A comparative DFT study of different structures of ZnTe: for optoelectronic and thermoelectric applications

In the present study, a comprehensive comparative investigation of ZnTe in its zinc-blende, wurtzite, and tetragonal structural phases was performed employing density functional theory to analyze their electronic, optical, and thermoelectric properties for potential optoelectronic and thermoelectric applications. All three phases possess a direct band gap at the Γ point, with computed energy gap values of 2.1 eV (zinc-blende), 1.5 eV (wurtzite), and 1.3 eV (tetragonal), revealing their semiconductivity. The density of states study found that Zn and Te orbitals made significant contributions across the valence and conduction bands, with substantial variations in bonding interactions between these phases. Optical investigation revealed that the tetragonal phase has the highest static dielectric constant (7.65) and refractive index (2.70), while the zinc-blende phase has superior absorption properties and the highest peak in the optical conductivity spectrum at 6.3 eV, demonstrating increased photon absorption efficiency. The energy loss function also shows that the tetragonal phase has greater energy dissipation potential. The Seebeck coefficient increased with temperature in all phases, with the tetragonal structure reaching the greatest value of 115 μV K^-1 at 500 K. At high temperatures, the wurtzite phase had the maximum electrical conductivity, which can be associated with its favorable electronic band dispersion near the Fermi level. The figure of merit (ZT), an essential indicator for thermoelectric efficiency, is highest for the tetragonal phase (ZT = 0.387 at 500 K), overcoming both the wurtzite (ZT = 0.36) and zinc-blende structures. These results show that structural configuration has an essential effect on the multifunctional properties of ZnTe. The tetragonal phase is a very attractive candidate for thermoelectric applications, while the zinc-blende structure provides superior optical performance for optoelectronic devices.