Corrections of band gaps and optical spectra of N-doped Sb2Se3 from G0W0 and BSE calculations

Abstract

Nitrogen (N) doped Sb2Se3 semiconductor material shows potential as promising candidate for solar cell application. However, accurate calculations of its basic physical properties have been lacking. In this paper, G0W0 band gap and absorption spectrum of N-doped Sb2Se3 were studied theoretically using G0W0 approximation in combination with Bethe-Salpeter Equation (BSE), which consider the effects of electron-electron (e-e) and electron-hole (e-h) interactions. These methods are chosen and converged carefully in order to yield quantitative results in agreement with experimental data. Our band structure results revealed that apart from a rigid shift of the conduction bands in the G0W0 approach the qualitative features with that obtained within bare DFT are identical. The calculated bandgap values for Sb15N1Se24, Sb14N2Se24, Sb16Se23N1 and Sb16Se22N2 with G0W0 approximation were found to be 1.02, 0.82, 0.92 and 0.81 eV, respectively. These results showed that the bandgap values reduced by substituting N atom at Se and Sb sites in comparison to the undoped Sb2Se3. Reduction of bandgap values by substituting N atoms at Sb and Se sites are in good agreement with previous works. In the BSE calculations, inclusion of e-e and e-h interactions lead to the existence of strong exciton below the G0W0 optical band gap. The value of optical gaps which corresponding to the first peak in the BSE calculations were found to be 0.89, 0.76, 0.86 and 0.76 eV for Sb15N1Se24, Sb14N2Se24, Sb16Se23N1and Sb16Se22N2 respectively. Our theoretical study of N-doped Sb2Se3 suggests that a device fabricated from this materials can be operated on a wide range of the energy scale such as solar cell and broadband photodetector.