Dual Dynamic Covalent Bond Adaptive Networks for High-Performance, HTL-Free Carbon-Based Perovskite Solar Cells

Hole-transport layer-free carbon-based perovskite solar cells (HTL-free C-PSCs) have garnered significant attention in the photovoltaic field due to their low cost and excellent stability. However, further enhancing their stability and achieving sustained, effective defect passivation remain challenges. This study proposes a passivation encapsulation strategy based on in situ polymerizable additive engineering. By introducing Bis(2-furylmethyl)disulfide (BFDS) and diphenylmethane dimaleimide (DMI) into the perovskite precursor, multiple synergistic optimizations are achieved: BFDS and DMI interact strongly with PbI₂ and FAI, regulating the perovskite crystallization process; During annealing, the additives undergo in situ polymerization via Diels-Alder reactions, forming the polymer dual-dynamic covalent bond adaptive networks (DDCAN) at grain boundaries and significantly enhancing its intrinsic moisture resistance. The optimized device achieved a champion efficiency of 22.00%, ranking among the highest efficiencies for HTL-free C─PSCs. The unencapsulated device retained over 95% of its initial efficiency after 5000 h of aging in N₂ atmosphere. Notably, the dual dynamic bond network within DDCAN endows the perovskite with self-recover capability. Devices degraded under high-temperature conditions (85% of initial efficiency) recovered to 95% of their original efficiency after 30 min of annealing at 100°C. The study introduces a novel approach to constructing dynamic networks that simultaneously enhance the efficiency and stability of simplified-structure perovskite photovoltaic devices.