Investigation of influence of redox species on the interfacial energetics of a dye-sensitized nanoporous TiO2 solar cell

The photoelectrochem. behaviors of dye-sensitized nanoporous TiO2 solar cells are studied under influences of light intensity, redox couple concn., temp., different cations and water in the nonaq. soln. The value of the ideality factor of dyed nanoporous TiO2 film is detd. to be 1.08. The diode behavior of the dyed nanoporous TiO2 film approaches an ideal rectification characteristic. The rate of the reaction of I3- with the electron at the surface of the dyed TiO2 electrode is of first order, like the redn. of I3- at the Pt electrode. By anal. of the relationship of the photovoltage with temp., the activation energies of the back-reaction for dyed nanoporous TiO2 electrodes in different solns. are obtained. Cations of different kinds and water are found to modify the interfacial properties of the dyed TiO2 electrode. Finally, a quant. relationship between the short-circuit photocurrent and the light intensity, the I3- concn. is obtained and used to explain the diffusion-controlled photocurrent. The cor. diffusion coeff. of I3- is 5.4-6.2×10-6 cm2/s in a CH3OCH2CN soln.