Improvements of electron injection efficiency using subphthalocyanine mixed with lithium fluoride in cathode structures of organic light emitting diodes

Abstract The improvement of current injection efficiency in organic light emitting diodes is demonstrated with incorporation of lithium fluoride (LiF) mixed with subphthalocyanine (SubPc) as electron injection layers. The photoemission spectra indicate that the lithium released from LiF would remove chlorine atoms from SubPc molecules and create large density of gap states at the interfaces. These gap states, resulted from the addition of SubPc in conventional aluminum/LiF/ tris-(8-Hydroxyquinoline)-aluminum (Alq 3 ) cathode structures, further enhance the electron injection efficiency in OLEDs. The results demonstrate a relatively unique feature of SubPc which can be used to improve both electron and hole injection efficiency.