有機発光素子の電界発光と電気伝導特性

抄録

We discussed the electrical properties (carrier injection and carrier transport) of the organic electroluminescent diodes (ELD) with triphenyl diamine derivative (hole transport layer) and aluminum quinoline (emission layer). The apparent activation energy of current in organic ELD was estimated to be 0.12eV from Arrhenius plot. As it was consistent with the activation energy of hole mobility of TPD, we suggested that the carrier transport in organic ELD is closely related to hole transport of hole transport material. The introduction of TPD layer between Alq3 and cathode suppressed the current density and the EL efficiency per current density. The EL efficiency of organic ELD was thought to depend upon the electron injection from cathode into emission layer. We estimated the trap depth and the trap density of Alq3 thin film using the thermally stimulated current method and the space charge limited current model for the first time. They are estimated to be about 0.8eV and 1017cm-3, respectively. We showed from the discussion of energy diagram that the trap center act as an carrier trap, but not as an recombination center.