Electrolyte effects on photoelectron injection and recombination dynamics in dye-sensitized solar cells

In this study, the influence of electrolyte on the charge recombination, electron injection efficiency (Φinj) and performance of dye-sensitized solar cells (DSCs) was investigated. A negative shift in the flatband potential (Vfb) of the TiO2 electrode indicated that 1-methylbenzimidazole (MBI) chemisorbed on the TiO2 surface and reduced the Li+ adsorption in the nanostructured electrode. Electrochemical impedance spectra for the DSCs showed that the addition of MBI in the LiI electrolyte could increase the electron lifetime and reduce the rate constant (ket) for I3− reduction with electrons in the TiO2 conduction band. The increase in Voc for solar cells with MBI was mainly attributed to the negative shift in the Vfb of the TiO2 electrode and the decrease of recombination reaction at the dyed TiO2/electrolyte interface. Analysis of the short-circuit current density (Jsc) depended on the light intensity for dye-sensitized solar cells indicated that there was no obvious effect on Φinj when the LiI concentration was up to 0.7 M in the electrolyte. Due to the negative shift in Vfb of the TiO2 electrode by the addition of MBI in the electrolyte, Φinj could be reduced to obtain a decreased Jsc.