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Item Fabrication of CdS/CdTe Thin Film Solar Cells via the Technique of Electrodeposition(Development of Solar Power Generation and Energy Harvesting, 2018) Atapattu, H.Y.R.; De Silva, D.S.M.; Ojo, A.A.; Dharmadasa, I.M.This study focused on fabrication of CdS/CdTe solar cells using the technique of electrodeposition as it is simple, low cost and scalable method. Initially, CdS and CdTe materials were individually deposited on fluorine doped tin oxide (FTO) glass substrates and optimum growth conditions were obtained by analyzing their structural, compositional, electrical, optical and morphological properties using the techniques of X-ray diffraction, Energy Dispersive X-ray spectroscopy, photo-electrochemical cell study, optical absorption spectroscopy and scanning electron microscopy respectively. Thereafter, final device structure ofglass/FTO/CdS/CdTe/Au was fabricated using the optimum growth conditions obtained for the two materials, CdS and CdTe. Finally the current density-voltage characteristics of the devices were obtained to assess devices. The best device structure exhibited short circuit current density (L) of 24.4 mA cm- 2, open circuit voltage (V) of 681.9 mV, Fill Factor (FF) of 0.32 and conversion efficiency of 5.4 per cent.Item An investigation into the effect of rate of stirring of bath electrolyte on the properties of electrodeposited CdTe thin film semiconductors(2018) Atapattu, H.Y.R.; De Silva, D.S.M.; Pathirane, K.A.S.; Dharmadasa, I.M.Electrodeposition (ED) has been recognized as a low cost and scalable technique available for fabrication of CdS/CdTe solar cells. Photovoltaic activity of these electrodeposited semiconductor materials drastically depends on the ED growth parameters namely; electrodeposition potential, concentrations and ratios of concentrations of precursors used to prepare the bath electrolyte, pH of the electrolyte, deposition temperature and rate of stirring of the electrolyte, In order to grow thin films with good photovoltaic properties, it is essential to maintain these variables at their optimum ranges of values during electpcKlepositions. Hence, this study was conducted to investigate the dependence of the properties of electrodeposited CdTe thin film material on the rate of stirring of the bath electrolyte. The CdTe material was grown on glassfFTO (2 x3 cm2) and glassIFTO/CclS (2 x 3 cm2) surfaces in bath electrolytes containing 1.0 motIL Cd504 and 1.0 mmolit TeO, solutions at differ¬ent rates of stirring within the range of 0-350 rpm while keeping the values of pH of the electrolyte, deposition temperature and cathodic deposition potential with respect to the saturated calomel electrode at 2.3, 65 0and 650 mV respectively. After the heat treatment at 400 c'C in air atmosphere, the deposited samples with a good visual appearance were selected and evaluated based on their morphological, elemental, structural, optical and electrical properties in order to identify the optimum range of rate of stirring for electrodeposition of CdTe thin film semiconductors. Results revealed that, rates of stirring in the range of 60-85 rpm in a 100 mG volume of electrolyte containing the substrate and the counter electrodes in the center of the bath with a separation of 2.0 cm between them can ekctrodeposit CdTe layers exhibiting required levels of morphological, structural, optical and electrical properties on both glass/FTO and glasslFTO/CdS surfaces.Item Necessity and relevance of precipitate free clear electrolytes for electrodeposition of CdS semiconductor materials with enhanced photovoltaic properties(. Journal of Materials Science: Materials in Electronics, 2018) Atapattu, H.Y.R.; De Silva, D.S.M.; Pathirane, K.A.S.; Olusola, O.I.; Dharmadasa, I.M.Cadmium sulfide (CdS) is a well-known window material used for fabrication of second generation thin film solar cells including CdS/CdTe and CdS/CuInGaSe2. Among the CdS fabrication techniques, electrodeposition is a simple, cost effective and scalable method that has been stepped towards large scale commercialization. However, the presence of precipitates in baths used for electrodeposition of CdS has been found to be a persistent problem which had produced CdS thin films with poor photovoltaic properties. Hence, an investigation was carried out to identify a set of optimum physiochemical conditions that can produce clear stable electrolyte for electrodeposition of CdS thin film semiconductors using CdCl2 and Na2S2O3 precursor salts. The study revealed that, electrolytes containing 0.10 mol/L CdCl2 and 0.01 mol/L Na2S2O3, within the pH range of 1.50-2.00 and the temperature range of 55-65 ºC can provide clear and stable electrolytes for electrodeposition of CdS thin films. Further, the results showed that, the electrical, optical, morphological and structural properties of CdS layers electrodeposited from electrolytes within above physiochemical conditions were remarkably better to those electrodeposited from the turbid electrolytic baths formed beyond the ranges of predetermined optimum physiochemical conditions.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 Is it possible to grow stable p-type CdS layers suitable for fabrication of electronic devices?(University of Malaya, Malaysia, 2013) Kiriarachchi, H.D.; Lamahewage, L.H.S.N.S.; Wickramasinghe, W.A.S.; de Silva, D.S.M.; Pathiratne, K.A.S.; Dharmadasa, I.M.CdS is a technologically important wide bandgap window material with some unique properties showing highest conversion efficiencies in thin film solar cells based on CdTe and CuInGaSe2 absorber materials. n-CdS/CdTe and n-CdS/CuInGaSe2 hetero-interfaces based solar cells have demonstrated 18.7% and 20.3% lab-scale solar cell efficiencies to date. Both these devices are fabricated based on n-type CdS window material. Recent work on graded bandgap devices using p-type AlGaAs window materials experimentally demonstrated highest Voc values of 1175 mV together with highest possible FF values ~0.85, and therefore if p-CdS can be grown, it provides another route to improve solar cell efficiencies and open doors for many other electronic devices. There are several attempts to grow Cu-doped p-CdS in the literature but the follow-up research work or devices based on p-CdS are scarce. In this research programme of solar energy materials development, using electrochemical growth method, p-type CdS was observed for certain layers. However, the stability of p-type CdS is found to be weak and these results are presented and discussed in this paper.