Browsing by Author "de Silva, K.T.L."

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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.
Electrodeposition and Characterisation of CuInSe2 for applications in thin film solar cells
(Thin Solid Films, 2001) de Silva, K.T.L.; Priyantha, W.A.A.; Jayanetti, J.K.D.S.; Chithrani, B.D.; Siripala, W.; Blake, K.; Dharmadasa, I.M.
Copper indium diselenide (CuInSe2) layers have been grown at room temperature by electrochemical deposition technique in an aqueous medium. Resulting thin films have been characterised using XRD, XRF, XPS, GDOES and SEM for structural, stoichiometric and morphological properties. A considerable influence of the deposition potential on the atomic composition of In and Se present in the film was observed. Cu composition remains the same within the deposition potentials used in this investigation. The deposited layers are polycrystalline and annealing at 350�C for 30 min improves the crystallinity. The film quality deteriorates due to dissociation when annealed at temperatures above 350�C. Excessive annealing results in a surface which is depleted in Cu and rich in In and Se.
Fabrication and Characterisation of CuinS2/ZnSe/Metal Structures for Solar Cell Applications
(2000) Kalingamudali, S.R.D.; Wijesundera, R.P.; Gunatunga, N.P.; Siripala, W.; Jayasuriya, K.D.; de Silva, K.T.L.; Jayanetti, J.K.D.S.
Thin film solar cell structure of Ti/CuInS2/ZnSe/Metal was fabricated using simple electrochemical and sulphurisation techniques. Copper lndium Disulphide (CuInS2 thin films were prepared by sulphurisation of Cu-In alloy on Ti substrates. Films were characterised usrng X-ray diffraction (XRD)1 scanning electron microscopy (SEM), spectral response and t-V measurements. XRD measurements snowed the characteristic peaks of CulnSz and SEM showed that the crystallites are of the size 1-3 J.1m. ZnSe thin fitms were deposited on Ti/CuInS2 using electrodeposition technique, TiCuInS2/ZnSe/Metal structures were characterised using C-V, I-V and spectral response measurements. Light and dark I-V measurements revealed the phctovoltaic activity of the structure while the C-V measurements confirmed the formatlon of the heterojunction. Spectral response showed that the photocarriers are generated by the absorption of light in the CuJnS2 tayer.
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.
Growth and Characterization of Copper Indium Diselenide
(Proceedings of the Technical Session of Institute of Physics, Sri Lanka, 1996) Chithrani, B.D.; de Silva, K.T.L.; Jayanetti, J.K.D.S.; Siripala, W.
CuInSe2 thin films were prepared on Ti plates by electrodeposition from an aqueous solution containing CuCl2, InCl3 and SeO2. The deposition was carried out at -0.5V Vs SCE. X-ray diffraction and Scanning electron microscopy have been used to study the crystallographic and morphological properties of the samples. Effects of annealing in air have also been monitored. Apparent bulk structure changes have been observed during annealing. Annealing of films at 350 0C was found to result in the formation of CuInSe2 films having a chalcopyrite structure, indicating that the samples are of good quality.
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.
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.
IV characteristics of ITO/Cu2O/ metal junctions
(1996) Perera, L.D.R.D.; Siripala, W.; Kalingamudali, S.R.D.; Jayanetti, J.K.D.S.; de Silva, K.T.L.
Cuprous oxide is an inexpensive and non-toxic semiconductor material having the potential for use in low-cost photovoltaic devices. Electrodeposition is a low-cost method t0 produce thin Cu2O films and electrodeposited CU2O has been reported to be n-type, In order to investigate the possibility of using electrodeposited Cu2O in solar cells, Cu2O/metal junctions were studied using their I-V characteristics. Thin films of Cu20 were electrodeposited on Indium tin oxide (ITO) coated glass substrate using an aqueous solution of cupric acetate. Electrodeposition was carried out under potentiostatic condition of -250 mV vs SCE at 55"C for a period of 1 h. These Cu20 samples were used to make junctions with Al, Hg,Cu, Ag and Au. The I-V plots of these junctions were obtained in dark and when illuminated. The I-V characteristics of the Cu2O/Hg junction show good rectifying properties.The plots for the junction in dark and under illumination indicate that the electrodeposited Cu2O behaves as an n-type semiconductor. The I-V profile fits into the standard diode equation with I0 = 2.8 x 10 -10 A, ideality factor n=0.48 and series resistance Rs = 40U. Also, the Junction exhibits a contact potential of about 150 mV.
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.
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.
Potentiostatic electrodeposition of cuprous oxide thin films
(Journal of the National Science Council of Sri Lanka, 1996) Perera, L.D.R.D.; Siripala, W.; de Silva, K.T.L.
Current-potential scans were used to investigate the electrodeposition of coprous oxide thin films in an acetate bath. We found that a narrow potential domain, from OV vs SCE, is available for the potentiostatic electrodeposition of cuprous oxide thin films and extension of this domain towards more cathodic potentials will result in the co-deposition of copper. These results were further verified by the x-ray diffraction measurements on the thin films formed by the electrodeposition at various electrode potensials. Optical transmission studies revealed that electrodeposited cuprous oxide is a direct band gap semiconductor of 2.0 eV.
Study of annealing effects of cuprous oxide grown by electrodeposition technique
(Solar Energy Materials and Solar Cells, 1996) Siripala, W.; Perera, L.D.R.D.; de Silva, K.T.L.; Jayanetti, J.K.D.S.; Dharmadasa, I.M.
