Macromonomer crosslinking polymerized scaffolds for mechanically robust and flexible perovskite solar cells

The in situ polymerization controlled growth of perovskites has been demonstrated as a general strategy to effectively repair grain boundary defects. However, the highly active, volatile, and brittle cross-linked scaffolds of small molecular monomers simultaneously limit the efficiency and mechanical endurance of perovskite solar cells (PSCs). Here, we first adopt macromonomer poly(ethylene glycol)dimethacrylate (PEGDMA) to achieve an effective in situ cross-linking polymerization for flexible PSCs. PEGDMA can chemically anchor at the grain boundaries during thermal annealing of perovskite films, thus effectively regulating the crystallization and reducing grain boundary defects. In addition, the in situ cross-linking of PEGDMA can limit the thermal expansion of perovskites during thermal annealing, which releases the residual strain to enhance the mechanical stability of the perovskite film. Overall, the power conversion efficiency (PCE) of the rigid and flexible PSCs with PEGDMA reaches 23.15% and 21.41%, respectively, retaining over 90% of the initial PCE after 3500 h of storage in a glove box. Furthermore, the efficiency retention of the PSCs is maintained at more than 86% after 5000 bending cycles (bending radius: 5 mm), which is of great significance for the practical application of PSCs in portable and wearable electronics.