Facile fabrication of mesoporous TiO2 electrodes for dye solar cells: chemical modification and repetitive coating

A chemical dispersing technique for preparing a coating paste of TiO2 nanoparticles is disclosed to fabricate mesoporous electrodes for dye-sensitized TiO2 solar cells. The suspension of TiO2 (P-25) powder was stirred in aqueous nitric acid at 80°C, and then evaporated to dryness, giving the nitric acid-adsorbed P-25 powder. The coating paste was obtained by mixing the nitric acid-adsorbed P-25 with PEG (Mw 20,000) as a porosity-controlling agent and cellulosic polymer as a thickener. The mesoporous TiO2 films were fabricated on conducting glasses by repetitive coating and calcined at 500°C (30 min). The TiO2 film obtained by the five times repetitive coating (20 μm thickness) resulted in the 1.4 times higher energy conversion efficiency of the dye-sensitized solar cells than that of the one time coating TiO2 film (Voc=690 mV, Jsc=12.2 mA/cm2, the fill factor=0.71 and η=6.0%).