Physics
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Item Electrodeposited thin film SnO2 photoelectrode for PEC applications(Institute of Physics, Sri Lanka, 2024) Kafi, F.S.B.; Gunaratna, B.H.; Jayathilaka, K.M.D.C.; Wijesundera, R.P.Tin oxide (SnO2) is a promising semiconductor material to develop photoelectrodes for photoelectrochemical (PEC) cells. Indeed, an effective PEC cell could be developed only if the photoelectrode is stable and free of corrosion in the selected electrolytic solution. In other words, the choice of an electrolyte for a PEC cell determines the stability of the photoelectrode in the PEC cell. In this study, we propose aqueous 0.1 M sodium nitrate (NaNO3) as an effective electrolyte for the PEC cell where thin film SnO2 is a photoelectrode. Current-voltage (I-V) measurements obtained by illuminated chopped ultra violate (UV) radiation established the electrodeposited thin films of SnO2 are stable and free of corrosion/photocorrosion in our PEC cell. In addition, we report the dependence of the photoresponses of electrodeposited thin film SnO2 in this PEC on the bath temperature and the deposition time.Item Effect of pre-surface treatments on p-Cu2O/Au Schottky junctions(Journal of the National Science Foundation of Sri Lanka,, 2021) Kafi, F.S.B.; Jayathilaka, K.M.D.C.; Wijesundera, R.P.; Siripala, W.Cuprous oxide (Cu2O) is a suitable semiconducting material in fabrication for low-cost, eco-friendly semiconductor junction devices. Besides the parameterization of the growth conditions of Cu2O, formation of metal contacts impact the overall performance of these type of devices. The existence of unavoidable dangling bonds and/or dislocated surface atoms could lead to form imperfect contacts with metals, for example in Cu2O/Au junction devices. Nevertheless, modification of the Cu2O thin film surfaces prior to make contacts with Au has shown the capability to alter the junction properties. Here we report that, the application of surface treatments; annealing and/or sulphidation on specifically the electrodeposited p-Cu2O thin film surfaces, where p-Cu2O thin films were grown in low cupric ion concentrated acetate bath, has influenced the interfacial properties of particular p-Cu2O/Au Schottky junctions compared to the untreated p-Cu2O/Au Schottky junction. This has been well-established by the results of SEM and C-V characterizations of p-Cu2O/Au Schottky junctions. The subsequent annealing and sulphidation of p-Cu2O thin film surfaces have lowered the built-in potential value by 121 mV compared to the untreated Schottky junction. This result reveals the possibility of employing surface treatments on electrodeposited Cu2O thin films in fabrication of high efficient Cu2O based junction devices.Item Effect of pre-surface treatments on p-Cu2O/Au Schottky junctions(Journal of the National Science Foundation of Sri Lanka, 2021) Kafi, F.S.B.; Jayathilaka, K.M.D.C.; Wijesundera, R.P.; Siripala, W.Cuprous oxide (Cu2O) is a suitable semiconducting material in fabrication for low-cost, eco-friendly semiconductor junction devices. Besides the parameterization of the growth conditions of Cu2O, formation of metal contacts impact the overall performance of these type of devices. The existence of unavoidable dangling bonds and/or dislocated surface atoms could lead to form imperfect contacts with metals, for example in Cu2O/Au junction devices. Nevertheless, modification of the Cu2O thin film surfaces prior to make contacts with Au has shown the capability to alter the junction properties. Here we report that, the application of surface treatments; annealing and/or sulphidation on specifically the electrodeposited p-Cu2O thin film surfaces, where p-Cu2O thin films were grown in low cupric ion concentrated acetate bath, has influenced the interfacial properties of particular p-Cu2O/Au Schottky junctions compared to the untreated p-Cu2O/Au Schottky junction. This has been well-established by the results of SEM and C-V characterizations of p-Cu2O/Au Schottky junctions. The subsequent annealing and sulphidation of p-Cu2O thin film surfaces have lowered the built-in potential value by 121 mV compared to the untreated Schottky junction. This result reveals the possibility of employing surface treatments on electrodeposited Cu2O thin films in fabrication of high efficient Cu2O based junction devices.Item Growth of (Cu2O)1-x (Cu2O)x thin films for PV applications(Sri Lanka Association for the Advancement of Science, 2013) Kalubowila, K.D.R.N.; Wijesundera, R.P.; Siripala, W.Item Improved n-type photoconductive Cu2O thin films(Sri Lanka Association for the Advancement of Science, 2013) Gunawardhana, L.K.A.D.D.S.; Wijesundera, R.P.; Siripala, W.Item Plantain Pith Battery Powered Lighting System(Institute of Physics, Sri Lanka, 2015) Kumara, K.S.J.; Wijesundera, R.P.; Jayasuriya, K.D.Item Electrodeposited CuO/Cu2O heterojunction for PV applications(Institute of Physics, Sri Lanka, 2015) Kalubowila, K.D.R.N.; Wijesundera, R.P.; Siripala, W.Anodic electrodeposition was carried out to grow CuO thin films on Ti substrate at a deposition potential of 700 mV vs. SCE in an aqueous solution containing 0.4 M CuSO4 and 3.0 M lactic acid. CuO thin films were annealed at 375 o C for 15 min in air to improve the surface quality prior to the growth of Cu2O films, in order to fabricate the heterojunction. After growth of n-Cu2O, zero bias spectral response and dark and light I-V characteristics in PEC were employed to investigate n-Cu2O growth conditions on p-CuO thin films. CuO/Cu2O heterojunction solar cells were fabricated by electrodeposition of n-Cu2O thin film on Ti/CuO electrode at -200 mV vs. SCE for 60 min in an acetate bath. Ti/CuO/Cu2O/Au solar cell structure was characterized using zero bias spectral response and dark and light I-V characteristics and the cell produced VOC of 290 mV and ISC of 2.63 mA/cm2.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 Cu2O homojunction solar cell(HETC Symposium, 2014) Gunawardena, L.K.A.D.D.S.; Wijesundera, R.P.; Siripala, W.Item Effects of NH3 concentration and annealing temperature on CBD CdS thin films(Postgraduate Institute of Science Research Congress, Sri Lanka, 2014) Kumarage, W.G.C.; Wijesundera, R.P.; Seneviratne, V.A.; Jayalath, C.P.; Dassanayake, B.S.