Design, synthesis of organic sensitizers containing carbazole and triphenylamine π-bridged moiety for dye-sensitized solar cells

A series of novel push–pull-based D–π–A-containing organic dyes have been synthesized using triphenylamine and carbazole act as π-conjugated donor and cyanoacrylic acid acceptor as well as anchoring group for application of dye-sensitized solar cells. These organic dyes D1, D2 and D3 exhibited excellent photophysical, electrochemical properties, superior stoke shift, high thermal stabilities and sufficient HOMO–LUMO energy levels, which is facilitated to dye regeneration and effective injection of electron from the excited state of the dyes into the conduction band (TiO2). Our results suggested that carbazole π-bridge has an important role in the photovoltaic performance. The D1 and D2 dyes are planar linear structure, longer π-conjugated bridging units, when compared to the starburst structure of D3 organic dye. Moreover, the carbazole π-bridged conjugated D1 dye showed promising photovoltaic conversion efficiency (η) of 1.4%, Voc = 735 mV, Jsc = 2.7 mA/cm2, ff = 0.73 (fill factor), when compared with the conventional N719 and D5 organic dyes.