Effects of 4-tert-butylpyridine on the quasi-Fermi levels of TiO2 films in the presence of different cations in dye-sensitized solar cells

The effects of additives on the quasi-Fermi levels (QFL) of TiO2 films in dye-sensitized solar cells (DSCs) were investigated by a direct method. We observed that the values of QFL of TiO2 at short circuit and open circuit are different and found for the first time the linear relationships between QFL shifts at short circuit and open circuit induced by 4-tert-butylpyridine (TBP), and that the slopes of the lines were significantly influenced by the nature of cations in the electrolyte. Different QFL shifts at short circuit and open circuit were observed in the presence of TBA(+). These quantitative results suggest that the QFL of TiO2 films at short circuit and open circuit can be adjusted separately by developing suitable additives and cations, which will be helpful to further improve the efficiency of DSCs.