| 초록 |
A new benzo[1,2-b:4,5-b']dithiophene (BDT) derivative with conjugated substituent, 5-ethylhexylbenzothiophene group, were synthesized as donor unit and copolymerized with two acceptor units, fluoro-thieneothiophene (TT-F) and diketopyrrolopyrrole (DPP), respectively, using Stille coupling reaction to afford two new copolymers, P1 and P2. All polymers exhibited highest occupied molecular orbital (HOMO) energy levels that were deeper than -5.4 eV due to the conjugated substituent. Small band gaps were successfully achieved for P1 (1.54 eV) and P2 (1.37 eV) and were attributable to the strong intramolecular charge transfer within the D–A alternating structure. The resultant photovoltaic performances showed high Voc ranging from 0.70 V to 0.85 V, whereas the PCEs depended strongly on the blend morphologies. The polymer solar cell based on the blend of P1 and PC71BM gave the best photovoltaic performance among the series, with a high Voc of 0.82 V and a PCE of 4.51%. |
