The effect of the rutile content on the photovoltaic performance of dye-sensitized solar cells (DSSCs) composed of mixed-phase TiO(2) photoelectrode has been investigated. The mixed-phase TiO(2) particles with varied amounts of rutile, relative to anatase phase, are synthesized by an in situ method where the concentration of sulfate ion is used as a phase-controlling parameter in the formation of TiO(2) using TiCl(4) hydrolysis. The surface area (S(BET)) varies from 33 (pure rutile) to 165 (pure anatase) m(2) g(-1). Generally, both the current density (J(sc)) and photo-conversion efficiency (η) decrease as the rutile content increases. The incorporation of rod-shaped rutile particles causes low uptake of dye due to the reduced surface area, as well as slow electron transport in less efficiently-stacked structure. However, maximum J(sc) (14.63 mA cm(-2)) and η (8.69%) appear when relatively low rutile content (16%) is employed. The reported synergistic effect by the efficient interparticle electron transport from rutile to anatase seems to overbalance the decrease of surface area when small amount of rutile particles is incorporated.

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The carrier transport kinetics of the TiO 2 film doped with N (TiO 2 :N) were investigated by measuring the current and open circuit potential transients under light on/off illumination. These measurements were compared to an undoped film. The N in TiO 2 not only shifted the light absorption into a longer wavelength region (known effect) but also enhanced the carrier transport. The combination of these two effects improved the photogeneration of the electron-hole pairs and suppressed their recombination, resulting in much better photoelectrochemical performance, compared to that of the undoped TiO 2 . #

Nitrogen-doped TiO2 crystallites were prepared via the hydrolysis of TiCl4 using an ammonia medium in an aqueous solution for DSSC photoelectrodes. The optimized photoelectrode for the DSSC was prepared with 9.4 nm sized N-doped TiO2 crystal (BET; 200 m2/g), which provides a relatively high short circuit current and energy conversion efficiency in the DSSC. The photovoltaic performance of the N-doped TiO2 electrode was confirmed using incident photon-to-current efficient spectra, impedance analyses, and Bode-phase plots which proved that the N-doped TiO2 electrode has a significantly enhanced electron lifetime compared with that of the P25 electrode.

In this study, C-doped TiO2 particles were successfully synthesized by a hydrothermal method. Three binding energy peaks were observed at 284.6, 286.2, and 288.5 eV in the C is region of the XPS. The signals at 286.2 and 288.5 eV were attributed to chemically bound C-O and Ti-C-O linkages within the crystalline TiO2 lattice, respectively. The introduction of carbon did not affect the crystallite structure or BET surface area of TiO2. The JSC value of DSSCs based on a C-doped TiO2 electrode was increased by 20% compared to DSSCs using a pure TiO2 electrode, and the energy conversion efficiency was increased by 23%. This was due to the enhancement of dye adsorption and high electrical conductivity of the carbon. High energy conversion efficiency was achieved with the DSSCs based on the C-doped TiC2 electrode.