Preparation and Characterization of Cds Thin Films Grown By Chemical Bath Deposition Method for Photovoltaic Applications
International Journal for Research in Applied Science and Engineering Technology
A thin film of CdS is a semiconducting material for the use in the fabrication of hetero-junction solar cell. Chemical Bath Deposition is a simple, cheap and inexpensive method of depositing thin films of large area. CdS thin films have been deposited on the glass substrates at 70°C temperature by Chemical Bath Deposition method, using aqueous solutions of cadmium chloride, thiourea and triethanolamine. At higher deposition time period polycrystalline films are obtained with preferential
... tion along (111) plane, cubic structure is observed. As the deposition time period increases the intensity of preferential orientation also increases. The grain size increases as the deposition time period increases. The absorbance spectra, the material is found to be highly absorbant in nature. Transmittance decreases with increase in film thickness, which leads to a decrease in light scattering losses. The band gap energy determined shows an inverse dependence on film thickness Keywords: Thin Films, Chemical Bath Deposition, Grain size, Absorbance I. INTRODUCTION CdS thin film belongs to Cadmium chalcogenide family. It is an II-VI wide direct band gap (2.42 eV) semiconductor. This specific property makes it a key element for solar cell applications. Cadmium sulphide (CdS), a wide energy gap semiconductor, has appeared as an vital material due to its applications in photovoltaic cell as window layers, optical filters, multilayer light emitting diodes, fuel cells, optical coatings, photo detectors, thin film field effect transistors, gas sensors and obvious conducting semiconductor for optoelectronic devices. Among the numerous n-type semiconductor materials, it has been perceived that CdS is the most hopeful heterojunction companion for the well-known polycrystalline photovoltaic materials. CdS thin films developed on glass substrate consuming chemical bath deposition scheme have been comprehensively investigated. Many techniques for deposition of CdS thin films are such as sputtering, electro-deposition, metal oxide chemical vapor deposition (MOCVD), spray deposition chemical vapor deposition, vacuum evaporation, spray pyrolysis, pulsed laser deposition and chemical bath deposition (CBD) technique [2, 3] . Amongst the various system Chemical bath deposition is now broadly used for the elaboration of low cost polycrystalline thin film solar cells because it offers the advantages of cheap, accessibility and the proficiency of large area deposition    . The chemical bath deposition method is an economically simple method for the preparation of thin films suitable for scientific studies and for many applications in technology and industry in the research area which is fast, simple, and a low cost technique. In this work the CdS thin films can be prepared by chemical bath deposition method and their categorizations are dignified by the structural and optical properties of the films. II. EXPERIMENTAL DETAILS The deposition of CdS thin films is created on the reaction of Cd 2+ and S 2ions in deionised water solution. Chemical baths used for the deposition of CdS thin films comprise of cadmium chloride, thiourea, triethanolamine and ammonia. The pH of the solution can be adjusted by adding ammonia thin film deposition is agreed out at different temperature form 60ᵒ to 90ᵒC. Molar proportions of cadmium chloride and thiourea namely 1:1 are used. The deposition is performed at various pH values of the bath from 9 to 14. The substrates placed vertical in the bath for different deposition time varying from 30 to 120 min. It is perceived that molar concentration of 1:1 have given noble excellence films. While dumping the films at temperature 70ᵒC the surface of the film has become more uniform. While varying the pH of the bath, it is establish that the films prepared pH value 10 was even and compact. Thus deposition parameters such as temperature, concentration of ions in the bath and dipping time have been elevated.