Electron Transport in Thin Films of Polymer and Small-Molecule Acceptors Visualized by Conductive Atomic Force Microscopy
Electron Transport in Thin Films of Polymer and Small-Molecule Acceptors Visualized by Conductive Atomic Force Microscopy
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DOI：
10.1021/acs.jpcc.1c03837
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发表时间：
2021-06
期刊：
影响因子：
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通讯作者：
Anjar Taufik Hidayat;H. Benten;Toshiki Kawanishi;N. Ohta;Azusa Muraoka;M. Nakamura
中科院分区：
文献类型：
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作者：
Anjar Taufik Hidayat;H. Benten;Toshiki Kawanishi;N. Ohta;Azusa Muraoka;M. Nakamura
本研究利用导电原子力显微镜对苝二亚胺（PDI）、萘二亚胺（NDI）基受体和[6,6]-苯基c61 -丁酸甲酯（PCBM）薄膜中电子传递的空间变化进行了表征。纳米尺度下的电子流图像显示，PDI和ndi基聚合物受体薄膜中的电子传递在空间上是不均匀的，形成了几十纳米到200纳米的良好导电区。相比之下，在pdi基小分子受体和PCBM膜中相对均匀。由于聚合物链的局部有序，流过ndi基聚合物薄膜良好导电区的局部电流比流过PCBM薄膜的电流大。这表明可以通过形态优化进一步提高电子迁移率。相反，在pdi基聚合物和小分子受体薄膜中，由于扭曲的链内（分子内）结构导致松散的链间（分子间）π -π堆积，电子传递被固有地抑制。对局部电子电流的纳米尺度观察提供了对非富勒烯受体薄膜的电子传输相关性能限制的见解，这是无法通过宏观电流-电压测量来估计的特征。
In this study, spatial variations in electron transport in thin films of perylene diimide (PDI)- and naphthalene diimide (NDI)-based acceptors and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) were characterized by conductive atomic force microscopy. Electron flow images at the nanometer scale revealed that electron transport was spatially inhomogeneous in the PDI- and NDI-based polymer acceptor films, with the formation of good conducting regions with sizes of several tens of nanometers to 200 nm. In contrast, it was relatively uniform in the PDI-based small-molecule acceptor and PCBM films. The local electron currents flowing through the good conducting region of the NDI-based polymer film were higher in magnitude than those flowing in the PCBM film as a consequence of the local ordering of the polymer chains. This suggests that the electron mobility can be further improved via morphological optimizations. Conversely, electron transport was inherently inhibited in the PDI-based polymer and small-molecule acceptor films because of a loose interchain (intermolecular) π–π stacking because of the twisted intrachain (intramolecular) structures. Nanoscale observation of the local electron currents provides insights into the electron transport-related performance limitations of the nonfullerene acceptor films—a feature that cannot be estimated via macroscopic current–voltage measurements.