Effect of Intrinsic Defects on Electrical and Optical Properties of CdS Thin Films Deposited by Chemical Bath Deposition

CdS thin films were deposited on soda-lime glass (SLG) substrates by chemical bath deposition (CBD). Effects of intrinsic defects on electrical and optical properties of CdS thin films deposited at various concentration of CdSO4 in solution were systemically investigated. Photoluminescence (PL), UV-Visible spectrophotometer and Hall-effect system were used to study intrinsic defects, optical and electrical properties of CdS thin films. Two intrinsic defects (Cd-i and V-S) were found to be existed in CdS films using photoluminescence (PL), and these defects are donor defects. It is found that the intrinsic defects (V-S) decrease with the reduction of CdSO4 concentration. The variation of the intrinsic defects results in the shifts of transmittance and conductivity. According to the related equations of transmittance, it is indicated that the transmittance is inversely proportional to conductivity of semiconductor materials. Therefore, the decrease of donor defects (V-S) results in the reduction of conductivity and significant increase of the transmittance of CdS thin films, well supporting our experimental results.