What are perovskite?
Perovskites are a class of materials that share a similar structure, which display a myriad of exciting properties like superconductivity, magnetoresistance and more. These easily synthesized materials are considered the future of solar cells, as their distinctive structure makes them perfect for enabling low-cost, efficient photovoltaics. They are also predicted to play a role in next-gen electric vehicle batteries, sensors, lasers and much more.
How does the PV market look today?
In general, Photovoltaic (PV) technologies can be viewed as divided into two main categories: wafer-based PV (also called 1st generation PVs) and thin-film cell PVs. Traditional crystalline silicon (c-Si) cells (both single crystalline silicon and multi-crystalline silicon) and gallium arsenide (GaAs) cells belong to the wafer-based PVs, with c-Si cells dominating the current PV market (about 90% market share) and GaAs exhibiting the highest efficiency.
Thin-film cells normally absorb light more efficiently than silicon, allowing the use of extremely thin films. Cadmium telluride (CdTe) technology has been successfully commercialized, with more than 20% cell efficiency and 17.5% module efficiency record and such cells currently hold about 5% of the total market. Other commercial thin-film technologies include hydrogenated amorphous silicon (a-Si:H) and copper indium gallium (di)selenide (CIGS) cells, taking approximately 2% market share each today. Copper zinc tin sulphide technology has been under R&D for years and will probably require some time until actual commercialization.
What is a perovskite solar cell?
An emerging thin-film PV class is being formed, also called 3rd generation PVs, which refers to PVs using technologies that have the potential to overcome current efficiency and performance limits or are based on novel materials. This 3rd generation of PVs includes DSSC, organic photovoltaic (OPV), quantum dot (QD) PV and perovskite PV.
A perovskite solar cell is a type of solar cell which includes a perovskite structured compound, most commonly a hybrid organic-inorganic lead or tin halide-based material, as the light-harvesting active layer. Perovskite materials such as methylammonium lead halides are cheap to produce and relatively simple to manufacture. Perovskites possess intrinsic properties like broad absorption spectrum, fast charge separation, long transport distance of electrons and holes, long carrier separation lifetime, and more, that make them very promising materials for solid-state solar cells.
Perovskite solar cells are, without a doubt, the rising star in the field of photovoltaics. They are causing excitement within the solar power industry with their ability to absorb light across almost all visible wavelengths, exceptional power conversion efficiencies already exceeding 20% in the lab, and relative ease of fabrication. Perovskite solar cells still face several challenge, but much work is put into facing them and some companies, are already talking about commercializing them in the near future.
What are the advantages of Perovskite solar cells?
Put simply, perovskite solar cells aim to increase the efficiency and lower the cost of solar energy. Perovskite PVs indeed hold promise for high efficiencies, as well as low potential material & reduced processing costs. A big advantage perovskite PVs have over conventional solar technology is that they can react to various different wavelengths of light, which lets them convert more of the sunlight that reaches them into electricity.
Moreover, they offer flexibility, semi-transparency, tailored form factors, light-weight and more. Naturally, electronics designers and researchers are certain that such characteristics will open up many more applications for solar cells.
What is holding perovskite PVs back?
Despite its great potential, perovskite solar cell technology is still in the early stages of commercialization compared with other mature solar technologies as there are a number of concerns remaining.
One problem is their overall cost (for several reasons, mainly since currently the most common electrode material in perovskite solar cells is gold), and another is that cheaper perovskite solar cells have a short lifespan. Perovskite PVs also deteriorate rapidly in the presence of moisture and the decay products attack metal electrodes. Heavy encapsulation to protect perovskite can add to the cell cost and weight. Scaling up is another issue - reported high efficiency ratings have been achieved using small cells, which is great for lab testing, but too small to be used in an actual solar panel.
A major issue is toxicity - a substance called PbI is one of the breakdown products of perovskite. This is known to be toxic and there are concerns that it may be carcinogenic (although this is still an unproven point). Also, many perovskite cells use lead, a massive pollutant. Researchers are constantly seeking substitutions, and have already made working cells using tin instead. (with efficiency at only 6%, but improvements will surely follow).
