Fermi‐level pinning and effect of deposition bath pH on the flat‐band potential of electrodeposited n‐Cu2O in an aqueous electrolyte

Abstract

Capacitance–voltage (C–V) and modulated light‐induced current–voltage measurements were employed to investigate the Cu2O/electrolyte junction of electrodeposited n‐Cu2O thin films. The Mott–Schottky plots resulting from the C–V measurements revealed that the extrapolated flat‐band potential of n‐Cu2O films was strongly influenced by the pH of the bath where the films were grown. The flat‐band potential change was 300 mV for a pH difference of 0.8 and showed that the surface chemistry at an n‐Cu2O/aqueous electrolyte interface was strongly affected by the pH of the film deposition bath. In addition, current–potential measurements revealed that at the measured flat‐band potential the photocurrent did not vanish for n‐Cu2O films and the Fermi level at the interface was pinned due to the presence of electrically active surface states. Information on the presence of electrically active surface states and the shift in flat‐band potential will be very useful for applications of n‐Cu2O films in various devices.