High‐Performance White Emission from Cu‐Based Perovskite Compound

Abstract The white emissions based on lead‐free perovskites with broadband emission due to self‐trapped excitons (STEs) are considered as an ideal candidate for next‐generation white light‐emitting diodes (WLEDs). Recently, copper‐based halide perovskites Cs₃Cu₂I₅@CsCu₂I₃ composites films with a high color‐rendering index (CRI) have been developed for WLEDs. However, the Cs₃Cu₂I₅@CsCu₂I₃ composites generally exhibit a relatively low photoluminescence quantum yield (PLQY). Herein, a high PLQY up to 86.75% copper‐based perovskite Gua₃Cu₂I₅ (Gua = guanidine) films with a broadband strong yellow STEs emission centered at 544 nm is synthesized. By combining with efficient blue STEs emission Cs₃Cu₂I₅ component via composition engineering of Cs₃Cu₂I₅@Gua₃Cu₂I₅, a high PLQY of up to 96.1% is achieved on the white emission composites films. Moreover, a high CRI of 93 WLEDs is achieved by integrating Cs₃Cu₂I₅@Gua₃Cu₂I₅ composites film onto a UV LED chip. These findings provide a simple and effective strategy for designing highly efficient white light‐emitting diodes.