Two newly designed donor-acceptor (D-A) conjugated polymers were prepared from the Stille coupling reactions by incorporating phthalimide derivative as a co-acceptor unit into 2,1,3-benzooxadiazole (BO) and thiophene with different ratios of 5mol.% and 10mol.% of TBO-I 5, TBO-I 10, respectively. Polymers possess moderate molecular weights and excellent thermal properties with a 5% weight loss temperatures (T-d) around 300 degrees C. Compared to poly{5,6-bis(decyloxy)-4-(thiophen-2-yl)benzo[c][1,2,5]oxadiazole} (TBO), adding phthalimide unit in TBO-I 5 and TBO-I 10 shifted UV-Vis absorption spectra and changed the HOMO and LUMO levels of polymers. Bulk hetero junction (BHJ) polymer solar cells (PSCs) based on polymers blended with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) were fabricated to investigate photovoltaic properties. As a results, with increasing the composition of phthalimide, the J(sc) of the devices based on polymers were reduced in the order of TBO (4.74mA/cm(2)) > TBO-I 5 (3.94mA/cm(2)) > TBO-I 10 (1.90mA/cm(2)) due to the blue-shifted in absorption spectra and twisting in polymer main chain of TBO-I polymers. The decrease in J(sc) led to low photovoltaic performances and the device based on TBO showed higher performances than those of TBO-I 5 and TBO-I 10 with the PCE of 1.66%, the J(sc) of 4.74mA/cm(2), the V-oc of 0.82V and the FF of 42.4% under the illumination of AM 1.5G, 100 mW/cm(2).