The low doping efficiency of n-doped systems limits the development of n-type organic conducting materials. Oligo(ethylene glycol) (OEG) as the flexible chain in conjugated small molecules and polymers may improve doping efficiency. However, OEG side chains also bring unexpected low mobility and poor film morphology. Herein, we propose the stronger solution-state aggregation plays a dominated role in charge transport and morphology of OEG-substituted polymer. The solution-state aggregation also affects doping process. Therefore, we develop a series of polymers based on 3,7-bis((E)-7-fluoro-1-(2-octyldodecyl)-2-oxoindolin-3-ylidene)-3,7-dihydrobenzo[1,2-b:4,5-b']difuran-2,6-dione (FBDPPV) with different ratios of OEG side chain to investigate the effect of side chain on solution-state aggregation and n-doping process. After n-doped by hexahydro-1H,3a1H,4H,7H-3a,6a,9a-triazaphenalene (TAM), FBDPPV with 50% OEG affords the highest doping efficiency and conductivity, while FBDPPV with 100% OEG shows lower conductivity. Combination of ultraviolet–visible–near infrared absorption spectra, grazing-incidence wide-angle X-ray scattering and atomic force microscopy, we reveal that serious aggregated extent in solution of OEG-substituted polymer result in phase separation and rough morphology, which are the origins of poor conductivity. Our work provides a new perspective on the effect of the OEG side chain on the doped polymer systems, suggesting suitable solution-state aggregation is crucial to high doping efficiency and high conductivity.

中文翻译：

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揭示低聚（乙二醇）侧链对 FBDPPV 基聚合物中 n 掺杂过程的影响

n型掺杂体系的低掺杂效率限制了n型有机导电材料的发展。低聚（乙二醇）（OEG）作为共轭小分子和聚合物中的柔性链可以提高掺杂效率。然而，OEG 侧链也带来了意想不到的低迁移率和较差的薄膜形态。在此，我们提出更强的溶液态聚集在 OEG 取代聚合物的电荷传输和形态中起主导作用。溶液状态聚集也影响掺杂过程。因此，我们开发了一系列基于 3,7-bis(( E )-7-fluoro-1-(2-octyldodecyl)-2-oxoindolin-3-ylidene)-3,7-dihydrobenzo[1,2 - b :4,5- b']difuran-2,6-dione (FBDPPV) 与不同比例的 OEG 侧链研究侧链对溶液态聚集和 n 掺杂过程的影响。经六氢-1 H ,3a1 H ,4 H ,7 H n 掺杂后-3a,6a,9a-triazaphenalene (TAM)，具有 50% OEG 的 FBDPPV 提供最高的掺杂效率和电导率，而具有 100% OEG 的 FBDPPV 显示较低的电导率。结合紫外-可见-近红外吸收光谱、掠入射广角 X 射线散射和原子力显微镜，我们发现 OEG 取代聚合物溶液中严重的聚集程度导致相分离和粗糙的形貌，这是导电性差的原因。我们的工作为 OEG 侧链对掺杂聚合物系统的影响提供了新的视角，表明合适的溶液状态聚集对于高掺杂效率和高导电性至关重要。