While major challenges indeed exist, perovskite solar cells are still touted as the PV technology of the future, and much development work and research are put into making this a reality. Scientists and companies are working towards increasing efficiency and stability, prolonging lifetime and replacing toxic materials with safer ones. Researchers are also looking at the benefits of combining perovskites with other technologies, like silicon for example, to create what is referred to as “tandem cells”.
Commercial activity in the field of perovskite PV
In September 2015, Australia-based organic PV and perovskite solar cell (PSC) developer Dyesol declared a major breakthrough in perovskite stability for solar applications. Dyesol claims to have made a significant breakthrough on small perovskite solar cells, with “meaningful numbers” of 10% efficient strip cells exhibiting less than 10% relative degradation when exposed to continuous light soaking for over 1000 hours. Dyesol was also awarded a $0.5 million grant from the Australian Renewable Energy Agency (ARENA) to commercialize an innovative, very high efficiency perovskite solar cell.
Also in 2015, Saule Technologies signed an investment deal with Hideo Sawada, a Japanese investment company. Saule aims to combine perovskite solar cells with other currently available products, and this investment agreement came only a year after the company was launched.
In October 2020, Saule launched sunbreaker lamellas equipped with perovskite solar cells. The product is planned to soon be marketed across across Europe and potentially go global after that.
In August 2020, reports out of China suggested that a perovskite photovoltaic cell production line has gone into production in Quzhou, east China's Zhejiang Province. The 40-hectare factory was reportedly funded by Microquanta Semiconductor and expected to produce more than 200,000 square meters of photovoltaic glass before the end of 2020.
In September 2020, Oxford PV's Professor Henry Snaith stated that the Company's perovskite-based solar cells are scheduled to go on sale next year, probably by mid 2021. These will be perovskite solar cells integrated with standard silicon solar cells.
The latest perovskite solar news:
Researchers at the University of Helsinki are developing thin films for perovskite solar cells, and matching ALD processes.
Doctoral Researcher Georgi Popov focuses on perovskites and atomic layer deposition (ALD). In 2019, He and his colleagues identified suitable chemicals and were able to design a reaction that enabled them to create a metal iodide coating through deposition for the first time. The researchers were able to demonstrate that this can actually be done through atomic layer deposition. The first successful trial was carried out with lead iodide, which was then processed into CCH₃NH₃PbI₃ perovskite through a further reaction. Later on, the researchers also developed ALD processes for caesium iodide and CsPbI₃ perovskite.
Chinese perovskite solar technology company Renshine Solar (Suzhou) has announced achieving steady-state efficiency of 24.50% for all-perovskite tandem cell module, which it called 'a world record'.
It was reported that the efficiency was achieved for a perovskite module with an area of 20.25 cm², which exceeds that of perovskite single-junction components. The new efficiency level has been certified by Japan’s JET, it added without sharing other details.
Researchers from China's Huazhong University of Science and Technology and Singapore's National University of Singapore have introduced an eco-friendly and low-cost organic polymer, cellulose acetate butyrate (CAB), to the grain boundaries and surfaces of perovskites, resulting in a high-quality and low-defect perovskite film with a nearly tenfold improvement in carrier lifetime.
The CAB-treated perovskite films have a well-matched energy level with the charge transport layers, thus suppressing carrier nonradiative recombination and carrier accumulation. As a result, the optimized CAB-based device achieved a champion efficiency of 21.5% compared to the control device (18.2%).
Researchers from Helmholtz-Zentrum Berlin (HZB) and Potsdam University have reported perovskite–silicon tandem solar cells with periodic nanotextures that offer various advantages without compromising the material quality of solution-processed perovskite layers. Textured tandem devices have been presented before, aiming at improved optical performance, but optimizing film growth on surface-textured wafers has thus far remained challenging.
