Film Thickness Effects on Morphology, Optical and Structural Properties of Chemical Bath Deposition Grown CdS Thin Films for Solar Cell Applications

Abstract

CdS thin films of varying thickness were deposited on the glass substrate by chemical bath deposition (CBD) using Cadmium Chloride (CdCl2) and Thiourea ((NH2)2CS) as Cd and S sources respectively with ammonia as a complexing agent. The synthesized CdS thin films have been characterized using X-ray diffractometer (XRD), Raman spectroscopy, UV-Vis-NIR spectrophotometer, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Energy dispersion X-ray analysis (EDAX). From XRD analysis it is inferred that the obtained CdS films have highly orientated hexagonal structure with the preferential orientation along (002) plane. The optical characterization raveled that the films are highly transparent (60%–80%) in the visible region. From TEM analysis it has been observed that the inter planner spacing for CdS thin film is ∼0.31 nm and average crystallite size is 7–8 nm. The EDAX data revealed nearly stoichiometric characteristics of the CdS thin films. The SEM analysis showed that CdS thin films are smooth, homogeneous and uniform without cracks with randomly oriented spherical nanocrystallites. The CdS thin films have very high transmission in the range 600–1200 nm with the band gap >2.54 eV. The purpose of the present study is to develop window/buffer layer for CZTS solar cells.