Structural Modulation Enables Bright and Efficient Cs–Cu–Cl Electroluminescence

Cesium-copper-halide (Cs-Cu-X) perovskites are potential substitutes to lead-halide perovskites for broadband electroluminescence (EL) in white light-emitting diodes (LED) due to their non-toxicity and unique self-trapped exciton (STE) characters. Many efforts have been devoted to pushing up EL efficiencies of Cs-Cu-I LED devices, while there is no report of EL based on their Cl-based counterparts yet. In this work, the EL of the Cs-Cu-Cl nanocrystals (NCs) was first demonstrated by a holistic structural modulation, whose champion device reached an external quantum efficiency of 2.02% and a high luminance of 3345 cd m^-2. The efficient bluish-white EL was explored to collectively derive from the smooth film morphology, exciton inter-band transition, triplet STE behavior, and promising electron transport ability of the Cs-Cu-Cl NC film. Additionally, the potential photophysical process for the broadband emission was proposed, collectively expanding the Cu-based perovskite EL family for displays and lighting applications.