On the origin of increased open circuit voltage of dye-sensitized solar cells using 4-tert-butyl pyridine as additive to the electrolyte

A combination of electrical measurements and surface analysis techniques was used to investigate the electronic structure of the TiO2/electrolyte interface and its change upon addition of 4-tert-butyl pyridine to the electrolyte. A reduced interface defect density and a resulting reduction of charge carrier recombination were found to be the main mechanism for an increased open circuit voltage of dye-sensitized solar cells with 4-tert-butyl pyridine in the electrolyte. The reduction of interface defect states was traced back to specific binding of 4-tert-butyl pyridine at defect sites on the TiO2 surface.