The research team showed a reduction in reflection losses in comparison to planar tandems, with the new devices being less sensitive to deviations from optimum layer thicknesses. The nanotextures also enabled a greatly increased fabrication yield from 50% to 95%. Moreover, the open-circuit voltage was improved by 15 mV due to the enhanced optoelectronic properties of the perovskite top cell. The optically advanced rear reflector with a dielectric buffer layer resulted in reduced parasitic absorption at near-infrared wavelengths. As a result, the team achieved a certified power conversion efficiency of 29.80%.
Researchers from Empa, EPFL, Sichuan University, Jiaxing University, Soochow University, University of Cologne, University of Potsdam, HZB and the University of Oxford have developed a flexible all-perovskite tandem solar cell with a mitigated open-circuit voltage deficit and reduced voltage loss. The team reported flexible tandem efficiency of almost 24% on small area cells using the spin coating method.
Flexible all-perovskite tandem cells are currently less developed than rigid cells, due to a difficult deposition process for the cell's functional layers and a lower open-circuit voltage. This is due to high defect densities within the perovskite absorber layer and at the perovskite/charge selective layer interface.
Researchers from Ulsan National Institute of Science and Technology (UNIST), Wuhan University of Technology and Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory have manufactured high efficiency, stable, and scalable perovskite solar cells (PSCs) via vacuum deposition, a method of fabricating organic light-emitting display devices (OLEDs).
In their study, the research team demonstrated efficient and stable PSCs with a vacuum-processed Ruddlesden-Popper (RP) phase perovskite passivation layer. By controlling the deposition rate of the RP phase perovskite, which directly influenced its crystallographic orientation, the research team successfully obtained a highly ordered 2D perovskite passivation layer.
A team of scientists, led by Professor Hairen Tan of Nanjing University, has demonstrated (for was the team states is the first time) bifacial all-perovskite monolithic tandem solar cells and examined their output power potential.
The research team demonstrated the design and fabrication of bifacial all-perovskite tandem solar cells using transparent conductive oxide (TCO) as the back electrode. The bandgap technique of the top subcell was used to obtain current matching under different backlights. The influence of the albedo on the photovoltaic parameters and the spectral sensitivity was systematically investigated. The bifacial tandems reportedly showed a high output power density of 28.51 mW cm−2 under a realistic rear illumination (30 mW cm− 2). Further energy yield calculation showed substantial energy yield gain for bifacial tandems compared with the monofacial tandems under various ground albedo for different climatic conditions. This work provides a new device architecture for higher output power for all-perovskite tandem solar cells under real-world conditions.
Toray Engineering says that it will ship a slot-die coater to a new perovskite PV production line. The shipment is scheduled by the end of 2022, or in early (Q1)2023. The new coater can handle subsrates up to 1 meter In size, which will enable the world's largest size perovskite PV production line. Products to be manufactured on this line will include BIPV and roof mounted panels, with an annual production capacity of 100 MW.
Toray Engineering has been supplying slot-die coaters and many other process and inspection tools worldwide for the display, semiconductor, and LiB industries. Having two solutions available in slot-die coating, which are Roll to Roll (R2R) and sheet-to-sheet, Toray Engineering is the a leader in slot die equipment supply with a sales record of over 1,000 units.
Chinese perovskite solar PV company Wuxi UtmoLight Technology recently achieved 18.2% power conversion efficiency for an in-house developed large-scale perovskite solar module with an area of 756 cm², as reports suggest.
UtmoLight refers to this as a breakthrough in large size perovskite module technology after having reported the same 18.2% efficiency for a smaller size module with 300 cm² dimension in the past. This shows the module can maintain a high conversion efficiency despite the enlargement of the module area. Mass production of this technology is now becoming mature, it added.
Korean PV company Hanwha Q Cells reportedly aims to mass-produce perovskite-based tandem cells by June 2026.
According to Hanwha Q Cells, its researchers in Germany have collaborated with Helmholtz-Zentrum Berlin, to develop tandem cells using both perovskite and silicon, which is regarded as an intermediary step to developing cells using perovskite only.