Achieving Precise Control of Defect States and Residual Strain in Perovskite Solar Cells Using π-Conjugated Dual-Anchor Molecules

Cesium lead bromide (CsPbBr3) shows promise for high-stability perovskite solar cells (PSCs), but interface defects and residual tensile strain at the top interface limit the achievement of high efficiency and long-term stability. Here, we introduce meta-aminobenzoic acid (MABA) and para-aminobenzoic acid (PABA), π-conjugated molecules with delocalized π-electron systems. The π-conjugation enables stronger coordination between the additives and the perovskite top interface. This effectively passivates defects from uncoordinated Pb2+ ions, Cs+ ions, and Br– vacancies. Additionally, strain relaxation is enabled by the dual-anchoring geometry of the molecules. Together, defect passivation and strain relaxation enhance the efficiency and stability of PSCs. Finally, we achieved champion efficiencies of 11.02% for a CsPbBr3 PSC, 14.67% for a CsPbI2Br PSC, and 23.66% for a FA0.97Cs0.03PbI3 PSC. Long-term stability tests revealed improved humidity and heat stability, confirming the benefits of addressing both interface defects and residual strain.