LAUSR

The photophysics and solar cell efficiency of organic sensitizers comprising a cyanoacrylic acid group are greatly influenced by an equilibrium between the neutral (“non-deprotonated”, COOH) and anionic (“deprotonated”, COO–) forms, whose ratio depends on the solvent polarity and its H-bonding properties, dye concentration, and temperature used. Herein, we report a detailed investigation on the relationship between the portions of COOH and COO– dye forms and the photophysical and solar cell properties of an organic dipolar sensitizer, BTZA-II, bearing triphenylamine electron-donating and benzothiazole electron-withdrawing moieties. The photophysics has been studied by stationary and time-resolved fluorescence spectroscopy in apolar and polar solvents with a dye concentration ranging from 5 × 10–7 to 5 × 10–5 M, also upon addition of small amounts of an external acid or base to change the solvent acidity, allowing us to distinguish the contribution and lifetime of the neutral and anionic forms. The fluores...