Structural, electronic, optical, and thermoelectric properties of beta phase spinel : prospects for solar cells application

Abstract

Using all electron based density functional theory calculations, within full potential linearized augmented plane wave plus local orbitals, electronic, structural, optical and thermoelectric properties of the β-phase spinel compound have been investigated. Tetragonal β-phase spinel indium (III) sulfide is the most stable and promising phase for various applications, in particular, photovoltaic devices, and, therefore, it can be use to replace CdS for environmental issues. The unit cell volume and atomic positions are optimized with the PBE energy functional and our calculated optical band gap for the indirect transition is in good agreement with the experimental value. The peaks of the real part of optical conductivity σ(ω) correspond to the peak of the imaginary part of dielectric function εi (ω) for the two polarization axes, which perfectly agree with the Drude theory. Charge carrier concentration are observed to attain the maximum value at about 2.8899 eV at fixed temperature, and drops at high energies, which indicates less photon excitation to the conduction bands at energies greater than 2.8899 eV. The electrical and thermal conductivity that depends on the sulfur concentration show a similar trend for variable and fixed temperature. Large amount of thermopower S occurs at low temperature, which agrees with the requirement to improve performance of photovoltaic materials, that is high voltage output at small amount of heat