Compressive Strain Induced With Lattice‐Matching Molecule for Efficient and Stable Perovskite Solar Cells

The tensile strain concentrated at the film surface has been demonstrated to be harmful to the photovoltaic performance and stability of perovskite solar cells (PSCs). Thus, we have employed a facile strategy of lattice‐matching chelation with a multidentate molecule, namely [3,4‐bipyridine]‐6‐carboxylic acid (BPC), to stress engineering of the wide‐bandgap Cs 0.05 FA 0.8 MA 0.15 Pb(I 0.77 Br 0.23 ) 3 perovskite films. Due to the strong anchoring effect of BPC, the tensile strain of perovskite films has been successfully transformed into compressive strain. We find that not only the high‐quality perovskite films with decreased defect density and suppressed phase segregation is obtained but also the carrier dynamics and energy alignment of PSCs are optimized. Consequently, the champion device with BPC modification achieves a high efficiency of 21.82% with an enhanced stability under various aging conditions.