Environmentally Friendly Flexible Perovskite Solar Cells with Promoted Thermal Diffusivity and Suppressed Lead Leakage

Flexible perovskite solar cells (f‐PSCs) have manifested promising applications in wearable electronics, whereas their practical deployments are seriously restricted by inhomogeneous perovskite crystallization on soft substrates, poor mechanical endurance at grain boundaries, and potential exposure of toxic lead ions. Here, durable f‐PSCs is reported by incorporating a new type of nanocomposites of polyacrylic acid grafted graphene oxide (GO‐PAA). It is revealed that the perovskite crystallization is initiated from the surface of GO‐PAA on account of their exceptionally high thermal diffusivity and strong association with perovskite components. This allows the formation of uniform perovskite crystals with suppressed lattice strain and strengthened trans‐grain interconnection. Owing to the excellent mechanical properties, the presence of GO‐PAA within the perovskite grains reduced the Young's modulus and boosted the mechanical resistance against cyclic bending of the perovskite thin films. Moreover, the incorporated nanocomposites can prevent lead leakage from the f‐PSCs because of the increased energetic barrier for water permeation and effective adsorption of leaked Pb2+ by GO‐PAA, effectively preventing environmental pollution in case of accidental damage during practical application. As a result, environmentally friendly f‐PSCs with a champion efficiency up to 24.2%, a power‐to‐weight ratio of 1.436 W g−1, and remarkable mechanical stability are ultimately achieved.