Synthesis and photovoltaic properties of new conjugated polymers based on di(2-furyl)thiazolo[5,4-d]thiazole and benzo[1,2-b:4,5-b′]dithiophene

Di(2-furyl)thiazolo[5,4-d]thiazole (DFTT) has been studied as building block for conjugated polymers. New polymer PBDTODFTT and PBDTTDFTT based on DFTT and two different benzo[1,2-b:4,5-b′]dithiophene (BDT) repeating units have been synthesized and applied as donors in bulk hetero-junction polymer solar cell devices. The polymer PBDTODFTT and PBDTTDFTT have optical bandgap of 2.00 eV and 1.98 eV, and show HOMO energy level of −5.46 eV and −5.36 eV, respectively. The solar cell devices based on PBDTTDFTT:PC61BM blend as active layers have achieved an open-circuit voltage of 0.83 V and a power conversion efficiency of 3.06% under the illumination of AM 1.5 G (100 mW/cm2).