Top-Emitting Microcavity Light-Emitting Diodes Based on All-Thermally Evaporated Lead-Free Copper Halide Self-Trapped-Exciton Emitters

Lead-free metal halide light-emitting diodes (LEDs) based on cesium copper halide (CsCu₂I₃) self-trapped-exciton (STE) emissions show great potential in lighting and color display applications, especially because of their nontoxicity and earth abundance. However, so far, the efficiency and color purity of CsCu₂I₃-based LEDs remain low. Here we demonstrate the emission of a CsCu₂I₃ emitter can be enhanced and narrowed in a top-emitting microcavity device. Consequently, the CsCu₂I₃-based LED device with the assistance of a top-emitting microcavity has significantly narrowed and enhanced the emission spectrum with a full width at half-maximum of 59 nm and a maximum forward brightness of 14767 cd m^-2. To the best of our knowledge, this work achieves the narrowest CsCu₂I₃ LED spectra and demonstrates the potential of employing the microcavity effect to increase the efficiency and color purity of STE-based light-emitting devices.