Synergistic Ionogel Strategy for Lead Leakage Suppression and Mechanical Stability Enhancement in Flexible Perovskite Solar Cells

The combination of flexibility and superior power-to-weight performance makes flexible perovskite solar cells (FPSCs) strong candidates for next-generation photovoltaics. However, their development is constrained by challenges in perovskite crystalline quality, together with poor long-term and mechanical stability. Herein, we successfully synthesized an ionogel (IG) containing imidazolium-based ionic liquids. The IG exhibits strong interactions with perovskites, and the polymer network within the IG can significantly suppress lead leakage. The IG was incorporated into lead iodide, resulting in a porous lead iodide film structure. This structure facilitates the organic-inorganic reaction, yielding high-quality perovskite films while reducing lead iodide residues. Moreover, owing to the inherent elasticity of the IG, the Young's modulus of the perovskite film is effectively lowered. Consequently, rigid PSCs and FPSCs incorporating the IG additive demonstrated stable power conversion efficiencies of 24.37% and 22.11%, respectively. The unpackaged device maintained over 90% of its initial PCE after continuous operation at the maximum power point (MPP) under 1 sun illumination for 1200 h. Moreover, the flexible PSCs demonstrated excellent mechanical durability, retaining 84.9% of their initial PCE after 10,000 bending cycles (bending radius = 5 mm).