Browsing by Author "Kalubowila, K.D.R.N."

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Construction of Cu2O Thin Film based Light Detector
(Proc. 28th Technical Sess. of Institute of Physics, Sri Lanka, 2012) Kalubowila, K.D.R.N.; Jayathilaka, K.M.D.S.; Siripala, W.; Jayanetti, J.K.D.S.
Development of copper oxides and copper indium disulphide based solar cells using electrodeposition technique
(2016) Kalubowila, K.D.R.N.
Effect of temperature on photosensitivity of electrodeposited n-Cu2O/p-CuxS thin film junctions
(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Madusanka, H.D.P.; Kalubowila, K.D.R.N.; Jayathilaka, K.M.D.C.; Jayanetti, J.K.D.S.
The purpose of this study was the construction of a standalone microcontroller based ambient light sensing device to interface an ambient light sensor with a temperature correction and to study the effects of temperature on photosensitivity of electrodeposited Cu2O based thin film p-n junction diodes. Environmentally friendly, low cost, nontoxic cuprous oxides have highly acceptable electrical and optical properties. It has a direct energy gap of about 2 eV at room temperature and has a good absorption coefficient. Cuprous oxide has a good mobility for the majority carriers and a diffusion length of the minority carriers is several micrometers. In this study, an electrolytic solution of 0.1M sodium acetate and 0.01M cupric acetate was used to fabricate Cu2O thin films on top of Ti substrates using electrodeposition. Electrodeposition was carried out potentiostatically at a potential of -200 mV with respect to the saturated calomel electrode. A Na2S solution was used to make the n- Cu2O/p-CuxS junction. In order to increase the photocurrent from the fabricated n- Cu2O/p-CuxS junction, the sulphided Cu2O sample was exposed to ammonium sulphide gas. Then the photocurrent of the n-Cu2O/p-CuxS thin film junction was measured by a constructed microcontroller based light sensing device simultaneously monitoring the intensity of light with a luminance meter HS1010. An important observation made in this study was that the photocurrent of the electrodeposited Cu2O/CuxS thin film junctions depended greatly on the variation of temperature during exposure to light. Thus the junction photocurrent was studied by exposing the junctions to light while monitoring the variation in the photocurrent with the temperature using a DS18B20 temperature sensor. The resulting data were plotted using MATLAB software and it was found that the photocurrent of the thin film p-n junction displayed a variation that was very much linear at low intensities of light. The measured output currents obtained from the p-n junctions and the output values obtained from the temperature sensor were used to display the intensity of light with the temperature correction using an electronic circuit.
Electrodeposited (Cu2O)1-x (CuO)x/Cu2O heterojunction solar cell
(Technical Ses., Institute of Sri Lanka, 2014) Kalubowila, K.D.R.N.; Wijesundera, R.P.; Siripala, W.
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.
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.
Growth of(Cu2O)1-x(CuO)x thin films for PV applivations
(Srilanka association for the advancement od science proceedings of 69th Anuual Session., 2013) Kalubowila, K.D.R.N.; Wijesundera, R.P.; Siripala, W.
Improved n-type behaviour of Cu2O by successive electrodeposition of Cu and Cu2O
(University of Kelaniya, 2013) Kalubowila, K.D.R.N.; Wijesundera, R.P.; Siripala, W.
Cuprous oxide (Cu2O) is a non-toxic, low cost and potentially attractive material as an active semiconductor for solar cell applications. Further, it has an added advantage of direct band gap of 2 eV. Cu2O typically shows p-type conductivity due to copper vacancies created in the lattice. In 1986, it was reported that electrodeposition of Cu2O in slightly acidic solutions shows n-type conductivity due to the excess of Cu or oxygen vacancies in the Cu2O lattice. However, n-type conductive Cu2O reported so far has both n-type and p-type photoactivity showing n-type behavior predominantly. This effect of n-Cu2O is a major problem in the fabrication of solar cells, as it affects the overall performance of the device. In the present study, to avoid the formation of p-type photoconductivity in n-Cu2O, environment was made Cu rich by depositing a very thin Cu film before the growth of Cu2O. Electrodeposition of n-Cu2O was carried out in an acetate bath by growth of very thin Cu film followed by Cu2O deposition. A very thin Cu film was potentiostaticaly electrodeposited on the Ti substrate at -700 mV Vs Ag/AgCl2 for a few minutes in a three electrode electrochemical cell containing aqueous solution of 0.1 M sodium acetate and 0.01M cupric acetate at a temperature of 55 o C and the deposition potential was switched to – 200 mV Vs Ag/AgCl2 for 60 min in order to grow n-Cu2O with sufficient thickness. Thickness of the Cu layer was adjusted by varying the Cu deposition time. Photoactivity of n-Cu2O films were characterized by dark and light current-voltage measurements and spectral response measurements in a PEC cell containing 0.1 M sodium acetate. Results revealed that, in general, electrodeposited n-Cu2O thin films produced p-type photoconductivity in addition to the n-type photoconductivity. Growth of very thin Cu film prior to the Cu2O improves the n-type photosignal and shifts the flat band potential significantly towards negative direction by removing the p-type conductivity of electrodeposited films. In conclusion, our study revealed, for the first time, that the n-type behaviour of Cu2O thin films can be improved with consecutive growth of very thin Cu film prior to the Cu2O deposition.
Methods for improving n-type photoconductivity Cu2O thin films
(Semiconductor Science and Technology, 2014) Kalubowila, K.D.R.N.; Gunawardena, L.K.A.D.D.S.; Wijesundera, R.P.; Siripala, W.
Electrodeposition technique is very useful for depositing n-type Cu2O thin films on various substrates. However, most of the reported n-type Cu2O thin film electrodes exhibit not only n-type photoactivity but also p-type photoactivity in photoelectrochemical cells. In this study, current?voltage characteristics and zero bias spectral response measurements were employed to investigate the possibilities to remove/minimize this unwanted p-type behaviour of n-type Cu2O thin films electrodeposited on Ti substrate. For this, prior deposition of Cu thin films on Ti substrate, low temperature annealing of Cu2O films in air and optimization of deposition bath pH were investigated. Growth of a very thin Cu film improved the n-type photosignal significantly and reduced the p-type photoresponse of the films. Films electrodeposited using an acetate bath of pH 6.1 produced only the n-type photoresponse. Low temperature annealing of Cu2O films in air improved the n-type photoresponse and it was found that annealing at 100 �C for 24 h produces the best result. These methods will be very useful to obtain electrodeposited Cu2O thin film with improved n-type photoactivity suitable for applications in thin film solar cells and other devices.
Methods for improving n-type photoconductivity of electrodeposited Cu2O thin films
(Semiconductor Science and Technology, 2014) Kalubowila, K.D.R.N.; Gunawardena, L.K.A.D.D.S.; Wijesundera, R.P.; Siripala, W.