The theoretical calculations are used to find that D-pi-A-pi-A style conjugated polymer PC-TBTBT is more efficient for solar cells application than the D-pi-A analog PC-TBT because the D-pi-A-pi-A structure has a narrower band gap and higher molar absorption coefficient and redshift spectrum. Motivated by the theoretical prediction, 5,6-bis(octyloxy)-2,1,3-benzothiadiazole and 2,7-carbazole are adopted to synthesize the D-pi-A-pi-A style PC-TBTBT (M-w = 31.1 kDa) and D-pi-A analog PC-TBT (M-w = 87.5 kDa) by Suzuki coupling reaction. Experimental results confirm that D-pi-A-pi-A PC-TBTBT-based solar cell shows a power conversion efficiency (PCE) of 4.74% with high V-OC of 0.99 V and enhanced J(SC) of 9.70 mA cm(-2). The PCE and J(SC) achieve improvements of 17% and 26%, respectively, compared to the D-pi-A PC-TBT-based solar cell.