Impact of backbone linkage positions on the molecular aggregation behavior of polymer photovoltaic materials,Physical Chemistry Chemical Physics

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Impact of backbone linkage positions on the molecular aggregation behavior of polymer photovoltaic materials
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2022-05-21 , DOI: 10.1039/d2cp01060g
Jinyue Zhu _{1,

2} , Yanfang Liu ₃ , Shaohua Huang ₄ , Shuguang Wen ₅ , Xichang Bao ₅ , Mian Cai ₂ , Jingwen Li ₁

Affiliation

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 (meta-, para-) 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[c,h][2,6]-naphthyridine-5,11-(6H,12H)-dione (DBND) as the building block. This study shows that the para-connected polymer exhibits an unexpected 0.2 eV higher ionization potential and a resultant higher open-circuit voltage than the meta-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(p-DBND-f-2T) performs a segregated stacking of f-2T and DBND units, while P(m-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.

中文翻译：

主链连接位置对聚合物光伏材料分子聚集行为的影响

推进共轭材料的结构设计以实现对光伏器件性能的实际影响势在必行。然而，骨架的连接位置（间位，对位）对分子堆积的影响相对较少。在这项研究中，我们使用二苯并[ c , h ][2,6]-naphthyridine-5,11-(6 H ,12 H )-dione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(DBND) 作为构建块。本研究表明，对与元连接的对应物相比，连接的聚合物表现出出乎意料的高 0.2 eV 的电离电位和由此产生的更高的开路电压。我们发现不同的连接位置会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HOMO能级和光伏性能。具体而言，理论计算和 2D-NMR 表明 P( p -DBND-f-2T) 执行 f-2T 和 DBND 单元的分离堆叠，而 P( m-DBND-f-2T) 薄膜在 f-2T 和 DBND 之间形成 π-重叠。这些结果表明，聚合物骨架上的键位调整对材料的分子聚集产生了深远的影响。此外，异构对聚合物主链的影响对于设计用于光伏应用的聚合物结构至关重要。

更新日期：2022-05-21

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