The electronic structure of sulvanite structured semiconductors Cu3MCh4 (M = V, Nb, Ta; Ch = S, Se, Te): prospects for optoelectronic applications

Abstract

The electronic structure of a family of ternary copper chalcogenide systems Cu₃MCh₄ (M = V, Nb, Ta; Ch = S, Se, Te) has been explored to ascertain the compounds' potential for optoelectronic device applications. The lattice parameters, density of states, band gap, optical absorption, and effective mass of each of the nine systems were determined with PBEsol+U, and a valence band alignment was performed to assess the doping limits of the series. The calculated optical band gaps of the materials range from 1.19 eV for Cu₃VTe₄ to 2.60 eV for Cu₃TaS₄, with the former also predicted to have the highest valence band maximum and the lowest hole effective mass of the series, indicative of a p-type material with photovoltaic potential. The wide range of band gap energies predicted in this series of isostructural materials evidences how selective combination of elements in ternary systems can be used to tune electronic properties through alloying and thus target ideal values for specific applications. Five materials in the series are predicted to have optical band gaps suitable for solar cell absorbers, with Cu₃NbTe₄ and Cu₃TaTe₄ being of particular interest due not only to their respective band gaps of 1.46 eV and 1.69 eV but also their potential to be alloyed based on their similar lattice constants and valence band energies.