Structural optimization of 2,5-diarylsiloles as excellent electron-transporting materials for organic electroluminescent devices

We have already reported that 2,5-di(2-pyridyl)silole (PySPy) has high performance as an electron-transporting material (ETM) for organic electroluminescent devices (OELDs). For the purpose of developing more practicable ETMs, we have now prepared three new 2,5-diarylsilole derivatives, PPySPyP, PyPySPyPy, and PyPSPPy, having 6-phenyl-2-pyridyl, 6-(2-pyridyl)-2-pyridyl, and 3-(2-pyridyl)phenyl as the aryl groups, respectively, and have studied their structure-properties relationships. These derivatives have higher glass transition temperatures when compared to PySPy. Among these compounds and tris(8-hydroxyquinolino)aluminum (Alq), the bipyridylsilole derivative, PyPySPyPy, showed the highest electron-transporting abilities. The efficiency of a device consisting of ITO/triphenyldiamine derivative/Alq/PyPySPyPy/MgAg reached 2.2 lm/W at 3.4 V. Furthermore, the half-life time of a device consisting of ITO/triphenylamine dimer derivative/Alq/PyPySPyPy/LiF/Al was nearly 3 times longer than that of the control device without PyPySPyPy under a constant current.