Spontaneous Hybrid Cross-Linked Network Induced by Multifunctional Copolymer toward Mechanically Resilient Perovskite Solar Cells

Mechanically resilient optoelectronic devices are relevant for a wide range of applications, including portable and wearable devices. Perovskite thin film-based devices are a suitable choice for designing such resilient systems as it demonstrates high performance while preserving moderate mechanical compliance. Yet its mechanical property can be improved further by integrating the energy dissipation system and self-healing ability into the thin film. Copolymers containing Lewis-base functional groups, elastomer chains, and cyclic linkages are synthesized and introduced into the perovskite precursor. The polymers impart multifunctional effect of controlled crystal growth, defect passivation, protection against moisture, mechanical energy dissipation, and self-recoverability. The polymer-added perovskite solar cells are shown to provide a power conversion efficiency of 23.25% (a steady-state efficiency of 22.61%), due to the strong coordinative covalent interaction between the polymer and the perovskite. An operational lifetime of solar cells under harsh conditions is also substantially extended by the polymer incorporation. Furthermore, the interchain hydrogen-bond strength controlled by the cyclic linkage, and hybrid cross-linked network formed within the thin film significantly improves the mechanical stability and self-recoverability of the thin film. As a result, the devices demonstrate robustness under 2000 cyclic flex tests at a bending radius of 1 mm.