of Toronto and the University of Toledo team is introducing in a new type of solar cell produced without silicon. Not only does the new cell have extremely high efficiency and record-setting voltage, it also bypasses the need for silicon, which is energetically costly to produce and purify.

In a new paper published this week in Nature , the international team of researchers used two different layers of perovskites — a type of nanocrystal dispersed in a liquid and coated onto a surface using low-cost, well-established techniques. The researchers then tuned each perovskite layer to a different part of the solar spectrum, producing a tandem solar cell.

The team’s prototype solar cell measures one square centimeter in area and produces an open-circuit voltage of 2.19 electron volts, a record for all-perovskite tandem solar cells. Its power-conversion efficiency reached 27.4%, which also breaks the current record for traditional silicon solar cells .

“Further improvements in the efficiency of solar cells are crucial for the ongoing decarbonization of our economy,” said corresponding author Ted Sargent. “While silicon solar cells have undergone impressive advances in recent years, there are inherent limitations to their efficiency and cost, arising from material properties. Perovskite technology can overcome these limitations, but, until now, it had performed below its full potential. Our latest study identifies a key reason for this and points a way forward.”

Sargent joined Northwestern this fall as the Lynn Hopton Davis and Greg Davis Professor of Chemistry at the Weinberg College of Arts and Sciences and a professor of electrical and computer engineering in the McCormick School of Engineering.

By adjusting the thickness and chemical composition of the perovskite crystal films, manufacturers can selectively “tune” which wavelengths of light are absorbed and converted into electricity. This is a beneficial contrast to silicon, which always absorbs the same limited section of the solar spectrum.

“In our cell, the top perovskite layer absorbs well in the ultraviolet part of the spectrum, as well as some visible light,” said Chongwen Li, a postdoctoral researcher in Sargent’s lab and one of five co-first authors of the new paper. “The bottom layer has a narrow band gap, which is tuned more toward the infrared part of the spectrum. Between the two, we cover more of the spectrum than would be possible with silicon.”

The tandem design enables the cell to produce a very high open-circuit voltage, which in turn improves its efficiency. But the key innovation came when the team analyzed the touchpoints between the perovskite layer, where light is absorbed and transformed into excited electrons, and the adjacent layer, known as the electron transport layer.

“What we found is that the electric field across the surface of the perovskite layer — we call it the surface potential — was not uniform,” co-lead author and Ph.D. student Aidan Maxwell said. “The effect of this was that in some places, excited electrons were moving easily into the electron transport layer, but, in others, electrons were being lost to the circuit.”

To address this challenge, the team coated the surface of the perovskite layer with a substance known as 1,3-propanediammonium (PDA).

“PDA has a positive charge, and it is able to even out the surface potential,” postdoctoral fellow Hao Chen said. “When we added the coating, we got much better energetic alignment of the perovskite layer with the electron transport layer, and that led to a big improvement in our overall efficiency.”

The cell was independently certified at the National Renewable Energy Laboratory in Colorado, delivering an efficiency of 26.3%. The team used industry standard methods to measure the stability of the new cell and found that it maintained 86% of its initial efficiency after 500 hours of continuous operation.

"Continuing to advance the efficiency and stability of next-generation solar cells is a crucial priority for decarbonizing the electricity supply,” said Professor Alberto Salleo, chair of the department of materials science and engineering at Stanford University, who was not involved in the study. “The team developed a deep chemical understanding of what was limiting a crucial interface in perovskite solar cells. These insights from basic science, acted on with innovative materials engineering strategies, will continue to drive the field forward.”

Next, the team hopes to scale their production for commercial use, further enhance the tandem cell’s efficiency and improve its stability.

“In this work, we’ve focused on the interface between the perovskite layer and the electron transport layer, but there is another important layer that extracts the ‘holes’ those electrons leave behind,” Sargent said. “One of the intriguing things in my experience with this field is that learning to master one interface doesn't necessarily teach you the rules for mastering the other interfaces. I think there's lots more discovery to be done.”

Maxwell said that the ability of perovskite technology to hold its own against silicon, even though the latter has had a multi-decade head start, is encouraging. The industry’s ability to incorporate new materials and diversify the products it offers will accelerate the economy toward decarbonization.

“In the last 10 years, perovskite technology has come almost as far as silicon has in the last 40,” Maxwell said. “Just imagine what it will be able to do in another 10 years.”

Additional reporting by Tyler Irving / University of Toronto Engineering.

Editor’s Picks

Redevelopment of Norris University Center’s East Lawn to begin this summer

‘the night watchman’ named next one book selection, six northwestern faculty named 2024 guggenheim fellows, related stories.

Northwestern receives ENERGY STAR’s highest honor for fifth consecutive year

Understanding how soil traps carbon, great lakes project selected to receive up to $160 million from nsf.

Suggestions or feedback?

MIT News | Massachusetts Institute of Technology

• Machine learning
• Social justice
• Black holes
• Classes and programs

Departments

• Aeronautics and Astronautics
• Brain and Cognitive Sciences
• Architecture
• Political Science
• Mechanical Engineering

Centers, Labs, & Programs

• Abdul Latif Jameel Poverty Action Lab (J-PAL)
• Picower Institute for Learning and Memory
• Lincoln Laboratory
• School of Architecture + Planning
• School of Engineering
• School of Humanities, Arts, and Social Sciences
• Sloan School of Management
• School of Science
• MIT Schwarzman College of Computing

Researchers improve efficiency of next-generation solar cell material

Press contact :, media download.

*Terms of Use:

Images for download on the MIT News office website are made available to non-commercial entities, press and the general public under a Creative Commons Attribution Non-Commercial No Derivatives license . You may not alter the images provided, other than to crop them to size. A credit line must be used when reproducing images; if one is not provided below, credit the images to "MIT."

Previous image Next image

Perovskites are a leading candidate for eventually replacing silicon as the material of choice for solar panels. They offer the potential for low-cost, low-temperature manufacturing of ultrathin, lightweight flexible cells, but so far their efficiency at converting sunlight to electricity has lagged behind that of silicon and some other alternatives.

Now, a new approach to the design of perovskite cells has pushed the material to match or exceed the efficiency of today’s typical silicon cell, which generally ranges from 20 to 22 percent, laying the groundwork for further improvements.

By adding a specially treated conductive layer of tin dioxide bonded to the perovskite material, which provides an improved path for the charge carriers in the cell, and by modifying the perovskite formula, researchers have boosted its overall efficiency as a solar cell to 25.2 percent — a near-record for such materials, which eclipses the efficiency of many existing solar panels. (Perovskites still lag significantly in longevity compared to silicon, however, a challenge being worked on by teams around the world.)

The findings are described in a paper in the journal Nature by recent MIT graduate Jason Yoo PhD ’20, professor of chemistry and Lester Wolfe Professor Moungi Bawendi, professor of electrical engineering and computer science and Fariborz Maseeh Professor in Emerging Technology Vladimir Bulović, and 11 others at MIT, in South Korea, and in Georgia.

Perovskites are a broad class of materials defined by the fact that they have a particular kind of molecular arrangement, or lattice, that resembles that of the naturally occurring mineral perovskite. There are vast numbers of possible chemical combinations that can make perovskites, and Yoo explains that these materials have attracted worldwide interest because “at least on paper, they could be made much more cheaply than silicon or gallium arsenide,” one of the other leading contenders. That’s partly because of the much simpler processing and manufacturing processes, which for silicon or gallium arsenide requires sustained heat of over 1,000 degrees Celsius. In contrast, perovskites can be processed at less than 200 C, either in solution or by vapor deposition.

The other major advantage of perovskite over silicon or many other candidate replacements is that it forms extremely thin layers while still efficiently capturing solar energy. “Perovskite cells have the potential to be lightweight compared to silicon, by orders of magnitude,” Bawendi says.

Perovskites have a higher bandgap than silicon, which means they absorb a different part of the light spectrum and thus can complement silicon cells to provide even greater combined efficiencies. But even using only perovskite, Yoo says, “what we’re demonstrating is that even with a single active layer, we can make efficiencies that threaten silicon, and hopefully within punching distance of gallium arsenide. And both of those technologies have been around for much longer than perovskites have.”

One of the keys to the team’s improvement of the material’s efficiency, Bawendi explains, was in the precise engineering of one layer of the sandwich that makes up a perovskite solar cell — the electron transport layer. The perovskite itself is layered with a transparent conductive layer used to carry an electric current from the cell out to where it can be used. However, if the conductive layer is directly attached to the perovskite itself, the electrons and their counterparts, called holes, simply recombine on the spot and no current flows. In the researchers’ design, the perovskite and the conductive layer are separated by an improved type of intermediate layer that can let the electrons through while preventing the recombination.

This middle electron transport layer, and especially the interfaces where it connects to the layers on each side of it, tend to be where inefficiencies occur. By studying these mechanisms and designing a layer, consisting of tin oxide, that more perfectly conforms with those adjacent to it, the researchers were able to greatly reduce the losses.

The method they use is called chemical bath deposition. “It’s like slow cooking in a Crock-Pot,” Bawendi says. With a bath at 90 degrees Celsius, precursor chemicals slowly decompose to form the layer of tin dioxide in place. “The team realized that if we understood the decomposition mechanisms of these precursors, then we’d have a better understanding of how these films form. We were able to find the right window in which the electron transport layer with ideal properties can be synthesized.”

After a series of controlled experiments, they found that different mixtures of intermediate compounds would form, depending on the acidity of the precursor solution. They also identified a sweet spot of precursor compositions that allowed the reaction to produce a much more effective film.

The researchers combined these steps with an optimization of the perovskite layer itself. They used a set of additives to the perovskite recipe to improve its stability, which had been tried before but had an undesired effect on the material’s bandgap, making it a less efficient light absorber. The team found that by adding much smaller amounts of these additives — less than 1 percent — they could still get the beneficial effects without altering the bandgap.

The resulting improvement in efficiency has already driven the material to over 80 percent of the theoretical maximum efficiency that such materials could have, Yoo says.

While these high efficiencies were demonstrated in tiny lab-scale devices, Bawendi says that “the kind of insights we provide in this paper, and some of the tricks we provide, could potentially be applied to the methods that people are now developing for large-scale, manufacturable perovskite cells, and therefore boost those efficiencies.”

In pursuing the research further, there are two important avenues, he says: to continue pushing the limits on better efficiency, and to focus on increasing the material’s long-term stability, which currently is measured in months, compared to decades for silicon cells. But for some purposes, Bawendi points out, longevity may not be so essential. Many electronic devices such as cellphones, for example, tend to be replaced within a few years anyway, so there may be some useful applications even for relatively short-lived solar cells.

“I don’t think we’re there yet with these cells, even for these kind of shorter-term applications,” he says. “But people are getting close, so combining our ideas in this paper with ideas that other people have with increasing stability could lead to something really interesting.”

Robert Hoye, a lecturer in materials at Imperial College London, who was not part of the study, says, “This is excellent work by an international team.” He adds, “This could lead to greater reproducibility and the excellent device efficiencies achieved in the lab translating to commercialized modules. In terms of scientific milestones, not only do they achieve an efficiency that was the certified record for perovskite solar cells for much of last year, they also achieve open-circuit voltages up to 97 percent of the radiative limit. This is an astonishing achievement for solar cells grown from solution.”

The team included researchers at the Korea Research Institute of Chemical Technology, the Korea Advanced Institute of Science and Technology, the Ulsan National Institute of Science and Technology, and Georgia Tech. The work was supported by MIT’s Institute for Soldier Nanotechnology, NASA, the Italian company Eni SpA through the MIT Energy Initiative, the National Research Foundation of Korea, and the National Research Council of Science and Technology.

Share this news article on:

Related links.

