International Research Symposium on Pure and Applied Sciences (IRSPAS)

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Subject: search.filters.subject.Cuprous oxide

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    Fabrication of Cu2O homojunction thin films for photovoltaic applications.
    (International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Kafi, F. S. B.; Jayathilaka, K.M.D.C.; Wijesundera, R. P.; Siripala, W.
    Environmentally friendly cuprous oxide (Cu2O) is an attractive cost effective material for developing photovoltaic devices due to its astounding properties. Interestingly, the fabrication of low cost Cu2O homojunction devices is possible due to Cu2O is abundant and the ability of forming the p-Cu2O and n-Cu2O thin films using cost effective electrodeposition technique. Indeed, it is necessary to optimize p-n junction devices by varying deposition parameters. Vividly, the pH of the deposition bath controls the quality of the electrodeposited Cu2O thin films. Hence, it is important to optimize the pH value of the bath use for the electrodeposition of n-Cu2O and p-Cu2O films for developing Cu2O based devices. In this study, Cu2O thin film homojunction device was fabricated using a successive deposition of an n-Cu2O film followed by a p-Cu2O film, in two different baths; acetate and lactate respectively. The Cu2O homojunction was fabricated on a Ti substrate by the two-step potentiostatic electrodeposition process. A set of n-Cu2O thin films were electrodeposited on Ti substrate in a three electrode aqueous electrochemical cell containing 0.1 M sodium acetate and 0.01 M cupric acetate at potential of -200 mV vs. Ag/AgCl electrode, bath temperature of 55 °C and the film deposition time of 1 hour at two different pH values of n-Cu2O thin film deposition baths; 6.1 and 6.5. Then to optimize the Cu2O homojunction, Ti/n-Cu2O/p-Cu2O junction was fabricated by consequently electrodepositing p-Cu2O thin film on n-Cu2O film by changing the pH value from 7.0 to 13 of the p-Cu2O thin film deposition bath. The electrochemical bath used for the deposition of p-Cu2O thin films contained 3 M lactic acid, 0.4 M copper sulfate and 4 M NaOH. pH of the deposition baths were controlled by adding NaOH and HCl. Then Ti/n-Cu2O/p-Cu2O/Au structure was fabricated by sputtering Au on the resulted Cu2O homojunction. The highest photoactive film observed for Ti/n-Cu2O/p-Cu2O/Au structure that was fabricated at pH values of 6.1 and 11.0 for n-Cu2O and p-Cu2O deposition baths respectively. The observed VOC and JSC values for the optimum Ti/n-Cu2O/p-Cu2O/Au structure was 344 mV and 1.13 mA/cm2 respectively, under AM 1.5 illumination. The resulted high VOC and ISC values evident for the possibility of fabrication of Cu2O homojunction devices by employing consecutive electrodeposition of an n-Cu2O layer followed by a p-Cu2O layer using the relevant baths at different growth conditions. Promisingly, fabricated Cu2O homojunction may further improved by surface treatments and optimizations, to produce high efficient Cu2O homojunction devices.
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    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.