Improved color rendering index of Cs₃Cu₂I₅-based white light-emitting diodes via a co-doping strategy with manganese...

Lead-free cesium copper iodide (Cs₃Cu₂I₅) has attracted considerable attention to fabricate white light-emitting diodes (LEDs) due to its superior photophysical properties. Since Cs₃Cu₂I₅ merely emits blue light, white LEDs made from Cs₃Cu₂I₅ usually exhibit a low color rendering index (CRI) due to the severe lack of green to red spectral components. In this work, a heterovalent co-doping strategy with manganese (Mn²⁺) and europium (Eu³⁺) via a simple, low-cost grinding method was introduced to compensate for the spectral deficiency of Cs₃Cu₂I₅ to produce white LEDs. The structural and optical measurements confirmed the successful co-doping of Mn²⁺ and Eu³⁺ into the Cs₃Cu₂I₅ lattice, without having an apparent impact on the crystal structure of Cs₃Cu₂I₅ and the valence state of Cu⁺. Since yellow and red spectral components were supplemented by the Mn²⁺ and Eu³⁺ dopants, respectively, white LEDs that emitted nearly standard white light with CIE coordinates of (0.33, 0.35) were successfully achieved by modulating the contents of the Mn²⁺ and Eu³⁺, and the CRI was enhanced up to 84.4. Our findings verified the feasibility of the co-doping strategy with transition metals (e.g., Mn²⁺) and rare earth (e.g., Eu³⁺) into the copper-based halide Cs₃Cu₂I₅ to produce high-performance white LEDs.