Influence of cycle numbers on optical parameters of nanostructured Bi2S3 thin films using SILAR method for solar cells light harvesting

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 degrees 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 degrees 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 (> 10(4) cm(-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.