In this work, we investigate the influence of weak intermolecular interactions, which have not previously been carefully considered, in hole transport material (HTM)/tris(8-hydroxyquinoline)aluminum (Alq 3)-based organic light-emitting diodes (OLEDs). Although such weak interactions quench Alq3 fluorescence, no significant spectral shift is identified. Electroluminescence of OLEDs containing HTM:Alq3 codeposited (mixed) emitter is quenched by the formation of such exciplexes. In general, the electroluminescence quantum efficiency of OLEDs correlates closely with the photoluminescence quantum yields of HTM:Alq3 codeposited films. In contrast, in an OLED containing a layered structure of HTM/Alq 3, exciplexes are less effective at quenching the electroluminescence of Alq3. Because exciplexes form only at the interface between the HTM and Alq3 layers in HTM/Alq3-based OLEDs, exciplex formation is affected not only by the electron donating nature of the HTM but also by the position of the electron-hole recombination zone and the application of an external electric field during OLED operation.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films