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

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 Pb2+ 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.