College of Chemistry/Institute of Polymers and Energy Chemistry, Nanchang University, Nanchang, 330031, P. R. China.
Beijing National Laboratory for Molecular Science, CAS State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry Chinese Academy of Science, Beijing, 100190, P. R. China.
Macromol Rapid Commun. 2019 Apr;40(8):e1800906. doi: 10.1002/marc.201800906. Epub 2019 Feb 19.
A trade-off between open-circuit voltage (V ) and high short-circuit (J ) becomes one of the most vital problems limiting further improvement in polymer solar cells' (PSCs) efficiency. In this work, two asymmetric polymer donors PBDT-F-2TC and PBDT-SF-2TC are designed and synthesized. When blended with a state-of-the-art acceptor IT-4F with low lowest-unoccupied molecular orbital level, simultaneously high V (up to 0.94 V) and J (up to 20.73 mA cm ) are obtained for both copolymers. Note that the V value of 0.94 V is the highest value of PSCs based on IT-4F reported so far. The simultaneously improved V and J in resulting devices are discovered from the deep highest-occupied molecular orbital levels (-5.5 to -5.7 eV) and the hyperchromic effect of the polymers, the small driving force, and the small energy loss during the charge transfer, due to the synergistic effect of asymmetric carboxylate unit and fluorine/sulfur atoms. More importantly, thanks to the asymmetric 2TC, both PBDT-F-2TC- and PBDT-SF-2TC-based PSCs can be successfully processed by non-halogenated solvent 1,2,4-trimethylbenzene (TMB) to yield device efficiencies of 10.29% and 10.39%, respectively, which are the maximum values for non-fullerene PSCs fabricated using the eco-friendly solvent TMB.
开路电压（V ）和高短路电流（J ）之间的权衡成为限制聚合物太阳能电池（PSCs）效率进一步提高的最关键问题之一。在这项工作中，设计并合成了两种不对称聚合物给体 PBDT-F-2TC 和 PBDT-SF-2TC。当与具有低最低未占据分子轨道能级的最先进受体 IT-4F 共混时，两种共聚物同时获得了高 V （高达 0.94 V）和 J （高达 20.73 mA cm ）。需要注意的是，0.94 V 的 V 值是迄今为止基于 IT-4F 的 PSCs 的最高值。由于不对称羧酸盐单元和氟/硫原子的协同效应，导致聚合物的深最高占据分子轨道能级（-5.5 至-5.7 eV）和增色效应、较小的驱动力以及在电荷转移过程中的能量损失，导致所得器件中同时提高的 V 和 J 。更重要的是，由于不对称的 2TC，基于 PBDT-F-2TC 和 PBDT-SF-2TC 的 PSCs 都可以成功地用非卤化溶剂 1,2,4-三甲基苯（TMB）处理，分别得到 10.29%和 10.39%的器件效率，这是非富勒烯 PSCs 用环保溶剂 TMB 制造的最高值。
