Disilane- and siloxane-bridged biphenylene and bithiophene derivatives as electron-transporting materials in OLEDs
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Optical, electrochemical, and electron-transporting properties of disilane- and siloxane-bridged biphenyl and bithiophene derivatives were investigated, in comparison with those of the monosilane-bridged analogues (siloles). The UV spectra and cyclic voltammograms indicated that elongation of the silicon bridge suppresses the π-conjugation, in accordance with the results of DFT calculations. The DFT calculations indicated also that the dislane-bridged biphenyl and siloxane-bridged bithiophene should have the low-lying HOMOs and LUMOs. The electron transporting properties were evaluated by the performance of triple-layered OLEDs having vapor deposited films of the Si-bridged compound, Alq3, and TPD, as the electron-transport, emitter, and hole-transport, respectively. Of these, the device with a disilane-bridged biphenyl exhibited the high performance with the maximum current density of 590 mA/cm2 at the applied electric field of 12 × 107 V/m (applied bias voltage = 12 V) and the maximum luminance of 22,000 cd/m2 at 13 × 107 V/m.
Journal of Organometallic Chemistry
Elsevier Science S.A.
Copyright (c) 2008 Elsevier B.V.