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

In this study, we proposed an asynchronous cross-linking strategy, in which a multifunctional cross-linking initiator, divinyl sulfone (DVS), was firstly pre-embedded into perovskite precursor solutions. DVS, as a unique co-solvent, facilitated intermediate-dominated perovskite crystallization manipulation, favouring a formamidine-DVS based solvate transition, which is completely different from the standard dimethylsulfoxide based solvent system. Subsequently, the as-cast DVS-embedded perovskite films were post-treated with a nucleophilic reagent, glycerinum, to trigger controllably three-dimensional co-polymerization. The resulting cross-linking scaffold provided superior water-resistance, released residual tensile strain near perovskite surface, and suppress deep-level defects. We achieved a maximum power conversion efficiency (PCE) over 25% (certified 24.6%) and a maximum VOC of 1.229 V, corresponding to a 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 PCEs approaching 26%. All-around protection significantly improved PSC’s operational longevity.