Kim Hyung Do, Iriguchi Ryo, Fukuhara Tomohiro, Benten Hiroaki, Ohkita Hideo
Department of Polymer Chemistry Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan.
Division of Materials Science Graduate School of Materials Science, Nara Institute of Science and Technology, Takayama, Ikoma, Nara, 630-0192, Japan.
Chem Asian J. 2020 Mar 16;15(6):796-801. doi: 10.1002/asia.201901743. Epub 2020 Feb 17.
Herein, the hole transport in a quinoxaline-thiophene based conjugated polymer (PTQ1) mixed with an insulating polystyrene (PS) was studied by macroscopic and local current density-voltage characteristics measurements. As a result, we found that the hole conductivity in PTQ1 : PS blends increases as the weight ratio of PTQ1 is reduced down to 20 wt%. This is mainly ascribed to increases in mobility because the charge carrier density would be constant in the insulating PS matrix. With decreasing PTQ1 weight ratio in the blends, the absorption bandwidth of PTQ1 and additional emission due to excimer decreased, suggesting that interchain interactions are suppressed. By measuring the temperature-dependent conductivity, we also found that the activation energy for the hole conductivity is smaller in PTQ1 : PS blends than in PTQ1 neat films. These findings suggest that trap sites decrease because of the suppressed interaction between PTQ1 chains in blend films. We also measured conductive atomic force microscope images of the blend films to clarify the local conductive property. For PTQ1 neat films, a low conductive image was observed over the entire film. For PTQ1 : PS blends, on the other hand, many highly conductive spots were locally found. We thus conclude that the dilution of PTQ1 chains in the PS matrix leads to a lower formation of trap sites, resulting in more conductive transport in PTQ1 : PS blends than in PTQ1 neat films.
在此，通过宏观和局部电流密度-电压特性测量，研究了喹喔啉-噻吩基共轭聚合物（PTQ1）与绝缘聚苯乙烯（PS）混合体系中的空穴传输。结果发现，当PTQ1的重量比降低至20 wt%时，PTQ1 : PS共混物中的空穴电导率增加。这主要归因于迁移率的增加，因为在绝缘的PS基质中载流子密度保持恒定。随着共混物中PTQ1重量比的降低，PTQ1的吸收带宽以及准分子引起的额外发射减少，这表明链间相互作用受到抑制。通过测量温度依赖性电导率，我们还发现PTQ1 : PS共混物中空穴传导的活化能比PTQ1纯膜中的小。这些发现表明，由于共混膜中PTQ1链间相互作用的抑制，陷阱位点减少。我们还测量了共混膜的导电原子力显微镜图像，以阐明局部导电特性。对于PTQ1纯膜，在整个膜上观察到低导电图像。另一方面，对于PTQ1 : PS共混物，局部发现了许多高导电斑点。因此，我们得出结论，PS基质中PTQ1链的稀释导致陷阱位点形成减少，从而使得PTQ1 : PS共混物中的传导传输比PTQ1纯膜中的更多。
