Electrodeposited Cuprous oxide for low cost soalr energy Applications

Abstract

Cuprous oxide (Cu2O), one of the earliest known semiconductor materials, is attractive for solar energy applications because it is low cost, non toxic and has a direct band gap of 2 eV. It is considered as one of the candidate materials for the applications in the third generation of solar cells. Cu2O is generally a p-type semiconductor material due to the Cu vacancies exist in the crystal lattice. Earlier attempts to fabricate efficient thin film solar cells with this material were unsuccessful because the unavailability of n-type Cu2O. However, it has been reported that corrosion layers on Cu electrodes in aqueous baths produce n-type films. We have exploited this growth mechanism of n-type Cu2O films to electrodeposit n-type films on various conducting substrates. This technique of electrodeposition is attractive because it provides a low cost method for growing thin films, in addition to the n-type behavior. We found that a narrow potential window is available for the electrodeposition of Cu2O thin films. Also the conductivity type of the films is very sensitive to pH of the aqueous bath. Single phase Cu2O polycrystalline films can be obtained in the narrow potential domain and at more negative depositing potentials co-deposition of Cu is resulted. Cu2O thin films can be obtained by this method to produce n-type conductivity. This n-type behavior and the quality of the Cu2O films produced by the technique will be presented. Further, evidence for the existence of oxygen vacancies in the electrodeposited n-type Cu2O films is presented. Possibility of application of these n-type films in low cost solar cell devices is demonstrated with the n-Cu2O/p-CuxS junction obtained by sulphiding Cu2O thin films and with other junction formations.