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 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 Fabrication of CUO!CU2O Heterojunction and Its Local Structural Characterization(2011) Siripala, W.; Wijesundera, R.P.; Perera, L.D.R.D.; Jayasuriya, K.D.Cuprous oxide (Cu20) thin films on Ti substrate were potentiostatically electrodeposited at -200 mV in an acetate bath. For the growth of p-type cupric oxide (CuO) thin films , CU20 thin film s were annealed at 500 oC (for 30 min in air. In order to fabricate CuO/Cu20 hetorojunction, thin film of Cu20 was potentiostatically electrodeposited on Ti/CuO electrode . Deposits were characterized by using X-ray diffraction (XRD) and scanning electron micrographs (SEM). Results revealed that well covered n-tvpe polycrystall ine Cu20 thin film can be electrodeposied on Ti/CuO electrode at -550 mV VS the SCE in an acetate bath. The CuO/Cu20 heterojunction gave the open circuit voltage (Voc)of 210 mV and short circuit current (Jsc) of 310 uA/cm2. Layer by layer structural properties of the electrodeposited Ti/CuO/Cu20 thin film heterojunction have been studied by means of the XRD and the X-ray absorption spectra (XAS) with different grazing angles of the incident Xray beam. Results reveal that Cu20 and CuO are high quality semiconducting thin films but amorphous structure is formed between CuO and Cu20 while Cu20 deposition on CuO. It can be expected that amorphous structure formed in the middle of the CuO/Cu20 heterojunction attributes better lattice matching between CuO and Cu20 interface .Item Photoelectrochemical Characterisation of ZnSe coated Copper Indium Sulphide Thin Film Electrodes(1999) Wijesundera, R.P.; Siripala, W.; Jayasuriya, K.D.; Kalingamudali, S.R.D.; de Silva, K.T.L.; Jayanetti, J.K.D.S.Capper Indium Sulphide thin films were prepared by sulphidation of Cu-In alloy on Ti substrate. Cu-In alloy was potentiostatically electrodeposited at ~1.4 V Vs SCE in an aqueous bath containing 5 mM CuCl2) 37.5m1 InCl3,1% (V/V) TEM and .75% (V/V) ammonia. Sulphidation was carried out in saturated H2S gas at 550�C for 30 min. XRD measurement reveals that the crystal structure of the films is CuInl1S17. ZnSe was deposited on CuInS electrode by electrodeposition in an aqueous bath of 0.1 M ZnS04 and 10 -5 M Se02 at -0.5 V Vs SCE for 90 min. XRD measurement reveals that the ZnSe films are amorphous. Ti/CulnS/ ZnSe thin film system in a PEC cell containing KI produces n-type photocondutivity. Dark and illuminated I-V measurement shows the existence of a main junction. However, some departure is also evident suggesting the possibility of existence of another junction. Spectral response of the Ti/CuInS/ZnSe system in a PEC cell shows the photoresponse of born n-CuInS/p-ZnSe and p-ZnSe/electrolyte interfaces. Normally, for shorter wavelength the spectral response is p-type while for the long wavelength it is n-type. The preliminary results of the study suggest the possibility of utilising electrodeposited n-CuInS in combination with electrodeposited p-ZnSe in developing a low-cost thin film solar cell.Item Sulphurisation of sequentially electrodeposited Cu-In alloy for the preparation of semiconductor thin films(2000) Wijesundera, R.P.; Siripala, W.; Jayasuriya, K.D.; Kalingamudali, S.R.D.Copper indium disulphide thin films were fabricated by suiphurisation of CuIn alloy prepared by a sequential electrodeposition method. Thin film layers of copper and indium were sequentially electrodeposited on a well-cleaned Ti substrate and on Ti/Cu thin film respectively. The Ti/Cu/In films were then heated at 130�C for 4 hours in air to form Cu-In alloy. Sulphurisation of Cu-In alloy was carried out at 550�C for 30 minutes in 1000/0 HzS gas with a constant flow rate. XRD measurement revealed that the chalcopyrite structure of single phase CulnS2 can be obtained by adopting a proper In concentration in Cu-In alloy. The photoresponse of the CulnS2 films in polysulphide showed the n-type behavior of the films. A p-type ZnSe thin film was deposited on CulnS2, by electrodeposition to produce Ti/CuInS2/ZnSe heterostructure. XRD measurement also revealed that the ZnSe films were amorphous. Spectral response of Ti/CulnS2/ZnSe structure in a PEC cell containing sodium acetate showed the photoactivity of both interfaces n-CulnS2/p-ZnSe and p-ZnSe electrolyte, This study reveals that the thin film solar cell structure Ti/CulnS2/ZnSe/metal may be developed to an efficient solar cell device. The solar cell parameters that we have observed so far are V? =330mV and Isc=2mA/cm2Item Design of an Inexpensive Digital Watt-hour Meter(2003) Chandana, A.W.S.; Wijesundera, R.P.; Jayasuriya, K.D.; Kalingamudali, S.R.D.An inexpensive digital watt-hour meter has been designed and tested using MCap 7 simulation package since commercially available digital watt-hour meters are very expensive. One of the major usages of watt-hour meters is to measure the power consumption of electricity consumers for billing purposes. Although digital watt-hour meters are commercially available,all electrical power supply companies through out the world including well-developed countries like the United States ofAmerica and the United Kingdom use analogue watt-hour meters to measure the power consumption. This is probably due the expensiveness ofdigital watt-hour meters. The designed digital watt-hour meter consists with analogue multiplier, analogue to digital converters, adder, registers, digital clocks, dividers, accumulators and digital displaying unit. Basically the current and voltage will be multiplied by using a four-quadrant analogue multiplier and then converted to digital signals using analogue to digital converters, which is clocked at a frequency significantly higher than mains frequency, to produce instantaneous values. The algebraic average of the output product per second will be the power consumption per second Finally, this will continuously be added and sent to the digital displaying unit to display watt-hour output. One of the major advantageous of the digital walthour meter is that the power consumption cannot be tampered like in analogue watt-hour meters where the power consumption can be very easily disturbed by changing the rotation power ofthe rotating disk.Item Growth and Characterisation of CuInS2 Thin Films(1999) Wijesundera, R.P.; Siripala, W.; Jayasuriya, K.D.; Kalingamudali, S.R.D.; de Silva, K.T.L.; Jayanetti, J.K.D.S.; Samantilleke, A.P.; Dharmadasa, I.M.Copper Indium Disulphide thin films were grown by electrodeposition of Cu-ln alloy followed by sulphurisation in H2S gas. It was observed that the ionic concentration of Cu2+/ In3+ in the electrodepositing bath determines the composition of the materials formed after the sulphurisation. CuInS2 thin films having the chalcopyrite crystal structure can be produced using this technique and the films are n-type semiconductors.