Modulating phase composition and crystallization of 2D Ruddlesden–Popper perovskite films <i>via</i> a polyvinylidene fluoride buried interface

perovskite films while promoting preferential out-of-plane orientation and enhanced crystallinity. The optimized devices with enhanced film morphology and phase purity lead to improved charge transport properties compared to the control devices fabricated directly on PEDOT:PSS. As a result, the PVDF-modified 2D RP perovskite solar cells achieve a champion power conversion efficiency of 11.03%, representing a 17.47% enhancement over reference devices without interfacial modification.