Physics
Permanent URI for this collectionhttp://repository.kln.ac.lk/handle/123456789/3750
Browse
45 results
Search Results
Item Spectral responses of electrodeposited cuprous oxide thin film electrodes(Natural Resources, Energy and Science Authority of Sri Lanka, 1995) Siripala, W.Item n-type electrical conductivity in cuprous oxide thin films(Natural Resources, Energy and Science Authority of Sri Lanka, 1988) Siripala, W.; Kumara, K.P.Electrodeposited cuprous oxide thin films were investigated to determine whether their electrical conductivity is n-type or p-type. The experimental results based on the measurements of thermoelectric e.m.f, sheet resistance, dark and light current-voltage characteristics of Cu2O/CuxS and Cu2O/CuCNS heterojunctions reveal that the electrodeposited cuprous oxide films produce n-type electrical conductivity. These observations are in very good agreement with the previously reported n-type behavior of the electro-deposited Cu2O film electrodes in a photo-electrochemical cell.Item Characterisation of CuInS2 thin film prepared by electrodeposition and sulphurisation with photoluminescence spectroscopy(Solar Energy Materials and Solar Cells, 2003) Garuthara, R.; Wijesundera, R.P.; Siripala, W.Potentiostatic electrodeposition and sulfurization techniques were used to prepare polycrystalline CuInS2 thin films. X-ray diffraction and photoresponse measurements in a photoelectrochemical cell (PEC) revealed that photoactive polycrystalline CuInS2 films can be deposited on Ti substrate. Photoluminescence (PL) spectroscopy was used to investigate the prepared thin films and optically characterize them. PL spectra revealed the defect structure of the samples with an acceptor energy level at 109 meV above the valance band and a donor energy level at 71 meV below the conduction band. The CuInS2 thin films prepared in this investigation are observed to be In-rich material with n-type electrical conductivity.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 Use of Cu2O microcrystalline thin semiconductors for gas sensing(Technical sess., Institute of Physics, Sri Lanka, 2009) jayantha, P.A.P.; Perera, L.N.L.; Jayathileke, K.M.D.C.; Jayanetti, J.K.D.S.; Dissanayake, D.P.; Siripala, W.Item Fabrication and characterization of electrodeposited nanocrystalline/microcrystalline cuprous oxide thin films(Proc. Annual Research Symposium, University of Kelaniya, 2008) Jayathilaka, K.M.D.S.; Wanninayake, W.T.M.A.P.K.; Siripala, W.; Jayanetti, J.K.D.S.The quest and need for clean and economical energy sources have increased interest in the development of solar energy applications. In particular, direct conversion of solar energy to electrical energy and chemical energy using semiconductor photoelectrodes has attracted attention for many decades. Among the various metal oxide materials for solar energy applications, a promising material is cuprous oxide (Cu2O) and is one of the oldest known semiconductors. It is low cost and non toxic and its component elements are readily available. It has a direct band gap of about 2 eV and a high optical absorption coefficient. Nanocrystalline thin films increase the effective surface area of the films as compared with the microcrystalline thin films. Therefore preparation of nanoparticles of Cu2O is of special importance to improve the solar energy conversion efficiency. In this study, Cu2O films were deposited electrochemically on Ti substrates. In this study, a simple electrochemical technique was developed to fabricate the Cu2O/CuxS heterojunction to be used in a thin film photovoltaic solar cell. Electrodeposited Cu2O thin films on Ti substrates were sulphided by directly applying an aqueous solution of Na2S on to Cu2O films and annealed at 200 0C for a few minutes. Then the samples were exposed to NH4S gas for a few seconds. It was observed that the photovoltaic properties and the diode characteristics of nano/micro/Cu2O/CuxS structures were better than that of micro/Cu2O/CuxS structures. The maximum conversion efficiency of the micro/Cu2O/CuxS cell was 0.12% (Voc= 240 mV, and Isc= 0.86 mA/cm2) and that of the nano/micro/Cu2O/CuxS cell was 0.28% (Voc= 420 mV, and Isc= 2.1 mA/cm2) under AM1.5 illumination.Item Eelctrodeposition of Nanocrystalline Cuprous Oxide Thin Films(Asian Conference on Solar Energy Materials and Solar Cells, 2006) Weerasinghe, W.J.L.D.; Siripala, W.; Jayanetti, J.K.D.S.Cuprous oxide is an attractive material for solar energy applications because it is low cost, non toxic and has a direct band gap of 2 eV. Electrodeposition for preparing cuprous oxide thin films is important because it provides the possibility of depositing n-type Cu2O thin films on conducting substrates, compared with p-type Cu2O films resulted in many other techniques. Electrodeposition of cuprous oxide is possible in a near neutral aqueous bath containing cupric ions and in a potential domain about 0 