Copper Mixed‐halide Hybrids with Intrinsic Broadband White‐Light Emission for WLED Application with Ultrahigh Color Rendering Index

The development of single-component white-light emissive phosphors has become a key research area in white light-emitting diode (WLED) technology. However, achieving real color reproduction with an ultrahigh color rendering index (CRI) remains challenging. Herein, a series of 0D hybrid copper halides (TEA)₂Cu₂Br_{4- x}Cl_x (TEA = tetraethylammonium, x = 0-4) crystals are designed and prepared by a facile solvothermal method. By controlling the composition ratio of Cl^- and Br^-, the emission spectra are tunable in visible light region from blue to yellow, and a single-component crystal (TEA)₂Cu₂Br₂Cl₂ with broadband white-light emission and ultrahigh CRI is obtained. Detailed studies on photophysical mechanism demonstrate that the unique 0D structure of (TEA)₂Cu₂Br₂Cl₂ can produce effective emission of self-trapped excitons (STEs), and its dual-band emission phenomenon stems from two STE states in the [Cu₂Br₂Cl₂]^2- dimer. Moreover, the CIE coordinates of (TEA)₂Cu₂Br₂Cl₂ (0.32, 0.33) are approximated to pure white light (0.33, 0.33), making it an ideal choice for natural WLED applications. A WLED device is fabricated by coating this emitter on a 310 nm UV chip, achieving an ultrahigh CRI of Ra = 95 and R9 = 90. This work provides new design principles for developing eco-friendly white-emission phosphors for single-component solid-state WLEDs.