Fabrication of High-Performance Flexible Perovskite Solar Cells Based on Composite Modification Layers

Flexible perovskite solar cells (F-PSCs) exhibit broad application prospects due to their lightweight and bendable properties. However, uneven substrates and thermal–mechanical deformation during bending hinder the growth of high-quality perovskite films. Meanwhile, stress accumulation at the interfaces of flexible devices aggravates carrier recombination, resulting in deteriorated device performance and stability. Thus, we construct a poly(methyl methacrylate) (PMMA)/[1,1′-biphenyl]-4-carboxamidine hydrochloride (BPhADCl) composite modification layer to synergistically optimize the performance of F-PSCs. Specifically, PMMA can passivate interfacial defects and buffer bending stress. BPhADCl enables the in situ formation of 2D perovskite as nucleation sites to induce the growth of high-quality films, and the formed 2D/3D perovskite heterojunction can block moisture erosion and improve device stability. The optimized F-PSC delivers a champion power conversion efficiency (PCE) of 24.33%, remarkably higher than 20.71% of the control device. After 5000 bending cycles at a bending radius of 5 mm, the device retains 83% of its initial PCE. Moreover, the unencapsulated device maintains 91% of its original efficiency after 1100 h storage under ambient conditions.