Photoelectrochemical Properties of Nanomultiple CaFe₂O₄/ZnFe₂O₄pn Junction Photoelectrodes

Nanomultiple CaFe 2 O 4 /ZnFe 2 O 4 pn junctions are prepared by a pulsed laser deposition method to explore their photoelectrochemical properties as the photoelectrodes. It is demonstrated that the multiple- pn -junction structure is favorable to enhancing the photocurrent density and the onset potential of the photoelectrode. Furthermore, the 20-junction photoelectrode-based PEC cell yields a high open circuit photovoltage of up to 0.97 V, which is much higher than that for a single pn junction photoelectrode PEC cell that yields an open circuit photovoltage of 0.13 V. A multiple - junction band structure model is assumed to describe the behavior of the CaFe 2 O 4 /ZnFe 2 O 4 multiple-junction photoelectrodes. It is suggested that the open circuit photovoltage is dominated by the number of pn junctions in a multiple-junction photoelectrode and the carrier transfer inside the photoelectrode is improved by narrowing the single-layer thickness. These findings provide a new approach to designing the multiple-junction structure to improve the PEC properties of the photoelectrodes.