PMMA passivated CsPbI2Br perovskite film for highly efficient and stable solar cells

Cesium-based inorganic perovskite solar cells (PSCs), especially for the CsPbI2Br-based solar cells, have attained extensive attention due to its excellent thermal and phase stability. Solution-prepared CsPbI2Br films usually have some defects which demand to be passivated for PSCs and also their degradations often happen at the grain boundaries (GBs). Herein, by using polymethylmethacrylate (PMMA) solution, we optimize the perovskite film growth and further investigate the effect of PMMA treatment on the properties of the CsPbI2Br films. Time-resolved photoluminescence (TRPL) displays that the PMMA coating can improve the photoluminescence lifetime of CsPbI2Br perovskite films. Therefore, it is proved that PMMA coating film can effectively passivate the defects of the pure CsPbI2Br films, suppress the charge recombination with increased electron extraction efficiency, which improves the performance of solar cells. Consequently, the devices based on CsPbI2Br films with PMMA solution treatment exhibit average power conversion efficiency (PCE) over 11.18%, which is much higher than the efficiency of 9.69% for pure CsPbI2Br-based solar cells.