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 × 1016, 2.80 × 1016, and 1.83 × 1016 cm−2 were determined in PN, 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 × 1016, 2.38 × 1016, and 1.19 × 1016 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.
N,N 0 -Bis(salicylidene)ethylenediamine zinc(II) iodide (ZnLI 2 ) was synthesized and characterized by elemental analysis, UV-Vis and IR spectroscopies. This new Schiff base complex was, for the first time, applied as the electrolyte of a dye-sensitized solar cell. ZnLI 2 has high reductive activity and conductivity, resulting in larger IPCE and photoelectric conversion efficiency in the DSSCs. The best results were obtained in the optimized composite electrolyte E2, with a photoelectric conversion efficiency of 7.75% under 100 mW cm À2 irradiation. This work provides a new approach for the improvement of the photoelectrochemical properties of dye-sensitized solar cells.
Transparent nanostructured SrTiO3 film electrodes were fabricated on conductive substrates from SrTiO3 nanocrystals. Band energetics were determined with spectroelectrochemical measurements, and its trap states were investigated with electrochemistry. The flat band edges (E
fb) of nanostructured SrTiO3 electrodes were highly dependent on the pH of the electrolyte, and measured to be −0.71, −0.96, and −1.19 V versus saturated Ag/gCl at pH 3.0, 6.8, and 13.0, respectively. The time-resolved current at different applied potentials positive of the flat band edge clearly indicate a trap-filling process. The results showed that trap state densities are also highly pH dependent. Total trap state densities of 2.0 × 1015, 8.08 × 1015, and 1.21 × 1016 cm−2 were determined at pH 3.0, 6.8, and 13.0, respectively with maximum located at −0.25, −0.50, and −0.70 V. The results obtained from cyclic voltammograms are in good agreement with that obtained from the measurements of time-resolved currents. The size of the peak potentials related to the trap states (−0.25, −0.51, and −0.72 V for pH 3.0, 6.8, and 13.0, respectively) in the cyclic voltammograms increases dramatically with increase of pH, indicating that traps are mostly surface-related.
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