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Item THE EFFECT OF CONCENTRATION AND PH OF CdC12 SOLUTION USED IN CdC12 TREATMENT ON THE PROPERTIES OF CdS THIN FILMS(Solar Asia 2018 Int. Conf. National Institute of Fundamental Studies, Kandy, Sri Lanka., 2018) Atapattu, I I.Y.R.; De Silva, D.S.M.; Pathiratne, K.A.S.; Dharmadasa, I.M.Among the post deposition treatments available for development of CdS/CdTe solar cells, CdCl2 treatment has been identified as one of the key processing steps that can be effectively used for improving power conversion efficiency of the CdS/CdTe solar cell. This method was identified in late 1970s and currently is used for the CdS layers as well. The present study focuses on the effect of the concentration and pH of the CdCl2 solution used for the CdCl2 treatment on the quality of CdS layers based on their electrical, optical and morphological properties. In this study, CdS layers were potentiostatically electrodeposited on glass/FTO substrates at cathodic deposition potential of 660 mV verses a saturated calomel electrode at pH of 1.80 for 30 minutes in electrolytic baths containing 0.10 mol/L CdCl2 and 0.01 mol/L Na2S2O3. The temperature and the stirring rate of electrolytic baths were maintained constant at 55 °C and 60 rpm respectively. After the depositions, the samples were rinsed in de-ionized water and dried under a high purity N2 gas flow and conveyed for the CdCl2 treatment. Nine sets of samples with two replicates in each were treated separately with aqueous CdCl2 solutions having concentrations of 1.0, 0.5 and 0.1 mol/L and for each concentration three different pH values; as-prepared (5.60, 6.30 and 7.10 respectively), 2.00 and 6.50 were used. To perform the treatment, CdCl2 solutions were sprayed for 1 minute on the CdS layer until the layers were fully covered by the solution, allowed to dry and the samples were transferred for the process of annealing at 400 °C for 15 minutes in air. Subsequently, samples were rinsed in de-ionized water and dried under a high purity N2 gas flow. The electrical, optical and morphological properties of the CdS layers were then studied using photo-electrochemical cell measurements, UV-Vis absorption spectroscopy and scanning electron microscopy respectively. As results revealed, the CdCl2 solution with the concentration of 1.0 mol/L and the pH of 2.00 is suitable for achieving good material properties in the CdS layers.Item Evaluation of solution parameters for CdCl2 solutions to be used in post-deposition treatments of CdTe thin films in CdS/CdTe solar cells.(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Atapattu, H. Y. R.; Silva, D. S. M. D.; Pathiratne, K. A. S.Owing to its high absorption coefficient and the near ideal band gap, CdTe has become one of the topmost solar energy materials available for conversion of solar energy into electricity. It exhibits excellent power conversion efficiencies, when coupled with the CdS window material to form CdS/CdTe heterojunction solar cells. Further, CdCl2 treatment has been identified as one of the promising post-deposition treatments available for achieving drastic improvements in the performance of CdTe material. However, no extensive investigations have yet been carried out to identify suitable solution parameters for the CdCl2 solutions used in the post-deposition treatment process. Hence, the present study was designed to investigate the effect of concentration and pH of CdCl2 solutions used for post-deposition treatments of CdTe material grown on glass/FTO/CdS surfaces. In this study, CdTe layers were potentiostatically electrodeposited on glass/FTO/CdS substrates in electrolytic baths containing 1.0 mol/L CdSO4 and 1.0 mmol/L TeO2 at pH 2.3. A cathodic deposition potential of 650 mV with respect to saturated calomel electrode and temperature of 65 °C at a continuous stirring rate of 60 rpm were maintained through the deposition. At the end of electrodeposition process, all the glass/FTO/CdS/CdTe samples were rinsed in de-ionized water and dried under a high purity nitrogen gas stream and conveyed for the CdCl2 treatment followed by air annealing at 390 °C for 15 min. For CdCl2 treatment, three different CdCl2 concentrations (1.0, 0.5 and 0.1 mol/L) were used. For each concentration, three different pHs; as prepared (5.6, 6.3 and 7.1 for 1.0, 0.5 and 0.1 mol/L CdCl2 solutions respectively), 2.0 and 6.5 at 25 °C were selected. Hence, nine sets of samples with two replicates in each were subjected to the CdCl2 treatment. Once the treatment process was over, samples were inspected for their optical, electrical and morphological properties using the techniques of optical absorption spectroscopy, photo-electrochemical cell studies and scanning electron microscopy. The results revealed that, two solutions; one with 1.0 mol/L CdCl2 solution at pH of 5.6 and the other with 0.1 mol/L CdCl2 solution at pH of 2.0 can be effectively used for the post-deposition treatment of CdTe material for improving its properties and eventually to produce power efficient CdS/CdTe based solar cells with ~80 % efficiency improvement compared to the untreated devices.