In-Situ Cross-Linked Polymers for Enhanced Thermal Cycling Stability in Flexible Perovskite Solar Cells

Flexible perovskite solar cells (FPSCs) are a promising emerging photovoltaic technology, with certified power conversion efficiencies reaching 24.9 %. However, the frequent occurrence of grain fractures and interface delamination raises concerns about their ability to endure the mechanical stresses caused by temperature fluctuations. In this study, we employ an in situ polymerization molecule with extended functional end groups to preserve mechanical integrity during thermal cycling. The AMPS-DEA molecule chemically anchors to grain boundaries and cross-links neighboring grains, protecting the structure from stress accumulation. Additionally, its hydroxyl groups form bidentate chelation with SnO₂, enhancing interfacial adhesion and preventing delamination. More importantly, the relaxed residual stress provided by AMPS-DEA allows the perovskite layer to adapt to temperature changes, effectively matching adjacent layers and preventing mechanical failure. Our findings demonstrate that AMPS-DEA modification not only boosts PCE to 25.78 % in rigid PSCs and 24.54 % in flexible PSCs but also improves stability, maintaining over 95 % efficiency after 10,000 bending cycles and 200 thermal cycles.