Bright and Efficient CsSnBr₃ Light-Emitting Diodes Enabled by Interfacial Reaction-Assisted Crystallization

Tin-based perovskites are more environmentally friendly than their lead-based alternatives. Perovskite light-emitting diodes (PeLEDs) using iodide-based tin perovskites have achieved considerable advancements in efficiency. However, PeLEDs using bromide-based tin perovskites have not progressed as rapidly, primarily due to challenges in controlling their crystallization processes. Here, an interfacial reaction-assisted crystallization method is introduced to achieve bright and efficient CsSnBr₃ PeLEDs. It is started by forming an intermediate phase through the coordination of SnBr₂ with ethylenediamine derivatives. Subsequently, a protonation reaction is designed between the intermediate phase and the acidic polyethylenedioxythiophene: poly(styrene sulfonate) hole-transport layer to generate high-quality CsSnBr₃ films. Additionally, the use of potassium thiocyanate additives effectively enhances the photoluminescence efficiency of the CsSnBr₃ films. These efforts result in CsSnBr₃-based PeLEDs achieving a maximum luminance of 787 cd m^-2 and a peak external quantum efficiency of 0.91%, demonstrating the most efficient and brightest CsSnBr₃-based PeLEDs to date. This work opens an avenue to better control the crystallization of tin-based perovskite.