International Research Symposium on Pure and Applied Sciences (IRSPAS)
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Item Fabrication of natural dye sensitized solar cells with eastern black nightshade extract.(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Kulathilaka, D. S. V.; Wanninayake, W. T. M. A. P. K.; Jayathilaka, K. M. D. C.; Wijesundera, R. P.Energy crisis is one of the biggest challenges for the humans in the world today. Considerable efforts have put by many researchers to tackle this issue. Solar cells represent critical role for extracting energy from the sun which is the most promising natural energy source. The dye-sensitized solar cells (DSSCs) have attracted much attention owing to their simple structure, transparency, flexibility, low production cost, and wide range of application. The function and structure of the dye-sensitized solar cells are based on the sensitization of the wide band gap semiconducting materials which are arranged as a sandwich-liked structure that consists of a photo-sensitized semiconductor formed between an anode and a cathode (an electrolyte). The essential sensitization of wide bandgap semiconductor electrodes is achieved by incorporating dye molecules in its structure. In this study, we focused on the Eastern black nightshade (Solanum ptycanthum) natural dye as the sensitizer of TiO2 photoelectrode. The power conversion efficiency of the Eastern black nightshade dye incorporated solar cells was 0.00616%. It was a clear improvement of the power conversion efficiency of the reference solar cell which was made up with the Grapes dye under the same experimental conditions. The power conversion efficiency of the reference solar cell was 0.00265%. These results reveal that the Eastern black nightshade natural dye has improved the power conversion efficiency of dye-sensitized solar cells compared to those with Grapes dye which is one of the most popular dye among the researches.Item Electrodeposited homojunction Cu2O solar cell on FTO substrate(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Kafi, F. S. B.; Jayathilaka, K. M. D. C.; Wijesundera, L. B. D. R. P.; Siripala, W.Cuprous oxide (Cu2O), an abundant photoactive semiconducting material has optimum optoelectronic properties to develop efficient, inexpensive and eco-friendly solar cells. Even though, it is possible to fabricate Cu2O based hetero or Schottky junction solar cells, it is believed that the reduction of interface strains via application of surface treatments can produce best efficient homojunction Cu2O solar cell. Apart from the homogeneity of a p-n junction, reduction of contact resistances of a solar cell also has a great impact on its overall performance. Previous studies have shown that, annealing and/or sulphidation of thin film Cu2O enhances the surface properties while sulphided p-Cu2O/Au junction exhibits ohmic behavior as well. Thus, in this study possibility of developing efficient thin film homojunction Cu2O solar cell on FTO substrate was tested by improving the surface properties of n- and p-Cu2O thin film layers. n-Cu2O thin film was potentiostatically electrodeposited in a three electrode photoelectrochemical cell, contained 0.1 M sodium acetate and 0.01 M cupric acetate, acetic acid at bath pH value of 6.1 and then, this thin film FTO/n-Cu2O photoelectrode was annealed at temperature of 4000C to form very thin p-Cu2O layer with lower surface defects. Subsequently, for a thicker absorber layer a thin film ptype Cu2O was electrodeposited on annealed FTO/n-Cu2O photoelectrode using a lactate bath, consisted 3 M lactic acid, 0.4 M copper(II) sulphate and 4 M sodium hydroxide at bath pH value of 13.0. Finally, to form ohmic back contact this bi-layer is directly exposed to ammonium sulphide vapor for 8s and sputtered thin film of Au on it. Photoresponses and modulated light induced current-voltage characterization of this final thin film Cu2O homojunction is given the highest VOC and JSC values of 154 mV and 3.905 mA/cm-2 respectively. This result revealed that application of surface treatments to the thin film n-Cu2O and the bi-layers ameliorates surface properties, thereby the optoelectronic properties. Parameterization of surface treatments and improvements in the front contact will further improve this homojunction solar cell.Item Comparison study of mechanical and chemical properties of ancient and modern clay pots(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Madhuwanthi, H. M. L. U.; Katugampola, M.; Jayathilaka, K. M. D. C.; Sumathipala, H. H.In this study, the ancient clay pottery samples from archaeological site Devalapola, Minuwangoda, Sri Lanka (3000 years, radiocarbon age) which were found by the Department of Archaeology, University of Kelaniya, were collected and compared their physical properties with modern clay pottery samples. Also to analyze the mineralogical components and the compositions, the Scanning Electron Microscopy (SEM) coupled with the Energy Dispersive X-Ray spectroscopy (EDX) analysis were performed on the both ancient and modern clay pot samples on both side and top surfaces of them. The firing clay objects is an irreversible process, which produces ceramic materials characterized by new chemical-mineralogical composition and different physical and microstructural features. Physical properties of the shards such as pottery density and water absorption capacity were analyzed. There was no significant difference in the pottery density. The values for the water absorption of the ancient clay pot samples have a wider range than the modern clay pot samples. According to the SEM results, the grain sizes of the modern clay pot samples are comparatively larger than the ancient clay pot samples. The grain sizes of the ceramic indicate the open porosity of the matrix. Based on the SEM-EDX results, SiO2 and Al2O3 were the major components of the both ancient and modern clay pot samples while CaCO3, MgO, MAD-10-Feldspar, CaSO3, Ti, and Fe are present in trace amounts. Further albite, FeS2 and KCl were only present in the modern clay pot samples. By analyzing the EDX results it can be concluded that when the production of the ancient potteries was happening, the furnace atmosphere was filled with more CO2 and the firing temperature of the ancient clay pot samples at the production was around 850 - 9000C.Item Optimization of growth parameters of photoactive Cu2ZnSnS4.