High Color Rendering Index White-Light Emission from UV-Driven LEDs Based on Single Luminescent Materials: Two-Dimensional Perovskites (C 6 H 5 C 2 H 4 NH 3 ) 2 PbBr x Cl 4- x .

Two-dimensional (2D) white light-emitting hybrid perovskites (WHPs) are promising active materials for the single-component white light-emitting diodes (WLEDs) driven by UV. However, the reported WHPs exhibit low quantum yields (≤9 %) and low color rendering index (CRI) values less than 85, which does not satisfy the demand of solid-state lighting applications. In this work, we report a series of mixed-halide 2D layered WHPs (C6H5C2H4NH3)2PbBrxCl4-x (0＜x＜4) obtained from the phenethylammonium cation. Unlike the reported WHPs including (C6H5C2H4NH3)2PbCl4, the mixed-halide perovskites display morphology-dependent white emission for the different extent of self-absorption. Additionally, the amount of Br imposes huge influence on the photophysical properties of the mixed-halide WHPs. With the increasing content of Br, the quantum yields of the WHPs increase gradually from 0.2 % to 16.9%, accompanied by tunable color temperature ranging from 4000 K ("warm" white light) to 7000 K ("cold" white light). When applied in the WLEDs, the mixed-halide perovskite powders exhibit tunable white electroluminescent emission with very high CRI of 87-91.