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 copperhalide (CsCu2I3) self-trapped-exciton (STE) emissions show great potential in lighting andcolor 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 wedemonstrate the emission of a CsCu2I3emitter can be enhanced and narrowed in a top-emitting microcavity device. Consequently, the CsCu2I3-based LED device with the assistanceof a top-emitting microcavity has significantly narrowed and enhanced the emission spectrumwith a full width at half-maximum of 59 nm and a maximum forward brightness of 14767 cdm-2. To the best of our knowledge, this work achieves the narrowest CsCu2I3LED spectra anddemonstrates the potential of employing the microcavity effect to increase the efficiency andcolor purity of STE-based light-emitting devices.