Stress Release via Thermodynamic Regulation towards Efficient Flexible Perovskite Solar Cells

Abstract

Flexible perovskite solar cells (f-PSCs) have garnered increasing research interest owing to their high power-to-weight ratio and ability to integrate into buildings. However, the mismatch of the thermal expansion coefficient between the perovskite film and substrate will result in strain in the perovskite layer, which significantly impairs the photovoltaic and mechanical performance of f-PSCs. Herein, a thermodynamic regulation strategy was proposed to release the stress of perovskite film, realizing highly efficient f-PSCs with excellent flexibility. Camphor exhibits a strong affinity with Pb2+ or FA+ due to the strong electronegativity of the carbonyl functional group. During annealing, the sublimation of camphor exerts a force on the compressed lattice, driving the transformation of the distorted [PbI6]4− into a symmetry arrangement. Furthermore, the camphor-modified perovskite film exhibits lower defect state density, and the obtained f-PSCs achieved a power conversion efficiency of 24.48%, which exhibited outstanding mechanical and operational stability.