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Highly efficient sky-blue light-emitting diodes based on Cu-treated halide perovskite nanocrystals

Light-emitting diodes (LEDs) based on lead halide perovskite (LHP) nanocrystals (NCs) have received plenty of attention in recent years, owing to their excellent colour purity and easily tunable emission colour. However, the efficiency of LHP NC-based LEDs generally lags behind that of polycrystalline LHP thin-film-based LEDs, especially for blue LEDs. In this work, we synthesize bromide-based LHP NCs, treat them with CuCl2 in a simple post-processing way, and apply the obtained NCs for the fabrication of sky-blue LEDs. The results of device characterization indicate a significant impact of the solvent used in the NC dispersion on the efficiency and spectral stability of the LEDs. The champion device, based on NCs with optimized ligands, results in an external quantum efficiency (EQE) of 5.02% and a luminance of 130 cd m−2 at the maximum EQE. This work provides a novel and promising way for the fabrication of highly efficient LHP NC-based blue LEDs.