Triazine-branched mono- and dianchoring organic dyes: Effect of acceptor arms on optical and photovoltaic properties

Three triazine-cored organic dyes containing triarylamine donor and cyanoacrylic acid acceptor were synthesized and used as sensitizers in dye-sensitized solar cells. Mono- and dianchoring dyes were designed by varying the number of donor/acceptor arms and conjugation length of the acceptor arm to study the effect of molecular structure on charge transfer characteristics and photovoltaic performance. They exhibited intense longer wavelength absorption with high molar extinction coefficients tunable depending on the number of acceptor arms and the nature of its composition. The electron accepting triazine linker favorably alters the energies of the frontier molecular orbitals which facilities the electron injection into the conduction band of TiO ₂ and dye regeneration by the electrolyte. A dye containing two donor arms and a acceptor composed of bithiophene spacer displayed promising power conversion efficiency (4.29%) in the series owing to high photocurrent density and open circuit voltage arising from the comparatively low charge transfer resistance and high recombination resistance in the device.