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.
The latest perovskite solar news:
A research team led by Prof. GAO Peng from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences has developed high-performance perovskite solar cells with enhanced environmental stability.
The team reported a 2-(4-fluorophenyl)ethylamine (FPEA: 4-FC6H4C2H4NH3) bulky cation to grow a 2D perovskite overlayer on the top of the Cs/FA/MA triple-cation 3D perovskite to combine the high stability of 2D perovskite with high efficiency of 3D perovskite simultaneously.
Researchers at Nanjing University in China and the University of Toronto in Canada have fabricated all-perovskite tandem solar cells (PSCs) with remarkable independently certified PCEs of 24.8% for small-area devices (0.049 cm2) and 22.1% for large-area devices (1.05 cm2).
Fabricating all-perovskite tandem solar cells, based on both wide-bandgap and narrow-bandgap perovskites, could lead to a higher power conversion efficiency (PCEs) than that attained by single-junction cells without increasing fabrication costs. In order to build this new type of solar cell, however, researchers need to find a way to enhance the performance of each subcell, while also integrating the wide-bandgap and narrow-bandgap cells synergistically.
HZB's cooperation with Slovenian University on perovskite silicon tandem solar cells gets a financial push
An HZB team has successfully raised funds from the “Helmholtz European Partnering Program” of the Helmholtz Association to expand cooperation with partners of the University of Ljubljana, Slovenia. The topics of the cooperation are tandem solar cells made of perovskite and silicon and, in particular, their precise characterization.
The TAPAS project is funded by the Helmholtz European Partnering programme for the next three years with 250,000 euros per year each. Following an evaluation, the funding period can be extended by two years. The Helmholtz European Partnering programme was set up to strengthen the European research area, in particular cooperation with countries in Southern, Central and Eastern Europe.
Solar cells made from perovskite materials have the potential for use in powering electronics in space. Before considering them for space applications, it is crucial to understand how resilient they would be in such a high radiation environment. In previous experiments by other groups, the effect of high-energy protons and electrons has been tested, with the results suggesting that this type of solar cell is particularly resilient to radiation effects. This experiment, on VESUVIO at ISIS, is the first to test cells in operando while being exposed to high-energy neutrons, and found that the cells suffered minimal irreversible damage during the process.
Chinese manufacturer GCL recently indicated that it is nearing commercialization of perovskite solar technology. “Once the conversion rate [of] perovskite is close to what monocrystalline product does, which is coming soon, the only obstacle for perovskite to take [the] place of mono is the limitation of its production capacity,” GCL Nano Technology general manager Fan Bin said at a recent industry conference which considered the potential of perovskite.
Discussing GCL’s work with perovskites, Fan said his company’s lab has achieved a conversion efficiency of 16% on a large panel and he is confident 18% could be achieved by the end of the year. With a theoretical conversion limit of around 33% thought to apply to perovskite cell efficiency – and possibly up to 47% for a tandem device – the manager voiced confidence perovskites would soon surpass the 18% threshold.