Efficient molecular organic light-emitting diodes based on silole derivatives

We report the performance of molecular organic fight-emitting diodes (MOLEDs) using silole derivatives as emissive and electron transport materials. Two siloles, namely 2,5-di-(3-biphenyl)-1,1-dimethyl-3,4-diphenylsilacyclopentadiene (PPSPP) and l,2-bis(1-methyl-2,3,4,5,tetraphenylsilacyclopentadienyl)ethane (2PSP), with high PL quantum yields of 94% and 85%, respectively, were used as emissive materials. Another silole, namely 2,5-bis-(2',2"-bipyridin-6-yl)-1,1-dimethyl-3,4-diphenylsilacyclopentadiene (PyPySPyPy), was used as the electron transport material. MOLEDs using these two siloles and NPB as the hole transport material show a low operating voltage of approximately 4.5 V at a luminance of 100 cd/m(2) and high external 2 electroluminescence (EL) quantum efficiencies of 3.4% and 3.8%, respectively, at 100 A/m(2). MOLEDs based on PPSPP exhibit a red-shifted EL spectrum which is assigned to an exciplex formed at the PPSPP:NPB interface.