Dual-site molecular passivation at the buried interface for high-efficiency and stable perovskite solar cells

Buried interface defects in perovskite solar cells (PSCs) critically limit the device performance and operational stability due to their role in promoting non-radiative recombination and interfacial degradation. Herein, we propose a molecular interface engineering strategy employing a bifunctional small molecule, 3,5-dimethylpyrazole-1-carboxamidin nitrate (DPN), to simultaneously modulate crystallization behavior and passivate undercoordinated Pb²⁺ ions at the buried interface. Morphological and crystallographic analyses reveal that DPN promotes large grain size, enhanced surface uniformity, and improved vertical crystal orientation. Spectroscopic characterizations confirm a dual-site coordination mechanism, where the pyrazole group acts as the primary coordination site, and the nitrate group provides auxiliary binding to Pb²⁺, collectively reducing defect densities. As a result, the DPN-modified films exhibit suppressed non-radiative recombination, extended carrier lifetimes, optimized interfacial energy alignment, and improved charge extraction. The corresponding photovoltaic devices deliver a champion power conversion efficiency (PCE) of 25.3%, along with enhanced operational and storage stability. This work demonstrates the efficacy of dual-site molecular passivation at the buried interface, offering a viable strategy for developing highly efficient and stable perovskite photovoltaics.