STRUCTURAL AND OPTICAL CHARACTERIZATION OF NANOCRYSTALLINE CDS THIN FILMS SYNTHESIZED BY SILAR

Abstract

Cadmium sulfide (CdS) is one of the most important II–VI semiconductor materials extensively investigated for optoelectronic devices, such as solar cells, photodetectors, and sensors. It is used particularly as a window or buffer layer for thin film photovoltaic devices due to its direct band gap, absorption in visible radiation and proper electronic properties. Successive ionic layer adsorption and reaction (SILAR) is regarded as one of the simple, low cost, low temperature and scalable chemical methods for preparation of nanocrystalline CdS thin films. The paper discusses the literature-based research of structural and optical characterization of CdS thin films prepared by SILAR technique. There are several techniques for examining structural properties, such as X-ray diffraction, scanning electron microscopy, atomic force microscopy, and energy-dispersive X-ray spectroscopy. Typically, the optical properties are studied by UV–visible spectroscopy and Tauc plot analysis. In reported work, it is found that the CdS films deposited by SILAR are generally polycrystalline, which may be cubic, hexagonal or mixed. The number of cycles, the precursor concentration, the dipping time, the rinsing time, the pH of the solution and the temperature of annealing affect their crystallite size, morphology, thickness, optical absorption and band gap. The CDs films prepared by SILAR process have been concluded as a promising technique in the production of thin films for low cost photovoltaic and optoelectronic applications.