Tailored Additive‐Mediated Bidentate Coordination Achieves Simultaneous Efficiency‐Stability Enhancement in Inverted Perovskite Solar Cells

ABSTRACT Inverted perovskite solar cells (PSCs) garner extensive attention for improved operating stability but the power conversion efficiency (PCE) still lags behind its theoretical limit. The energetic losses responsible for this PCE deficit primarily stem from non‐radiative recombination induced by crystalline defect states in the perovskite bulk and at interfaces, coupled with inefficient carrier extraction caused by energy level mismatches across adjacent interfaces. Here, a tailored additive engineering strategy is proposed by designing a planar molecule 4‐Cyanobenzamide (4‐CBA) that features multifunctional active sites for the perovskite precursor. The dual electron‐rich moieties C═O and C≡N can strongly anchor uncoordinated Pb 2+ , thereby stabilizing the [PbI 6 ] 4− framework and alleviating internal residual strain. The enhanced ─NH 2 group, acting as both a hydrogen bond acceptor and donor, compensates for vacancy defects through interactions with FA + /I − , regulating the preferential growth of crystal planes, and reducing non‐radiative recombination. Notably, 4‐CBA with a planar structural orientation can also tune energy level matching, minimize interfacial steric hindrance, and optimize carrier transport balance. The champion PSC device based on 4‐CBA achieves a PCE of 26.25% and an exceptional fill factor ( FF ) of 85.97%.