Ultraviolet and Blue Emissions of Ce- and Eu-Doped Lead-Free Halides Cs₃ZnCl₅ for White LEDs

Due to the unique electronic structure of rare-earth elements, Ce and Eu doping has emerged as an effective strategy to induce luminescence phenomena in rare-earth doped metal halides. This study investigates the luminescent properties of zero-dimensional (0D) lead-free metal halides, Cs3–xZn1–xCexCl5 (x = 0.03–0.15) and Cs3Zn1–xEuxCl5 (x = 0.03–0.18), focusing on the effects of rare-earth doping on their optoelectronic properties. Specifically, Ce doping at Zn sites results in long-wavelength ultraviolet (UVA) emission centered at 360 nm, while Eu doping leads to high-energy blue emission centered at 445 nm. The photoluminescence lifetimes for Cs2.91Zn0.91Ce0.09Cl5 and Cs3Zn0.85Eu0.15Cl5 are 4.12 and 5.47 μs, respectively. Furthermore, Cs3Zn0.85Eu0.15Cl5 was successfully utilized as a blue phosphor to fabricate a white light-emitting diode (WLED) by combining it with red and green phosphors. The WLED achieved a correlated color temperature (CCT) of 4628 K and a color rendering index (CRI) of 79.2, demonstrating its suitability for solid-state lighting applications. The robust UVA and blue emissions, coupled with their excellent optoelectronic performance, position these materials as promising candidates for advanced optoelectronic devices.