• Moungi Bawendi
• Vladimir Bulović
• Bawendi Group
• Department of Chemistry
• Department of Electrical Engineering and Computer Science

Related Topics

• Photovoltaics
• Electronics
• Nanoscience and nanotechnology
• Renewable energy
• Electrical Engineering & Computer Science (eecs)

Related Articles

Experiments show dramatic increase in solar cell output

Quantum dots can spit out clone-like photons

Unleashing perovskites’ potential for solar cells

Nanoparticles open new window for biological imaging

Cheap, flexible solar

Previous item Next item

More MIT News

“No one can work in civil engineering alone”

Read full story →

This tiny chip can safeguard user data while enabling efficient computing on a smartphone

Researchers detect a new molecule in space

Erin Bahm, Steven Parks named 2024–25 UPS Fellows

Twenty-three MIT faculty honored as "Committed to Caring" for 2023-25

Featured video: Moooving the needle on methane

• More news on MIT News homepage →

Massachusetts Institute of Technology 77 Massachusetts Avenue, Cambridge, MA, USA

• Map (opens in new window)
• Events (opens in new window)
• People (opens in new window)
• Careers (opens in new window)
• Accessibility
• Social Media Hub
• MIT on Facebook
• MIT on YouTube
• MIT on Instagram

• News & Events
• Contact & Visit
• Faculty & Staff
• McCormick Advisory Council
• Departments & Institutes
• Diversity Data
• Faculty Journal Covers
• Areas of Study
• Bachelor's Degrees
• Music & Engineering
• Combined BS / MS Program Collapse Combined BS / MS Program Submenu
• Murphy Scholars Program Projects
• Undergraduate Honors
• Certificates & Minors Collapse Certificates & Minors Submenu
• Integrated Engineering Studies
• Engineering First® Program
• Theme Requirement
• Research Opportunities
• Personal & Career Development
• Global Opportunities
• Existing Groups
• McCormick Community
• Transfer AP/IB Credits
• ABET Course Partitioning
• Enrollment and Graduation Data
• Full-time Master's
• Part-time Master's
• MS with Interdepartmental Minors
• Application Checklist
• Application FAQs
• Financial Aid
• International Students
• Student Groups
• Career & Professional Development
• All Areas of Study
• Departments & Programs
• Apply to Northwestern Engineering
• Faculty Fellows
• Office of the Dean
• Administration, Finance, Facilities, & Planning
• Alumni Relations & Development
• Career Development
• Corporate Engagement
• Customer Service Center
• Faculty Affairs
• Global Initiatives
• Graduate Studies
• Information Technology
• Marketing & Communications
• McCormick Advising System
• Personal Development StudioLab
• Professional Education
• Research Offices
• Undergraduate Engineering
• Newsletter Signup
• Information for the Media
• Tech Room Finder

Researchers Take a Step Closer to Better, More Affordable Solar Cells

Innovative technique leads to perovskite-based solar cells with record-breaking efficiency, the problem:.

Scaling single-junction perovskite solar cells (PSCs) has been challenging.

A new technique applied during crystal formation that allows PSCs with an ‘inverted’ or ‘pin’ structure – known for their stability – to exhibit high efficiency.

Why it Matters:

The breakthrough means PSCs are closer to scaling, bringing them nearer their potential to contribute to the decarbonization of the electricity supply.

Professor Ted Sargent, Research Assistant Professor Bin Chen, Postdoctoral Researcher Hao Chen, Postdoctoral Fellow Cheng Liu

An international team of researchers, including a group from Northwestern Engineering and Northwestern Chemistry , has set a new world record for power conversion efficiency (PCE) of single-junction perovskite solar cells (PSCs).

These solar cells – created from an emerging solar material – have the potential to generate greater solar energy at a lower cost than today’s industry-standard silicon solar cells, but scaling the technology has its challenges. Until now, PSCs have shown either high stability and lower efficiency or vice versa, depending on their structure.

Yet this team’s work has resulted in a highly stable, highly efficient 0.05cm 2 perovskite solar cell with a PCE of 26.15 percent certified by a National Renewable Energy Laboratory -accredited facility. The prior certified world record published in a scientific journal was 25.73 percent.

A 1.04 cm 2 device had a certified power conversion efficiency of 24.74 percent, also a record for its size. The best devices retained 95 percent of their initial PCE following 1,200 hours of continuous solar illumination at a temperature of 65 degrees.

“Perovskite-based solar cells have the potential to contribute to the decarbonization of the electricity supply once we finalize their design, achieve the union of performance and durability, and scale the devices,” said Ted Sargent , Lynn Hopton Davis and Greg Davis Professor of Chemistry and Electrical and Computer Engineering at Northwestern University, co-executive director of the Paula M. Trienens Institute for Sustainability and Energy , and co-corresponding author of the paper. “Our team has discovered a new technique applied during crystal formation that allows PSCs with an ‘inverted’ or ‘pin’ structure – known for their stability – to exhibit high efficiency. It’s the best of both worlds.”

Our team has discovered a new technique applied during crystal formation that allows perovskite solar cells with an ‘inverted’ or ‘pin’ structure – known for their stability – to exhibit high efficiency. It’s the best of both worlds.

Ted Sargent Lynn Hopton Davis and Greg Davis Professor of Chemistry and Electrical and Computer Engineering

"Until today, a promising and more stable perovskite solar cell - inverted perovskite solar cells - have suffered lower energy efficiencies than those achieved in their non-inverted counterparts. This work represents an important milestone by crossing the efficiency-parity threshold," said Zhijun Ning, co-corresponding author and assistant professor at ShanghaiTech University.

Findings were reported April 11 in the journal Science.

A new approach to treating defects

The basic structure of “inverted” PSCs consists of an outer electron-transporting layer (ETL), a hole transporting layer (HTL), an anode, and a cathode. The energetic losses for the cells occur primarily at the interfaces between the perovskites and the ETL and HTL layers in places where there are tiny defects in the crystals.

Prior attempts at reducing energy loss have included the use of additive or surface treatments to passivate the defects. Sargent’s team noted that the molecules in these treatments bonded at a single site on the defects in a perpendicular orientation, forcing the electrons to travel a long distance up through the material, causing resistance and lowering efficiency.

The team set out to find a molecule that would bond on two neighboring sites on the defects in a horizontal orientation, reducing the distance the electrons needed to travel and improving efficiency. They identified one molecule – 4- chlorobenzenesulfonate – that could lay down at the surface of the perovskites by forming strong Cl-Pb and SO 3 -Pb bonds with the undercoordinated Pb 2+ and led to improved performance of the devices.

“By carefully selecting molecules that lie flat on the perovskite surface, binding to two sites simultaneously, our new strategy reduced the interface resistance:  the result is much higher fill factor in solar cells, reaching 95 percent of the theoretical limit," said Jian Xu, co-first author and postdoctoral fellow at the University of Toronto.

“Not only did the addition of these molecules improve efficiency, they also simplified the manufacturing process,” noted Hao Chen , a postdoctoral researcher at Northwestern Engineering and co-first author of the paper. “When added to the perovskites precursor, these molecules automatically go to the surface of the perovskite layer to patch defects during the crystallization process. This removes the need to treat the surface defects, an extra step that often results in uneven coverage of passivators and poor stability of the devices.”

This discovery builds on prior research conducted by the Sargent Group , which has explored various strategies to improve PSC performance and stability to make them a viable alternative to silicon solar cells. Next, the team will look toward scaling the devices.

“Northwestern is really at the forefront of renewable energy technology research,” said Bin Chen , co-corresponding author and research assistant professor at Northwestern Engineering. “By focusing on stable inverted perovskites and making breakthroughs in their performance, we are  developing a solar technology that can be a gamechanger in the field.”

"With the efficiency discrepancy solved, the large and growing perovskite community will focus even more of its firepower on the inverted perovskite solar cell architecture in light of its stability advantages," said Aidan Maxwell, co-first author of the paper and a graduate student at the University of Toronto.

“We were thrilled when we achieved an independently certified efficiency of 26.1 percent for inverted perovskite solar cells: this was the first to surpass the record for the conventional structure,” added Cheng Liu , postdoctoral fellow at Northwestern Chemistry and co-first author of the paper. “The accomplishment motivates not only our own team but will also inspires further collective efforts across the wide and productive global perovskite community."

Additional authors on the paper include Yi Yang, Abdulaziz S. R. Bati, Yuan Liu, and Mercouri G. Kanatzidis of Northwestern Chemistry; Haoyue Wan, Zaiwei Wang, Lewei Zeng, Junke Wang, Sam Teale, Yanjiang Liu, Sjoerd Hoogland, Peter Serles, and Tobin Filleter of the University of Toronto; Wei Zhou and Qilin Zhou of ShanghaiTech University; Makhsud I. Saidaminov of the University of Victoria; and Muzhi Li and Nicholas Rolston of Arizona State University.

Get our news in your inbox.

Sign up for our newsletter.

Check out our magazine.

Find more in depth stories and get to know Northwestern Engineering.

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• Materials (Basel)

Perovskites-Based Solar Cells: A Review of Recent Progress, Materials and Processing Methods

With the rapid increase of efficiency up to 22.1% during the past few years, hybrid organic-inorganic metal halide perovskite solar cells (PSCs) have become a research “hot spot” for many solar cell researchers. The perovskite materials show various advantages such as long carrier diffusion lengths, widely-tunable band gap with great light absorption potential. The low-cost fabrication techniques together with the high efficiency makes PSCs comparable with Si-based solar cells. But the drawbacks such as device instability, J-V hysteresis and lead toxicity reduce the further improvement and the future commercialization of PSCs. This review begins with the discussion of crystal and electronic structures of perovskite based on recent research findings. An evolution of PSCs is also analyzed with a greater detail of each component, device structures, major device fabrication methods and the performance of PSCs acquired by each method. The following part of this review is the discussion of major barriers on the pathway for the commercialization of PSCs. The effects of crystal structure, fabrication temperature, moisture, oxygen and UV towards the stability of PSCs are discussed. The stability of other components in the PSCs are also discussed. The lead toxicity and updated research progress on lead replacement are reviewed to understand the sustainability issues of PSCs. The origin of J-V hysteresis is also briefly discussed. Finally, this review provides a roadmap on the current needs and future research directions to address the main issues of PSCs.

1. Introduction

The organic-inorganic halide perovskite solar cells (PSCs) have attracted a great deal of attention of solar cell research community due to an incredible device efficiency improvement from 3.8% to 22.1% since 2009 [ 1 , 2 ]. The perovskite already gained much attention as a potential replacement of the silicon photovoltaic (PV) devices, which is still occupied the most dominant position in the current PV market, with record efficiency of about 26% [ 3 ]. This small gap of solar cell efficiency attracted recent attention especially from the researchers with experience in dye-sensitized solar cells (DSSCs) or organic solar cells because some materials can be used in both PSCs and organic solar cells. The structure of PSCs also origins from the device structure of DSSCs [ 1 ]. The perovskite materials have been demonstrated with largely tunable band gap (e.g., CH 3 NH 3 PbX 3 has a band gap from 1.5 eV to 2.3 eV) [ 4 ] and great light absorption coefficient (higher than 10 4 cm −1 ) [ 5 , 6 ], which is similar to other thin film solar cell materials such as CdTe [ 7 ] and copper zinc tin sulfide (CZTS) [ 8 ]. Its low-cost and convenient fabrication techniques also serve as the possible advantages over silicon-based devices that require complicated and costly high-vacuum deposition methods. Reports of successful cell fabrication on flexible substrates even indicated a greater possibility to the large-scale roll-to-roll manufacturing of PSCs that can be used in the industries [ 9 , 10 , 11 ].

The initial meaning of “perovskite” was about the crystal structure of calcium titanate, which was discovered in 1839 by the German mineralogist Gustav Rose and was named by the Russian mineralogist Lev Perovski. Since then, the term “perovskite” was referred to all compounds with the same crystal structure as calcium titanate. The perovskite light absorption layer has a general formula of ABX 3 , where A is an organic cation (e.g., methyl-ammonium CH 3 NH 3 + ), B is a metal cation (e.g., Pb 2+ ) and X stands for the halide anion (e.g., I − ).

The first record of perovskite-based solar cell efficiency, however, was reported by Miyasaka et al. [ 1 ] only less than one decade ago. They reported an efficiency of 3.8% based on a DSSC structure. Due to the application of liquid electrolyte in the hole-transporting material (HTM), the stability of solar cell was very weak and did not attract much attention. Similar trial was done by Park et al. [ 12 ] with the increased efficiency of 6.5% but stability was still the main problem because of the instability of HTM layer due to the liquid medium.

