Two new low-bandgap copolymers containing 1-(2,6-diisopropylphenyl)-2,5-di(2-thienyl)pyrrole, 2,1,3-benzothiadiazole and indenofluorene or fluorene (PTPTIFB and PTPTFB, respectively) were synthesized and characterized. The absorption spectrum of the polymer PTPTIFB covers the region from 300 to 750 nm, whereas polymer PTPTFB shows the absorption band up to 975 nm. The electrochemical bandgaps of the polymers were calculated to be 1.67 and 1.57 eV, respectively. The bulk heterojunction solar cells were fabricated with the configuration of ITO/PEDOT:PSS/PTPTIFB or PTPTFB:PC70BM (1:3 or 1:4 or 1:5 wt%)/TiO (x) /Al, and the best performance was obtained with the blend of polymer:PC70BM (1:5 wt%) as an active layer. The device made from PTPTIFB showed the highest power conversion efficiency (PCE) of 1.18 %, while the device made from PTPTFB showed the PCE of 0.90 % measured using AM 1.5 G solar simulator at 100 mW cm(-2) light illumination.