A series of narrow-band-gap conjugated copolymers (PFO-DPT) derived from pyrrole, benzothiadiazole, and 9,9-dioctylfluorene (DOF) is prepared by the palladium-catalyzed Suzuki coupling reaction with the molar feed ratio of 4,7-bis(N-methylpyrrol-2-yl)-2,1,3-benzothiadiazole (DPT) around 1, 5, 15, 30, and 50%. The obtained polymers are readily soluble in common organic solvents. The solutions and the thin solid films of the copolymers absorb light from 300 nm to 600 nm with two absorbance peaks at around 380 run and 505 nm. The PL emission consists mainly of DPT unit emission at around 624-686 nm depending on the DPT content in solid film. The EL emission peaks are red-shifted from 630 nm for PFO-DPT1 to 660 nm for PFO-DPT50. Bulk heterojunction photovoltaic cells fabricated from composite films of copolymer and [6,6]-phenyl C-61 butyric acid methyl ester (PCBM) as electron donor and electron acceptor, respectively, in device configuration: ITO/PEDOT : PSS/PFO-DPT : PCBM/Ba/Al shows power conversion efficiencies 0.15% with open-circuit voltage (V-oc) of 0.60 V and short-circuit current density (J(sc)) of 0.73 mA/cm(2) under AM1.5 solar simulator (100 mW/cm(2)). (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 1462-1468, 2010