Synthesis, characterization and application of trans-D–B–A-porphyrin based dyes in dye-sensitized solar cells

A series of metal-free trans-D–B–A porphyrin dyes have been synthesized and characterized as photo-sensitizers for dye-sensitized solar cells (DSSCs). These dye molecules contain a porphyrin unit as a π-bridge, a substituted phenyl group as an electron donor and cyanoacrylic acid or carboxylic acid group as an electron acceptor (anchoring groups). This phenomenon is more pronounced for porphyrins (Dye 4 and Dye 5) that have conjugated diphenyl aniline at the opposite side of the anchoring group. A solar conversion efficiency of 2.38% has been achieved with a short circuit current (Jsc) of 7.63 mA/cm2, an open circuit voltage (Voc) of 0.613 V and a fill factor (ff) of 51.0% for Dye 5 under standard global AM 1.5 solar irradiation. Results of time-dependent density functional theory (TD-DFT) calculations on these five organic dyes support the electrochemical data.