The application of solid-state HTM (2,2′,7,7′-tetrakis( N , N -di-pmethoxyphenylamine) -9,9′-spirobifluorene, i.e., Spiro-OMeTAD), rather than liquid HTM, onto the highly-crystallized perovskite layer triggered the efficiency boosting during the past several years. Lee et al. [ 13 ] reported a breakthrough device efficiency of 10.9% in 2012 with the open-circuit voltage higher than 1.1 V. Wang et al. [ 14 ] introduced graphene into PSCs and acquired an efficiency of 15.6% in 2013 and the application of another perovskite material, formamidinium iodide (HC(NH 2 ) 2 PbI 3 ) together with poly-triarylamine (PTAA) as a new HTM brought a remarkable 20.1% efficiency in 2015 [ 15 ]. The current record efficiency of PSCs was 22.1%, created in 2016 by Seong Sik Shin et al. [ 16 ]. They also accomplished a long-term and stable efficiency of 21.2% in another work [ 17 ]. The perovskite-inserted tandem cell also achieved a promising efficiency of 26.7% by combining with Si cells [ 18 ]. During this progress, various HTM and vacuum/non-vacuum fabrication methods have been developed, which would be discussed later in this review. Figure 1 compared the efficiency progress of PSCs with other 3rd generation photovoltaics up to date [ 19 ]. The rapid improvement of the efficiency of PSCs make perovskite being expected to be comparable with the stable performance of c-Si solar cells whereas all other kinds of non-silicon solar cells suffered great barriers in further improvements. According to the theoretical calculation based on the well-known Shockley-Queisser limit, the perovskite devices, which have (CH 3 NH 3 PbI 3−x Cl x ), could achieve an efficiency around 25–27% [ 20 ]. This result indicates that there is still opportunity for the improvement of PSCs.

A comparison of perovskite efficiency progress with other kinds of photovoltaic (PV) devices (Reprinted with permission) [ 19 ].

Although laboratory scale PSCs exhibited a great progress, perovskite-based PVs still needs to overcome several barriers. In general, there are two major problems currently blocking the improvement pathway: device instability of device performance [ 21 , 22 ] and hysteresis of J-V (current density-voltage) [ 23 ]. At present, long-term efficiency measurements (>1000 h) is still not adequate for the commercialization of PSCs. The PSCs must pass a series of testing under harsh conditions and environments for similar duration (>1000 h) [ 24 ]. Thus, it is very important to understand the degradation mechanism of both perovskite materials and other device components such as hole transport medium (HTM) and electron transport medium (ETM). The J-V hysteresis was discovered during cell testing when voltage sweeping routine changed. This phenomenon brings problems for standardizing the measurement protocol of PSCs. In addition, the toxicity from lead could be another problem during the manufacturing, using and recycling of perovskite [ 25 ]. Currently several trials on applying non-toxic alternative metal ions have been reported [ 26 , 27 ] but their device efficiency is still not promising. Detail information could be found later in this review.

Future research of PSCs, except efforts on improving the stability and reducing J-V hysteresis of PSCs, could also be focus on the large-area fabrication of PSCs (even small module area) and efforts on at least partial replacement of lead with other non-toxic metal ions inside the perovskite. Bi-facial illumination could also be considered for PSCs due to its structural advantages. Detail information could be found in the last part of this review.

It has been clear that the perovskite could be the next candidate to replace Si due to its outstanding structural, electrical and optical properties. This review, therefore, would start with the discussion from micro-scale observations on the crystal and electrical structures of perovskite materials. The next part is the discussions on device-level investigations: the evolution of device structure, the fabrication methods and their progresses and the exploration of each device component. We would then focus on the research efforts of device stability and toxicity of PSCs and finally show our suggestions for further directions of the perovskite research.

2. Structures

2.1. crystal structure.

The perovskite materials have a general crystal structure described as ABX 3 , where “A” and “B” are cations with varied sizes and “X” is an anion. A typical unit cell structure of a basic perovskite compound is shown in Figure 2 . Organometallic halide perovskites include an organic cation (e.g., methyl-ammonium CH 3 NH 3 + , ethyl-ammonium CH 3 CH 2 NH 3 + , formamidinium NH 2 CH=NH 2 + ), a metal cation of carbon family (i.e., Ge 2+ , Sn 2+ , Pb 2+ ) and a halogen anion (i.e., F − , Cl − , Br − , I − ). Among them, methyl-ammonium-lead-iodide (MAPbI 3 ) is the most widely used perovskite light absorber. Some recent research efforts also replaced lead with other metal ions due to the concern of toxicity of lead during device fabrication, especially for the future large-scale manufacturing [ 26 , 28 ]. In addition, several organic cations (CH 3 NH 3 + and NH 2 CH=NH 2 + ), inorganic cations (Cs 2+ and Sn 2+ ) and halide anions (Br − , Cl − and I − ) have been used to improve the efficiency and stability [ 29 , 30 ].

A generic perovskite crystal structure of the form ABX 3 (Reprinted with permission) [ 31 ].

Perovskite materials have different phases depending on the change of temperature. When temperature is lower than 100 K, the perovskite displayed a stable orthorhombic (γ) phase. With temperature increased to 160 K, the tetragonal (β) phase started to appear and replace the original orthorhombic (γ) phase [ 32 ]. As temperature increases further to about 330 K, the tetragonal (β) phase started being replaced by another stable cubic (α) phase [ 33 ]. Figure 3 displayed all those three crystal structures. The tetragonal-cubic phase transition at higher temperature partially influences the thermal stability of perovskite materials. Formamidinium iodide (HC(NH 2 ) 2 PbI 3 ), for example, has a phase transition occurred at a higher temperature, indicating that it is relatively stable compared with common MAPbI 3 . Moreover, a recent report suggested that light soaking could also trigger the reversible phase transition of perovskite materials [ 34 ] but more efforts are required to demonstrate this behavior.

Comparison of ( a ) orthorhombic; ( b ) tetragonal and ( c ) cubic perovskite phases obtained from structural optimization of MAPbI 3 . Top row: a-c-plane and bottom row: a-b-plane (Reprinted with permission) [ 35 ].

2.2. Electronic Structures

The electronic structure of perovskite, especially the typical MAPbI 3 , was already estimated by DFT (density functional theory) calculations. The calculated band gap had a good agreement with the measured band gap by absorption spectrum even after considering the spin orbit coupling and other interactions like van der Walls interaction. Zhou et al. [ 36 ] studied the band structure of both cubic and tetragonal MAPbI 3 and the results were shown in Figure 4 .

( a – c ) showed the band structure of cubic MAPbI 3 optimized with lead relaxed, corresponding to 001 − , 110 − and 111 − MAPbI 3 , respectively. The relative results of tetragonal phase results are shown in ( d – f ) (Reprinted with permission) [ 36 ].

Also, the unusual DOS (density of state) position of Pb 2+ and I - showed the p-p optical transition, which was similar to the charge transition of an ionic material [ 37 ]. On the valence band maximum (VBM), due to the s-p antibonding coupling, the valence band top tends to dispersion, which leaded to a smaller effective mass (m o ). According to other calculations [ 38 , 39 , 40 ], it is believed that MAPbI 3 had an effective mass with the same magnitude of widely-used Si and GaAs. Thus, a high carrier mobility could be expected. Although further investigation did not match this estimation with the same magnitude [ 41 ], the evidence of low radiative recombination coefficient of MAPbI 3 indicated the carrier mobility is high enough to overcome the radiative recombination [ 42 ]. Besides, long carrier lifetime and suitable diffusion length of MAPbI 3 were estimated [ 43 ]. Compared with the long diffusion length of Si and GaAs (10 1 –10 2 µm) [ 44 , 45 ], a shorter diffusion length (<10 µm) of polycrystalline thin film perovskite were interpreted as due to the grain boundary effects [ 46 , 47 ].

Moreover, by comparing the DOS and the absorption spectra of MAPbI 3 and GaAs shown in Figure 5 [ 48 ], it could be concluded that the p-p transition is stronger than typical p-s transition in GaAs. The clear difference of DOS close to the conduction band minimum (CBM) led to the difference in joint density of states (JDOS) and therefore, generated the higher light absorption shown in Figure 5 . Thus, the efficient charge generation and transition lead to a high photo-current and voltage with proper device structure.

( a ) The optical absorption, ( b ) Density of state (DOS) and ( c ) Joint density of states (JDOS) of MAPbI 3 , CsSnI 3 and GaAs. ( d ) Calculated maximum efficiencies of MAPbI 3 , copper indium sulfide (CIS), CZTS and GaAs as a function of film thickness (Reprinted with permission) [ 48 ].

2.3. Device Structure

The first reported perovskite device is designed based on the structure of DSSCs, where liquid electrolyte capped both mesoporous TiO 2 particles and perovskite material as the new “dye” molecules. Their work demonstrated the perovskite was not a stable “dye” due to its quick dissolving in the liquid hole-transport layer. The 3.1% and 3.8% device efficiency (depends on different halogen anions) could only last few minutes [ 1 ]. A later research used similar structure but thinner TiO 2 layer (from 8–12 µm to 3 µm) and the efficiency increased to 6.5%. The perovskite was also proved a better light absorption than the dye molecules (N719); however, the corrosion appeared in liquid electrolyte and destroyed the device after 10 min [ 12 ]. To avoid this degradation, a solid-state hole-transport material was applied and the device performance was significantly increased. According to Lee et al. [ 13 ], this improvement combined both features from thin-film PVs and DSSCs and many other works were accomplished on increasing the efficiency. Solar cells were fabricated similar to thin-film PV, where perovskite served solely as the light absorber without TiO 2 assistance. They finally acquired a planar PSC with a 1.8% efficiency [ 13 ]. They modified the growing condition of perovskite and boosted the efficiency to 11.4% but TiO 2 was still the charge blocking layer [ 49 ]. At present, both planar and mesoscopic structure-based cells have efficiency of 20.8% [ 50 ] and 21.6% [ 51 ], respectively. A schematic of both planar and mesoscopic structure could be found in Figure 6 [ 51 ]. The PCSs could be fabricated in both sequences rather than thin-film PV, whose device configuration was limited by the properties of absorber materials. Thus, there are four major types of PSCs: substrate/superstrate-configured mesoporous structure and substrate/superstrate-configured planar structure.

Schematic diagrams of ( a ) mesoscopic and ( b ) planar perovskite solar cells (PSCs) (Reprinted with permission) [ 52 ].

The most typical n-i-p mesoporous structure is the first demonstrated high-efficient structure for perovskite devices. Started with the TCO cathode (mostly fluorine-doped tin oxide, FTO), a thin compact blocking layer was applied to decrease shunting, a mesoporous metal oxide layer filled with highly crystalline perovskite absorber layer. A layer of HTM was applied and a metal contact layer was deposited on the top of the device.

The mesoporous structure is originated from typical DSSCs. The reason for the weak performance of DSSC-based perovskite devices, except the corrosion due to liquid electrolyte mentioned above, was the excess mesoporous TiO 2 part. The widely-spread TiO 2 nano-particles inside the perovskite layer reduced the growth of perovskite crystals and also decreased the distance between separated free carriers, giving extra change for carrier recombination between TiO 2 and HTM layer. Research results showed that the perovskite device acquired a higher efficiency with thinner mesoporous layer [ 12 ]. Therefore, in n-i-p mesoporous structure of PSCs, the mesoporous layer was normally less than 300 nm. Such structure allows perovskite to form a capping layer on top of the mesoporous part, serving as a light-sensitive intrinsic layer while reducing the carrier recombination process. Currently mesoporous structure is one of the most popular structures in the fabrication of PSCs with a power conversion efficiency (PCE) greater than 20% [ 50 ]. Other materials such as Al 2 O 3 and ZrO 2 have been also reported with great device efficiency [ 53 ].

