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

Abstract

In this study, the influence of electrolyte on the charge recombination, electron injection efficiency ( Φ inj) and performance of dye-sensitized solar cells (DSCs) was investigated. A negative shift in the flatband potential ( V fb) of the TiO 2 electrode indicated that 1 -methylbenzimidazole (MBI) chemisorbed on the TiO 2 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 ( k et) for I 3 − reduction with electrons in the TiO 2 conduction band. The increase in V oc for solar cells with MBI was mainly attributed to the negative shift in the V fb of the TiO 2 electrode and the decrease of recombination reaction at the dyed TiO 2/electrolyte interface. Analysis of the short-circuit current density ( J sc) depended on the light intensity for dye-sensitized solar cells indicated that there was no obvious effect on Φ inj when the LiI concentration was up to 0.7 M in the electrolyte. Due to the negative shift in V fb of the TiO 2 electrode by the addition of MBI in the electrolyte, Φ inj could be reduced to obtain a decreased J sc.