Substitution effect by selenium and tellurium elements on electronic structures, optical and thermoelectric features of FeS2: DFT + U

Abstract

The effects of selenium and tellurium substitution on structural, electronic, optical, and thermoelectric properties of FeS2 compound are investigated using the first-principal calculations and Hubbard potential (U). The phonon dispersion of each structure is simulated to examine the feasibility of the synthesis and evaluate the relative stability. FeS2 is an indirect semiconductor with an energy gap of 1.058 eV. The electronic properties can be tuned by substituting sulfur element with chalcogenide. The outcomes suggest that the band gaps are significantly reduced from 1.058 eV to 0.215 eV after substitution. The absorption ability is improved in various wavelength ranges by exceeding 1.10-6 cm−1 for FeTe and FeSTe compounds. Other optical properties such as optical band gap, Urbach energy, and dielectric function in both (xx) and (zz) directions are studied. The thermoelectric features of the studied compounds are strengthened and weakened under the temperature effect. The thermoelectric efficiencies are close to the unity ZT ∼ 1. The findings prove that substituting is an extremely promising technique for expanding the predicted structure applications and boosting their thermoelectric devices.