The planar PSC is successful because it utilizes thin-film PV structure and excellent optical and electrical properties of perovskite. It is also an extreme case for mesoporous structure, where the thickness of mesoporous layer is zero and unlike the mesoporous structure, this type of structure could be fabricated without high-temperature process [ 52 ]. This structure requires a better control of the formation of perovskite absorber and suitable choice of HTM/ETM layers. Research efforts demonstrated a PCE of 21.6% for this type of PSC [ 51 ]. However, an ultra-thin mesoporous charge transport layer was always applied at the interface of perovskite and mesoporous TiO 2 in order to enhance the carrier collection [ 15 ].

3. Fabrication Approaches

3.1. perovskite layer fabrication.

Because of the structural similarities of PSCs with both DSSCs and thin-film PVs, the fabrication approaches for both kinds of solar cells, including almost all vacuum and non-vacuum methods, could have a considerable improvement in PSCs as well. But the actual research showed something different: due to relatively easier process and great efficiency output, spin-coating is the most widely used method in the fabrication of PSCs but it is not suitable for large-scale manufacturing. Many other non-vacuum-based approaches were also developed and will be mentioned below. Some of them, such as doctor blading and screen printing, had been also successfully applied for the fabrication of larger-scale perovskite films [ 54 ]. However, thermal evaporation is the only vacuum-based methods that ever been demonstrated with a good cell performance. To the best of our knowledge, sputtering was never used possibly due to the lack of appropriate sputtering target and the possible damage of high-energy species to the unstable perovskite materials. According to different preparation procedures, the fabrication approaches of PSCs could be categorized as: one-step process; two-steps process; vapor-assisted process and thermal evaporation process.

3.1.1. One-Step Method

One-step deposition was widely used in perovskite cell fabrication due to its easier operation and low cost. The perovskite film could be fabricated with pinhole-free and suitable stoichiometry with wise control of perovskite precursors. Typically, the perovskite precursor solution was prepared with organic halide (MAI/FAI, methylammonium/formamidinium iodide) and inorganic halide (e.g., PbI 2 ) dissolved in gamma-butyrolactone (GBL), dimethylformamide (DMF), dimethyl sulfoxide (DMSO) or a combination of two or all three solvents. The mixed precursors were spin-coated and annealed in a range of 100–150 °C to form phase-pure, pinhole-free and dense perovskite layer.

One-step approaches had a great starting point of a 10.9% efficiency reported by Lee et al. [ 13 ], where the as-synthesized MAI and commercially-available PbCl 2 were dissolved in DMF in a molar ratio of 3:1 in order to adjust the halide anion ratio. The perovskite layer formed after 30 s of spin coating and 100 °C post-annealing. The device also displayed a great open circuit voltage (V oc ) of more than 1 V. Since then, various solution-based methods have been developed. One group found an intermediate state MAI·PbI 2 ·DMSO, which could assist the formation of uniform and dense bi-layer perovskite absorber layer (mp-TiO 2 with nano-scale MAPbI 3 /crystal MAPbI 3 ) as shown in Figure 7 [ 55 ]. This phenomenon was followed with various solution adjustment that tried to form the desired intermediate state: Rong et al. [ 56 ] reported the formation of non-stoichiometric MA 2 Pb 3 I 8 (DMSO) 2 in a DMSO/GBL mixed solvent (3:7 v/v ) and they suggest this phase would assist with forming smooth perovskite layer. In addition, their work also discovered strong dependence of process conditions on the device performance: their PCE varied from 8.07% to 15.29% with different post-annealing temperature and time. Guo et al. [ 57 ] showed the formation of a PbI 2 –MAI–DMF complex in a temperature range of 40–80 °C. At temperatures higher than 100 °C, the prepared perovskite films displayed a better phase purity.

( a ) Device structure of the bi-layered PSC; ( b ) X-ray diffraction (XRD) pattern of the annealed perovskite on fused silica. A surface scanning electron microscopy (SEM) image of fluorine-doped tin oxide (FTO)/bl-TiO 2 /bi-layered TiO 2 -perovskite composite is inserted; ( c ) one-step perovskite film fabrication steps (Reprinted with permission) [ 55 ].

The formation of one dimensional MA 3 PbI 9 (DMSO) 2 and MA 3 PbI 9 (DMSO) phases was also found, which brought a discussion of the perovskite formation mechanism. The results indicated that the DMSO was a better solvent [ 58 ]. Moreover, a controllable MAI·PbI 2 ·(DMSO) 1.5 was examined through TGA (thermogravimetry analysis) as shown in Figure 8 [ 59 ]. The perovskite was synthesized in a DMSO/DMF mixed solvent (85:15 v/v ) and the final device showed a high short-circuit-current density (J sc ) of 21.39 mA/cm 2 , a V oc of 1.06 V, a fill factor (FF) of 0.76 and a PCE of 16.41% [ 59 ]. The current record of PSC ( Figure 9 ), was a stable efficiency of 21.2% [ 17 ]. Except their replacement with Lanthanum (La)–doped BaSnO 3 (LBSO) of the typical mesoporous TiO 2 layer to increase the stability of perovskite, their precursor solution also included 2-Methoxyethanol, DMSO and GBL with the volume ratio of 7:3:4.

Thermogravimetric analysis (TGA) of ( a ) MAI·PbI 2 ·DMF x powder and ( b – d ) MAI·PbI 2 ·(DMSO) y (y = 0.6, 1.5, 1.9) powder. The black, red and blue solid lines indicate mass loss behavior of the DMF (DMSO), MAI and PbI 2 , respectively (Reprinted with permission) [ 59 ].

Photovoltaic performance of PSCs ( A ) Cross-sectional SEM image of LBSO-based PSCs (scale bar, 500 nm). ( B ) J-V curves and (inset) stabilized power conversion efficiencies (PCEs) at a maximum power point (LBSO: 0.96 V; TiO 2 : 0.91 V) for the best LBSO- and TiO 2 -based PSC. ( C ) External quantum efficiency (EQE) spectrum and J sc integrated from the EQE spectrum of the best LBSO-based PSC. ( D ) Histograms of PCEs extracted from an I sc stabilized at the maximum power point during 100 s for the LBSO-based PSCs (Reprinted with permission) [ 17 ].

Another factor on one-step fabricated PSC is the additives applied after the precursor deposition. Liang et al. [ 60 ] first discovered a controllable perovskite crystallization rate with the application of 1,8-diiodooctane (DIO) to the precursor solution. They found that the additives reduced transformation kinetics and allow a homogeneous crystal growth. Thus, more pinhole-free perovskite crystals were produced hence the surface morphology and device performance were improved. A PCE of 11.8% was accomplished through this process. Since then, more additives were demonstrated enhancing the device efficiency, such as NH 4 Cl [ 61 ], HI [ 62 ] and CH 3 NH 3 Cl [ 63 ].

The proper adjustment of composition would also benefit the PCE of devices. Recently, a PCE of 20.26% was claimed by Nazeeruddin et al. [ 64 ]. Their achievement was accomplished not only due to the complex additive of Li-bis(trifluoromethanesulfonyl) imide, FK209 [tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)-cobalt(III) tris(bis(trifluoromethylsulfonyl) imide) and 4-tertbutylpyridine but also a different precursor preparation technique by starting with a mixture of MAI and FAI. Also, the band gap tuning of perovskite would be accomplished by either modifying the organic cations or adjusting halide anion ratios [ 65 ]. Corresponding device performance change had already been appeared in some reports with reproducible results [ 15 , 66 , 67 ].

Although spin-coating is used for the fabrication of PSC layers, successful devices processed on other non-vacuum based approaches had also been reported, including doctor-blade coating [ 68 ], spray coating [ 69 ], inkjet printing [ 70 ] and slot die coating [ 71 ]. All those approaches could be considered as alternative pathways for the fabrication of PSC. However, a general disadvantage of those methods is the poor control on perovskite surface morphology, which would highly affect the performance of PCE of PSCs.

3.1.2. Two-Step Method

The perovskite deposition by two steps requires no complete precursor preparation but separate the coating of PbX 2 (X=Cl, Br or I) and MAI/FAI layers. First, a PbX 2 seed layer would be fabricated (spin-coating, doctor blading) on a substrate. Next, the MAI/FAI incorporation would be done by either dipping the PbX 2 -covered substrate into MAI/FAI solution (normally isopropanol) [ 72 ] or spin-coating of MAI/FAI [ 73 ] solution. The final perovskite films would be formed after proper baking. Although steps become more complicated, the morphology and quality of perovskite films could be better controlled via adjusting parameters in either step, which is more process-tunable than one-step fabrication.

In 1998, IBM [ 74 ] first synthesized perovskite on glass substrate. After 15 years, the Grätzel Group successfully fabricated the first perovskite cell that had 15% efficiency [ 75 ] by using this approach. Due to similar principles of one-step and two-step methods, proper solution engineering including solvent mixing and use of additives could be also applicable to two-step-fabricated PSCs: Li et al. [ 76 ] reported an improved PCE of 17.16% with mixing DMSO with DMF due to better coordination of DMSO with PbI 2 and an extra intermolecular exchange between DMSO and MAI, which assisted the decomposition of intermediate state and the formation of perovskite. Figure 10 showed a schematic process draw to display the reaction between MAI and PbI 2 at the outer solvent shell. Another work demonstrated the addition of a trace amount of H 2 O would also reduce voids and pinholes on the PbI 2 precursor layer and generated an efficiency of 18% and a remarkable fill factor of 85% [ 77 ]. The record PSC using two-step method could already achieved a PCE of 20.2% by introducing PTAA and taking advantage of intramolecular exchange with DMSO catalysis [ 15 ]. The device shown in Figure 11 had little hysteresis effect and this new method assisted grain growth.

A schematic draw of the DMSO-assisted two-step MAPbI 3 synthesis and film growth (Reprinted with permission) [ 76 ].

SEM observations and J-V and EQE measurements. ( A ) Cross-sectional FESEM image of the device; ( B ) The comparison of FESEM surface images of FAPbI3-based layer formed on mp-TiO 2 by IEP and conventional method. ( C ) ( a ) J-V curves of best device measured with a 40-ms scanning delay in reverse (from 1.2 V to 0 V) and forward (from 0 V to 1.2 V) modes under AM 1.5G illumination and ( b ) EQE spectra for best device and integrated JSC (Reprinted with permission) [ 15 ].

Since two-step fabrication relies on a second MAI immersion/layer fabrication, the perovskite formation may not be as complete as in one single precursor solution. Someone considered that due to low temperature and short-time mixing (less than 1 min) during spin-coating, the diffusion of MAI into PbI 2 lattice is not fast enough to form the perovskite crystals [ 78 ], or maybe only enough to form perovskite on the PbI 2 surface, in which the perovskite layer blocked further diffusion of MAI to the inner part of PbI 2 [ 79 ]. In general, the non-stoichiometry would have negative effect on the device efficiency. Another disadvantage comes from the partial dissolving of perovskite during the second step. Relevant researches have already proven that such mass migration speed in step two, as shown in Figure 12 , could be very fast, depending on the properties of solvent [ 80 ]. The most direct result could be a rough surface with pinholes and voids, which could be easily formed during two-step process. This drawback could be resolved with addition of suitable chemical or use of low-concentration of MAI/FAI solution in order to improve the perovskite crystal growth condition.

Cross-sectional FESEM and images of dissolved PCSs obtained after 30 s immersion of spiro-MeOTAD/MALI/mp-TiO 2 /TCG in ( a ) non-polar; ( b ) polar protic and ( c ) polar aprotic solvents. Diethyl ether, water and DMF, respectively, were used as the representative solvents. Scale bars, 700 nm (Reprinted with permission) [ 80 ].

