Synthesis, optical and electrochemical properties, and photovoltaic performance of a panchromatic and near-infrared (D)2–π–A type BODIPY dye with pyridyl group or cyanoacrylic acid

(D)2–π–A type boron dipyrromethene (BODIPY) dyes OMK-PY and OMK-CA bearing a pyridyl group or cyanoacrylic acid group, respectively, at the end of 8-positions on the BODIPY core, as an electron-withdrawing anchoring group to adsorb onto the TiO2 electrode and two diphenylamine–thienylcarbazole moieties as an electron-donating unit at the 3- and 5-positions on the BODIPY core, were designed and developed as a photosensitizer for dye-sensitized solar cells (DSSCs). It was found that the two BODIPY dyes adsorbed on a TiO2 film show a strong and broad absorption band in the range of 600 to 850 nm, and the onset of the absorption band reached 900 nm, that is, OMK-PY and OMK-CA possess the near-infrared (NIR) adsorption ability as well as the panchromatic adsorption ability, and good adsorption ability onto the TiO2 electrode. Moreover, cyclic voltammetry demonstrated that the two BODIPY dyes show two reversible oxidation waves, thus indicating that the redox processes of OMK-PY and OMK-CA are very stable. On the basis of the experimental results and density functional theory calculation, we propose that the (D)2–π–A BODIPY structure with two diphenylamine–thienylcarbazole moieties as strong electron-donating units at the 3- and 5-positions on the BODIPY core is an effective strategy to lead a high light-harvesting efficiency (LHE) in the range of visible light to NIR light, although the DSSCs based on (D)2–π–A type BODIPY dyes that have been developed in this current stage showed low photovoltaic performances.