Efficient Emission in Copper-Doped Cs3ZnX5 (X = Cl, I) for White LEDs and X-ray Scintillators

Recently, zinc halides have attracted much attention as a new lead-free family with superior optoelectronic properties. In this work, we studied the copper-doped Cs3ZnX5 (X = Cl, I) series (Cs3Zn1-xCuxX5-x (x = 0-0.15)) which crystallize in zero-dimensional (0D) structures with isolated [ZnX4](2-) tetrahedrons and Cs+ cations. Under ultraviolet (UV) light irradiation, for the Cu-doped Cs3ZnCl5, the as-synthesized samples show green emission (centered at & SIM;480 nm) with a maximum near-unity photoluminescence quantum yield (PLQY) of 90.2% (x = 0.03), while for the Cu-doped Cs3ZnI5, they exhibit blue light (centered at & SIM;450 nm) with a maximum PLQY of 11.6% (x = 0.03). The X-ray excited luminescence (XEL) spectra of Cs3Zn0.97Cu0.03Cl4.97 and Cs3Zn0.97Cu0.03I4.97 show that they have fast scintillation with green and blue lights under a X-ray source, which suggests they could be further used for high-resolution X-ray imaging. By encapsulating the as-synthesized materials with a commercial red phosphor, a UV-chip white light-emitting diode (WLED) was successfully fabricated with the performance of high color rendering index (CRI, Ra = 92.7) and low correlated color temperature (CCT, 4236 K). This work suggests that zinc halides are also an interesting lead-free family with superior photoluminescence properties, expanding the research of lead-free halides for optoelectronic applications.