Synergistic Toughening and Self-Healing Strategy for Highly Efficient and Stable Flexible Perovskite Solar Cells

Halide perovskites are qualified to meet the flexibility demands of optoelectronic field because of their merits of flexibility, lightness, and low cost. However, the intrinsic defects and deformation-induced ductile fracture in both perovskite and buried interface significantly restrict the photoelectric performance and longevity of flexible perovskite solar cells (PVSCs). Here, a dual-dynamic cross-linking network is schemed to boost the photovoltaic efficiency and mechanical stability of flexible PVSCs by incorporating natural polymerizable small molecule alpha-lipoic acid (LA). The LA therein can be autonomously ring-opening polymerized through dynamic disulfide bonds and hydrogen bonds, concurrently forming coordination bonds to interact with perovskite component. Importantly, the polymerization product can serve as efficacious passivating and toughening agents to simultaneously optimize interfacial contact, enhance perovskite crystallinity and sustain robust mechanical bendability. Subsequently, the rigid (or flexible) p-i-n device realizes a champion efficiency of 22.43% (or 19.03%) with prominent operational stability. Moreover, the dual-dynamic cross-linking network endows PVSCs with bendability and self-healing capacity, allowing the optimized devices to retain >80% efficiency after 3000 bending cycles, and subsequently restore to approximate to 95% of its initial efficiency under mild heat-treatment. This toughening and self-healing strategy provides a facile and efficient path to prolong operational lifetime of flexible device.