Engineering a surface reconstruction cascade via synergistic halide management for high-performance perovskite photovoltaics

The efficiency and stability of perovskite solar cells (PSCs) are limited by surface defect-induced non-radiative recombination and ion migration. Herein, we propose a cascading-cooperative reconstruction strategy based on synergistic post-treatment with methylammonium chloride (MACl) and phenethylammonium iodide (PEAI), which forms a uniform passivation layer on perovskite films via a two-step solution process. Unlike conventional single-step passivation, MACl treatment induces a dissolution-recrystallization process to enlarge the grain size, while subsequent PEAI treatment further passivates grain boundary defects through ion exchange and amine coordination. The synergistic post-treatment reduces the surface trap density of perovskite to 1/3 of the control sample, with an increase in the open-circuit voltage (Voc) to 1.15 V, and a champion power conversion efficiency (PCE) of 23.24%. Besides, the device retains over 90% of its initial PCE after 720 h. This strategy, by elucidating the mechanism of constructing robust interfaces through cascading passivation, provides a new design principle for fabricating highly stable inverted PSCs.