Tuning Optical Properties of Lead-Free 2D Tin-Based Perovskites with Carbon Chain Spacers

We prepare a series of two-dimensional (2D) tin-based perovskite (RNH2)2SnBr4 with different carbon chains. All of them have extra-large Stokes shifts, broad emission, and ultralong PL lifetimes. The PLQYs of (C8H17NH2)2SnBr4 and (OAm)2SnBr4 powders reach up to 54 and 60%, respectively. Density functional theory calculations and experimental results reveal that the properties of 2D Sn-based perovskites may originate from self-trapped excitons, which result from excited-state structural deformation. The results show that the [SnBr6]4– octahedron distorted by the carbon chain with arrangement distortion changes the photophysical properties of 2D tin-based perovskite. Furthermore, (OAm)2SnBr4 powders are used to engineer UV pumped light-emitting diodes. This work provides new strategies for the preparation of environmentally friendly perovskite materials.