Two medium gap semiconducting polymers, P(1)-Q-BDT-4TR and P(2)-FQ-BDT-4TR, based on alternate units of alkyl-dithiophene substituted benzodithiophene (BDT) and quinoxaline units (without or with fluorine substitution), are synthesized and fully characterized. The polymers exhibit optical and electrical properties favorable for being employed as donors in BHJ OPV devices, such as: absorption spectra extending up to around 720 nm for a high solar spectrum coverage, deep lying HOMO energy levels for a high device open circuit voltage and LUMO energy levels higher than those of PC61BM and PC71BM for an efficient exciton dissociation. In particular, the presence of alkyl-dithiophene side chains allows us to obtain a high 2D Ï-conjugation which promotes red shifted absorption profiles, low HOMO energy levels (<â5.6 eV) and enhanced environmental and thermal stability. Moreover, the introduction of the fluorine atom in the polymer backbone allows us to obtain efficient OPV devices, based on as-cast P(2)-FQ-BDT-4TR:PC61BM blend, showing a JSC of â10.2 mA cmâ2, VOC of 0.90 V, FF of 58% and PCE of 5.3%, without the need for any additional thermal treatment.
两种中间隙半导体
聚合物 P(1)-Q-BDT-4TR 和 P(2)-FQ-BDT-4TR,基于烷基二
噻吩取代的
苯并二
噻吩 (BDT) 和
喹喔啉单元(无或有
氟取代)的交替单元),被合成并充分表征。这些
聚合物表现出有利于在 BHJ OPV 器件中用作供体的光学和电学特性,例如:吸收光谱延伸至约 720 nm,实现高太阳光谱覆盖范围;深层 HO
MO 能级,实现高器件开路电压和 LU
MO能级高于
PC61BM 和
PC71BM,可实现有效的激子解离。特别是,烷基二
噻吩侧链的存在使我们能够获得高 2D π-共轭,从而促进红移吸收曲线、低 HO
MO 能级 (<±5.6 eV) 并增强环境和热稳定性。此外,在
聚合物主链中引入
氟原子使我们能够获得基于铸态 P(2)-FQ-BDT-4TR:
PC61BM 共混物的高效 OPV 器件,其 JSC 为 10.2 mA cm 2,VOC为0.90V,FF为58%,
PCE为5.3%,无需任何额外的热处理。