Halide perovskite is widely regarded as a “wonder material” for the next-generation of photovoltaic cells. While halide perovskite crystals are currently manufactured using a high-temperature process, a team of researchers at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia has recently discovered a “cooler” production method that yields crystals of a much higher quality. Photovoltaic cells that are based on the perovskite material made with this low-temperature process have achieved a conversion efficiency rate of almost 22%, which is among the highest on record for this type of solar cell technology. The KAUST team published its findings in ACS Energy Letters this January.
Perovskite is rapidly gaining popularity in the solar market because of its low cost and abundance. Compared with crystalline silicon, perovskite can be produced more cheaply and deposited on flexible substrates and glass. With these advantages, scientists can develop curved or bendable solar panels for integration with buildings (e.g., walls and roofs), vehicles, and even clothing. Abdullah Alsalloum, a graduate student at KAUST and one of the co-first authors of the study, said that the development of halide perovskite photovoltaic cells is now taking off at the fastest pace compared with other emerging solar photovoltaic technologies.
However, there is still some way to go before perovskite cells reach the commercialization and mass production stage. By definition, a perovskite material is any material that has the same type of crystal structure as calcium titanium oxide (CaTiO3). Also, those perovskite materials now used in photovoltaic cells are compounds that share the general chemical formula ABX3. The mainstream process for the manufacturing of halide perovskite is based on the solvent engineering method, which involves the key chemical ingredients being first dissolved in a solution and then joined together into crystals. The KAUST team pointed out that previously this process required the temperature of the solution to be maintained at 120°C.
When manufacturing a photovoltaic perovskite material known as methylammonium lead iodide (MAPbI3), the high temperature actually causes defects by hindering iodide and methylammonium ions from integrating into the crystal structure. Bekir Turedi, another co-first author of the study, said that his team tried out a variety of solvents for the dissolution and crystallization of the key ingredients. Eventually, the team discovered one that permits this process to be carried out at a temperature below 90°C and produces single crystals of significantly higher quality.
Osman Bakr, who also contributed to the study, said that the highest conversion efficiency rate of the photovoltaic cells featuring the low-temperature perovskite material is close to 22%. On the whole, the conversion efficiency rate of the perovskite cells developed by the KAUST team is among the highest reported for this type of solar cell technology.
The KAUST team noted that the single crystals resulted from the low-temperature process are still too small for use in commercial solar products. However, the issue of the crystal size has long been recognized as a hurdle that impedes the market entry of perovskite cells. Therefore, the successful commercialization of perovskite cells will require further studies and improvements on the process for manufacturing single perovskite crystals.
(News source: TechNews. Photo credit: SteFou! via Flickr CC BY 2.0.)
