Perovskite-Info: the perovskite experts

Researchers from the University of California San Diego, King Abdullah University of Science and Technology and the Air Force Research Laboratory have developed a technique that could enable the fabrication of longer-lasting and more efficient perovskite solar cells, photodetectors, and LEDs.

Strain-engineered, single crystal thin film of perovskite grown on a series of substrates with varying compositions and lattice sizes. Image Credit: David Baillot/UC San Diego Jacobs School of Engineering.

A major obstacle is the tendency of one of the best-performing perovskite crystals, α-formamidinium lead iodide (HC(NH₂)₂PbI₃, known as α-FAPbI₃), to assume a hexagonal structure at room temperature, in which photovoltaic devices are required to operate. This hexagonal structure cannot respond to most of the frequencies of light in solar radiation, and is hence not useful for solar applications as it could be. The team therefore set out to stabilize the structure of α-FAPbI3, using a simple but useful approach known as strain engineering, which has been used to tune the electronic properties of semiconductors.

In September 2019, a research team led by Prof. Steve Albrecht from the HZB (in close collaboration with Kaunas University of Technology in Lithuania) announced a tandem solar cell with certified efficiency of 23.26% that combines the semiconducting materials perovskite and CIGS. Now, the team shares further details on these cells and states that an unnamed Japanese manufacturer has acquired the rights to produce them.

The scientists said the self-assembling material used for the cell is made of molecules based on carbazole head groups with phosphonic acid anchoring groups, and consists of 1-2nm of self-assembled monolayers deposited on the surface of the perovskite by dipping it into a diluted solution.

Researchers at EPFL in Switzerland have reported on the use of Flash Infrared Annealing (FIRA) to rapidly produce efficient, stable perovskite solar cells.

FIRA shares many characteristics with thermal annealing techniques already used to grow pure crystal phases for the semiconductor industry. It works by using a short IR pulse to rapidly nucleate a perovskite film from a precursor solution, without the need for a high-temperature scaffold. The high speed and relatively low processing temperatures mean that FIRA is compatible with large-area deposition techniques, like roll-to-roll processing. For PSCs, it could offer a practical route to scaling-up production.

A team of scientists in Japan has used carbon nanotubes to reliably create perovskite crystal layers free of defects and holes. Their findings could improve the performance of perovskite-based solar panels.

In this study, researchers led by Professor Keiko Waki at Tokyo Institute of Technology, Japan, found a way to bond carbon nanotubes (CNT) to perovskite to improve the latter’s efficiency and stability.

A research team led by Tan Zhi Kuang from the Department of Chemistry and the Solar Energy Research Institute of Singapore (SERIS) has developed perovskite-based high-efficiency, near-infrared LEDs that can cover an area of 900 mm² using low-cost solution-processing methods.

Infrared LEDs are generally small point sources, and according to the institute this limits their efficacy if illumination is required in larger areas when in close proximity, such as those found on wearable devices.

By tuning the structure of a 2D perovskite solar material, researchers from KAUST and the Georgia Institute of Technology have shown they can prolong the lifetime of highly energetic hot carriers generated by light striking the material. The approach could offer a way to capture solar energy more efficiently.

"As an alternative to 3D hybrid perovskites, 2D hybrid perovskites have improved stability and moisture resistance," says Jun Yin, a member of Omar Mohammed's and Osman Bakr's research groups. However, hot carrier cooling in these materials has not been extensively studied, adds Partha Maity, a postdoctoral fellow on the KAUST team.

A joint research team from the Gwangju Institute of Science and Technology (GIST) and the Korea Photonics Technology Institute has developed perovskite-enabled hybrid flexible copper indium gallium selenide (CIGS) thin-film solar cells that can convert all ultraviolet, visible and infrared sunlight into electric energy.

Current flexible CIGS thin-film solar cells are limited by a short wavelength band, from 300 to 390 nanometers, which is absorbed from the transparent electrodes at the top of the solar cell. They cannot convert short wavelength solar energy into electricity. The research team succeeded in developing CsPbBr₃ perovskite high-efficiency fluorescents that light up visible light bands by absorbing the light in the ultraviolet region, and applied them to the top of the transparent photoelectric layer of CIGS solar cells.