Enhancement of photoelectric conversion properties of SrTiO3/?-Fe2O3 heterojunction photoanode.

The semiconductor films of SrTiO3, a-Fe2O3 and their heterojunction SrTiO3/a-Fe2O3 were prepared on FTO (SnO2 : F on glass) substrates by the spin-coating method and their structures and properties were characterized by XRD, SEM and photoelectrochemical measurements, respectively. It was observed that the photocurrent and the incident photon to current conversion efficiencies (IPCE or external quantum efficiencies) of the SrTiO3/a-Fe2O3 heterojunction were higher than that of the single SrTiO3 or a-Fe2O3 film, particularly under visible light irradiation. The band structures of SrTiO3 and a-Fe2O3 were calculated. It was found that the charge carriers in a-Fe2O3 had large effective masses while the charge carriers in SrTiO3 had small effective masses at the bottom of the conduction band and at the top of the valence band, which meant weak mobility of holes photo-generated in a-Fe2O3 and strong mobility of holes excited in SrTiO3. As to the SrTiO3/a-Fe2O3 heterojunction, the special valence band structures of SrTiO3 improved the separation efficiency of charge carriers which had been photo-generated in a-Fe2O3. This led to the enhancement of photocurrent densities and external quantum efficiencies in the SrTiO3/a-Fe2O3 heterojunction photoanode. [ABSTRACT FROM AUTHOR]