Air-processed and mixed-cation single crystal engineering-based perovskite films for efficient and air-stable perovskite solar cells.

Metal hybrid halide perovskite solar cells (PSCs) are very sensitive to air, and it is challenging to obtain air-processed, air-stable, and highly crystalline perovskite films. Photovoltaic performance decays dramatically due to air humidity influence with power conversion efficiency (PCE) of most air-processed PSCs < 15%. In this work, we develop a facile method to air-processed, highly crystalline (MA_0.2FA_0.8PbI₃)_1.0(CsPbBr₃)_0.05 perovskite films in ambient air with large grain size and low trap density based on mix-cation single crystal engineering. This method shows 75% increase in grain size and 28% decrease in trap density than conventional molecule/ion solution mixing-processed method. The large grain, low trap density, andhigh crystalline perovskite films result in high-efficient and air-stable PSCs. Consequently, the PCE increases to 36.7% from 12.56% for conventional molecule/ion solution mixing-processed devices and to 17.17% for single crystal engineering-based ones. Furthermore, benefiting from high moisture resistance of mix-cation single crystal engineering-based films, the PSC air stability has been improved significantly and 72% of the initial performance retains after 40 days of storage in ambient environment with a relative humidity of 60% at 25 °C without any encapsulation, with a 26% slower degradation rate than conventional solution-mixing method. [ABSTRACT FROM AUTHOR]