Photoelectric Conversion Properties of the LaFeO ₃ Cathode for Photoelectrochemical Capacitors

We investigated the photoelectrical conversion properties of various rare-earth ferrites (REFeO3) as photoelectrochemical capacitor cathode materials. Among electrodes of LaFeO3 with different crystallinities, the electrode using it prepared by solid-state synthesis showed the highest photovoltage. Its highest crystallinity probably suppressed the electron–hole recombination to promote the hole accumulation. In various REFeO3 (LaFeO3, NdFeO3, GdFeO3, and ErFeO3), electrical conductivity and photovoltage were increased with increasing rare-earth ion size. We consider that hole accumulation was facilitated because overlapping between Fe 3d and O 2p orbitals became weaker by broadening of the Fe–O–Fe bonding angle with increasing rare-earth ion size in the orthorhombic perovskite structure.