Modification of the optoelectronic properties of reactively evaporated In6Se7 thin films by Sn doping for photovoltaic applications

Abstract

Sn doped In6Se7 thin films with 5 wt% and 10 wt% Sn are prepared on glass substrate using reactive evaporation technique. The samples are characterized by XRD, FESEM, XPS and UV–Vis–NIR Spectrophotometer. XRD result shows that the samples are polycrystalline with monoclinic structure. Presence of compressive strain and lattice space shrinkage is observed in 10 wt% Sn doped sample. A detailed study of the optical properties demonstrated that a blue shift of 0.02 eV in the optical band gap of 5 wt% Sn doped sample is due to Burstein–Moss effect. Band gap narrowing in 10 wt% Sn doped sample is explained in terms of defect induced static disorder. 5 wt% Sn doped sample exhibits lowest resistivity and improved photoconductivity compared to undoped sample. This enhancement in optoelectronic properties facilitates the use of such films in photovoltaic applications.