3.1.3. Vapor-Assisted Solution Method

Vapor-assisted solution method could be considered as a modified two-step method. During the second step, vaporized MAI/FAI reacted with PbI 2 to form perovskite phase after further film annealing. Ideally, this approach could guarantee a better contact between both precursors than in the solution. Furthermore, this method successfully avoids the partial perovskite dissolving especially during the dipping process. Therefore, the perovskite film stoichiometry could be also improved. Chen et al. [ 81 ] developed this approach by using as-synthesized MAI vapor (very small particles) applied on spin-coated PbI 2 precursor under a 150 °C baking. The whole perovskite fabrication was done in glove box. They reported µm-scale grain formation, full phase transition and film coverage. Their best planar device revealed a PCE of 12.1%. The only disadvantage was the key process lasted for hours, rather than minutes for spin-coating. This approach was later modified with an as-grown perovskite layer, where a two-step as-deposited MAPbCl 3−x I x on ITO/PEDOT:PSS substrate was then transferred into a closed petri dish container and heated together with MACl powder starting from 100 °C, which resulted a great PCE improvement of 15.1% with a 60-day stability [ 82 ]. Figure 13 offered a detail description about this process, where both upper and lower dish are linked with a Teflon ring to against the possible leakage. But other details such as the heat-treatment duration was not mentioned. Recently, a device with a planar structure of FTO/compact-TiO 2 /C 60 /(FA) x (MA) 1−x PbI 3 /spiro-OMeTAD/Au was fabricated by heating FTO/c-TiO 2 /C 60 /PbI 2 with uniformly-spread FAI and MAI powders in low vacuum under 170 °C for 30 min. By adjusting the powder ratio, they finally achieved a PCE of 16.48% [ 83 ]. The vapor-assisted PSC, as an advanced two-step approach, is getting close to the champion PSC devices and could be expected great breakthrough in the future, if the heat treatment time could be reduced in the same level of one-step/two-step methods.

( a ) Schematic drawing of vapor-assisted perovskite deposition process; ( b ) actual lab set-up mentioned by Khadka et al. [ 82 ] (Reprinted with permission).

3.1.4. Thermal Vapor Deposition

Thermal vapor deposition is among the most widely used methods in device-level thin film fabrication. The ease of source control (element/compound) and parameters such as deposition time and current/voltage guarantees film composition and surface uniformity. The first reported thermal-vapor-deposited perovskite was reported by Mitzi et al. [ 84 ]. Liu et al. [ 85 ] applied a co-evaporation with sources of MAI and PbCl 2 /PbI 2 on rotated substrate and they fabricated a planar structure PSC of 15.4%. Figure 14 showed the evaporation system and film XRD spectra, where vacuum-deposited sample could also maintain same crystal structure after post-annealing. A further research unveiled that during co-evaporation, the reaction between PbCl 2 and MAI tended to form PbI 2 at first, then transferred into MAPbI 3 under continuous MAI incorporation. Finally, the residual MAI would be found in a form of MAPbI 3 ·xMAI [ 86 ]. This compositional change could be easily found out due to clear color change as shown in Figure 15 . Dual-source thermal evaporation was also applied for fabricating other kinds of PSCs: Ma et al. [ 87 ] reported a CsPbIBr 2 cell by using CsI and PbBr 2 as evaporation sources. They acquired a PCE of 3.7% under forward scan and an efficiency of 4.7% under reverse scan. MAPbI 3 compound source was also applied for vacuum thermal evaporation: Liang et al. [ 88 ] reported a successful MAPbI 3 film fabrication by using their synthesized MAPbI 3 crystals as the powder source. After a vacuum deposition under 500 W for 15 min with a 100 °C post-annealing for 20 min, they fabricated a smooth, densely-packed MAPbI 3 thin film with great visible light absorption. However, no further device fabrication and characterization information was found. Also, those vacuum-evaporated devices rarely showed a PCE comparable with solution-based PSCs.

( a ) Schematic draw of dual-source thermal evaporation and the organic source was methylammonium iodide (MAI) and PbCl 2 ; ( b ) XRD spectra of a solution-processed perovskite film (blue) and vapor-deposited perovskite film (red) (Reprinted with permission) [ 85 ].

( a ) XRD spectra, ( b ) UV-vis absorbance and ( c – g ) photographs of the evaporated films at different MAI/PbI 2 ratio (Reprinted with permission) [ 86 ].

Although few reports agreed the thermal vapor deposition could be an effective method on PSC fabrication due to both low efficiency and extra vacuum preparation, which could increase the total cost. Thermal evaporation has its own advantages on forming fully-covered, pinhole-free films and a combination of thermal evaporation with conventional solution-based method may be expected with a better surface coverage, which equals to better device performance. Tao et al. [ 89 ] reported a PCE of 17.6% with the perovskite layer prepared by first evaporating a PbI 2 layer and then spin-coating a MAI layer followed by annealing at 100 °C, 80 min, indicating future possibility for a hybrid fabrication approach. Besides, co-evaporated MAPbI 3 was also sandwiched between organic charge transport layers. With a slow deposition rate of 0.5 Å/s, Malinkiewicz et al. [ 90 ] claimed a PCE of 12%. This approach was later modified by Calio et al. [ 91 ] through applying different charge transport layers above and below perovskite layer. Their best device achieved an efficiency close to 15%.

Other similar vacuum-based methods, such as layer-by-layer evaporation [ 92 ] and chemical vapor deposition [ 93 ] was also reported. Carefully monitoring evaporation profile is necessary to enhance film quality because of the low thermal stability of perovskite materials like MAPbI 3 . Due to higher complexity of those vacuum-based approach than most widely-used spin-coating, thermal vapor deposition is still not the mainstream for PSC fabrication.

3.2. Fabrication of Other Components in PSC

The n -type electron transport layer is directly relevant to the performance of PSC. The generated electron-hole pairs inside perovskite would experience charge separation at ETM/perovskite interface and form the output current. Proper ETM could also affect the growth and coverage of perovskite. A suitable ETM should have a proper band alignment: a low-enough lowest unoccupied molecular orbit (LUMO) or CBM between contact and perovskite to allow electron separation and transport, also an adequate band gap to block holes. The ETM should be also stable enough to protect the internal perovskite with HTM layer to avoid external damages especially from moisture.

Metal oxides, such as TiO 2 , are the most common used ETMs. Originated from the successful service in DSSC, TiO 2 was the first ETM in PSC fabrication and is still used in many high-efficiency PSCs. Studies had shown TiO 2 a perfect band structure and great electron mobility for both crystal and mesoporous structures [ 94 ]. According to different device structures, the TiO 2 layer could be sorted as two-layer compact/mesoporous (mp) and one-layer planar structure. Mostly, the bi-layer TiO 2 was fabricated by a sequential deposition where the dense compact layer was done by spray pyrolysis and the mp-TiO 2 was fabricated by spin coating, which was also applied in one-layer TiO 2 fabrication. But many alternative fabrication methods have also been demonstrated successful and corresponding results are summarized in Table 1 . On considering the cost-effectiveness, most fabrication methods are non-vacuum based with a following high temperature annealing. However, TiO 2 was also found to be responsible for UV instability of perovskite and a UV filter was suggested for further TiO 2 -based PSCs’ application [ 95 ]. Detail mechanism would be discussed later in this review. Besides, the PSCs with planar TiO 2 were also mostly reported with a device hysteresis. Thus, more inorganic ETMs with similar band structure (ZnO, SnO 2 , BaSnO 3 , etc.) [ 11 , 17 , 96 ] are reported with great PCEs. N -type doping was also tried for band engineering in order to enhance the voltage potential and charge injection speed, which are directly relevant with V oc and J sc . The current published record 21.2% PSC was fabricated with a Li-doped BaSnO 3 (LBSO) [ 17 ]. Post-annealing treatments were also applied to improve surface morphology of ETM. Cojocaru et al. [ 97 ] reported an enhanced PCE with better TiO 2 morphology through TiCl 4 and UV treatment. Moreover, different ETM configurations, such as nano-rods [ 98 ], were also developed to enhance carrier transportation.

A summary of PSCs’ performance with different ETM/HTM pairs, fabrication methods were also labelled. All materials without labelling were spin-coated.

Organic ETMs, as a replacement of metal oxides, started from C 60 and PCBM [ 113 , 116 ]. However, the low PCE leaded to further modifications such as n-type doping, solution engineering and interface control. Also, pairs of organic-inorganic ETL had been reported in inverted mesoporous devices and recently, some self-synthesized n-type small organic molecules also appeared in high-efficiency PSCs. At present, organic ETMs only appeared in superstrate-configured devices. Although organic ETMs had been proved to be a suitable hole blocking layer, the possible low compact between those organic ETMs and ITO/FTO substrates could be the key to this issue.

The application of graphene/graphene oxide inside the ETM also started attracting research attention. Graphene has been demonstrated with great carrier mobility and transparency, which is expected to be an enhancement inside the typical ETM layers. Relevant research progress has achieved a device efficiency of 14.5% where small portion of r-GO was mixed with mesoporous TiO 2 ETM. The application of graphene-related component in either ETM or HTM, although still has distance with top-record PSCs, still deserved more attention and efforts [ 118 ].

The first demonstrated HTM was spiro-MeOTAD as a replacement of corrosive liquid electrolyte. This compound could be found in many top-level PSCs. Meanwhile, other HTMs with suitable electronic structure such as PEDOT: PSS [ 116 ], PTAA [ 102 ], NiO [ 114 ], CuSCN [ 100 ] were also applied in the fabrication of PSC. Among them, PTAA is becoming an excellent replacement of spiro-OMeTAD and it is already appeared in the current record device. These reported HTMs could be summarized into three categories: organic polymers, inorganic compounds and small molecules. While typical HTM fabrication approaches are spin-coating, few reports also mentioned other methods including spray [ 119 ] and sputtering [ 115 ] for inorganic HTMs. Corresponding information was listed in Table 1 .

Proper doping is also a common enhancement for HTMs as in ETMs. For spiro-MeOTAD, the widely accepted dopants are the bis(tri-uoromethylsulfonyl) amine lithium salt (Li-TFSI), 4-tertbutylpyridine (TBP) and a series of organic cobalt salt such as tris(2-(1H-pyrazol-1-yl) pyridine) cobalt(III) tris(hexafluorophosphate) (FK102) and tris(2-(1H-pyrazol-1-yl)-4-tert -butylpyridine)-cobalt(III)-tris(bis(tri-fluoromethylsulfonyl) imide) (FK209) [ 120 , 121 ]. However, Li-TFSI would have a side effect for perovskite degradation [ 122 ]. Other methods such as modifying the molecular structure could be found in other literature [ 123 ].

At present, PSCs without ETM or HTM part had also been developed to avoid the high cost of ETM and HTM synthesis and fabrication. In those designs, the ETM or HTM was replaced by contacts with modified band structure in order to extract carriers. The perovskite layer could also be blended to possibly enhance the charge separation. Delgado et al. [ 124 ] showed an ETM-free perovskite/fullerene cell with a PCE of 14.3%. Duan et al. [ 125 ] also applied an ultra-thin graphite as the hole-extractor and acquired a PCE of 14.07%. However, those designs still had a relative weak performance due to lack of efficient carrier extractor. However, they could be helpful to understand the solar cell physics inside the perovskite layer.

4. Challenges

4.1. cell stability.

Since PSCs has already achieved comparable performance against the Si-based PVs, the biggest challenge for PSC is to demonstrate device stability to be a suitable alternative PV technology of silicon. Reports about some long-term device characterization have been published during recent years [ 126 , 127 , 128 , 129 ] but most of those tests are processed in a relatively mild condition. Even under those conditions, the performance of PSCs was still not optimistic. Meanwhile, various works discovered the instability of perovskite under moisture [ 130 ], oxygen [ 131 ] and UV [ 132 ]. The perovskite materials and fabrication process also contain traps for perovskite degradation [ 133 ]. Thus, more understanding and improvement are required to upscaling of the performance of PSCs.

4.1.1. Stability of Perovskite Materials

Crystal structure stability.

