Inorganic modification all-inorganic Cs3Cu2I5 nanocrystals with near-unity deep-blue luminescence

Cu-based halide perovskites arouse broad interest in optoelectronics because of the low toxicity and superb optical properties. However, the uniformity of phase purity and crystallite size in Cs 3 Cu 2 I 5 nanocrystals (NCs) can hardly be controlled, restricting the material development. In this study, an efficient method is reported based on addition of an inorganic additive, MgI 2 , into the precursor solutions to improve crystallization and passivate ionic defects of Cs 3 Cu 2 I 5 NCs. This approach results in single-phase Cs 3 Cu 2 I 5 NCs of high crystalline quality that have markedly improved optical performance. The optimized synthesis of Cu-based perovskite NCs with MgI 2 produced samples that exhibited quantum yields as high as 98 % in the deep blue spectral region. The Cs 3 Cu 2 I 5 NCs also had good stability under elevated temperature, ultraviolet light, and air exposure. Light-emitting devices were manufactured based on Cs 3 Cu 2 I 5 NC powder as a phosphor, which exhibited good working stability over 6 h. This work deepens our understanding of the Cu-based perovskite materials, providing a theoretical basis for designing novel high-quality lead-free perovskites materials.