Triarylamine-Free Pyrenoimidazole-Containing Organic Dyes with Different π-Linkers for Dye-Sensitized Solar Cells

A series of arylamine-free organic dyes that have a pyrenoimidazole donor, a cyanoacrylic acid acceptor, and different pi-linkers were synthesized and characterized by optical, electrochemical, and theoretical investigations. The nature of the pi-spacer exerts a significant effect on electronic properties of these dyes. The absorption maxima red-shifts on progressive addition of thiophene units in the conjugation pathway. All the dyes displayed negative solvatochromism indicative of effective solvation of the dyes by polar solvents in the ground state. The oxidation potential of the dyes shifted negatively on introduction of electron rich spacer. TDDFT computations were also performed to explain the optical and electrochemical properties of the dyes. They were demonstrated as sensitizers in dye-sensitized solar cells, the efficiency of which is promising.