Electrical and optical properties of In-doped SnS thin films prepared by thermal evaporation

Tin monosulfide (SnS) and indium thin films were successively deposited onto glass substrates by thermal evaporation (with indium proportion of 0 at.% to 12.49 at.%). Then the films were annealed in vacuum at 300 degrees C for 2h in order to obtain different In-doped concentration SnS (SnS: In) films. The structural, electrical and optical properties of the SnS: In thin films were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), Hall Effect Measurement System and UV/VIS/NIR Spectrometer. The result shows that the films are polycrystalline SnS with orthogonal structure, and the crystallites in the films are exclusively oriented along (111) direction. All the films are of p-type conductivity. With the indium proportion increased from 0 at% to 12.49 at%, the optical bandgaps of the films are decreased from 1.37eV to 1.12eV, and the carrier concentration of the films is increased observably, whereas their resistivity and carrier mobility are decreased straightly. In-doping with a certain quantity can improve the semiconducting properties of the films and it is possible to produce suitable SnS: In thin films as absorbers in thin film solar cells.