Electroluminescence from multilayer organic light-emitting diodes using poly(methylphenylsilane) as hole transporting material

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Abstract
We have investigated the optical and electrical properties of polysilane-based multilayer electroluminescent (EL) devices, utilizing poly(methylphenylsilane) (PMPS) as the hole transporting material, in order to elucidate the mechanism of EL emission in these devices. The EL devices which we fabricated have two or three functional organic layers. These layers are composed of a PMPS layer as well as a 3-(2′-Benzothiazolyl)-7-diethylaminocoumarin (Coumarin 6) doped polystyrene (PS) layer and/or a tris-(8-hydroxyquinoline) aluminum (Alq3) layer. An indium-tin-oxide-coated glass and an Al electrode were used as the hole and the electron injecting electrode, respectively. On the basis of a combined analysis of the basic characteristics of these devices, photoexcited fluorescence spectra and decay curves as well as the band diagram of these devices, we concluded that the recombination of charge carriers and the EL emission in the three-layer device occur both in the Coumarin 6:PS and the evaporated Alq3 layers.