Abstract

Two strategies to solve the problem of instability of photoanodes against photocorrosion have been explored. The photocorrosion of photoanodes generally occurs when they enter the fabrication of efficient photoelectrochemical cells (i.e. showing high values of the open circuit voltage and photocurrent density).One of these strategies consists of protecting the photoanode against photocorrosion by a non-conducting oxide film deposited on its surface. The oxide must have a cationic valence band, or valence energy states, falling either above, or at the same level as, the top of the valence band of the anode. The significant photocurrent observed with the n-GaAs/Sr_0.98Na_0.01Ce_0.01TiO₃ hybridelectrode structure confirms the validity of the model.The second possibility deals with the protection of the photoanode by a conducting oxide film in which the carrier transport occurs, close to the Fermi level, via either a partially filled band or a sufficiently high density of localized states. We have illustrated this method of protection by depositing n-SrTiO₃ on n-GaAs. The n-SrTiO₃ films have the Fermi level pinned within the forbidden band by Ti:3d(t_2g) energy states. The corresponding electrochemical cells exhibit photoconversion efficiency as high as 18% for an illumination of 5 mW/cm².