Dynamic Iodide Regeneration Enabled by Piperazine‐Tailored PCBM Interfaces for Photothermally Stable and Efficient Inverted Perovskite Photovoltaics

Abstract

Abstract Molecular iodine release under working conditions remains a major obstacle to the long‐term stability of perovskite solar cells (PSCs). Despite significant progress, developing a simple yet effective strategy to suppress this degradation pathway—while reconciling high photothermal stability and high efficiency without sacrificing charge transport—remains challenging. Here, through integrated molecular design, theoretical modeling, and experimental validation, we develop a new class of piperazine (PA)‐tailored fullerene derivative, PCBM‐PA, that uniquely exhibits dual functionality in iodine capture and dissociation. Density functional theory (DFT) calculations reveal that PCBM‐PA promotes I 2 adsorption and I─I bond cleavage at the perovskite surface, facilitating dynamic iodide regeneration. Comprehensive experiments further confirm that PCBM‐PA effectively suppresses I 2 release through robust N···I halogen‐bonding (XB) interactions, while simultaneously promoting I─I bond cleavage and restoration of iodide ions, consistent with theoretical insights. This coupled “iodine adsorption–dissociation” behavior, unprecedented among previously reported XB acceptors, enables dynamic self‐repair of iodine vacancy defects. Consequently, inverted PSCs incorporating PCBM‐PA exhibit outstanding photothermal stability, retaining over 93% of their initial efficiency after 1000 h under maximum power point tracking (MPPT) at 65 °C, together with a champion efficiency of 26.26%. This work offers a new molecular‐engineering pathway toward iodine‐resilient, high‐performance perovskite photovoltaics.