First-principles calculations of electronic band structure and optical properties of ternary semiconductors Cd4P2Cl3 and Cd4P2Br3

Abstract

By first principles DFT calculations the structural, electronic and optical properties of Cd4P2Cl3 and Cd4P2Br3 compounds, a close analogue of CdS, have been determined. Both the ternary compounds are found to be direct band gap semiconductors with band gap energy ∼2.4 eV, about 0.1 eV lower than that of CdS. The density of states calculations reveal that the valence band maxima are predominantly contributed by the P-p states and conduction band minima are mainly contributed by the Cd-s states. From the study of optical properties it is found that both the compounds have very high absorption coefficient, exceeding 104 cm−1 in the blue region of the visible spectrum. It is found that both the compounds exhibit good transmittance of light with more than 85% in a significant portion of visible spectrum. Such a value of band gap energy together with high absorption coefficient and low reflectance make these compounds suitable for various electronic and optoelectronic devices especially in heterojunction solar cell.