Influence of Cycle Numbers on Optical Parameters of Nanostructured Bi 2S 3 Thin Films Using SILAR Method for Solar Cells Light Harvesting

Abstract

Bismuth Sulfide has attracted much interest as a semiconductor material for solar cell applications. Here we report the synthesis of Bi₂S₃, thin films through an economical and simply modified successive ionic layer adsorption and reaction (SILAR) method, with the use of 2-methoxyethanol C₃H₈O₂ as a complexing agent and with post- annealing of the thin films at 200 °C under inert Ar-atmosphere. The influence of the number SILAR cycles (N = 30, 40 and 50 cycles) on structural, morphological, and optical properties of the synthesized Bi₂S₃ thin films onto a glass substrate was investigated. The samples have been characterized using various techniques: X-ray diffraction, Raman spectroscopy, Scanning Electron Microscopy (SEM), EDS, and UV-vis spectrophotometry. The XRD spectra showed that the as-deposited thin films consisted of an amorphous structure, which justifies the annealing step under an inert argon atmosphere (Ar-200°C). All the annealed layers suit well with the orthorhombic polycrystalline structure , and showed an improvement in the crystallinity with N-SILAR cycles. Raman spectroscopy confirms the XRD findings. Thin films show a high absorption coefficient (> 10⁶cm^-1) in the visible range and the calculated band gap energy value, which strongly depends on cycles’ number, was in the range of 1.8-1.5 eV.