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:
New project called ATIP receives £6 million to drive next-gen solar technology into new applications
Researchers at Swansea University, Imperial College London and the University of Oxford have launched a project to drive next-generation solar technology into new applications. The team has been awarded a £6 million Engineering and Physical Sciences Research Council (EPSRC) grant to advance organic and perovskite solar cells into applications that current solar technologies are not suitable for.
The promise of such next-gen PV could make it suitable for new applications that will be critical to advances such as:
- 5G, which requires ultra-lightweight sources of power for pseudo-satellites and high altitude unmanned aerial vehicles (UAVs)
- The Internet of Things, for which sensors and computing devices are increasingly embedded into everyday objects
- Zero-carbon buildings and vehicles, which could use their roofs, walls and windows to generate power.
Researchers at Pusan National University, Gwangju Institute of Science and Technology and the Korea Institute of Machinery & Materials (KIMM) in South Korea have tackled perovskite solar cells' stability issues by designing a graphene-based encapsulation technique.
The team introduced a highly flexible and stable graphene encapsulant by adopting the dry transfer method based on a roll-based process.
Australian Scientists from the University of New South Wales have outlined a new method for ensuring more of the sun’s energy can be converted into electricity by using sunlight that would otherwise be wasted as heat.
In a photovoltaic solar cell, sunlight is converted into electricity through a process called the photoelectric effect, where individual packets of light, called photons, transfer their energy onto electrons within the solar cell material. If a sufficient amount of energy is transferred by light to an electron, an amount of energy known as the “bandgap”, the electron is knocked loose from its atom and creates an electric current. This is the process by which solar panels convert light into electricity.
Researchers from the Okinawa Institute of Science and Technology Graduate University (OIST) have created next-generation perovskite-based solar modules with high efficiency and good stability. These solar modules can reportedly maintain a high performance for over 2000 hours.
"There are three conditions that perovskites must meet: they must be cheap to produce, highly efficient and have a long lifespan," said Professor Yabing Qi, head of the OIST Energy Materials and Surface Sciences Unit, who led this study.
Researchers create hybrid perovskite materials that could help improve the quality of solar cells and light sources
A team of researchers from MIT and Northwestern University has created hybrid perovskite materials that could help improve the quality of solar cells and light sources. They demonstrated the ability to fine-tune the electronic properties of these hybrid perovskite materials.
The materials are classified as “hybrid” because they contain inorganic components like metals, as well as organic molecules with elements like carbon and nitrogen, organized into nanoscale layers. In the new paper, the researchers showed that by strategically varying the composition of the organic layers, they could tune the color of light absorbed by the perovskite and also the wavelength at which the material emitted light. Importantly, they accomplished this without substantially changing the inorganic component.