Precursor Tailoring Enables Alkylammonium Tin Halide Perovskite Phosphors for Solid‐State Lighting

Broadband emission with a large Stokes shift is of interest for applications in solid-state lighting. Such emission is often achieved with self-trapped excitons; however, in reduced-dimensional perovskites, high-performance self-trapped emission has, until now, been widely observed only in lead-based materials. Here, the synthesis in an air ambient of reduced-dimensional Sn-based perovskite phosphors R2 + xSnI4 + (x) [R = octylammonium (OTA), hexylammonium (HA) or butylammonium (BA)] is reported, an advance achieved by tailoring the synthesis of the Ruddlesden-Popper 2D perovskites R2SnI4. The lead-free R2 + xSnI4 + (x) phosphors have broadband self-trapped emission with over 80% photoluminescence quantum yield (PLQY) and more than a 150 nm Stokes shift. White-light-emitting diodes (WLEDs) based on OTA(2 +) xSnI4 + (x) phosphors exhibit warm-white emission (correlated color temperature = 2654K) suited to home lighting, and a CRI of 92, among the best for Pb-free perovskite WLEDs reported to date.