TiO₂ nanotubes (TNTs) with large aspect ratio and large specific surface area were prepared from P25 (Nippon Aerosil) and applied to dye-sensitized titanium dioxide solar cells (DSSCs). Optimization of fabrication conditions, i.e., pH of the starting paste, sintering temperature for the TiO₂ electrodes, electrolyte compositions of DSSCs gave the high conversion efficiency with improved open circuit voltage (V_oc) and fill factor (FF) when compared to DSSCs made of P25. The evaluation of dye adsorption and the photo-injected electron transport such as electron diffusion coefficient (D) and electron lifetime (τ) in TNTs electrodes revealed that the higher efficiency resulted from increase of electron density with keeping much longer τ in TNTs electrodes than in P25 electrodes.

Use of a new ionic liquid crystal, 1-dodecyl-3-methylimidazolium iodide, and iodine as an electrolyte of dye-sensitized solar cells leads to a high short circuit photocurrent density and a high light-to-electricity conversion efficiency, due to a self-assembled structure of the imidazolium cations, resulting in high conductivity of the electrolyte.

Poly(3,4-ethylenedioxythiophene) (PEDOT) is an excellent kind of conducting polymer, comparable to Pt in catalytic behavior in dye-sensitized solar cells. Electrochemical polymerization in the presence of different anions (doping ions) that work as counterions of the resulting oxidized state PEDOT has been carried out to verify the influence of doping ions on the photo-electron conversion performance in dye-sensitized solar cells. Electrochemical and photo-electrochemical measurements reveal that the interaction between polymer and substrate (FTO) directly influences the fill factor in I–V curves, especially in the PEDOT–PSS system.

A hydrophobic and 2-thiophen-2-yl-vinyl-conjugated ruthenium complex, cis-Ru(dhtbpy)(dcbpy)(NCS)₂ [dhtbpy = 4,4′-di(hexylthienylvinyl)-2,2′-bipyridyl; dcbpy = 4,4′-dicarboxy-2,2′-bipyridyl], was newly designed, synthesized and applied successfully to sensitization of nanocrystalline TiO₂-based solar cells, giving a conversion efficiency of 9.5% under irradiation with AM 1.5 solar light.

The thin Nb₂O₅ layer works as a remakable blocking layer when deposited by the rf magnetron sputtering method between fluorine-doped tin oxide and a mesoporous TiO₂ layer, improving open-circuit photovoltage (V_oc) and fill factor (FF) with power conversion efficiency over 5.5% at 1 sun irradiation of the dye-sensitized TiO₂ solar cells using ionic liquid electrolytes.