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

New titanium-based material shows promise for lead-free perovskite-based PV

Researchers at Brown University and University of Nebraska - Lincoln (UNL) have come up with a new titanium-based material for making lead-free, inorganic perovskite solar cells. The team shows that the material has significant potential, especially for making tandem solar cells.

Titanium as an attractive choice to replace the toxic lead in the perovskite solar cells

"Titanium is an abundant, robust and biocompatible element that, until now, has been largely overlooked in perovskite research," said the senior author of the new paper. "We showed that it's possible to use titanium-based material to make thin-film perovskites and that the material has favorable properties for solar applications which can be tuned."

Cintelliq reveals interesting details on the state of the perovskite solar cell patent landscape

A recent report by Cintelliq on the perovskite solar cell patent landscape shows massive growth in perovskite photovoltaic patent publications over the past two years. In 2016 and 2017 more than 1500 patents have been published representing 75% of all perovskite photovoltaic patents published since 2008.

Perovskite patents chart image

The total number of patents published to the end of December 2017 is 2030 and filed by 396 distinct assignees. These published patents arise from innovations that occurred in previous years, as can be seen in the chart of yearly patent filed and published. As can also be seen there are fewer patent filings in 2016 and even less in 2017. However, this is not a rapid fall in filings, but a probable side effect of the length of time it takes to go from initial filing through to initial publications.

The Graphene Handbook

Optimized laser patterning process to reduce ‘dead areas’ in perovskite PV

CHEOPS, a European research project with a focus on upscaling perovskite photovoltaic cells, has released a new research that shows a way to reduce the ‘dead area’ of photovoltaic cells by applying an enhanced laser patterning process. This new development means that more of the area of a cell can be used for energy conversion, making it more efficient.

For upscaling efforts to achieve suitable currents, photovoltaic cells are usually split into a series of interconnected segments. It is these breaks in the material that need to be made as small as possible to be able to optimize the cell for energy conversion. This so-called ‘dead area’ has been reduced to a width of 400μm by using a new laser patterning process.

Aalto team finds significant shortcomings in aging tests performed on perovskite-based solar cells

Researchers at Aalto University have found that only a fraction of stability tests done on perovskite-based solar cells and dye-sensitized solar cells meet proper requirements. The team analyzed 261 aging tests conducted on such solar and saw major shortcomings in both how the results had been reported and how tests had been implemented. Tests lack common standards and should have been done in real-world conditions and in groups of several cells.

"In about half of the aging studies, the data was published only for one solar cell. Studying only one cell does not yield a sufficient amount of data to reliably compare how different materials age, that is, lose efficiency over time," says the team.

EPFL team sheds light on the hidden path of perovskite formation

A study by EPFL researchers Michael Grätzel and Amita Ummadisingu offers valuable insight into the sequential deposition reaction. This process, used as one of the main methods for depositing perovskite films onto panel structures, was developed in 2013 by Michael Grätzel and co-workers at EPFL. Many studies have since tried to control this process with additives, compositional changes, and temperature effects, but none of these has provided a complete understanding of the entire sequential deposition reaction. This prevents adequate control over film quality, which determines the performance of the solar cell.

EPFL team reveals the hidden path of perovskite formation image

The EPFL scientists began with X-ray diffraction analysis and scanning electron microscopy to study in depth the crystallization of lead iodide (PbI2), which is the first stage of the reaction. They then used, for the first time, SEM-cathodoluminescence imaging to study the nano-scale dynamics of perovskite film formation.