| 초록 |
We developed a series of conjugated polymers with a backbone of thieno[3,4-b]thiophene-co-benzo[1,2-b:4,5-b’]dithiophene (TT-co-BDT) moieties and studied the effect of the polymer structure on photovoltaic properties. We demonstrated that fluorination of the polymer backbone affected the energy levels, the microstructures of polymer/fullerene blend films, and the intramolecular exciton splitting dynamics of the polymers, resulting in power conversion efficiencies (PCEs) of 2.3~7.2%. To further enhance the PCE, we synthesized copolymers with a backbone of thieno[3,4-b]thiophene-co-dithieno[2,3-d:2',3'-d']benzo[1,2-b:4,5-b']dithiophene (TT-co-DBD). Introduction of an extended conjugation system such as DBD into the polymer facilitates the delocalization of holes in the polymer formed after exciton-splitting, which improved exciton-splitting efficiency. As a result, solar cells made from the TT-co-DBD polymers showed a higher PCE of 7.7% than the TT-co-BDT polymers. |