Crystal structure and phase transition would largely affect material properties. For the ABX 3 perovskite materials, its stability could be described with the well-known tolerance factor from Goldschmidt (1927):

where, r A , r B and r 0 are ionic radius for organic cation A, inorganic cation B and halide anion X, respectively. The ideal cubic perovskite structure would have a t = 1 and the cubic structure can only be acquired when 0.89 < t < 1 [ 6 ]. Lower tolerance factor means lower symmetry and the perovskite would shift to orthorhombic or tetragonal structure, which would give a negative effect on the opto-electronic properties of perovskite [ 134 ]. Most stable perovskite materials have to satisfy a 0.8 < t < 1 [ 135 ] and the most stable perovskite material is still MAPbI 3 , which has a tolerance factor slightly higher than 0.9 [ 136 ].

Besides the ion radius, the temperature and pressure could also affect perovskite phase transition: MAPbI 3 was known to have a phase transition from cubic to tetragonal around 55 °C, which is within the operation temperature range of solar cells (−40 °C to 85 °C). Other researches about perovskite phase transition found that as temperature increased, the perovskite phase would transit from lower symmetry to higher symmetry (orthorhombic-tetragonal-cubic) [ 31 , 32 ]. Weber et al. also discovered MAPbBr 3 and MAPbCl 3 could maintain better symmetry than MAPbI 3 from −40 °C to 85 °C and further details are shown in Table 2 [ 137 ]. However, PSCs solely with those two kinds of light absorbers have not shown significant high efficiency and mixed halide PSCs, even though claimed to have a better performance than MAPbI 3 , was still not comparable with the record devices. Another early study showed FAPbI 3 had a better thermal stability. The corresponding phase transition temperature of FAPbI 3 lied at 150 °C [ 138 ]. However, FAPbI 3 is also reported highly unstable under moisture, which is also required during stability testing. Their work also reported a better thermal stability of an alternative MASnI 3 and could maintain cubic phase under room temperature [ 139 ]. The pressure could also trigger perovskite phase transition, as another study claimed—as pressure increased as from 0 to 0.3 to 2.7 GPa, their MAPbI 3 experienced phase transition of tetragonal-cubic-orthorhombic. After 4.7 GPa, the amorphous phase started appearing and lead a phase separation [ 140 ].

Phase transition points of MAPbX 3 (X=CI, Br, I) [ 137 ].

Figure 16 showed a clear XRD pattern change along with pressure loading and unloading. A more detailed discussion focused on lower pressure range (<200 MPa) showed pressure has much less impact on MAPbX 3 (X=Cl, Br, I) phase transition [ 141 ]. Therefore, perovskite is expected to be suitable for normal applications without high pressure.

XRD patterns of MAPbI 3 during ( a ) compression and ( b ) decompression. The highlighted by broken-lined boxes are peaks for cubic phase; ( c , d ) are 2D XRD patterns at specific pressures (Reprinted with permission) [ 140 ].

In addition, the temperature would also lead to perovskite decomposition. Pisoni et al. [ 142 ] reported the low thermal conductivity of MAPbI 3 and equivalent results were calculated by other groups [ 143 , 144 ]. Moreover, since the decomposition of MAPbX 3 (X=Cl, Br, I) was observed starting from 130 °C as new peaks shown in XRD patterns (see Figure 17 ) [ 145 ], those kinds of perovskite would most likely suffer an efficiency lost during the long-term device operation due to accumulated light-generated heat inside the light absorber.

XRD patterns of MAPbX 3 after each isotherm in the non-ambient reactor chamber (Reprinted with permission) [ 145 ].

Environmental Stability

During device operation, the moisture, oxygen from air and high-energy photon from UV would decompose the perovskite layer within adequate time duration. A possible reaction mechanism is shown below [ 146 ]. As described in Equations (2)–(5), with adequate moisture injected into perovskite, the MAI would be dissolved in moisture and left inorganic halide. The organic-halide would continue the hydrolysis and release HI. Since HI could be continually consumed with the assistance from oxygen and photon, the decomposition is irreversible with the existence of moisture. In addition, the perovskite itself and organic cation also tend to decompose under continuous sunlight exposure (Equations (6)–(9)). However, according to those decomposition mechanism, the oxygen itself could hardly trigger the perovskite decomposition and studies also suggested perovskite samples could be stored in dry and dark environment [ 13 ]. Aging test of PSCs under white light without UV source also demonstrated acceptable device stability [ 75 ].

Studies have shown the relations between air humidity and perovskite decomposition: Kelly et al. [ 147 ] showed a positive correlation between humidity and PCE: as relative humidity (RH) increased from 50% to 80% in N 2 , the absorption at 410 nm drastically decreased. Their work also proved proper HTM layer could reduce the moisture invasion rate by maintaining a good coverage. However, such effect could only last few hours and later, the absorption would continue fast decreasing. Moreover, Han et al. [ 148 ] showed the perovskite degradation could be more severe with the corporation of humidity and temperature: as shown in Figure 17 , the device PCE would be almost zeroed under AM 1.5G within 20 h under high temperature (55 °C in air and 85 °C for internal device temperature) and RH (80%).

Due to such side effects from oxygen, UV and mostly moisture, the preparation of perovskite was mostly processed inside the glove box. However, some studies showed that proper relative humidity. According to Gangishetty et al. [ 149 ], higher RH could be helpful on enlarging perovskite crystal sizes and better connections among crystals during two-step fabrication. A later study displayed a possible best combination of ambient humidity and annealing time during perovskite fabrication: Their best device was fabricated under 20% RH and 45 min post-annealing [ 150 ]. However, although the humidity-incorporated synthesis process had successfully produced a planar PSC with 19.3% PCE [ 151 ]. The moisture offered an extra solubility for organic precursors but also leaded a PCE decrease to less than 5% after few days under ambient atmosphere.

The degradation of perovskites by UV light could be originated at the TiO 2 layer. With assistance from UV light, TiO 2 could interact with I − and form I 2 as in typical DSSCs. Therefore, it could destroy the perovskite crystal structure and strengthen the ionic reaction process of organic cations [ 152 ]. Moreover, a further study on UV degradation mechanism found with UV-AM 1.5G illumination cycle could partially recover the device performance. It is the hole traps accumulated on the perovskite/TiO 2 interface and flowed into other charge transport layer due to insufficient charge neutralization [ 153 ]. Those traps were also reasons of lower J sc during following AM 1.5G illumination. Figure 18 and Figure 19 displayed their UV-1 sun cycling illumination test results and possible mechanism. Thus, several methods had been tried to separate perovskite and TiO 2 . Besides the Sb 2 S 3 inserting reported by Ito et al. [ 152 ]. Applying a UV-filter on the TCO substrate before TiO 2 deposition and several reports also showed the stability improvement. However, compared with other two approaches, the UV-filter might trigger an unavoidable fabrication cost increasing due to extra materials cost. Since PSCs have to pass the more important aging tests under high temperature and high RH in order to pass the stability standards of thin film PV, the UV problem is currently not owing high priority.

( A ) Stability testing of PSCs sealed by method A under three different environmental conditions; ( B ) comparison of the stability of devices sealed by method A and B and tested under environmental condition (iii). All PCEs are already normalized (Reprinted with permission) [ 148 ].

UV degradation/recovery cycle of ( a ) PCE; ( b ) FF; ( c ) R s and ( d ) J sc for device subjected to a range of UV exposure and 1-sun illumination. Purple regions represent UV exposure and yellow regions represent 1-sun light illumination periods (Reprinted with permission) [ 153 ].

Recently, the application of graphene and its relevant oxides in the PSCs has attracted attentions. Experiments already demonstrated that graphene, due to its outstanding carrier mobility and high transparency, could be able to enhance the device performance of PSCs [ 118 ]. The contribution of graphene to PSCs, however, could also contain the device stability and the extension of the lifetime of perovskite. Graphene/graphene-oxides could replace the HTM/ETM layer or inserted between perovskite and other HTM/ETM or between HTM/ETM and metal contacts. Due to the wetting transparency of 2D graphene [ 154 ], the decomposition of perovskite could be released. The small lattice size of 2D graphene could also resist the inter-diffusion of metal ions from either perovskite or metal contact [ 155 ]. Agresti et al. investigated the effect of graphene and graphene oxide [ 156 ] and their results indicated that the graphene oxide would join the perovskite decomposition reactions at high intensities. The graphene added inside the mesoporous TiO 2 , however, could improve the device stability under both dark and continuous illumination environment due to faster carrier transportation. They also suggested that PSCs with graphene/graphene oxide would suffer an efficiency and J sc loss under prolonged thermal stress. Doped graphene could be also suitable for increasing the stability of PSCs. Bi et al. [ 157 ] reported a stable PSCs with its PCBM layer mixed with n-type graphene. The device efficiency was stable for 500 h at 85 °C. Thus, it can be expected that, due to excellent electrical properties of graphene, new contacts based on graphene rather than metals could be considered. Therefore, both device stability and efficiency might be improved.

Graphene is not the only 2D material that helps improving the stability of PSCs. Other materials that can be prepared by the mechanical exfoliation method has been also tried in PSCs to increase the device stability and efficiency. One investigation applied a combined structure of graphene/MoS 2 at the interface of PCBM/Ag. The addition of this mixed interlayer increased the parameters of PSC as well as the stability of J sc , V oc and PCE for the initial several hours [ 158 ]. Chen et al. even fabricated the typical carrier transport material, TiO 2 , into a 2D structure (2D atomic sheets of titania) [ 159 ]. Their results showed that the PCE of their PSCs could be comparable with the standard PSCs by optimizing the number of 2D-TiO 2 layers. This new structure of TiO 2 , according to their investigation, could also reduce the UV absorption, which is one of the key to the decomposition of perovskite.

4.1.2. Stability of Other Components

Low stability of other components (HTM, electrodes and etc.), like lower-quality perovskite, would also largely minimized the device performance of PSC. Since most developed HTM candidates are organic compounds, such as the most typical spiro-OMeTAD based HTM series, the temperature control becomes a vital factor. A detailed report form Wu et al. [ 160 ] showed that, although low temperature annealing could enhance the formation and crystallization of spiro-OMeTAD, the transfer of additive Li-TFSI to the TiO 2 surface and the evaporation of 4-tert-butylpyridine (TBP), also another common additive, would both compress the device voltage potential by changing fermi level of TiO 2 . Therefore, the device acquired lower V oc . In addition, spiro-OMeTAD, as discussed by Kelly et al. [ 147 ], may suffer from cracking during the fabrication process. Thus, the internal perovskite would be easily exposed and device degradation may be accelerated. The mechanism of UV degradation and recovery of PSCs is given in Figure 20 [ 153 ].

Schematic draw of the proposed mechanisms for UV degradation and recovery of PSCs (Reprinted with permission) [ 153 ].

As a consequence, other stable HTM layers including o,p-dimethoxyphenyl-based biphenyl (HL-1) and carbazole (HL-2) [ 161 ], single-walled carbon nanotube (SWCNT) enhancement [ 162 ], tetrathiafulvalene derivative (TTF-1) [ 96 ], poly(3-hexylthiophene) (P3HT) [ 163 ] had been developed and literatures showed great progress on device stability. Recently, a French group reported a stable PSC with CuSCN inserted between Spiro-OMeTAD and gold electrode. The device efficiency only lost 5% after 1000 h running under 60 °C in nitrogen atmosphere. Another test under more realistic environment (85 °C, 1000 h, air, dark) showed a 15% efficiency loss. The thin layer of CuSCN was believed to block the metal diffusion, which is the reason for device degradation [ 164 ]. Although more realistic testing of durability (e.g., 85 °C, 1000 h and high humidity) is still necessary before the industrial application of perovskite, this result showed a noteworthy progress of the stability of PSCs. In addition, a hydrophobic HTM could be another plus due to the irreversible perovskite corrosion from the moisture.

4.2. J-V Hysteresis

Another barrier for PSC’s further development is the J-V hysteresis, which was observed when applying different voltage sweeping rates and directions [ 165 ]. The best efficiency results are usually acquired at V oc rather than J sc , P max or under reverse bias condition. Two major categories of hysteresis have been found: normal and invert hysteresis. The normal hysteresis leads to a higher efficiency during reversed bias scan (voltage decreases) but lower efficiency during the opposite scan. The inverted hysteresis goes exactly the opposite way. These two kinds of hysteresis could exist together or appear separately depending on the applied pre-poling bias [ 166 ]. Different voltage sweeping rate would also change efficiency results and these changes of device parameters are mostly random. Such phenomenon is also not relevant with device structure. Therefore, rather than other kind of PV technology, standardizing PSC measurement becomes a challenging task and even those reported progress, including both PCE and device stability breakthrough, might become questionable. Although recent reports claimed that their devices displayed a low or little J-V hysteresis during PCE measurements [ 167 , 168 ] although this J-V hysteresis is still noticeable during most of the PSC characterizations.

