International Research Symposium on Pure and Applied Sciences (IRSPAS)

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Author: search.filters.author.Kafi, F. S. B.

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    Electrodeposited homojunction Cu2O solar cell on FTO substrate
    (Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Kafi, F. S. B.; Jayathilaka, K. M. D. C.; Wijesundera, L. B. D. R. P.; Siripala, W.
    Cuprous oxide (Cu2O), an abundant photoactive semiconducting material has optimum optoelectronic properties to develop efficient, inexpensive and eco-friendly solar cells. Even though, it is possible to fabricate Cu2O based hetero or Schottky junction solar cells, it is believed that the reduction of interface strains via application of surface treatments can produce best efficient homojunction Cu2O solar cell. Apart from the homogeneity of a p-n junction, reduction of contact resistances of a solar cell also has a great impact on its overall performance. Previous studies have shown that, annealing and/or sulphidation of thin film Cu2O enhances the surface properties while sulphided p-Cu2O/Au junction exhibits ohmic behavior as well. Thus, in this study possibility of developing efficient thin film homojunction Cu2O solar cell on FTO substrate was tested by improving the surface properties of n- and p-Cu2O thin film layers. n-Cu2O thin film was potentiostatically electrodeposited in a three electrode photoelectrochemical cell, contained 0.1 M sodium acetate and 0.01 M cupric acetate, acetic acid at bath pH value of 6.1 and then, this thin film FTO/n-Cu2O photoelectrode was annealed at temperature of 4000C to form very thin p-Cu2O layer with lower surface defects. Subsequently, for a thicker absorber layer a thin film ptype Cu2O was electrodeposited on annealed FTO/n-Cu2O photoelectrode using a lactate bath, consisted 3 M lactic acid, 0.4 M copper(II) sulphate and 4 M sodium hydroxide at bath pH value of 13.0. Finally, to form ohmic back contact this bi-layer is directly exposed to ammonium sulphide vapor for 8s and sputtered thin film of Au on it. Photoresponses and modulated light induced current-voltage characterization of this final thin film Cu2O homojunction is given the highest VOC and JSC values of 154 mV and 3.905 mA/cm-2 respectively. This result revealed that application of surface treatments to the thin film n-Cu2O and the bi-layers ameliorates surface properties, thereby the optoelectronic properties. Parameterization of surface treatments and improvements in the front contact will further improve this homojunction solar cell.
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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.