Enhanced grain growth and improved optical properties of the Sn doped thin films of Sb2S3 orthorhombic phase

The applications of newer Sb₂S₃ material as a suitable absorber material for the solar cells have been effected by the toxicity of Sb. The present study is an effort to synthesize lower Sb contents Sn doped Sb₂S₃ materials by retaining or improving the morphological and optical properties. SnCl₂ and SbCl₃ are used respectively as Sn and Sb sources, while Na₂S₂O₃ has been used as a source of S in chemical bath deposition method. Bath temperature was maintained at 10 °C and the deposition time was 4 h and the annealing of the films in vacuum was done for 2 h at 250 °C. X-ray diffraction, Rutherford backscattering spectroscopy, scanning electron microscopy and ultraviolet/visible light spectroscopy have been used for the study of structural, morphological and the optical properties. The chemical composition determined from RBS is Sn_0.11Sb₂S₃. Phase analysis confirms the orthorhombic Sb₂S₃ phase with b and c axis as the preferred ones for the impurity Sn atoms. Grain growth at lower deposition temperature is enhanced on the account of doping. Nanosized spherical particles are seen in the optical micrographs. Annealing lowers the band gap, the values being 1.50 and 1.31 eV for the unannealed and the annealed samples respectively.