A series of novel conjugated polymers containing alternating electron-donating and electron-accepting units based on 9,9-dioctylfluorene,4,7-dithienyl-2-yl-2,1,3-benzothiadiazole, and(oligo)thiophene were synthesized.The polymers were synthesized by the Suzuki cross-coupling polymerization of 9,9-dioctylfluorene-2,7-diboronic acid and4,7-di(2-bromothien-5-yl)-2,1,3-benzothiadiazole with dibromo (oligo)thiophene (thiophene, bithiophene, and terthiophene). Optical properties of the copolymers were highly dependent on the length of the(oligo)thiophene unit. With the incorporation of three thiophene units in the polymer backbone, the copolymer absorption covers a broad range of the visible spectrum from 300 to 700 nm. The band gap energies derived from the absorption edge of the thin films pectra were in the range of 1.83–1.94 eV. The photovoltaic performance increases as the length ofthe(oligo)thiophene segments in the polymer backbone increases.The best performance of photovoltaic device was obtained by PFTBzTTT as the electron donor material with PCE of 1.25% under an AM 1.5 solar simulator.