| 초록 |
In recent development of synthesizing donor-acceptor type low-bandgap polymers, [1,2,5]thiadiazolo[3,4-g]quinoxaline (TQ) has attracted much attention as an acceptor unit due to strong electron-withdrawing property of four imine groups in the TQ unit. In most cases, however, the excessive electron deficiency of TQ unit have produced low-lying LUMO level (-3.8~-3.9 eV) of alternating copolymers, which is very close to that of PCBM (-4.0 eV) and thus prevents charge separation at the interface between donor and acceptor. Hence, it is required to raise the LUMO level of the copolymer by increasing the electron density in TQ unit. For this purpose, we have introduced two electron-rich thienyl groups on TQ unit to attenuate the electron-withdrawing property of the TQ unit. We have successfully synthesized alternating copolymers with carbazole or fluorene and fine-tuned TQ, and the photovoltaic performances of the copolymers are compared to those of copolymers with frequently-used TQs. |
