Efficient emission in copper-doped Cs3ZnX5 (X = Cl, I) for white LEDs and X-ray scintillators

Abstract

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 (Cs₃Zn_1−xCu_xX_5−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 ∼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 ∼450 nm) with a maximum PLQY of 11.6% (x = 0.03). The X-ray excited luminescence (XEL) spectra of Cs₃Zn_0.97Cu_0.03Cl_4.97 and Cs₃Zn_0.97Cu_0.03I_4.97 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.