Article last updated on: Jan 08, 2018
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.

Perovskite solar cell market image

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 cell image

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).

What’s next?

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.

Latest Perovskite Solar news

Researchers hail spray coating as a potential way to solve a major challenge in mass production of perovskite solar cells

Researchers from the universities of New York, Peking, Electronic Science and Technology of China, Yale and Johns Hopkins report they have solved a major challenge to the commercial production of perovskite solar cells, by turning to spray coating. The scientists say spraying can apply the electron transport layer (ETL) uniformly across a large area, and is suitable for manufacturing large solar panels and ensuring high performance.

Spray coating in applying ETL to perovskites image

The research team reported spray coating led to a 30% efficiency gain over other ETLs – translating to a power conversion efficiency leap from 13% to over 17% – and even resulted in fewer defects.

Oxford PV and HZB develop a simplified perovskite tandem solar cell

Oxford Photovoltaics, in collaboration with Helmholtz-Zentrum Berlin (HZB) and the Photovoltaics and Optoelectronics Device Group at the University of Oxford, produced a 1 cm2 perovskite-silicon two-terminal tandem solar cell with a verified conversion efficiency of 25.2%. The two-terminal tandem solar cell efficiency was certified by the Fraunhofer Institute for Solar Energy Systems ISE.

Oxford PV and HZB develop a simplified perovskite tandem solar cell image

Dr Chris Case, Chief Technology Officer at Oxford PV commented, “The unique, optically enhanced architecture developed as part of this collaboration, minimizes losses, and has helped us achieve this record setting efficiency”.

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Sungkyunkwan researchers develop highly stable pervoskite solar cells by improving passivation techniques

Researchers from Sungkyunkwan University recently reported the development of highly stable perovskite solar cells under extreme environments by improving passivation techniques.

The architecture of the solar cells has inverted planar devices (so-called p-i-n devices; light illumination through hole transport layers) with FTO/NiO/Perovskite/PCBM/AZO/Ag. AZO has been deposited via atmoic layer deposition method, which produces pinhole-free, uniform, and dense films. The AZO-deposited perovskite solar cells exhibited similar performances to the control solar cells due to negligible charge transporting retardation by the 3 orders of magnitude higher conductivity of AZO compared to that of PCBM. The ALD-grown AZO (ALD-AZO) layers also acted as dense, uniform, and impermeable passivation layers that prevented ingress of water into the perovskite films, egress of the volatile components of perovskite when heated, and interfacial degradation between the perovskite-PCBM heterojunction and the Ag electrode caused by unfavorable chemical reactions.

KAIST team proposes lead-free, efficient perovskite material for photovoltaic cells

A KAIST research team has proposed a perovskite material, Cs2Au2I6 that serves as a potential active material for highly efficient lead-free thin-film photovoltaic devices. This material is expected to lay the foundation to overcome previously known limitations of perovskite including its stability and toxicity issues.

KAIST team proposes lead-free, efficient perovskite material for photovoltaic cells image

The joint team led by Professor Hyungjun Kim from the KAIST Department of Chemistry and Professor Min Seok Jang from the School of Electrical Engineering analyzed a previously discovered perovskite material, Cs2Au2I6, consisting of only inorganic substances and investigated its suitability for application in thin-film photovoltaic devices. Theoretical investigations suggests that this new perovskite material is not only as efficient but also more stable and environment friendly compared to the conventional perovskite materials.

U.S team develops scale for measuring perovskite energy

Researchers from Rice University and Los Alamos National Laboratory have observed electronic properties of perovskites at the quantum scale, and made discoveries likely to impact the development of perovskite solar cells.

U.S. scientists develop scale for measuring perovskite energy image

The team has developed a scale to determine the binding energy of excitons, and thus the bandgap structures, in perovskite wells. This scale, according to Rice University, could assist scientists in developing new semiconductor materials.