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 Cs 3 Cu 2 I 5 @CsCu 2 I 3 composites films with a high color‐rendering index (CRI) have been developed for WLEDs. However, the Cs 3 Cu 2 I 5 @CsCu 2 I 3 composites generally exhibit a relatively low photoluminescence quantum yield (PLQY). Herein, a high PLQY up to 86.75% copper‐based perovskite Gua 3 Cu 2 I 5 (Gua = guanidine) films with a broadband strong yellow STEs emission centered at 544 nm is synthesized. By combining with efficient blue STEs emission Cs 3 Cu 2 I 5 component via composition engineering of Cs 3 Cu 2 I 5 @Gua 3 Cu 2 I 5 , 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 Cs 3 Cu 2 I 5 @Gua 3 Cu 2 I 5 composites film onto a UV LED chip. These findings provide a simple and effective strategy for designing highly efficient white light‐emitting diodes.