Synergistic Effect of Polyoxometalates and rGO for Enhancing the Photocurrents of TiO2-based Composite Film

Polyoxometalates possess unique electron-accepting ability while maintaining their structures; this makes them effective electron mediators in semiconductor-based optoelectronic system via retarding the photoexcited electron–hole recombination. H3PW12O40 (PW12) was introduced into TiO2 film using layer-by-layer method in the presence of reduced graphene oxide, serving as a conductive additive. The composite film had smooth surface and dense packing of TiO2 nanoparticles, and showed enhanced transient photocurrent compared to the films without PW12 or reduced graphene oxide (rGO). I–V measurement further confirmed that the power conversion efficiency of PW12/rGO/TiO2 film was remarkably improved compared to those of the films without PW12 or rGO. PW12 functions as an electron mediator and rGO serves as a conductive agent for enhancing the photocurrent and power conversion efficiency, due to the efficient dissociation of excitons and fast electron transfer.