The mechanism of hysteresis is still unknown but several hypotheses had been established. Ferroelectric polarization [ 169 ], ion migration [ 170 ], charge trapping [ 171 ] and capacitive effects [ 172 ]. Several reviews already offered intensive discussion about those hypothesis [ 173 , 174 ]. Recent research starts to support that both ion migration and charge trapping could the reasons for the J-V hysteresis and relevant detail discussion can be found elsewhere [ 175 ]. Since J-V hysteresis had such negative effect, improved PCE measurements technique was suggested [ 176 , 177 ].

5. Toxicity

The toxicity of perovskite comes from the widely-used lead inside MAPbI 3 and environmental concerns would be appeared especially on the issue of large-scale fabrication waste treatment. Although calculations already showed the possible contamination from perovskite would be relatively insignificant compared with other lead pollutions [ 178 ] and the production of PSC could be able to use waste lead from daily waste [ 179 ], studies on lead-free PSCs cannot be neglected. Tin was the first well-studied replacement metal cation since Sn and Pb are both carbon periodic elements, thus, MASnI 3 is believed to be able to maintain the same crystal structure as MAPbI 3 . The fact, as shown by Noel et al. [ 180 ], is that Sn 2+ could be easily oxidized to Sn 4+ , leading a weak device performance. Other trials of introducing organic/inorganic additives to retard tin oxidation had also been reported [ 181 , 182 ] but their device PCE was still not promising.

Due to this chemical instability of pure tin-based perovskite materials, the hybrid Sn-Pb metal cations in perovskite could be more realistic and the more advanced PCE also demonstrated this idea: Zhu et al. [ 183 ] reported a remarkable PCE of 15.2% with a light absorber of MASn 0.25 Pb 0.75 I 3 and a suitable control of DMSO additive and a PCBM:C 60 electron transport layer. Another study also indicated MASn 1-x Pb x I 3 could have an electronic structure closer to MASnI 3 than MAPbI 3 even with few Sn replacement [ 184 ]. All those results indicated that from the view of reducing process toxicity, tin is not a perfect candidate to totally replace lead due to its chemical instability.

Another intensive-studied candidate is the neighbor of lead: bismuth. Bi could form a stable (MA) 3 Bi 3 I 9 (MABI) perovskite material. Its crystal structure was shown in Figure 21 [ 185 ]. Similar as Sn-doped MAPbI 3 , MABI also showed better stability under ambient air for 1000 h [ 186 ]. The first reported MABI-based perovskite only reached a low efficiency of 0.12% with a relatively low V oc of 0.68 V and an extremely low J sc of 0.52 mA/cm 2 [ 187 ]. At present, the Bi-based perovskite could only able to reach an efficiency of 0.42% due to low J sc [ 188 ]. A recent study investigated the absorption and recombination dynamics of excitations inside the MABI crystals: the I(5p)-Bi(6p), I(6p) excitation [ 189 ] is localized in (BI 3 ) - units, resulting little free carriers released at the MABI/TiO 2 interface [ 190 ]. Therefore, they suggested considering bulk-heterojunction structure with nano-scale MABI crystals in order to possibly enhance the low J sc . Some other reports focused on Bi-based halide double perovskites such as Cs 2 AgBiX 6 (X=Br, Cl) [ 191 ] and (MA) 2 KBiCl 6 [ 192 ]. But no effective devices had been reported and deep understanding of optoelectronic properties are still suggested. Thus, Bi-based PSC is still not promising at present, even compared with Sn.

Crystal structure of (CH 3 NH 3 ) 3 Bi 2 I 9 (MBI): ( a ) local structure of the (Bi 2 I 9 ) 3− anion; ( b ) cation and anion positions in the unit cell (Reprinted with permission) [ 185 ].

Other types of lead-free perovskites such as CsGeI 3 [ 193 ], MAGeX 3 (X: Cl, Br, I) [ 194 ], MASrI 3 [ 195 ], MACaI 3 [ 196 ] had also been reported but those materials are either not suitable for visible light absorption due to large band gap [ 195 , 196 ], or only showed low efficiency of less than 1%. Most of the material characterizations are still in lack. Thus, non-toxic perovskite development and corresponding fabrication of PSCs still has a long way before replacing the position of lead.

6. Discussion and Future Research Efforts

The above research efforts indicated that the PSCs will have a greater potential for commercialization if the stability of cells can be improved. The high efficiency and low-cost manufacturability to harvest terawatt levels by solar energy are very attractive with this next generation solar cell technology. The cell degradability is identified as due to primarily the exposure of perovskite layer to water vapor and heating effects, which change the active phase of lead-based perovskites. There are numerous efforts to improve the stability of these solar cells by many groups worldwide. Development of perovskite layers using other metals has been tried with poor success to address the toxic issue and stabilizing the perovskite structures. Also, cell passivation has been investigated to stabilizing the cells by prevention of perovskite layer to the ambient. Another approach is to reduce the heating effect by utilizing IR absorbance layers or external components. Also, integration of few of these technologies may improve the stability of this solar cell technology from current stability records of around six months.

Also, it is important to address the harmfulness of lead-based compounds in PSCs. While development of other metal-based perovskite is also interested in the viewpoint of environmental protection, their effectiveness does not reach the efficiency of lead-based compounds. Furthermore, better recycling methodologies are important to prevent the transfer of lead compounds into the environments. Similar environmental issues have been addressed for CdTe solar cells and thus, it is possible to utilize already existing infrastructure for recycling and environmental protection issues. The environmental protection authority regulates the lead content of drinking water below 0.015 g/L. Authors believe that these areas can be further improved by research efforts.

It is also important to address that, due to the transparent nature of some of the HTM/ETM and the electrodes, the PSCs could be fabricated with a structure that could absorb sunlight from both directions. An investigation in 2016 already found out that, with the help of transparent solution-processed silver nanowires (AgNWs), an efficiency of more than 11% and 7.53% could be observed with front and back illumination, respectively [ 197 ]. Together with passivation of PCSs using transparent insulators such as polymers, the cell performance as well as durability may be enhanced. Thus, investigation on the bi-facial PSCs could also be another research direction for the improvements of PSCs.

7. Conclusions

The PSC has experienced a significant improvement from 3.8% to 22.1% since 2012 and the perovskite-based tandem cell has already achieved 26.7%, creating a new record in history of PV technology. Numerous research efforts on both PSC efficiency improvements and deeper understanding about perovskite materials’ outstanding electrical and optical properties, such as largely-tunable band gaps for light absorption, high absorption coefficients, large carrier diffusion lengths, great carrier mobility, have been established during the past few years. The current PSCs already combined structural advantages of both DSSCs and thin film PV since the discovery of perovskite and become a new challenger for Si-based PV dominant market share, not only due to record 22.1% efficiency for small area but also comparable larger-area device efficiency. The vast discovery and successful application of organic/inorganic charge transport materials and blocking layers also assisted the formation and crystallization of perovskites and helped charge transfers at the interfaces. Many kinds of PSC fabrication approaches have also been developed and most of them could fall into four major categories: one-step; two-step; vapor-assisted solution method; and thermal vapor deposition with a top PCE of 22.1% (current record), 20.26%, 16.48% and 17.6%, respectively. Also, numerous hybrid perovskite fabrication process was also invented, which is uncommon for other types of PVs. According to current progress, it is reasonable that the next high-efficiency PSC may be still based on solution-based approaches (e.g., spin coating) with a mixed perovskite phase, as applied in the record 22.1% and the stable 21.2% devices.

The PSCs still have great barriers for further improvements. The biggest problem comes with the natural instability of perovskite materials, especially the most widely-used MAPbI 3 . The phase transition within the range of solar cell operation temperature brought problems on device usage. The instability with varying temperature and pressure leads extra concerns for device fabrication. The moisture, UV light and oxygen would also bring irreversible damage to the perovskite layers, which largely reduced the device stability and commercialization of PSC. The efforts such as elemental adjusting, device sealing and extra blocking layer inside the device had been tried to solve these problems but more stability tests under harsh environments are strongly suggested for PSCs to reach the required standard.

Other drawbacks such as J-V hysteresis and toxicity of lead made it difficult to further improve the performance of PSCs. While the mechanism of hysteresis was still inconclusive, the lead toxic has attracted many research efforts on considering the non-toxic replacement pf perovskite materials. Research work found out that all candidates, from the neighborhood Sn, Bi and new candidates as Cs, Ge, suffered a great loss of J sc , which directly leads to the huge loss in PCE. A more complicated replacement profile might be the solution of lead-free PSCs. Although efforts claimed low hysteresis in some PSCs, deep theoretical understanding and standardized testing protocol is suggested for PSCs.

Perovskite, compared with other PV techniques (thin film, organic, dye-sensitized), could be the best alternative solar absorber. As efforts on better perovskite layer formation and longer device durability, even the lead-based PSCs could be able to share a certain part of PV market. Such trend could influence further research and development (R&D) efforts towards higher-stable and non-toxic devices.

Acknowledgments

One of the authors, Zhengqi Shi, would like to acknowledge the financial assistance given by the University of Toledo for this study.

Author Contributions

Both authors have analyzed the literature and prepared this manuscript. This manuscript was prepared only for the educational purpose.

Conflicts of Interest

The authors declare no conflict of interest.

Maintenance work is planned for Wednesday 1st May 2024 from 9:00am to 11:00am (BST).

During this time, the performance of our website may be affected - searches may run slowly and some pages may be temporarily unavailable. If this happens, please try refreshing your web browser or try waiting two to three minutes before trying again.

We apologise for any inconvenience this might cause and thank you for your patience.

Recent progress in the study of integrated solar cell-energy storage systems

* Corresponding authors

a Institute of Advanced Materials and Flexible Electronics (IAMFE), School of Chemistry and Materials Science, Nanjing University of Information Science & Technology, Nanjing, China E-mail: [email protected] , [email protected]

b Reading Academy, Nanjing University of Information Science & Technology, Nanjing, China

c State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing, China

As fossil fuels continue to deplete, the development of sustainable and green energy sources has become crucial for human societal advancement. Among the various renewable energies, solar energy stands out as a promising substitute for conventional fossil fuels, offering widespread availability and a pollution-free solution. Solar cells, as devices that convert solar energy, are garnering significant focus. However, the intermittent nature of solar energy results in a high dependence on weather conditions of solar cells. Integrated solar cell-energy storage systems that integrate solar cells and energy storage devices may solve this problem by storing the generated electricity and managing the energy output. This review delves into the latest developments in integrated solar cell-energy storage systems, marrying various solar cells with either supercapacitors or batteries. It highlights their construction, material composition, and performance. Additionally, it discusses prevailing challenges and future possibilities, aiming to spark continued advancement and innovation in the sector.

• This article is part of the themed collection: Recent Review Articles

Article information

Download citation, permissions.

Y. Lu, M. Chen, G. Zhu and Y. Zhang, Nanoscale , 2024, Advance Article , DOI: 10.1039/D4NR00839A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page .

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page .

Read more about how to correctly acknowledge RSC content .

Social activity

Search articles by author.

This article has not yet been cited.

Advertisements

• All Stories
• Journalists
• Expert Advisories
• Media Contacts
• X (Twitter)
• Arts & Culture
• Business & Economy
• Education & Society
• Environment
• Law & Politics
• Science & Technology
• International
• Michigan Minds Podcast
• Michigan Stories
• 2024 Elections
• Artificial Intelligence
• Abortion Access
• Mental Health

Climate change will increase value of residential rooftop solar panels across US, study shows

• Jim Erickson

Climate change will increase the future value of residential rooftop solar panels across the United States by up to 19% by the end of the century, according to a new University of Michigan-led study.

