Perovskite Passivation with a Bifunctional Molecule 1,2‐Benzisothiazolin‐3‐One for Efficient and Stable Planar Solar Cells

Abstract

Even though the perovskite material itself has a high defect tolerance compared with other semiconductors, the defects existing at grain boundaries (GBs) or the surface still cause high densities of the trap state which impair the efficiency and stability of perovskite solar cells (PSCs). Herein, the small molecule 1,2‐benzisothiazolin‐3‐one (BIT) is investigated to passivate the defects at the GBs and surface of perovskite films. The results reveal that the BIT molecule belongs to a type of bifunctional species, which functions as cations and anions to passivate the perovskite surface. The BIT passivation generates lower formation energy and a more stable perovskite structure, resulting in improved performance and stability of the PSCs. The power conversion efficiency (PCE) of the optimized inverted photovoltaic device reaches 21.83%. Meanwhile, high photostability is achieved for PSCs with an efficiency drop of less than 10% under continuous light illumination over 500 h.