Enhance current injection of organic light emitting diodes by inserting an organic superlattice

Poor electron injection is a great concern for organic light emitting diodes (OLEDs). In order to improve the electron mobility, inserting organic superlattice structures in the electron transport layer was investigated in conventional OLEDs configuration. The superlattices are composed of alternating tris(8-hydroxyquinoline aluminium (Alq3) and copper phthalocyanine (CuPc) thin films, which are used as electron and hole injection layers. Experimental results show superlattices with a 6-nm period have the largest injected current. Reduction of turn-on voltage and resistance of superlattice OLEDs were also observed. After thermal annealing, the current-voltage characteristic changes and shows the possibility of layer intermixing in organic superlattices.