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

Abstract 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) 2 Cu 2 Br 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) 2 Cu 2 Br 2 Cl 2 with broadband white‐light emission and ultrahigh CRI is obtained. Detailed studies on photophysical mechanism demonstrate that the unique 0D structure of (TEA) 2 Cu 2 Br 2 Cl 2 can produce effective emission of self‐trapped excitons (STEs), and its dual‐band emission phenomenon stems from two STE states in the [Cu 2 Br 2 Cl 2 ] 2− dimer. Moreover, the CIE coordinates of (TEA) 2 Cu 2 Br 2 Cl 2 (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.