Sustainable Molecular Passivation via Heat-Induced Disaggregation and Redox Reactions for Inverted Perovskite Solar Cells

Abstract

Molecular materials with high structure-design freedom are used as new interface passivators to reduce nonradiative recombination in inverted perovskite solar cells (PSCs). However, most molecular modifiers are unable to achieve a long-term passivation effect due to self-aggregation. Here, the molecular modifier 1-methyl-2-thiomethyl-1H-imidazole-5-carboxylate (SMC) with ester and thiol groups is carefully developed. The ester groups weaken self-aggregation triggered by intermolecular hydrogen bonds, making such aggregations easier to disassemble during heating to form a net-like insulating layer with random openings, which dramatically increase charge transport. More importantly, the electron transfer between thiol and disulfide can accelerate the elimination of Pb₀ and I₂ by redox reactions to prevent phase separation. Ultimately, the optimized inverted PSCs with bandgaps of 1.68 and 1.55 eV showed surprising fill factors of 84.83% and 86.18%, resulting in champion efficiencies of 23.45% (certified 22.98%, which is the highest to date for wide-bandgap) and 25.71% (certified 25.28%), respectively. Remarkably, both unencapsulated devices maintained over 94% of their initial efficiency under maximum power point tracking for 600 h (50 °C) and 1000 h (65 °C), respectively, confirming impressive long-term operational stability.