Study on dynamic properties of the photoexcited charge carriers at anatase TiO 2 nanowires/fluorine doped tin oxide interface

The photoexcited electrons transfer dynamics at the TiO2 film/fluorine doped tin oxide (FTO) interface of anatase TiO2 nanowire arrays (NWAs) and QD-sensitized TiO2 NWAs films have been studied by using surface photovoltage (SPV) and transient photovoltage (TPV) techniques. Various SPV and TPV responses were obtained when the laser beam was incident from the front side illumination and back side illumination. Based on the work function values of anatase TiO2 NWAs and FTO, the results indicate that diffusion is the major way for the separation and transfer of the photoexcited charge in the both anatase TiO2 NWAs and QD-sensitized TiO2 NWAs films under front side illumination. And the photoexcited charge were separated by drift under the built-in electric field at the TiO2 film/FTO interface for anatase TiO2 NWAs and QD-sensitized TiO2 NWAs films under back side illumination. In addition, under back side illumination the built-in electric field and band structure of CdS/CdSe QDs and anatase TiO2 NWAs lead to the separation and transfer of the photoexcited charge for CdS/CdSe QDs sensitized TiO2 NWAs/FTO film. As the intensity of illumination increases, the effect of built-in electric field on the separation and transfer of the photoexcited charge in the QD-sensitized TiO2 NWAs film decreases.