Browsing by Author "Perera, L.D.R.D."

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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 .
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.
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.
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.
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.