Dynamic Iodide Regeneration Enabled by Piperazine-Tailored PCBM Interfaces for Photothermally Stable and Efficient...

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 I₂ adsorption and I─I bond cleavage at the perovskite surface, facilitating dynamic iodide regeneration. Comprehensive experiments further confirm that PCBM-PA effectively suppresses I₂ 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.