Preparation of Highly Ordered Mesoporous Al2O3/TiO2 and Its Application in Dye-Sensitized Solar Cells

Highly ordered mesoporous Al2O3/TiO2 was prepared by sol−gel reaction and evaporation-induced self-assembly (EISA) for use in dye-sensitized solar cells. The prepared materials had two-dimensional, hexagonal pore structures with anatase crystalline phases. The average pore size of mesoporous Al2O3/TiO2 remained uniform and in the range of 6.33−6.58 nm while the Brunauer−Emmett−Teller (BET) surface area varied from 181 to 212 m2/g with increasing the content of Al2O3. The incorporation of Al content retarded crystallite growth, thereby decreasing crystallite size while simultaneously improving the uniformity of pore size and volume. The thin Al2O3 layer was located mostly on the mesopore surface, as confirmed by X-ray photoelectron spectroscopy (XPS). The Al2O3 coating on the mesoporous TiO2 film contributes to the essential energy barrier which blocks the charge recombination process in dye-sensitized solar cells. Mesoporous Al2O3/TiO2 (1 mol % Al2O3) exhibited enhanced power conversion efficiency (V oc = 0.74 V, J sc = 15.31 mA/cm2, fill factor = 57%, efficiency = 6.50%) compared to pure mesoporous TiO2 (V oc = 0.72 V, J sc = 16.03 mA/cm2, fill factor = 51%, efficiency = 5.88%). Therefore, the power conversion efficiency was improved by ∼10.5%. In particular, the increase in V oc and fill factor resulted from the inhibition of charge recombination and the improvement of pore structure.