Abstract: Double-layer heterojunction organic electroluminescent devices (OELDs) with a conventional structure of anode/N,N’-bis-(3-naphthyl)-N,N’-biphenyl-(1,1’-biphenyl)-4,4’-diamine [NPB(40 nm)]/tris-(8-hydroxyquinoline)-aluminum[Alq3(50 nm)]/cathode were fabricated using different materials as anode and cathode. The impact of electrode materials on device performance was studied by varying the electrodes of OELDs. The testing results of device electroluminescent characteristics showed that the current-voltage (I-V) relationship of the devices is in accordance with the theory of trapped charge limited current (TCLC) regime. Due to the disorder of organic material energy levels and the dependence of carrier mobility on temperature as well as electric field, charge carrier injection ability of different electrodes was not necessarily dependent on the work function of the electrodes. The introduction of hole transporting layer in double-layer devices enables the recombination zone of charge carriers to locate near the interface of organic heterojunction, which efficiently reduces the quenching effect of electrode on excitons, and thus largely enhances device performance. In addition, the microcavity effect in OELDs device with metallic electrode may lead to the shift of emissive spectra and the shrinkage of spectrum full width at half maximum. The results showed that enhanced device performance compared with conventional device can be anticipated by surface modification and optimization of metallic electrodes.

Key words: Organic electroluminescence, Electrode material, TCLC, Exciton quenching, Device performance