Methods for improving n-type photoconductivity Cu2O thin films

Abstract

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.