| 초록 |
Low bandgap polymers for OPVs should have a narrow band-gap and a low HOMO energy level in order to maximize the short circuit current and the open circuit voltage. For achievement of this purpose, many research groups have attempted to synthesize alternating copolymer with a pair of weak donor unit and strong acceptor unit. Since it is well known that the introduction of electron-withdrawing group on the donor unit lowers the HOMO level of alternating copolymer, in this work, we synthesize a low band gap polymer with deep HOMO by copolymerizing 2,1,3-benzothiadiazole (BT) as strong acceptor unit and quarterthiophene with alkyl ester group as weak donor through the Stille coupling. For comparison, BT is also copolymerized with quarterthiophene without substitution. We demonstrate improved photovoltaic properties of alkyl ester substituted polymer relative to those of unsubstituted polymer. |
