Structure–Property Study on Two New D–A Type Materials Comprising Pyridazine Moiety and the OLED Application as Host

作者：Shaojie Liu, Xunlu Zhang, Changjin Ou, Shulei Wang, Xinli Yang, Xin‐Hui Zhou, Baoxiu Mi, Dapeng Cao, Zhiqiang Gao · 发表于：ACS Applied Materials & Interfaces · 年份：2017 · DOI：10.1021/acsami.7b04859 · 被引用次数：45 · 研究领域：Organic Light-Emitting Diodes Research、Luminescence and Fluorescent Materials、Organic Electronics and Photovoltaics

In this paper, two new pyridazine based donor–acceptor type materials, i.e., 3CzPyaPy: 9,9′-(3-(6-(9H-carbazol-9-yl)pyridazin-3-yl)pyridine-2,6-diyl)bis(9H-carbazole) and 4CzPyPyaPy: 3,6-bis(2,6-di(9H-carbazol-9-yl)pyridin-3-yl)pyridazine, were synthesized with high yields. These two materials exhibited strong absorption/emission with high molar extinction coefficients and moderate photoluminescence quantum yield. The glass transition temperature of 3CzPyaPy was detected to be as high as 131 °C, showing its high thermal stability. Although the absorption energies and oxidation/reduction behaviors of the two materials were similar, the emission from 4CzPyPyaPy with longer effective-conjugation length presented hypsochromic shift both in films and in dilute solutions, contradicting to the common sense. The single crystal structure study disclosed their different space stretching and packing: 3CzPyaPy was twisted in larger angles and adopted dimerlike packing, while 4CzPyPyaPy showed smaller torsion angles and exhibited slipped herringbone packing. The dimerlike packing in 3CzPyaPy is responsible for its bathochromic shift of emission in solid state, while its unsymmetrical molecular structure accounts for that in solution. We believe that the unsymmetrical molecular structure of 3CzPyaPy is partially responsible for its high thermal-stability and also responsible for its HOMO dispersion which renders it slightly more difficult to oxidize. 3CzPyaPy was proved to be a bipolar-tra...