Zhu Jinyue, Liu Yanfang, Huang Shaohua, Wen Shuguang, Bao Xichang, Cai Mian, Li Jingwen
College of Chemistry and Chemical Engineering, China University of Petroleum (East China), Qingdao 266580, China.
Research and Development Center of Aluminum-ion Battery, College of Energy Storage Technology, Shandong University of Science and Technology, Qingdao 266590, China.
Phys Chem Chem Phys. 2022 Jul 27;24(29):17462-17470. doi: 10.1039/d2cp01060g.
It is imperative to advance the structural design of conjugated materials to achieve a practical impact on the performance of photovoltaic devices. However, the effect of the linkage positions (-, -) of the backbone on the molecular packing has been relatively little explored. In this study, we have synthesized two wide-bandgap polymer photovoltaic materials from identical monomers with different linkage positions, using dibenzo[,][2,6]-naphthyridine-5,11-(6,12)-dione (DBND) as the building block. This study shows that the -connected polymer exhibits an unexpected 0.2 eV higher ionization potential and a resultant higher open-circuit voltage than the -connected counterpart. We found that different linkage positions result in different intermolecular binding energies and molecular aggregation conformations, leading to different HOMO energy levels and photovoltaic performances. Specifically, theoretical calculations and 2D-NMR indicate that P(-DBND-f-2T) performs a segregated stacking of f-2T and DBND units, while P(-DBND-f-2T) films form π-overlaps between f-2T and DBND. These results show that linkage position adjustment on the polymeric backbone exerts a profound influence on the molecular aggregation of the materials. Also, the effect of isomerism on the polymer backbone is crucial in designing polymer structures for photovoltaic applications.
推进共轭材料的结构设计以对光伏器件的性能产生实际影响势在必行。然而，主链的连接位置（-，-）对分子堆积的影响相对较少被探索。在本研究中，我们以二苯并[,][2,6]-萘啶-5,11-(6,12)-二酮（DBND）为结构单元，从具有不同连接位置的相同单体合成了两种宽带隙聚合物光伏材料。本研究表明，与连接的聚合物相比，连接的聚合物表现出意想不到的高0.2 eV的电离势以及更高的开路电压。我们发现不同的连接位置导致不同的分子间结合能和分子聚集构象，从而导致不同的最高占据分子轨道（HOMO）能级和光伏性能。具体而言，理论计算和二维核磁共振（2D-NMR）表明，P（-DBND-f-2T）表现出f-2T和DBND单元的分离堆积，而P（-DBND-f-2T）薄膜在f-2T和DBND之间形成π重叠。这些结果表明，聚合物主链上连接位置的调整对材料的分子聚集有深远影响。此外，聚合物主链上的异构现象在设计用于光伏应用的聚合物结构中至关重要。
