Résumé
This paper reports on charge injection and transport in electroluminescent devices based on a silole deriv. 1,1-dimethyl-2,5-bis(p-2,2'-dipyridylaminophenyl)-3,4-diphenylsilole (DMPPS). The devices are composed of Sn doped In oxide (In2O3:Sn or I TO)/poly(3,4-ethylene dioxythiophene) doped with poly(styrene sulfonate)/DMPPS/metal. Current-voltage and luminance-voltage characteristics are 1st performed as a function of the electron injection barrier height and of the org. layer thickness. The voltage dependence of current and luminance varies with the metal cathode, i.e., Ca, Al, Cu, and Au. The effect of the DMPPS thickness in a double carrier device shows that electrons predominate and are bulk limited. An accurate study is carried out as a function of temp. for hole-only and bipolar devices, i.e., with Au and Ca cathodes. Hole-only devices (with Au cathode) exhibit an ohmic behavior for low voltages. A hopping mechanism (thermally assisted tunnel transfer between localized states) agrees with exptl. data, since activation energy is found close to 50 meV. The electron transfer limitation is located at the DMPPS/cathode interface and the Fowler-Nordheim mechanism is qual. consistent with exptl. data at high voltages. With a Ca cathode, electron conduction is preponderant and is bulk limited. A power dependence JµVm with m>2 is consistent with the model of trap charge limited conduction. The total electron trap d. is 2 ´ 1018 cm-3.