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Influence of Temperature on Evolution of Properties of Ammonia-Free Chemical Bath Deposited CdS Thin Films
I. Gupta, B.C. Mohanty
Chemical Bath Deposition, Morphology, CdS Thin Films, Crystal structure
Perovskites, other Non-Silicon-Based Photovoltaics and Multi-Junction Devices
Subtopic: CI(G)S, CdTe and Related Thin Film Solar Cells
Event: 36th European Photovoltaic Solar Energy Conference and Exhibition
Session: 3BV.1.60
704 - 707
ISBN: 3-936338-60-4
Paper DOI: 10.4229/EUPVSEC20192019-3BV.1.60
0,00 EUR
Document(s): paper


CdS thin films of varying thicknesses were grown by an ammonia-free chemical bath deposition technique onto well-cleaned glass substrates at various temperatures ranging from 40 to 80 °C. The bath temperature dependence of phase development, evolution of surface microstructure and roughness, and optical properties of the films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-visible transmittance. The precursor solution contained an appropriate molar mixture of separately prepared solutions of anhydrous cadmium chloride, thiourea, sodium tri-citrate and potassium hydroxide. After deposition for specified duration, the samples were removed from the bath solution and were rinsed well in deionised water followed by drying in air. The analysis of the XRD patterns of the films indicated the growth of single phase CdS suggesting that a post-deposition annealing, which has been routinely reported, was not necessary. For a given deposition time, the change in bath temperature yielded films of better crystallinity characterized by sharper XRD peaks. The changes in the morphology and optical properties of the films were correspondingly observed. The transmittance data analysis showed that the transmittance and the optical band gap are affected by both bath temperature and deposition time. A direct band gap ranging from about 2.0 to 2.5 eV was deduced. The changes in the film properties are discussed in terms of the temperature driven growth mechanisms of the films on the substrates inside the solution.