Modulate Stresses for Efficient Full-Air Processed Flexible Perovskite Solar Cells with Polymer Adhesive

With increasing demand for flexible wearable self-powered devices, flexible perovskite solar cells (FPSCs) with high photovoltaic conversion efficiency, and low-temperatures, solution-process have a promising future and attract great attention. However, flexible PSCs suffer from strain problems at both microscopic and macroscopic scales, which affect their photovoltaic performance and stability. To address this challenge, an in-situ polymerized "AB" adhesive polymer binder is developed that concurrently regulates strain distribution at both micro- and macro-scales. At the microscopic scale, the polymer creates a viscous environment that decelerates solute diffusion and retards molecular aggregation, thereby promoting the growth of high-crystalline-quality perovskite films with mitigated intrinsic strain. At the macroscopic scale, the resulting cross-linked gel-like layer reduces defects in the perovskite film and functions as a stress-dissipating layer. The low Young's modulus due to the protective layer makes the film no longer exhibit brittle properties prone to rupture, but rather viscoelastic stress dissipation through better toughness. Besides, the AB adhesive increases the interfacial adhesion energy between the perovskite film and SnO₂ layer. As a result, the PSCs achieve superior power conversion efficiencies of 23.57% and 20.32% for rigid and flexible devices, respectively. The modified flexible device retains over 90% of the initial PCE after 10,000 bending cycles. This work pioneers a dual-scale strain regulation paradigm using an adhesive polymer binder, providing valuable insights for the commercialization of durable and high-performance FPSCs in wearable electronics.