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

Abstract 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 CsSnBr 3 PeLEDs. It is started by forming an intermediate phase through the coordination of SnBr 2 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 CsSnBr 3 films. Additionally, the use of potassium thiocyanate additives effectively enhances the photoluminescence efficiency of the CsSnBr 3 films. These efforts result in CsSnBr 3 ‐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 CsSnBr 3 ‐based PeLEDs to date. This work opens an avenue to better control the crystallization of tin‐based perovskite.