Electrochemical studies on triarylamines featuring an azobenzene substituent and new application for small-molecule organic photovoltaics

Three N,N′-diaryl-4-amino-azobenzene derivatives containing donor (D) and acceptor (A) moieties have been synthesized for light harvesting. Their optical and electronic characteristics have been analyzed to determine the optical band gap between highest occupied molecular orbital (HOMO) and lowest occupied molecular orbital (LUMO). The electrochemical properties and electrochemical redox potential of the triarylamines exhibited linear relationship with respect to the Hammett equation. The stability of the oxidation products and spectral changes with different applied potentials were monitored with UV–vis spectroelectrochemical investigations and DFT calculations. A solution-processed organic photovoltaic cell employing N,N′-ditolyl-4-aminoazobenzene (DTAA) mixed with PC₆₀BM produced a power conversion efficiency (PCE) of 0.28% under 1 sun illumination.