Tuning of the electronic bandgap of SnSe compound by oxygen and sulphur doping and their optical characteristics for solar cell applications

Based on the ab-initio calculations, we have investigated the electronic, optical, and thermal properties of pristine SnSe and doped with oxygen (O) and sulphur (S) at the Se-site at concentration of 3.125%. The calculated negative formation energy indicates the stability of the pristine SnSe and doped system. We find that pristine SnSe possesses a direct bandgap value of 0.90 eV having good comparable to experimental value. The doping of O and S tunes the bandgap of SnSe, which can be promising for photovoltaic devices. Further, for the technological applications of O-/S-doped SnSe, we have analyzed optical properties in terms of absorption of photon energy and polarization. Strong absorption peaks confirms the direct transition of electrons from valence band to conduction band. Moreover, the thermal properties are calculated in terms of electrical/thermal conductivities, Seebeck coefficient, and figure of merit (ZT). At room temperature the ZT values are calculated round about 0.41 for O- and S-doped SnSe, respectively. We expect that our calculated thermoelectric parameters of the O- and S-doped SnSe could pave a new route for the application in the thermoelectric devices.