LAUSR

Abstract For figuring out the separation performance and transfer behavior of photogenerated charge carriers in porous spinel structured zinc ferrite (ZnFe2O4, ZFO) ultrathin films, novel ZFO nanoparticle films (LB-ZFO) were prepared on the fluorine-doped tin oxide conductive glass by the Langmuir-Blodgett (LB) method in this study. As illuminated by the light with the wavelength ranging from 320 nm to 440 nm, monolayer LB-ZFO film (LB-ZFO-1) showed relatively higher surface photovoltage than the 5-layered and 9-layered LB-ZFO films, which suggested the film thickness reduction facilitated the photogenerated charge carrier separation. Moreover, the LB-ZFO-1 film possessed lower flat band potential and larger space charge layer width in comparison with the 5-layered and 9-layered LB-ZFO films, further proving that stronger driving force was available for separating the photogenerated electrons and holes by reducing the film thickness. All the as-prepared LB-ZFO films exhibited the capacitor behavior because of their porous structure. The photoelectrocatalytic (PEC) activity of LB-ZFO-1 film was still low even though the electron transfer resistance at the LB-ZFO-1 film/electrolyte interface greatly decreased from 518.60 Ω to 92.56 Ω. Therefore, it suggests that the capacitor behavior existing in porous films is probably one of key factors that resulted in poor PEC activities of LB-ZFO films, which should be induced considerable attentions in future.