Te4+-doped zero-dimensional Cs2ZnCl4 single crystals for broadband yellow light emission

Abstract

As an all-inorganic zero-dimensional (0D) lead-free metal halide, Cs₂ZnCl₄ is a potentially excellent matrix for preparing chemically stable and environmentally friendly photoluminescent materials through an ion-doping strategy. Therefore, it is necessary to study the emission properties of every kind of doping ion in the tetrahedral coordination of Cs₂ZnCl₄. Here, for the first time, we successfully synthesized Te⁴⁺-doped Cs₂ZnCl₄ single crystals via a facile hydrothermal method. X-ray crystallography clearly reveals the strong distortion of the tetrahedral units in Cs₂ZnCl₄ caused by doping with Te⁴⁺. Broadband yellow-light emission covering the range from 450 nm to 700 nm with a large Stokes shift is observed in Cs₂ZnCl₄:Te⁴⁺ single crystals, and this is attributed to self-trapped excitons (STEs) caused by the lattice vibration of the distorted structure. It is worth mentioning that this broadband yellow phosphor can be excited by a wide range of blue light, implicitly giving it an excellent ability to adapt to multiple models of blue LED chips, thus serving as a suitable yellow phosphor that can be applied to fabricate WLEDs without the need to worry about the lack of red light.