In this study, the maleimide-thiophene copolymer-functionalized graphite oxide sheets (PTM21-GOS) and carbon nanotubes (PTM21-CNT) were developed for polymer solar cell (PSC) applications. The grafting of PTM21-OH onto the CNT and GO sheets was confirmed using FTIR spectroscopy. PTM21-CNT and PTM21-GOS exhibited excellent dispersal behavior in organic solvents. Better thermal stability was observed for PTM21-CNT and PTM21-GOS as compared with that for PTM21-OH. In addition, the optical band gaps of PTM21-GOS and PTM21-CNT were lower than that of PTM21-OH. We incorporated PTM21-GOS and PTM21-CNT individually into poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blends for use as photoconversion layers of PSCs. Good distributional homogeneity was observed for PTM21-GOS or PTM21-CNT in the P3HT/PCBM blend film. The UVvis absorption peaks of the blend films red-shifted slightly upon increasing the content of PTM21-GOS or PTM21-CNT. The band gap energies and LUMO/HOMO energy levels of the P3HT/PTM21-GOS and P3HT/PTM21-CNT blend films were slightly lower than those of the P3HT film. The conjugated polymer-functionalized PTM21-GOS and PTM21-CNT behaved as efficient electron acceptors and as charge-transport assisters when incorporated into the photoactive layers of the PSCs. PV performance of the PSCs was enhanced after incorporating PTM21-GOS or PTM21-CNT in the P3HT/PCBM blend. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013