Mg²⁺‐Doped Cesium Copper Halide for Bright Electroluminescent White Light‐Emitting Diodes

Abstract Lead‐based perovskite nanocrystals (NCs) as one of the most promising materials in the fields of display and lighting, have outstanding optical performance and simple solution preparation process. However, the toxicity of lead and poor stability limit their commercialization. Meanwhile, as a key component of display and lighting, white light‐emitting diodes (WLEDs) still faces challenges such as low luminance and complex preparation process. A method is proposed for preparing nontoxic and stable Cs₃Cu₂I₅ NCs by doping Mg²⁺ ions, achieved broadband blue light emission with a high PLQY of 96.2% and excellent thermal cycling stability and air stability. Then, the Mg²⁺ ions doped Cs₃Cu₂I₅ NCs are used as emissive layer, while the 1,3,5‐Tri (m‐pyridine‐3‐ylphenyl) benzene (TmPyPb) is selected as electron transport layer to interact with Cs₃Cu₂I₅ thin films for the formation of Cu‐I complex with broadband yellow light emission. This approach obviated the need for multi‐layer sedimentary emission layers, resulting in WLEDs featuring a high color rendering index (CRI) of 91, a peak external quantum efficiency (EQE) of 0.71% and maximum luminance of 2116 cd m⁻² that is the highest values of lead‐free perovskite WLEDs at present. Therefore, Cs₃Cu₂I₅ NCs have good application prospects in WLEDs.