The effect of tin doping on the band structure and optical properties of polycrystalline antimony selenide

In this study, we investigated the effect of Sn-doping on the antimony selenide (Sb2Se3) polycrystalline material to alter its optical properties and electronic band structure. Sb2Se3 polycrystals were isothermally annealed at 350 °C, 400 °C, 450 °C, and 500 °C, in the presence of tin diselenide (SnSe2) in degassed quartz ampoules to introduce Tin (Sn) into the material. X-ray diffraction (XRD), Raman scattering, and energy-dispersive X-ray spectroscopy measurements confirmed the single phase of the Sb2Se3 samples. Successful doping of the surface of the Sb2Se3 polycrystals with Sn was confirmed by X-ray photoelectron spectroscopy for the samples annealed at 400 °C, 450 °C, and 500 °C in the presence of SnSe2. An ultraviolet photoelectron spectroscopy (UPS) study revealed a decrease in the work function (Ф) of the Sb2Se3 polycrystals from 4.34 eV to 3.14 eV due to Sn doping implemented at 500 °C. Moreover, a small shift of the Fermi level towards the valence band maximum (VBM) by 30 meV resulted from Sn-doping at 500 °C as was detected by UPS, indicating a slightly enhanced p-type behaviour of the surface region of the Sb2Se3 polycrystals. Ultraviolet–visible spectroscopy (UV–Vis) confirmed that Sn doping did not change the bandgap energy of Sb2Se3 polycrystals, being 1.25 eV at room temperature (RT) for the undoped as well as Sn-doped material.