Tunability of the Band Energetics of Nanostructured SrTiO3 Electrodes for Dye-Sensitized Solar Cells

The flat band edges (E-fb) Of nanostructured SrTiO3 electrodes have been determined in propionitrile (PN), acetylacetone (Acac), and PN/Acac with spectroelectrochemistry measurements. Specifically, a very negative E-fb was measured when only tetrabutylammonium perchloride (TBAP) was used as Supporting electrolyte, while addition of Li+ ions shifts E-fb Positively. The trap state distribution was investigated by the measurements of time-resolved current. The total trap state densities of 5.51 x 10(16), 2.80 x 10(16), and 1.83 x 10(16) cm(-2) were determined ill PIN, PN/Acac, and Acac (all containing 0.2 mol.L-1 TBAP), respectively, with trap distribution maximum located at -2.4, -1.6, and -1.5 V. The addition of Li+ also reduced the trap state densities, and the total trap state densities were calculated to be 4.19 x 10(16), 2.38 x 10(16), and 1.19 x 10(16) cm(-2) in PN, PN/Acac, and Acac (all containing 0.2 mol.L-1 TBAP and 0.5 mol.L-1 LiClO4), respectively. Finally the nanostructured SrTiO3 electrode was sensitized with dye N3 and its photovoltage-photocurrent Curves were measured in three electrolytes with PN, PN/Acac, and Acac as solvents, respectively. The N3-sensitized SrTiO3 showed the highest open-circuit voltage (V-oc) and Short-circuit Current density (J(sc)) in Acac, in good agreement with the electrochemical measurements that the nanostructured SrTiO3 electrode has the flat band edge well matching with the excited state of N3 and the smallest trap state densities in Acac.