to 300 mV vs. SCE. Structural and morphological studies reveal that single phase polycrystalline films of crystalline size 1-2 ?m to 100nm of Cu2O can be electrodeposited by controlling the deposition parameters. It is revealed that for nanostructured film deposition low temperature deposition in galavanostatic mode is more suitable. Photoresponses of the films are very sensitive to the nature of the substrates. Particularly, n-type or p-type behavior of photoresponse is determined by the relative magnitudes of the photosignals produced by the photo electrodes. This is revealed by the spectral responses of the short and the long wavelengths of the illuminated light. The general photoresponse behavior is the same whether the electrode is in contact with an electrolyte or with a metal. This study reveals the possibility of electrodepositing nanocrystalline cuprous oxide thin films on conducting substrates. These films will be very useful in applications of solar energy converting devices.Item Ti/Cu2O photoelectrodes in photlectrolytic solar cells(proceedings of the Technical Session of Institute of Physics, Sri Lanka, 2003) Wijesundera, R.P.; Susantha, P.K.K.; Jayakody, J.R.P.; Siripala, W.Cuprous Oxide thin films deposited on Ti substrates were investigated as photoelectrodes in a photoelectrochemical cell. Electrodeposition was carried out in an electrochemical cell containing aqueous solutions of cupric acetate and sodium acetate.X-ray diffraction (XRD) and scanning electronmicrographs (SEM) confirmed that the films are polycrystaline Cu2O films. X-ray photoelectron spectroscopy (XPS) revealed that the films are pure CU2O and there are noanyother phases. The photoresponse of the films in a PEC produced a zero bias photocurrent (XBPC) with an n-type photoresponse. Comparing with the thermally grown Cu2O films, an enhanced spectral response in the long wavelength region could be obtained with electrodeposited Cu2O on Ti substrate. A charge separation mechanism at the Ti/Cu2O interface isproposed as the possible reason for the observed spectral response enhancement.Item A Photoluminescence Study on CuInS2 Thin Films Prepared by the Sequential Deposition Technique(Annual Research Symposium -Faculty of Graduate Studies, University of Kelaniya, 2001) Wijesundera, R.P.; Siripala, W.Solar energy conversion to electrical energy using low cost solar cells contributes substantially for a solution to the present global energy crisis. In this respect, various semiconductor materials are being studied for possible applications in low cost solar cell devices. Copper Indium Di Sulphide (CuInS2) is very promising semiconductor material because of its electronic and optical properties, which are suitable for these applications. Low-cost semiconductor material growth techniques normally produce unwanted electronic states in the material producing undesired effects on the solar cell application. In this investigation, CuInS2 thin films prepared by the electrodeposition of Cu films followed by the In deposition were used to prepare Cu-In alloy. Cu-In alloy was suplherized in an H2S chamber to grow CuInS2 films. X-ray diffraction and optical characterizations suggest that the films are of good quality. The photoluminescence study at low temperature produced two peaks at 815nm and 880 nm. This result suggests the band to band transition and the sulfur vacancy transition. Our study reveals that there are no other defect electronic states in the band gap except the S vacancies, confirming the good quality of the materialItem Optical and Structural Characrerization of Electrodeposited CuInSe2 thin films(Proceeding of the Technical Session of Institute of Physics, Sri Lanka, 2001) Seneviratne, L.P.; de Silva, K.T.L.; Siripala, W.; Rosa, S.R.D.; Sonnadara, D.U.J.CuInSe2 thin films were prepared on ITO coated glass substrates by electrodeposition from aqueous solution containing 0.005 M CuCl2 0.005 SeO2 and 0.01 M InCl3 at room temperature for a period of 30 minutes. To obtain better quality films, samples were annealed at different temperatures (200 0C, 350 0C and 500 0C) in Ar. XRD, optical absorption measurements, photovoltage measurements, spectral measurements and reflectance measurements were performed to characterize the films. According to the results, CuInSe2 is a p-type semiconductor. XRD shows three sharp CuInSe2 peaks of (112), (200) and (116) reflections for the samples annealed at 200 0C and 350 oC.Photovoltage of samples annealed at 400 0C and 500 0C were negligible (alomost zero). For the sample annealed at 200 0C, photovoltage was around 10 ? 15 mV. The highest photovoltage of around 150 mV was shown by the sample annealed at 350 0C. According to optical absorption measurements and reflectance measurements, the direct band gap was around 1.1 eV for both samples annealed at 200 0C and 350 0C. Only the sample annealed at 350 0C gave spectral responses.