The growth of anatase
TiO2 nanowires (NWs) on fluorine
doped tin oxide (FTO) substrates through hydrothermal reaction has
attracted wide attention and research, especially in the case of the
solar cells. Actually, the built-in electric field at the anatase
TiO2 NWs/FTO interface leads to the photoexcited holes
transfer to FTO conductive substrates because the Fermi energy of
anatase TiO2 NWs film is higher than that of FTO substrates.
Yet efficient transport of photoexcited electron to the FTO conductive
substrates is desirable. Hence, the built-in electric field at the
pure TiO2 NWs/FTO interface has prevented anatase TiO2 NWs-based solar cells from achieving a higher photoelectric
performance. In this work, we elaborately design and construct the
N-doped anatase TiO2 NWs/FTO interface with the desirable
orientations from FTO toward N-doped anatase TiO2 NWs,
which favors the photoexcited electron transfer to the FTO conductive
substrates. The surface photovoltage (SPV) and Kelvin probe measurements
demostrate that the N-doped anatase TiO2 NWs/FTO interface
favors the photoexcited electron transfer to the FTO conductive substrates
due to the fact that the orientation of the built-in electric field
at the N-doped TiO2 NWs/FTO interface is from FTO toward
TiO2. The photoexcited charge transfer dynamics of CdS
QD-sensitized TiO2 NWs and N-doped TiO2 NWs
electrodes was investigated using the transient photovoltage (TPV)
and transient photocurrent (TPC) technique. Benefiting from the desirable
interface electric field, CdS-based quantum dot-sensitized solar cells
(QDSCs) with the optimal N doping amount exhibit a remarkable solar
energy conversion efficiency of 2.75% under 1 sun illumination, which
is 1.46 times enhancement as compared to the undoped reference solar
cells. The results reveal that the N-doped anatase TiO2 NWs electrodes have promising applications in solar cells.