(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Fernando, W. T. R. S.; Jayathilaka, K. M. D. C.; Wijesundera, R. P.; Siripala, W.Cu2ZnSnS4 (CZTS) is a promising candidate for application in low-cost and environmentally friendly thin film solar cells due to its optoelectronics properties. It is a perfect absorber material for photovoltaic applications due to its high absorption coefficient (>10-4 cm-1) and direct optical band gap (1.4 - 1.5 eV). Among the CZTS preparation techniques, electrodeposition of Cu, Sn and Zn stack layers followed by sulphurisation in H2S is an attractive technique because of its simplicity, low cost and easy to control stoichiometry. In this investigation, optimization of growth parameters in order to obtain photoactive CZTS thin films by sulphurisation of electrodeposited Cu, Sn and Zn stack layers has been investigated. Cu thin film was electrodeposited on Mo substrate at –0.89 V Vs Ag/AgCl electrode in an electrochemical cell containing 0.4 M CuSO4, 3 M lactic acid and NaOH at pH 11. Deposition of Sn thin film on Mo/Cu electrode was carried out at -1.2 V Vs Ag/AgCl in an electrochemical cell containing 0.055 M, 2.25 M NaOH and 8 ml of sorbitol. Zn thin film was electrodeposited on Mo/Cu/Sn at -1.2 V Vs Ag/AgCl in an electrochemical cell containing 0.2 M ZnSO4. Deposition parameters of Cu, Sn and Zn have been obtained by voltammograms. In order to grow CZTS, Mo/Cu/Sn/Zn thin film electrodes were annealed at 550 oC for 60 min in H2S. Sulphurisation process was carried out at different temperatures and durations using set of identical Mo/Cu/Sn/Zn thin film electrodes and thereby optimized temperature and duration of the sulpurisation. Atomic ratios of initial Cu, Sn and Zn layers could be crucial parameters in determining properties of CZTS thin films. Therefore, atomic ratios of Cu/Sn/Zn layers were optimized by changing Cu, Sn and Zn deposition duration. Various combinations of deposition durations were carried out and optimized by monitoring the dark and light I-V measurements in a PEC containing 0.1 M sodium acetate. Dark and light I-V characteristics revealed that the best photoactive CZTS films can be grown by depositing Cu for 20 min, Sn for 10 sec and Zn for 10 sec. Results further showed that photoconductivity of CZTS thin films is p-type. It is evident from reflectance measurements that the band gap of the CZTS films is 1.5 eV. In conclusion, it is found that the highest photoactive p-CZTS thin films can be grown by sulphurisation of electrodeposited Cu, Sn and Zn stack layers on Mo substrate using H2S at 550 oC for 60 min. Cu: Sn: Zn ratios of the stack layers are the crucial parameters in determining photoactive CZTS thin films. The methodology developed in this study will be further investigated in order to develop the materials for wider applications.Item Photoelectrolysis of water using electrodeposited Cu2O electrodes.(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Silva, A. G. T. D.; Jayathilaka, K. M. D. C.; Wijesundera, R. P.; Siripala, W.At present, fossil fuels are the main energy contributor of the world’s energy needs but gradually depletion of fossil fuels is heading towards an energy crisis. Therefore it is very important for us to find out a renewable clean energy source to minimize the use of fossil fuels and environmental problems created by the burning fossil fuels. Among the suggested alternative fuels, hydrogen is one of the best and it can be produced by photoelectrolysis of water. Finding correct semiconducting materials and techniques are the key areas of research in the development of an efficient photoelectrolysis device. Ultra low cost electrodeposited cuprous oxide (Cu2O) is a good candidate material because it has required semiconductor properties for the process. p-Cu2O electrode electrolyte system requires external bias to produce photocurrent and this can be overcome by using n-Cu2O. However, in our previous studies, we have observed the possibility of enhancement of photocurrent at zero bias using double electrode system (electrodeposted n-Cu2O, thermally grown p-Cu2O, electrolyte system). In this investigation it was studied the possibility of photoelectrolysis of water using electrodeposited n- and p-Cu2O thin film electrodes as a double photoelectrode system in a 0.1 M sodium acetate photoelectrochemcal cell. n-Cu2O thin films on Ti substrates were potentiostatically electrodeposited at −200 mV Vs Ag/AgCl for 60 minutes in an aqueous solution containing 0.1 M sodium acetate and 0.01 M cupric acetate. The initial pH of the deposition bath was adjusted to 6.1. The temperature of the electrolyte was maintained at 55 °C and counter and reference electrodes were a platinum plate and a Ag/AgCl electrode, respectively. p-Cu2O thin films were electrodeposited on Ti substrate at -400 mV Vs Ag/AgCl for 40 min in a three-electrode electrochemical cell containing a 3 M sodium lactate and 0.4 M CuSO4 solution at pH 11. During the electrodeposition, the baths were continuously stirred using a magnetic stirrer. Prior to the film deposition, substrates were cleaned with detergent, dilute HCl, distilled water, and finally ultrasonicated in distilled water. Electrolytic solutions were prepared with distilled water and reagent-grade chemicals. n-Cu2O thin films are annealed at 150 oC for 10 min in air. Possibility of photoelectolysis using electrodeposited Cu2O has been investigated using dark and light current–voltage measurements in a three-electrode electrochemical cell containing 0.1 M aqueous sodium acetate solution. Results reveal that photoelectrolysis process is enhanced by 380% when n- and p-Cu2O double electrode system was operated compared to the n-Cu2O single electrode system.