Researchers from Ulsan National Institute of Science and Technology (UNIST), Wuhan University of Technology and Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory have announced their success in manufacturing a high-efficiency, stable perovskite solar cell through a vacuum thin film deposition process.
Vacuum thin film deposition is a technique that is already widely used in the manufacture of large OLED TVs by evaporating raw materials in a vacuum and coating them thinly on a substrate. The perovskite solar cell developed this way displayed a photovoltaic-to-electricity conversion efficiency of 21.4%, which the team said is the highest among perovskite solar cells manufactured by vacuum thin film deposition process.
In addition, the cell reportedly maintained more than 60% of its initial efficiency when the battery was operated for 1000 hours at 60-70% humidity without an encapsulation process that encapsulates the entire battery with a protective material.
The ‘Rudelsden-Popper’ structural film, which has been known to have excellent protective functions, has an irregular internal particle arrangement, which lowers the efficiency of generating electricity. The research team solved this problem by synthesizing a protective film that aligned the alignment direction of the internal atoms. The perovskite solar cell coated with this protective film showed excellent performance not only in moisture but also in thermal durability tests.
The team placed a highly oriented butylammonium Rudelsden-Popper (RP) film as a surface passivation layer with bottom-up growth on the bulk perovskite absorber layer via vacuum deposition. In this process, the crystal formation time directly affects the crystallographic orientation of the passivation layer. By leveraging the passivating properties and controlled crystallinity, the RP perovskite considerably reduces the trap density of bulk perovskite and enhances the charge transport. The proposed passivation strategy allows the growth of highly oriented RP phase perovskite passivation layers toward the development of efficient, stable, and scalable PSCs.
The first author, Researcher Yunseong Choi, said, “Thanks to the protective film deposited on the perovskite material. This protective film is excellent in protecting against moisture and heat stimulation, but unlike conventional protective films, it does not decrease battery efficiency.”
Professor Hye-Sung Park said, “Thin film deposition is a very advantageous manufacturing method for manufacturing perovskite solar cells in a large size that can be commercialized. It’s very encouraging”. The vacuum deposition-based protective film technology developed in this study is not only a perovskite solar cell, but also a tandem solar cell (a cell that combines a silicon cell and a perovskite cell), a perovskite-based light emitting diode, and an optical sensor. It can also be applied to others.”