Study of the exciton binding energy of nanostructured CdS thin film fabricated by chemical bath deposition method

Nanomaterials can be classified into four different groups: zero-dimensional, one-dimensional, two-dimensional, and three-dimensional. Thin films used as window materials in solar cells fall into the category of two-dimensional nanomaterials. In this study, CdS, a II-VI semiconductor compound that is also used as a window material in solar cells, was produced. CdS thin films were deposited on glass substrates using the chemical bath deposition (CBD) method. The bath temperature in the CBD method was kept constant at 80℃, and the deposition process lasted a total of 80 minutes. The structural, optical, and morphological properties of the obtained CdS thin films were examined using XRD (X-ray diffraction), UV-vis (Ultraviolet-visible) spectroscopy, SEM (Scanning Electron Microscopy), respectively. Elemental analysis was performed using EDS (Energy Dispersive Spectroscopy). According to the XRD data, the CdS thin film produced by the CBD method has a cubic structure. Based on the UV-vis results, the band gap of the thin film was found to be 2.46 eV using the Tauc method. Using the Elliott-Toyozawa theory, the band gap energy was obtained to be 2.46 eV and the exciton binding energy was obtained as 4.1 meV. In this thesis, CdS thin films were produced by the CBD method, and the optical, structural, and morphological properties of the obtained thin films were examined through nanocharacterization. The low cost and easy applicability of the CBD method reduced production costs.