College of Chemistry and Chemical Engineering, Central South University , Changsha 410083, China.
Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China.
ACS Appl Mater Interfaces. 2017 Jun 7;9(22):18816-18825. doi: 10.1021/acsami.7b03947. Epub 2017 May 30.
Through introducing six fluorine atoms onto quinoxaline (Qx), a new electron acceptor unit-hexafluoroquinoxaline (HFQx) is first synthesized. On the basis of this unit, we synthesize a new donor-acceptor (D-A) copolymer (HFQx-T), which is composed of a benzodithiophene (BDT) derivative donor block and an HFQx accepting block. The strong electron-withdrawing properties of fluorine atoms increase significantly the open-circuit voltage (V) by tuning the highest occupied molecular orbital (HOMO) energy level. In addition, fluorine atoms enhance the absorption coefficient of the conjugated copolymer and change the film morphology, which implies an increase of the short-circuit current density (J) and fill factor (FF). Indeed, the HFQx-T:ITIC blended film achieves an impressive power conversion efficiency (PCE) of 9.4% with large short-current density (J) of 15.60 mA/cm, high V of 0.92 V, and FF of 65% via two step annealing (thermal annealing (TA) and solvent vapor annealing (SVA) treatments). The excellent results obtained show that the new copolymer HFQx-T synthesized could be a promising candidate for organic photovoltaics.
通过在喹喔啉（Qx）上引入六个氟原子，首次合成了一个新的电子受体单元-六氟喹喔啉（HFQx）。在此单元的基础上，我们合成了一种新的给体-受体（D-A）共聚物（HFQx-T），它由苯并二噻吩（BDT）衍生物给体块和 HFQx 受体块组成。氟原子的强吸电子性质通过调节最高占据分子轨道（HOMO）能级，显著提高开路电压（V）。此外，氟原子增强了共轭共聚物的吸收系数并改变了薄膜形貌，这意味着短路电流密度（J）和填充因子（FF）的增加。实际上，HFQx-T:ITIC 共混膜通过两步退火（热退火（TA）和溶剂蒸气退火（SVA）处理）实现了令人印象深刻的功率转换效率（PCE）为 9.4%，具有大的短路电流密度（J）为 15.60 mA/cm、开路电压（V）为 0.92 V 和填充因子（FF）为 65%。所获得的优异结果表明，所合成的新型共聚物 HFQx-T 可能是有机光伏的有前途的候选材料。
