Can a bistable amphoteric native defect model explain the photo-induced transformation of MAPbI3 thin films?

Hybrid organic-inorganic perovskites such as MAPbI₃ hold great promise for photovoltaic applications with power conversion efficiencies already exceeding 26 %. Despite the unprecedented advantages of these materials in photovoltaics and optoelectronics they exhibit a range of complex phenomena under light illumination that remain poorly understood. Here we use a combination of photoluminescence (PL) spectroscopy, cathodoluminescence imaging and theoretical calculations to correlate PL fluctuations in MAPbI₃ thin films with changes in the spatial distribution and concentration of native defects. We demonstrate that short-term illumination results in a more homogeneous distribution of emitting and quenching sites, whereas prolonged illumination causes PL quenching. Our findings support the conclusion that the photo-induced transformation of MAPbI₃ can be explained within a bistable amphoteric native defect model, wherein a neutral native defect can undergo a transition between a donor-like and acceptor-like configuration.