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 (CsCu 2 I 3 ) 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 CsCu 2 I 3 -based LEDs remain low. Here we demonstrate the emission of a CsCu 2 I 3 emitter can be enhanced and narrowed in a top-emitting microcavity device. Consequently, the CsCu 2 I 3 -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 CsCu 2 I 3 LED spectra and demonstrates the potential of employing the microcavity effect to increase the efficiency and color purity of STE-based light-emitting devices.