Two D-A conjugated polymers containing benzo[1,2-b:4,5-b'] dithiophene (BDT), benzo[1,2-b:4,5-b'] difuran (BDF) donor units and 4,7-di(thiophen-2-yl)- 5,6-bis(n-octyloxy)[2,1,3]benzoselenadiazole (DTBSe) acceptor unit, namely PBDTDTBSe and PBDFDTBSe have been synthesized by Stille coupling polymerization. The two polymers show good solubility in common organic solvents, good film forming properties, broad absorption (350-700 nm), low optical band gap (about 1.60 eV) and relatively high hole mobility [1.22 x 10(-2) cm(-2)/(V.s)]. The devices based on the blend film of PBDFDTBSe and PC71BM (1:1, w/w) exhibited the best device performance with PCE of 3.28 %, V-oc of 0.71 V, J(sc) of 10.37 mA cm(-2) and FF of 44.6 % under illumination of AM 1.5 G (100 mW cm(-2)).