Organic oxide/Al composite cathode in small molecular organic light-emitting diodes

This study addresses the feasibility of using an organic oxide/Al composite cathode to fabricate the small molecular organic light-emitting diodes (OLEDs). A supplementary organic buffer film is placed at the interface between the tris(8-hydroxyquinoline) aluminum (Alq3) and the organic oxide/Al complex layers. Incorporating the rubrene/poly(ethylene glycol) dimethyl ether (PEGDE) buffer layers into the composite cathode structure markedly improves the performance of devices. The luminous efficiencies of Alq3-based OLEDs biased at ∼100mA∕cm2 are 4.8 and 5.1cd∕A for rubrene (50Å)/PEGDE (15Å)∕Al and rubrene (50Å)/PEGDE (15Å)∕LiF (5Å)∕Al cathode devices, and 1.3 and 3.8cd∕A for devices with Al and LiF (5Å)∕Al cathodes, respectively.