Physics
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Item Plantain Pith Battery Powered Lighting System(Institute of Physics, Sri Lanka, 2015) Kumara, K.S.J.; Wijesundera, R.P.; Jayasuriya, K.D.Item ITO/n-Cu2O/p-CuxS Thin Film Solar Cell(Sri Lanka Association for the Advancement of Science, 1997) Perera, L.D.R.D.; Wijesundera, R.P.; Siripala, W.; Jayasuriya, K.D.; de Silva, K.T.L.; Jayanetti, J.K.D.S.Item A Study of CuInS2 Thin Films for Photovoltaic Applications(Proceedings of the Technical Session of Institute of Physics, 1999) Wijesundera, R.P.; Nadesalingam, M.P.; Siripala, W.; Jayasuriya, K.D.; Kalingamudali, S.R.D.; Jayanetti, J.K.D.S.; de Silva, K.T.L.Thin films of copper indium disulphide (CuInS2) on Ti Substrate were prepared by annealing potentiastatically electrodeposited Cu-In alloy in H2S gas at 5500 C. Films were characteristised by X-ray diffraction (XRD), scanning electron microscopy (SEM), and spectral response in a polysulphide electrolyte. XRD measurements revealed the formation of the polysrystaline CuInS2 thin films and the abscence of any other phases. SEM showed the formation of crystallites having the size about 0.2 ?m. Variations of spectral response, open-circuit voltage (Voc) and short circuit current (Isc) with annealing in air have been studied. As deposited CuInS2 films exhibit a direct band gap of 1.5 eV, and shows n-type behaviour when used in a Photoelectrochemical (PEC) cell. Heat treatment shows a considerable enhancement of the photoresponse.Item Computational Study of I-V characteristics of ITO/Cu2 O/Metal junctions, Technical Session of Institute of Physics(Processing of the Technical Session of Institute of Physics, 1999) Wijesinghe, W.M.P.L.; Siripala, W.; Jayasuriya, K.D.; Kalingamudali, S.R.D.A theoretical model for current-voltage (I-V) characteristics of back-to-back diode systems was developed using the ideal diode equation. A computer model was developed using the language C++ to fit the experimental data to the theoretical equation and to determine the ideality factors and reverse saturation currents of each diode. This model was tested with commercial back-to-back diode systems. The values obtained for the above parameters from the theoretical fits were in very good agreement with the standard values. The experimental I-V characteristics data obtained for fabricated ITO/Cu2O/Metal (Au, Ag and Hg) structures were fitted to the model and values for the relevent parameters were obtained. These values indicate that the fabricated systems are back to back diodes except the ITO//Cu2O/Hg structure. Using this model, a good understanding of I-V characteristics of metal-semiconductor-metal diodes can be gained and thereby the quality of junction devices can be tested.Item A Home Made Double Slab Pyranometer for Irradiance Measurements(Proceedings of the 44th Technical Session of the Sri Lanka Association for the Advancement of Science (SLAAS), 1988) Punyasena, M.A.; Jayasuriya, K.D.Item ITO/ u-Cu2O/ p-Cu2S thin film solar cell(Srilanka association for the advancement od science proceedings of 53rd Anuual Session., 1997) Perera, L.D.R.D.; Wijesundara, R.; Jayasuriya, K.D.; de Silva, K.T.L.; Jayanetti, J.K.D.S.Item Construction of a Near Ideal Nanoammeter(1998) Wijesundera, R.P.; Kalingamudali, S.R.D.; Jayasuriya, K.D.A near ideal ac/dc nanoammeter was constructed using two operational amplifiers (op-amp) and a voltmeter. Small currents were converted into a voltage by the first op-amp and this was amplified into a larger voltage by the second op-amp. The amplified voltage was measuredby the voltmeter. The constructed meter has 10 and 100 nA ranges for the dc current measurements and 100 nA range for the ac current measurements.All the ranges were calibrated using a digital picoammeter. As compared to commercially available nanoammeters with similar features this meter has higher advantages such as almost zero internal resistance and negligible operating bias current. The construction cost of the meter is very low compared to a commercial ac/dc nanoammeter.Item Study of Sulphidation of Electrodeposited Cu2O Thin Films for Solar Cell Applications(1998) Siripala, W.; Wijesundera, R.P.; Perera, L.D.R.D.; Jayasuriya, K.D.Cuprous oxide (Cu20 ) layers were potentiostatically electrodeposited on