| Dye sensitized solar cell (DSSC) is a new generation photovoltaic device. Efforts from both laboratories and industries have been concentrated on the study of the device, because of its relatively high photo-electric energy conversion efficiency and low mass production cost. In order to further upgrade the performance, cut the cost and explore the working principle of such a new generation photovoltaic device, three topics have been chosen in this thesis, namely,1. Platinum/Titanium bilayers counterelectrode,2. Residential resistance in the devices,3. Hydrothermal synthesis of TiO2 nanocry stall ine.Platinum/Titanium (Pt/Ti thereafter) bilayers counterelectrodes were fabricated by sputtering Pt/Ti bilayers on glass substrates, where the titanium layer was utilized as an adhesion layer. Structural properties and surface morphologies of the as-fabricated counterelectrodes were characterized by X-Ray diffraction (XRD), atomic force microscopy(AFM), and scanning electron microscopy (SEM), respectively. The electrical, electrochemical along with the optical properties of the counterelectrodes were tested by four-probe measurements, electrochemical impedance spectroscopy, cyclic voltammetry and UV-Vis, respectively. It was found that the sputtered titanium metal thin films were amorphous when annealed in situ below 600 degree centigrade, despite of different substrates used. Pt/Ti inter-metallic phase was identified in the Pt/Ti bilayers counterelectrode, which benefited the adhesion of the Pt layer and then the anti-corrosion property of the counterelectrode. With the increase of metal film thickness, both the sheet resistance and electron-transfer resistance (Rct) decreased quickly first, and then changed a little. Titanium was found to be a poor catalyst. Rct of the counterelectrode was found to be determined by the Pt particle size and the electrochemical active surface area (EAS) of the counterelectrode. Smaller particles were found to be superior to larger ones in catalysis. With increment of the Pt film thickness, both Pt particle size and EAS increased, hence Rct changed a little. The catalysis efficiency of the counterelectrode was further upgraded by utilizing sandblasted substrate.The performance of the photovoltaic cell was affected much by residential resistance, which includes the residential series resistance (Rs) and the residential shunt resistance (Rsh).Exact relationship between the residential resistances and the performance of the DSSCs was unclear due to the difficulty in fabrication of photovoltaic devices with varied resistance values. We thereafter set up a circuit using a typical DSSC and a resistance box. The resistance box was put in series or in parallel with the cell so as to act as Rs or Rsh of the cell. When the resistance was changed gradually, the current-voltage (IV) curves of the whole system was tested in dark and under irradiation. It was found that, the characteristic resistance (Rch) played a role in the relationship between the residential resistances and IV curves and that between the residential resistances and performance parameters of the devices. As Rs/Rch increased, or Rsh/Rch decreased, the characteristics of the IV curves changed from that like a diode to that like a resistance; on the other hand, fill factor and photo-electric energy conversion efficiency went down quickly. Such a trend was found to be the same like that observed in silicon solar cells. This is because the N-type semiconductor/electrolyte interfaces involved in DSSCs have the same IV characteristics like that of a PN junction. Moreover, from the electrochemical impedance spectroscopy study of the cell, it was found that the electron-transfer resistance of the TiO2/electrolyte interface contributed little to Rsh-The TiO2 nanoporous thin films were synthesized by hydrothermal method. In order to cut down cost, a kind of cheaper titanium alkyoxide or titanium butyoxide was utilized as titanium source to synthesis TiO2 sols. The TiO2 sols were concentrated and used to coat nanoporous thin films on F-doped SnO2 glass (FTO). Then DSSCs were fabricated by using the nanoporous film and liquid electrolyte, and the performance of the device was tested. The synthesis routines were modified by varying the reaction temperature, or by adding surfactants. Particle size distribution, crystallinity and morphologies of the TiO2 nanocrystalline in the sols were characterized by XRD, dynamic laser scattering (DLS), transmission electron microscope (TEM) and selected area electron diffraction (SAED), respectively. The morphology of the nanoporous thin films was monitored by SEM.With the hydrothermal temperature (T) increasing, particle size of TiO2 increased, while scale of the size distribution in the sols first narrowed until T reached 220℃, and then broadened again. When T<220℃, larger sols were formed by amorphous gel and nanocrystallines. When 7>220℃, larger sols were formed by the aggregation between large particles. The sols obtained at 220℃were well dispersed, at which the as-fabricated DSSCs came out with best performance. It was found that the increased dispersion of the sols increased the internal surface area, and hence upgraded the short circuit current density and the photo-electric energy conversion efficiency of the solar cells.The addition of Acetylacetone (AcAc) in the solution of Titanium butyloxide could retard the reactions of hydrolysis/condensation of the alkyoxide. With ratio of AcAc/Ti increasing, the average particle size of the anatase crystallites first decreased, until the ratio reached 0.2, and then increased again. In the presence of AcAc, the nanocrystallines tended to form ordered structure like "nano-chain", which was conducted by the so-called "oriented attachment" between these crystallines. Such ordered structure could increase the short circuit current and photo-electric energy transfer efficiency of the DSSCs.The particle size and crystallinity of the TiO2 crystallite in the sols was also affected by the addition of polyethylene glycol (PEG) to hydrothermal reaction. With concentration of PEG increasing, the particle size of anatase particles first decreased quickly, from～20nm to～10nm, and then changed a little. On the other hand, after PEG reached certain concentration, rutile crystallites appeared in the forms of nanowire, twin crystal and so on. It was suggested that, the PEG molecules could be absorbed by the nanocrystallites. The steric hindrance brought on by PEG thus prevent aggregation between the nanocrystallites. Therefore, particles of uniform sizes were obtained. The existence of PEG made it easier for rutile crystallite to form. At lower concentration of PEG, the as-fabricated DSSCs with liquid electrolyte showed increased short circuit current density up to 20 mA/cm2, and hence upgraded photo-electric energy conversion efficiency up to 7.5% (thickness of photoanode was～6μm, and tested under AM 1.5 G,100mW/cm2), which was benefited by the narrowed size disperse of the particles.
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