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.