The Synergistic Effect of Pemirolast Potassium on Carrier Management and Strain Release for High‐Performance Inverted Perovskite Solar Cells

Abstract The quality of the perovskite absorption layer is critical for the high efficiency and long‐term stability of perovskite solar cells (PSCs). The inhomogeneity due to local lattice mismatch causes severe residual strain in low‐quality perovskite films, which greatly limits the availability of high‐performance PSCs. In this study, a multi‐active‐site potassium salt, pemirolast potassium (PP), is added to perovskite films to improve carrier dynamics and release residual stress. X‐ray photoelectron spectroscopy (XPS) and Fourier‐transform infrared spectroscopy (FTIR) measurements suggest that the proposed multifunctional additive bonds with uncoordinated Pb 2+ through the carbonyl group/tetrazole N and passivated I atom defects. Moreover, the residual stress release is effective from the surface to the entire perovskite layer, and carrier extraction/transport is promoted in PP‐modified perovskite films. As a result, a champion power conversion efficiency (PCE) of 23.06% with an ultra‐high fill factor (FF) of 84.36% is achieved in the PP‐modified device, which ranks among the best in formamidinium‐cesium (FACs) PSCs. In addition, the PP‐modified device exhibits excellent thermal stability due to the inhibited phase separation. This work provides a reliable way to improve the efficiency and stability of PSCs by releasing residual stress in perovskite films through additive engineering.