The study defines the value of solar, or VOS, as household-level financial benefits from electricity bill savings plus revenues from selling excess electricity to the grid—minus the initial installation costs.

For many U.S. households, increased earnings from residential rooftop solar could total up to hundreds of dollars annually by the end of the century, say the authors of the study, which was published April 19 in the journal Nature Climate Change.

“Given the average 25-year lifespan of a rooftop solar installation, a system built today will nearly experience 2050 weather,” said study senior author Michael Craig , assistant professor of energy systems at the U-M School for Environment and Sustainability and of industrial and operations engineering at U-M’s College of Engineering.

“So, it’s important for households to think of future value when building solar. If households do so, our findings indicate they would see even greater value from solar, and might decide to build more.”

Public awareness of the increased future value of rooftop solar could spur greater adoption of the technology, which in turn could accelerate efforts to decarbonize the power-generation system in the United States and globally, the study shows.

The expected financial gains seen in the study were driven largely by increased demand for residential air-conditioning as the climate warms. The other key factor affecting the value of rooftop photovoltaic systems, the researchers say, is future solar-panel performance in response to climate change.

Craig and colleagues analyzed data from 2,000 households in 17 U.S. cities and estimated air-conditioning demand and solar-panel performance under future climates using a moderate climate-warming scenario called RCP-4.5.

The value of rooftop solar panels increased in nearly all the cities, in both warm and cold locations. Miami saw the largest increase in value, while only Minneapolis saw a decrease in the financial benefits of rooftop solar for households.

“This is the first study to quantify the value of rooftop solar under climate change, and we show that households across the U.S. will realize greater cost savings from rooftop solar under future weather than under historic weather,” said study lead author Mai Shi, a former U-M visiting doctoral student now at Tsinghua University in Beijing.

As home-cooling demands rise, a greater proportion of solar-generated electricity will be used to cool the home, rather than being sold to the electrical grid, benefiting owners of rooftop solar systems, according to the study.

That’s because—in many states—solar energy used to power a home reduces the homeowner’s electric bill by the full retail cost of electricity, while electricity that is sent to the grid is credited at a lower rate.

“Greater cooling demand means more solar power is consumed at the household rather than sent back to the grid,” Craig said. “And it’s generally more valuable for a rooftop photovoltaic owner to consume the power generated by their PV panel, rather than exporting it to the grid.”

Under the moderate RCP-4.5 climate scenario, demand for residential space cooling is expected to increase in all 17 cities studied. Cooling demand will increase by an average of 35% by mid-century and by an average of 64% by the end of the century, across all households in all of the cities, the researchers say.

The other key factor affecting the future value of residential rooftop photovoltaics is solar-panel performance in response to rising air temperatures and changes in cloud cover.

Solar panels work best in cool, sunny weather. As air temperature or cloud cover increase, the amount of electricity generated by a solar panel declines. The study found that future solar-panel performance will vary from place to place across the U.S., depending on weather conditions.

In cities such as Ann Arbor, Austin, Chicago, Dallas, Detroit, Houston, Louisville and Milwaukee, rising air temperatures will decrease solar panel efficiency, but reduced cloud cover will likely increase the amount of sunlight reaching panels, on average. The two factors “are opposing but roughly comparable,” meaning they cancel each other out, the researchers say.

But cities such as Baltimore, Boston, Los Angeles, Minneapolis, New York City and Phoenix are expected to be both warmer and cloudier in response to climate change, which will “significantly decrease” the electrical output of rooftop solar.

Even so, increased cooling demand in all 17 cities will likely outweigh changes in panel electrical output, resulting in financial gains for owners of rooftop solar in nearly every case, according to the study. Minneapolis, where limited future increases in cooling demand will combine with decreased electrical output from rooftop solar panels, is an exception.

While future financial gains from rooftop solar will be reaped mainly by households that can afford to install panels, various programs are in place to increase accessibility, so that more people share in the anticipated benefits, Craig says.

For example, there are programs that defray the costs of solar, opening it up to lower-income individuals. Governments can also install rooftop solar on public buildings, such as subsidized housing, to cover the capital costs while providing solar benefits to tenants. And community solar programs can benefit entire communities, including households that lack the means or ability to access rooftop solar themselves.

In addition to Craig and Shi, the other author of the Nature Climate Change paper is Xi Lu of Tsinghua University.

The study was supported by the National Key R&D Program of China, U.S. National Science Foundation, National Natural Science Foundation of China and Carbon Neutrality and Energy System Transformation Project.

412 Maynard St. Ann Arbor, MI 48109-1399 Email [email protected] Phone 734-764-7260 About Michigan News

• Engaged Michigan
• Global Michigan
• Michigan Medicine
• Public Affairs

Publications

• Michigan Today
• The University Record

Office of the Vice President for Communications © 2024 The Regents of the University of Michigan

Language selection

• Français fr

Budget 2024 Fairness for every generation

The 2024 federal budget is the government’s plan to build more homes, faster, help make life cost less, and grow the economy in a way that helps every generation get ahead.

How our economic plan can help you

Buy or rent a home.

We’re turbocharging the construction of homes across the country, and protecting the rights of renters, first-time buyers, and homeowners.

Tax-free First Home Savings Account

Over 750,000 Canadians have opened an account to save for their first down payment, and save faster with the help of tax relief.

Protecting Renters’ Rights

Our new Canadian Renters’ Bill of Rights will protect renters from unfair practices, make leases simpler, and increase price transparency.

Enhancing the Canadian Mortgage Charter

The Canadian Mortgage Charter is helping to protect homeowners who are struggling with rising mortgage payments. We are enhancing it to make it easier for younger Canadians to buy their first home, by making sure renters get credit for their rent payments and allowing up to 30-year mortgage amortizations on new builds for first-time home buyers.

Raise your family

Transforming Canada’s social safety net to help young parents with the cost of raising a family.

National School Food Program

A new National School Food Program will ensure that children have the nutritious meals they need to succeed and get a fair start in life.

More $10-a-day Child Care Spaces

We’re on track to securing Canada-wide $10-a-day child care in every province and territory by 2026, and fees have already been cut by 50 per cent everywhere, saving families thousands of dollars. We’re building more spaces and training more early childhood educators to ensure every family can access affordable child care.

Dental Care for Canadians Who Need It

The Canadian Dental Care Plan is already rolling out for uninsured Canadians with a family income of less than $90,000, to ensure everyone can afford the dental care they deserve. By 2025, nine million Canadians will be covered.

Get a good-paying job

Creating new opportunities for younger Canadians to get the education and skills they need for good-paying jobs.

Increasing Interest-Free Student Loans

Increasing Canada Student and Apprentice Loans and Grants, because everyone who wants to go to school should have the support they need to cover the costs.

More Work Experience and Skills Training for Youth

Helping young Canadians develop the skills and gain the work experience they need to achieve their dreams and get a good-paying job.

Canadian Apprenticeship Strategy

Supporting skilled trades workers by tooling up training programs and creating more apprenticeship positions to ensure young apprentices succeed.

Afford everyday essentials

Helping Canadians keep more of their money and build a better life by stabilizing the cost of everyday essentials.

Stabilizing the Cost of Groceries

Enhancing competition and monitoring grocers’ work to help stabilize prices, and lowering costs for the farmers who grow our food.

National Pharmacare Program

New programs to help with the cost of going to the dentist and pharmacy, including the cost of contraceptives and insulin, will further ease the financial burden on Canadians.

Cheaper Internet, Home Phone, and Cell Phone Plans

Lowering costs of plans, reducing junk fees, and giving Canadians more choice to switch providers and find better deals.

Retire safely and securely

After a lifetime of working hard—Canadians deserve to know they will be secure and comfortable in retirement.

A Stronger Canada Pension Plan

Enhancing the CPP to increase pension benefits by up to 50 per cent.

Supporting Long-Term Care

Advancing the Safe Long Term Care Act to support new national long-term care standards.

Bigger Benefits for Seniors

Increased Old Age Security and Guaranteed Income Supplement ensures seniors have the financial support they need in retirement.

Budget 2024 highlights

750,000+ Tax-Free First Home Savings Accounts opened by Canadians

Solving the Housing Crisis: Canada’s Housing Plan

Unlocking 3.87 million net new homes by 2031, to ensure everyone can find an affordable place to call home. And, we’re making it easier to rent while saving for that first home.

• Changing how we build homes
• Unlocking 250,000 new homes on public lands
• The strengthened Canadian Mortgage Charter

Learn more about making homes more affordable .

Fairness for younger generations

The government is helping restore fairness for Millennials and Gen Z by making education, housing, and the everyday costs of living more affordable.

• Increasing student grants and loans to keep up with the costs of an education
• Launching a new Youth Mental Health Fund for access to support they need
• Providing job placement and employment support opportunities through the Youth Employment and Skills Strategy

90,000 new job opportunities for youth

Investing $2.4 billion to secure Canada’s AI advantage

Economic growth and productivity

Budget 2024 makes investments in innovation, growth, and increased productivity in Canada.

Budget 2024 includes new measures to accelerate job growth in Canada’s AI sector and beyond, boost productivity by helping researchers and businesses develop and adopt AI, and ensure this is done responsibly.

• Investing in Canada’s AI ecosystem
• Enhancing research support with $1.8 billion more in core research grant funding
• Creating the Canadian Entrepreneurs’ Incentive

Learn more about the government’s plan to enhance innovation and productivity in Canada .

Unlocking 3.87 million new homes by 2031.

Over 1.1 million more Canadians employed today than before the pandemic.

Affordable child care is supporting a record high 85.4% labour force participation rate for working aged women.

Economic and Fiscal Overview

The state of canada’s economy.

The Canadian economy is outperforming expectations. Both the IMF and the OECD project Canada to see the strongest economic growth in the G7 in 2025. In the face of higher interest rates, Canada has avoided the recession that some had predicted. Headline inflation has fallen significantly from its June 2022 peak of 8.1 per cent to 2.8 per cent in February 2024.

Chart 6 Consumer Price Inflation Outlook

Note: Last data point is 2024Q4.

Sources: Statistics Canada; Department of Finance Canada March 2024 survey of private sector economists.

Economic and Fiscal Projections

We’re asking the wealthiest to pay a bit more, their fair share, to keep taxes lower on the middle class, and ensure the next generation inherits not more debt, but Canada’s prosperity.

Budget 2024 is investing in fairness for every generation while delivering on our fiscal objectives. Canada is maintaining the lowest net debt- and deficit-to-GDP ratios in the G7, preserving Canada’s long-term fiscal sustainability.

Chart 21 Federal Debt-to-GDP Ratio Under Economic Scenarios

Sources: Department of Finance Canada March 2024 survey of private sector economists; Department of Finance Canada calculations.

Improving Tax Fairness for Every Generation

Tax fairness is important for every generation, and it is particularly significant for younger Canadians.

To make the tax system more fair for 99.87 per cent of Canadians, the inclusion rate for capital gains—the portion on which tax is paid—for the wealthiest with more than $250,000 in capital gains in a year will increase from one-half to two-thirds. Only 0.13 per cent of Canadians with an average income of $1.42 million are expected to pay more personal income tax on their capital gains in any given year.

Principal residences will continue to be exempt from capital gains.

Chart 8.4 Canada Has the Lowest Marginal Effective Tax Rate in the G7

Backgrounders

• Key Measures (available in non-official languages)
• Key Measures
• More Affordable Homes
• A Stronger Social Safety Net
• Fairness for Younger Generations
• Economic Growth and Productivity
• Growing Small Businesses
• Safer, Healthier Communities
• A Fair Future for Indigenous Peoples
• Tax Fairness for Every Generation
• The New Canadian Entrepreneurs' Incentive

Related documents

• News Release
• Address by the Deputy Prime Minister and Minister of Finance
• Canada’s Consumer-Driven Banking Framework
• Statement and Impacts Report on Gender, Diversity, and Inclusion
• Legislative Measures
• Tax Measures: Supplementary Information

PDF downloads

Page details