Low temperature electrochemical deposition of cuprous oxide from aqueous solutions has been investigated. X-ray diffraction, scanning electron microscopy, optical absorption, and photo-response of liquid/cuprous oxide junctions have been used to study the deposits' crystallographic, morphological, optical, and electrical properties. Effects of annealing in air have been studied using the above mentioned methods. As-deposited cuprous oxide exhibits a direct band gap of 2.0 eV, and shows an n-type behaviour when used in an liquid/solid junction. Annealing below 300�C enhances the n-type photocurrent produced by the junction. Type conversion occurs after heat treatments in air at temperatures above 300�C. No apparent bulk structure changes have been observed during annealing below this temperature, but heat treatments above this temperature produce darker films containing cupric oxide and its complexes with water.
Study of Annealing Effects of Cuprous Oxide Grown by Electrodepostion Technique
(Solar Energy Materials and Solar Cells, 1996) Siripala, W.; Perera, L.D.R.D.; de Silva, K.T.L.; Jayanetti, J.K.D.S.; Dharmadasa, I.M.
Low temperature electrochemical deposition of cuprous oxide from aqueous solutions has been investigated. X-ray diffraction, scanning electron microscopy, optical absorption, and photo-response of liquid/cuprous oxide junctions have been used to study the deposits' crystallographic, morphological, optical, and electrical properties. Effects of annealing in air have been studied using the above mentioned methods. As-deposited cuprous oxide exhibits a direct band gap of 2.0 eV, and shows an n-type behaviour when used in an liquid/solid junction. Annealing below 300�C enhances the n-type photocurrent produced by the junction. Type conversion occurs after heat treatments in air at temperatures above 300�C. No apparent bulk structure changes have been observed during annealing below this temperature, but heat treatments above this temperature produce darker films containing cupric oxide and its complexes with water.
Sulphidation of electrodeposited cuprous oxide thin films for photovoltaic applications
(Solar Energy Materials and Solar Cells, 2000) Wijesundera, R.P.; Perera, L.D.R.D.; Jayasuriya, K.D.; Siripala, W.; de Silva, K.T.L.; Samantilleke, A.P.; Dharmadasa, I.M.
Electrodeposited cuprous oxide thin films on indium-doped tin oxide (ITO) substrates were sulphided by exposing them to a spray of aqueous solution of sodium sulphide or to a mixture of hydrogen sulphide and nitrogen gases. Both methods produced light darker and darker films having different photovoltaic characteristics in a solar cell structure. The photovoltages produced by the light darker films under AM 1.5 illumination was negative as compared to the positive photovoltages produced by the darker films. Spectral response measurements revealed that most of the light darker films produced positive photovoltages in the shorter wavelengths and negative photovoltages in the longer wavelengths. However, some of the light darker films produced only the negative photovoltage for the entire spectral range and their photovoltaic properties were comparatively better. Darker films resulted in only the positive photovoltages in the entire spectral range. As a result of the sulphidation, the bulk crystal structure of the cuprous oxide thin films was not changed, however, the interfacial characteristics of the solar cell structure were modified.
Type Conversion of Electrodeposited Cuprous Oxide
(1996) Perera, L.D.R.D.; de Silva, K.T.L.; Siripala, W.; Jayanetti, J.K.D.S.
Cuprous oxide is an inexpensive and non-toxic semiconductor material having a direct band gap of 2.0 eV. In view of its possible applications in low-cost solar energy converting devices thin films were fabricated and their crystallographic and optoelectronic properties were investigated using X-ray diffraction and spectral response measurements. Thin films of polycrystalline cuprous oxide were electrodeposited on indium tin oxide (ITO) coated glass substrates using an aqueous electrolyte under potentiostatic conditions. The photo-response of both the as deposited and annealed samples were investigated. The films were used in a three electrode photoelectrochemical cell for spectral response measurements. The experimental set up consisted of a potentiostat, a lock-in-amplifier, a monochromator and a chopper. At rest potential, the photoresponse of the as deposited Cu2O films illuminated through the Cu2O/electrolyte interface (front illumination) was n-type in the whole spectral range. When illuminated through the ITO substrate (back illumination) the photocurrent was p-type for shorter wave lengths and n-type for longer wave lengths. These results indicate the existence of two n-type Schottky barriers at the Cu2O/electrolyte interface and at the Cu2O/ITO interface, and show that electrodeposited Cu2O thin films behave as an n-type material in a PEC cell. The samples were annealed in air and their XRD patterns were obtained as a function of annealing. No significant change in the XRD spectra could be observed for samples annealed at temperatures below 300 0C. for samples annealed at temperatures above 3000C, the XRD spectra showed peaks corresponding to CuO and its complexes with water. Also, heat treatments at higher temperatures resulted in darker films. In both the cases of front and back illuminations, the photoresponses of Cu2O annealed at 200 0C was n-type in the whole spectral range. When compared with the spectral response of the as deposited samples, these observations suggest that the Schottky barrier at the Cu2O/ITO interface has been removed by annealing at 200 0C. The films annealed at 300 0C showed a p-type photocurrent in the entire spectral range on front illumination. This observation suggests that the conductivity type of Cu2O has changed from n-type to p-type upon annealing at 300 0C.