Modification of SnO2 with Phosphorus‐Containing Lewis Acid for High‐Performance Planar Perovskite Solar Cells with Negligible Hysteresis

Expeditious charge transfer at the interfaces between photoactive and charge transport layers is critical in perovskite solar cells (PSCs). Defects on the surface of charge transport layers usually lead to the degradation of carrier mobility, resulting in low power conversion efficiency (PCE) and serious hysteresis. Herein, phosphorus‐containing Lewis acids are applied to modify the SnO 2 /perovskite interface and neutralize redundant OH − on the SnO 2 surface. The interaction between the Lewis acids and SnO 2 significantly accelerate the electron transfer and greatly reduce the energy barrier at the SnO 2 /perovskite interface, boosting the PCE of the PSCs. By modifying the SnO 2 /pervoskite interface with diphenylphosphine oxide, the PCE of a small area device was increased from 18.94% to 22.14%, along with negligible hysteresis and improved stability. Moreover, the 5 × 5 cm 2 solar modules with an aperture area of 22.56 cm 2 achieved a best efficiency of 15.69%.