高分辨固体核磁共振法分析聚3-己基噻吩∶苝二酰亚胺衍生物的共混结构

Investigation of Structure of Perylene Diimides Based Materials by Using Advanced Solid State Nuclear Magnetic Resonance Techniques: A Study on Molecular Assembly,Interfacial Interaction and Miscibility

苝二酰亚胺(PDI)衍生物是异质结太阳能电池中可替代[6,6]-苯基-C61-丁酸甲酯(PCBM)的受体材料。本研究选取了两种不同化学结构的PDI衍生物作为研究体系,分别命名为PDI和PDI,采用高分辨固体核磁共振技术,探讨了PDI衍生物在与聚3-己基噻吩(P3HT)共混前后其分子聚集态结构的变化。发现PDI和PDI的纯净物体系中,分子均通过π-π作用形成了有序的堆叠结构,且PDI的有序度高于PDI。在分别与P3HT共混后,两种共混物表现为两相分离的结构。其中,PDI在与P3HT共混后,其晶区的有序度降低,但分子的堆叠结构没有变化;而PDI在与P3HT共混后,其晶区的有序度保持不变,但分子的堆叠结构发生了变化。通过Back-to-Back(BaBa)边带技术可以定量检测出PDI分子间酰胺位CH氢原子间的距离为3.66。依据13 C-1H FSLG-HETCOR谱图的相关信息,发现两组分的界面区中,PDI的酰亚胺取代基位于P3HT噻吩环的屏蔽区。此外,使用REREDOR技术定量检测了两种PDI衍生物在与P3HT共混前后分子基团的局部运动性。研究发现,在与P3HT共混后,PDI的分子局部运动性没有变化,而PDI的分子局部运动性降低。本研究揭示了两种PDI衍生物在与P3HT共混前后的分子聚集态结构,总结了适用于研究PDI衍生物共混体系的固体核磁共振技术方案,用于表征分子的聚集态结构、组分相容性及分子基团的局部运动性能。

In recent years, perylene diimide (PDI) derivatives have attracted enormous attentions owing to their favorable properties as the alternative electron acceptor to PCBM in bulk heterojunction (BHJ) materials. It has been noted that the molecular local arrangement largely affects the performance of the BHJ devices. In this work, two PDI derivatives (named PDI and PDI ) and their blends with poly(3-hexylthiophene)(P3HT) were investigated by using advanced solid state nuclear magnetic resonance(SSNMR). The 1H- 1H SQ-DQ spectra revealed that both PDI and PDI molecules had ordered arrangement through π-π interaction. PDI showed higher molecular ordering than PDI . The blends of PDI and P3HT(PDI ∶ P3HT) as well as PDI and P3HT(PDI ∶ P3HT) were also investigated. Based on the features of 13 C- 1H frequency switched Lee-Goldburg heteronuclear dipolar-correlation spectroscopy (FSLG-HETOCR) spectra, we revealed the phase-segregated structures for both PDI ∶ P3HT and PDI ∶ P3HT. Moreover, PDI exhibited reduced local ordering when blended with P3HT. Whilst PDI demonstrated different molecular local assembling structure. By fitting the BaBa DQ sideband pattern, the inter-nuclear distance of two neighboring PDI molecules was calculated. The interfacial information of PDI ∶ P3HT was also obtained from 1D 13 C{ 1H} CP and 13 C- 1H FSLG-HETOCR spectra. Based on the 13 C chemical shifts and 13 C- 1H correlation peaks, we suggested that in the interfacial area the PDI imide alkyl units located in the shielding zone of P3HT thiophene rings. The quantitative local mobility study was conducted through analyzing the rotor-encoded rotational echo double resonance (REREDOR) data. The deduced heteronuclear coupling constants via fitting the sideband patterns showed identical trend as the findings from the structural characterization. In addition to the structural investigation, this work suggested a possible characterizing strategy by using SSNMR techniques for the PDI based materials or other conjugated systems.