(E)-3-{4-[Bis(4-tert-butylphenyl)amino]phenyl}-2-cyano-acrylic acid and its related compounds were synthesized by the Knoevenagel condensation of the corresponding 4-aminobenz-aldehydes with cyanoacetic acid. Cyclic voltaminetry measurements showed that these organic dyes exhibited reversible oxidation waves. The tert-butyl substituents also decreased molecular stacking in the crystals, thus affecting the photovoltaic properties of the dyes. A solar cell using the tert-butyl-substituted dye exhibited higher performance than that for the analog without tert-butyl group substitution.