Graduate School of Materials Science, Nara Institute of Science and Technology , 8916-5 Takayama-cho, Ikoma, Nara 630-0192, Japan.
Department of Chemistry, The Chinese University of Hong Kong , Shatin, New Territories, Hong Kong, China.
ACS Appl Mater Interfaces. 2017 Mar 8;9(9):8211-8218. doi: 10.1021/acsami.6b13988. Epub 2017 Feb 21.
Tetrabenzoporphyrin (BP) is a p-type organic semiconductor characterized by the large, rigid π-framework, excellent stability, and good photoabsorption capability. These characteristics make BP and its derivatives prominent active-layer components in organic electronic and optoelectronic devices. However, the control of the solid-state arrangement of BP frameworks, especially in solution-processed thin films, has not been intensively explored, and charge-carrier mobilities observed in BP-based materials have stayed relatively low as compared to those in the best organic molecular semiconductors. This work concentrates on engineering the solid-state packing of a BP derivative, 5,15-bis(triisopropylsilyl)ethynyltetrabenzoporphyrin (TIPS-BP), toward achieving efficient charge-carrier transport in its solution-processed thin films. The effort leads to the selective formation of a brickwork packing that has two dimensionally extended π-staking. The maximum field-effect hole mobility in the resulting films reaches 1.1 cm V s, which is approximately 14 times higher than the record value for pristine free-base BP (0.070 cm V s). This achievement is enabled mainly through the optimization of three factors; namely, deposition process, cast solvent, and self-assembled monolayer that constitutes the dielectric surface. On the other hand, polarized-light microscopy and grazing-incident wide-angle X-ray diffraction analyses show that there remains some room for improvement in the in-plane homogeneity of molecular alignment, suggesting even higher charge-carrier mobilities can be obtained upon further optimization. These results will provide a useful basis for the polymorph engineering and morphology optimization in solution-processed organic molecular semiconductors.
四苯并卟啉（BP）是一种 p 型有机半导体，具有大的刚性π-骨架、优异的稳定性和良好的光吸收能力。这些特性使 BP 及其衍生物成为有机电子和光电设备中突出的活性层组件。然而，BP 骨架的固态排列的控制，特别是在溶液处理的薄膜中，尚未得到深入探索，并且在基于 BP 的材料中观察到的电荷载流子迁移率与最佳有机分子半导体中的迁移率相比仍然相对较低。这项工作集中在对 BP 衍生物 5,15-双（三异丙基硅基）乙炔基四苯并卟啉（TIPS-BP）的固态堆积进行工程设计，以实现其溶液处理的薄膜中的有效电荷载流子输运。该努力导致了砖式堆积的选择性形成，该堆积具有二维扩展的π-堆叠。所得薄膜中的最大场效应空穴迁移率达到 1.1 cm V s，比原始自由碱基 BP（0.070 cm V s）的记录值高约 14 倍。这一成就主要得益于三个因素的优化；即沉积工艺、铸膜溶剂和构成介电表面的自组装单层。另一方面，偏振光显微镜和掠入射广角 X 射线衍射分析表明，分子排列的面内均匀性仍有改进的空间，这表明通过进一步优化可以获得更高的电荷载流子迁移率。这些结果将为溶液处理的有机分子半导体中的多晶工程和形态优化提供有用的基础。
