Exploring Particular Electronic and Optical Properties of CsLnZnTe3 Compounds (Ln = Dy, Er, ho, and tb), Promising Phosphors for Solar Photovoltaics and Optoelectronics: A Theoretical Study

Abstract

Zinc telluride serves as a versatile semiconductor with a broad band gap, used in many applications. The structural and optoelectronic properties of CsDyZnTe₃, CsErZnTe₃, CsHoZnTe₃, and CsTbZnTe₃ compounds have been investigated using the full potential linear augmented plane wave (FP-LAPW) method in the framework of density functional theory (DFT). All the physical properties like band structures and optical properties were calculated using the GGA + U potential. The calculated band gaps for CsDyZnTe₃, CsErZnTe₃, CsHoZnTe₃, and CsTbZnTe₃ compounds are 1.348, 1.670, 1.342, and 1.887 eV for spin-up and 0.099, 0.122, 0.098, and 0.138 eV for spin-down states, respectively, which indicates that the investigated materials are narrow band gap materials as well as direct band gap nature. When considering applications in visible light, the wider band gap materials, such as CsErZnTe₃ and CsTbZnTe₃, hold potential for utilization in light-emitting diodes (LEDs) that emit light in the visible spectrum (blue to violet region). In addition, the density of states and optical properties such as absorption coefficient, real and imaginary parts of the dielectric function, reflectivity, energy loss function, and refractive index are also calculated. There is no absorption in the infrared region; absorption starts in the visible region and increases as energy increases and reaches a maximum in the ultraviolet region. There is very small energy loss in the visible region, so the investigated material can be used in visible light applications. The reflectivity of the investigated materials is very small, which may be due to the transparent behavior of the materials in the UV region, so these compounds can be used as transparent materials.