Dopant-Induced Photoluminescence Emission in Zero-Dimensional Cesium Zinc Halide Phosphors

Zero-dimensional (0D) metal halides with isolated polyhedral structures have attracted attention in optoelectronic applications because of their distinctive optical properties, including strong light absorption, large Stokes shift, and tunable emission wavelength. These 0D metal halides exhibit wide structural diversity, such as Cu⁺, Sn²⁺, Zn²⁺, Mn²⁺, Sb³⁺, Ag⁺, and Ln³⁺-based metal halides. As a branch within the 0D metal halides, Zn metal halides exhibit numerous interesting characteristics, including simple synthesis, a wide bandgap, and stability of Zn²⁺ ions. The large separation between [ZnX₄]^2- polyhedra provides space that minimizes interactions between polyhedral units and allows wavelength-dependent excitation, making Zn metal halides potential host materials that can accommodate dopant ions to induce a desired emission wavelength. As a newly emerging class of nonperovskite metal halides, it is necessary to provide a review article to develop a deeper understanding of the impact of ion doping on the optical, electronic, and spectroscopic properties of Zn metal halides. Elucidation of these properties is essential for tailoring emission wavelengths, optimizing luminescence performance, and elucidating photophysical mechanisms such as self-trapped excitons (STE), energy transfer, and defect states, thereby guiding the rational design of optoelectronics materials and devices.