We have used Grignard metathesis polymerization to prepare poly(3-hexylthiophene)-based copolymers containing electron-withdrawing 4-tert-butylphenyl-1,3,4-oxadiazole-Phenyl moieties as side chains. We characterized these copolymers using H-1 and C-13 nuclear magnetic resonance spectroscopy, thermogravimetric analysis, and gel permeation chromatography. The band gap energy of copolymer was determined from the onset of the optical absorption. The quenching effects were observed in the photoluminescence spectra of the copolymers incorporating pendant electron-deficient 1,3,4-oxadiazole moieties on the side chains. The photocurrents of devices were enhanced in the presence of an optimal amount of the 1,3,4-oxadiazole moieties, thereby leading to improved power conversion efficiencies. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3331-3339, 2010