Enhanced photogenerated charge separation in α-Fe₂O₃-ZnFe₂O₄ related to the higher level in the conduction band of α-Fe₂O₃

Abstract

The photogenerated charge separation mechanism in α-Fe2O3-ZnFe2O4 is investigated with surface photovoltaic response. The enhanced photovoltaic response of α-Fe2O3-ZnFe2O4 clearly presents a special position near 373 nm (3.32 eV) for molar ratio 1:1 and a larger wavelength range for the molar ratio 6:1. The special position near 373 nm (3.32 eV) is also observed in absorption spectra for a pristine α-Fe2O3 and α-Fe2O3-ZnFe2O4 composite with molar ratios of 2:1 and 1:1. The same position indicates that a possible higher level in the conduction band of α-Fe2O3 corresponding to the position near 3.32 eV could exist. The result suggests that, besides the reported photogenerated electrons transfer in α-Fe2O3-ZnFe2O4 composite from ZnFe2O4 with higher conduction band to α-Fe2O3 with lower conduction band, the first transition could occur from the higher level in the conduction band of α-Fe2O3 to ZnFe2O4 due to energy level matching.