Highly stable perovskite solar cells with 0.30 voltage deficit enabled by a multi-functional asynchronous cross-linking.

The primary challenge in commercializing perovskite solar cells (PSCs) mainly stems from fragile and moisture-sensitive nature of halide perovskite materials. In this study, we propose an asynchronous cross-linking strategy. A multifunctional cross-linking initiator, divinyl sulfone (DVS), is firstly pre-embedded into perovskite precursor solutions. DVS, also as a special co-solvent, facilitates intermediate-dominated perovskite crystallization manipulation, favouring formamidine-DVS based solvate transition. Subsequently, DVS-embedded perovskite as-cast films are post-treated with a nucleophilic reagent, glycerinum, to trigger controllably three-dimensional co-polymerization. The resulting cross-linking scaffold provides enhanced water-resistance, releases residual tensile strain, and suppresses deep-level defects. We achieve a maximum efficiency over 25% (certified 24.6%) and a maximum V of 1.229 V, corresponding to mere 0.30 V deficit, reaching 97.5% of the theoretical limit, which is the highest reported in all perovskite systems. This strategy is generally applicable with enhanced efficiencies approaching 26%. All-around protection significantly improves PSC's operational longevity and thermal endurance.