Synthesis of two tri-arylamine derivatives as sensitizers in dye-sensitized solar cells: Electron injection studies and photovoltaic characterization

Two organic sensitizers with the structure donor-π-acceptor, having tri-arylamine as electron donor, cyano-acetic acid as electron acceptor and a phenyl or thiophene ring as π-bridge, are synthesized. The synthetic procedure, the photophysical and electrochemical properties of both dyes are described in detail. In particular, cyclic voltammetry and spectroscopic measurements were performed while the energy gap between highest occupied and lowest unoccupied molecular orbital for both dyes was calculated. Besides, electron injection dynamics on a series of titanium dioxide nanostructured films sensitized with the two dyes were investigated with time resolved fluorescence spectroscopy using femtosecond temporal resolution, while nanostructured alumina films were used as reference. The photovoltaic performances of both dyes in quasi-solid state dye sensitized solar cells were also investigated. A maximum overall conversion efficiency of 3.8% was monitored for two micrometer thin titanium dioxide films and quasi-solid state electrolyte. The performances of the solar cells are explained in terms of photophysical properties and electron injection dynamics of both dyes.