Cesium Copper Iodide Perovskite Nanoscale-Thick Films with Tunable Photoluminescence for White Light-Emitting Diodes

Cu-based halide perovskite derivatives (PDs) have emerged in recent years due to their low toxicity, high stability, and earth-abundant source. In particular, due to the special photophysical properties, such as broadband visible photoluminescence (PL), large Stokes shift, and high luminous efficiency, Cs–Cu–I PDs have attracted more attention in white light and short-wavelength light-emitting device applications. Here, Cs–Cu–I nanoscale-thick films with a mixed phase of CsCu₂I₃ and Cs₃Cu₂I₅ are prepared by thermal evaporation. By adjusting the proportion of the evaporation source, different phase structures and tunable PL characteristics are realized. Subsequently, with a UV light-emitting diode (310 nm) as the excitation source, standard white emission with Commission International de l’Eclairage coordinates of (0.333, 0.338) is observed when the molar ratio of CsI and CuI powders is 0.75:1. Cs–Cu–I nanoscale-thick films with excellent air stability might have promising potential applications in white lighting sources.