Semiconductor surfaces play an important role in the behavior of their electronic devices. The vulnerable lattice of metal-halide perovskite renders a fragile surface, where defect states can easily form. Very recently, most of the highly efficient perovskite optoelectronic devices have been reported to employ effective surface passivation strategies, further confirming the significance of surface states in regulating their device performance. Here, we present methodical studies towards understanding the surface states in perovskite thin films utilizing a strategy of molecular “defect indicator” that is able to interact with specific surface defects. In formamidinium (FA)-methylammonium (MA) mixed cation perovskite thin films, a nonuniform distribution of cations is uncovered with FA cations being close to the top and MA close to the bottom of the film, leading to unique surface defect energetics. Antisite FA<sub>I</sub> was found to become a dominant deep trap on the surface of this system.

Unraveling the surface states of photovoltaic perovskite thin film

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.