glass/ITO substrates and then they were partially sulphided using Na2S and H2S. Resulting layers were used to fabricate ITO/n-Cu20/p-CuxS thin film solar cells. Spectral response measurements showed that the cell structure exhibits both n- and p-type behavior. Sulphidation of Cu20 does not produce CuxS thick layers adequate for efficient heterojunction solar cell, but improved the photovoltaic activity. The best device fabricated shows V? = 240 mV and Isc= 1.6mA/cm2 under AM 1 artificial illumination.Item An experimental determination of the effect of pressure on the Fe3+/?Fe ratio of an anhydrous silicate melt to 3.0 GPa(American Mineralogist, 2006) Jayasuriya, K.D.; O-Neill, H.S.C.; Berry, A.J.; McCammon, C.C.; Campbell, S.J.; Foran, G.The effect of pressure on the Fe3+/?Fe ratio of an anhydrous andesitic melt was determined from 0.4 to 3.0 GPa at 1400 �C with oxygen fugacity controlled internally by the Ru + RuO2 buffer. Values of Fe3+/?Fe were determined by M�ssbauer spectroscopy on quenched glasses with a precision of �0.01, one standard deviation. This precision was verified independently by XANES spectroscopy of the same samples. The XANES spectra show a systematic increase in energy and decrease in intensity of the 1s ? 3d transition with increasing pressure. The results to 2.0 GPa are in good agreement with predictions from density and compressibility measurements fitted to a Murnaghan equation of state, but the datum at 3.0 GPa has higher Fe3+/?Fe than predicted from the trend established by the lower-pressure data. This might be due to a coordination change in Fe3+ at high pressure; although there is no evidence for this in the M�ssbauer spectra, such a change could account for the change in intensity of the 1s ? 3d transition in the XANES spectra with pressure.Item A Mössbauer study of the oxidation state of Fe in silicate melts(American Mineralogist, 2004) Jayasuriya, K.D.; O-Neill, H.S.C.; Berry, A.J.; Campbell, S.J.Fe3+/?Fe ratios were determined from M�ssbauer spectra recorded for a series of 17 anorthite-diopside eutectic glasses containing 1 wt% 57Fe2O3 quenched from melts equilibrated over a range of oxygen fugacities from fO2~ 105 bars (Fe3+/?Fe = 1) to 10?13 bars (Fe3+/?Fe = 0) at 1682 K. Fe3+/Fe2+ was found to be proportional to fO2 to the power of 0.245 � 0.004, in excellent agreement with the theoretical value of 0.25 expected from the stoichiometry of the reaction Fe2+O + 0.25 O2 = Fe3+O1.5. The uncertainty in the Fe3+/?Fe ratios determined by M�ssbauer spectroscopy was estimated as � 0.01 (1?) from the fit of the data to the theoretical expression, which is significantly less than that quoted for previous measurements on silicate glasses; this results from fitting the spectra of a large number of systematically varying samples, which allows many of the ambiguities associated with the fitting procedure to be minimized. Fe3+/?Fe ratios were then determined for samples of the anorthite-diopside eutectic composition equilibrated at selected values of fO2, to which up to 30 wt% Fe2O3 had been added. Fe3+/?Fe was found to vary with ?Fe (or FeOT), but both the 1 wt% and high FeOT data could be satisfactorily fit assuming the ideal stoichiometry (i.e., Fe3+/Fe2+ ?fO2 1/4) by the inclusion of a Margules term describing Fe2+-Fe3+ interactions. The large negative value of this term indicates a tendency toward the formation of Fe2+-Fe3+ complexes in the melt. The resulting expression, using the ideal exponent of 0.25, gave a fit to 289 Fe3+/?Fe values, compiled from various literature sources, of similar quality as previous empirical models which found an exponent of ~0.20. Although the empirical models reproduce Fe3+/?Fe values of glasses with high FeOT reasonably well, they describe the data for 1 wt% FeOT poorly. The non-ideal values of the exponent describing the dependence of Fe3+/?Fe on fO2 at high FeOT are an artifact of models that did not include a term explicitly to describe the Fe2+-Fe3+ interactions. An alternative model in which Fe in the silicate melt is described in terms of three species, Fe2+O, Fe3+O1.5, and the non-integral valence species Fe2.6+O1.3, was also tested with promising results. However, at present there is no model that fits the data within the assessed accuracy of the experimental measurements.