Chiral molecule-induced interface passivation for high-efficiency and stable perovskite solar cells

Buried interface passivation is a critical strategy to optimize the electron transport layer (ETL) and achieve high-efficiency, stable perovskite solar cells (PSCs). Here, two chiral molecules rich in benzene rings and PO groups, (R)-[1,1'-binaphthalene]-2,2'-diylbis[1,1-diphenyl-1,1'-phos] (R-BINAPO) and (S)-[1,1'-binaphthalene]-2,2'-diylbis[1,1-diphenyl-1,1'-phos] (S-BINAPO), are designed for the post-treatment of SnO₂ ETLs. The PO groups act as strong Lewis bases that coordinate with undercoordinated Sn⁴⁺ on the SnO₂ surface and Pb²⁺ on the perovskite, thereby passivating interfacial defects and suppressing non-radiative recombination. Among the two enantiomers, S-BINAPO exhibits a superior passivation effect due to its distinct electrostatic potential distribution, resulting in more effective defect passivation, enhanced carrier extraction, and reduced non-radiative recombination. As a result, hole transport layer (HTL)-free carbon-based PSC devices modified with S-BINAPO achieve a power conversion efficiency (PCE) of 16.27%, significantly surpassing control devices (12.65%). Moreover, the S-BINAPO-modified devices show exceptional environmental stability, retaining 93% of the original PCE after aging under a relative humidity of 30-40% for 1000 h.