Surface Defect Engineering of Metal Halide Perovskites for Photovoltaic Applications

In recent years, surface defect passivation has become essential in the fabrication of perovskite solar cells (PSCs) with record-high efficiencies. However, the exact mechanism and all possible effects of surface passivation on the performance and stability of the PSCs have not been elucidated clearly. In this Perspective, we summarize the status of the current research on halide perovskite surfaces and their passivation, followed by a discussion of the important issues yet to be resolved. The most widely used surface passivation approach-the one that uses alkylammonium halide-is the focused of this Perspective. We emphasize the need for decoupling all possible effects of the passivation process, including their advantages and undesired side effects, to maximize the performance enhancement attainable through surface modification. Gaining thorough knowledge of the perovskite surfaces and their proper management will be the key to the practical use of PSCs with higher performance and longevity.