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Effect of the chlorine substitution position of the end-group on intermolecular interactions and photovoltaic performance of small molecule acceptors
Energy & Environmental Science ( IF 32.5 ) Pub Date : 2020-10-17 , DOI: 10.1039/d0ee02251a
Xiaojun Li 1, 2, 3, 4, 5 , Indunil Angunawela 6, 7, 8, 9 , Yuan Chang 10, 11, 12, 13, 14 , Jiadong Zhou 13, 15, 16, 17, 18 , He Huang 13, 19, 20, 21 , Lian Zhong 13, 19, 20, 21 , Alex Liebman-Pelaez 9, 22, 23, 24 , Chenhui Zhu 9, 22, 23, 24 , Lei Meng 1, 2, 3, 4, 5 , Zengqi Xie 13, 15, 16, 17, 18 , Harald Ade 6, 7, 8, 9 , He Yan 10, 11, 12, 13, 14 , Yongfang Li 1, 2, 3, 4, 5
Affiliation  

The structure–property relationships of small molecular acceptors (SMAs) are a key issue in the molecular design of new-generation acceptor materials for further improving the device efficiencies of polymer solar cells (PSCs). Herein, three couples of SMA isomers were synthesized, based on three central fused ring units and two 1,1-dicyanomethylene-3-indanone (IC) isomer electron-withdrawing terminal units with chlorine substitutions in different positions of its benzene ring: Cl-1 with chlorine on the same side as a C[double bond, length as m-dash]O group of IC and Cl-2 with chlorine on the same side as the CN groups of IC. Through systematical investigation, we found that the chlorine substitution position of the terminal groups has a regular and significant influence on the molecular packing and photovoltaic performance of the SMAs. The molecular packing behavior of the SMAs is closely related to and determined by the configuration of their terminal groups, no matter which central fused ring of the SMAs is used. In particular, the Cl-1-based SMAs possess a stronger crystallinity with long range ordering packing in their molecular plane direction, while the more abundant and stereoscopic π–π intermolecular interaction in the Cl-2-based SMAs promotes the molecules to form three-dimensional charge transporting channels and leads to their red-shifted absorption and higher electron mobilities. Therefore, the Cl-2-based PSCs exhibit a higher power conversion efficiency (PCE) compared to that of the Cl-1-based devices, and the best PCE of a Cl-2 SMA-based PSC reached 16.42%. These results highlight the importance of the investigation of intermolecular interactions, packing and the arrangement of the SMAs in the solid-state, which may provide direct insights for exploring the relationship between the molecular structure and property of the photovoltaic materials. Moreover, we envision that if fragments such as end groups or side chains with more diverse molecular interactions are added into the design and the subsequent synthesis of the SMAs, this may be beneficial to promoting molecular π–π accumulation and further improving the molecular order, forming suitable molecular packing and morphology in the resulting blend films, and finally affecting the efficiency of the PSCs.

中文翻译:

端基氯取代位置对小分子受体间分子间相互作用和光伏性能的影响

小分子受体(SMAs)的结构与属性之间的关系是新一代受体材料的分子设计中的一个关键问题,用于进一步提高聚合物太阳能电池(PSC)的器件效率。在此,基于三个中心稠合环单元和两个在苯环的不同位置具有氯取代基的1,1-二氰亚甲基-3-茚满酮(IC)异构体吸电子末端单元,合成了三对SMA异构体。 1,氯与C相同[双键,长度为m-破折号]IC的O基和Cl-2与IC的CN基位于同一侧。通过系统的研究,我们发现末端基团的氯取代位置对SMA的分子堆积和光伏性能具有规则而重要的影响。无论使用哪种SMA中心稠环,SMA的分子堆积行为都与它们的端基结构密切相关并由其决定。特别是,基于Cl-1的SMA具有更强的结晶度,并在其分子平面方向上具有长程有序堆积,而基于Cl-2的SMA中更丰富和立体的π-π分子间相互作用促进了分子形成三个维电荷传输通道,并导致其红移吸收和更高的电子迁移率。因此,与基于Cl-1的设备相比,基于Cl-2的PSC表现出更高的功率转换效率(PCE),而基于Cl-2 SMA的PSC的最佳PCE达到16.42%。这些结果突出了研究分子间相互作用,固态中SMA的堆积和排列的重要性,这可能为探索光伏材料的分子结构与性能之间的关系提供直接见解。此外,我们设想,如果将具有更多样化分子相互作用的端基或侧链之类的片段添加到SMA的设计和后续合成中,这可能有利于促进分子π-π的积累并进一步改善分子序,在所得的共混膜中形成合适的分子堆积和形态,
更新日期:2020-11-03
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