Orange–red emissive organic–inorganic hybrid copper halide for white light-emitting diode application

Organic-inorganic hybrid copper(I)-based metal halides (OIHCMHs) have emerged as promising alternatives to lead perovskites due to their exceptional optical properties. However, the lack of low-energy light-emitting compounds prohibits their further applications. Herein, we report an orange-red emissive (C₁₉H₁₈P)₂Cu₄Br₆ with a zero-dimensional structure. The photoluminescence (PL) peak of (C₁₉H₁₈P)₂Cu₄Br₆ locates at 640 nm with a PL quantum yield of 69.3%, and the large Stokes shift is 245 nm. Experimental analyses demonstrate the bright broadband orange-red light emission derived from the synergistic effect of metal-to-ligand charge transfer or halide-to-ligand charge transfer (MLCT/HLCT) excited state and cluster-centered (CC) excited state. Furthermore, (C₁₉H₁₈P)₂Cu₄Br₆ can be used as phosphor for orange-red light-emitting didoes (LEDs), and by adding other blue- and cyan-emitting phosphors, a white LED with a high color rendering index over 94 is achieved. This work not only demonstrates material design strategies for preparing low-energy emissive OIHCMHs but also inspires the potential of low-dimensional metal halides in high quality white LED applications.