Defect Passivation via a Bidentate Anchoring Molecule Enables Efficient and Stable Perovskite Solar Cells.

The cation and anion defects at the perovskite interfaces, such as undercoordinated Pb and undercoordinated I, severely limit the long-term stability and efficiency potential of the devices. The dual-functional passivation group -NH in the 4-3-amino-1,2,4-triazole (4-HTAZ) molecule, and the pyridinic- and pyrrolic- groups in its triazole ring could be bidentately anchored at the cationic (undercoordinated Pb) and anionic (undercoordinated I) defects on the surface of the perovskite film. The bidentate passivation of 4-HTAZ optimizes the energy level alignment between the perovskite and hole transport layer in perovskite solar cells (PSCs), promotes charge extraction and inhibits interfacial recombination. More importantly, the stable passivation and inherent hydrophobicity of 4-HTAZ form a dense barrier on the perovskite surface, effectively enhancing device stability against moisture and thermal stress. Following 4-HTAZ passivation, the PSCs exhibited a champion power conversion efficiency (PCE) of 25.12%, while retaining 92.7% of the initial efficiency after 500 h of continuous light exposure and maximum power point tracking. This passivation strategy significantly improved both the performance and stability of PSCs.