Effect of the reactant concentration, bath temperature and deposition time on the properties of CdS thin film prepared by the chemical bath deposition method

Abstract

CdS thin films for window layers in CdTe solar cells were deposited by the chemical bath deposition method without stirring. The influences of the deposition parameters were studied, such as the reactant concentration, deposition temperature and time on the film properties and solar cell performances, in order to apply in the fabricating of large-area solar cells. Here, we have considered the optical, morphological and structural properties of CdS films with the variation of deposition parameters by using UV–Vis spectroscopy, scanning electron microscopy and X-ray diffraction. Optical measurements revealed that maximum transmittance was obtained for S/Cd ratio of 6. It was found that film grown at 85 °C had better transmittance and showed more compact and smooth surface by means of UV–Vis and SEM measurements. We have demonstrated the transition of cubic and hexagonal crystal phases by the variation of solution PH with NH4Cl concentration through the XRD analysis. The performance of solar cells were estimated by measuring I–V characteristics with different S/Cd ratio, the open circuit voltage and fill factor at different deposition temperature and time. We have determined the optimal parameters such as reactant concentration of CdCl2: 1 mM, (NH2)2CS: 6 mM, NH4Cl: 20 mM, NH3H2O: 1 M, PH: 10.5, bath temperature: 85 °C, deposition time: 1 h.