Multilayer cathode for organic light-emitting devices

A thin layer of samarium (Sm) was introduced in the cathode fabrication of the organic light-emitting devices (OLEDs). An efficient cathode Sm/LiF/Al used to improve the performance of OLEDs was reported. Standard N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl 4,4′-diamine (NPB)/tris-(8-hydroxyquinoline) aluminum (AlQ) devices with Sm/LiF/Al cathode showed dramatically enhanced electroluminescent (EL) brightness and efficiency. The optimized device with the 0.5 nm layer of Sm with the cathode structure of Sm/LiF/Al showed the improved power efficiency of 40% than the control device of the conventional LiF/Al cathode at 100 mA/cm2. The drive voltage of the device with the Sm/LiF/Al cathode was decreased about 2 V at 500 mA/cm2 compared with the conventional LiF/Al cathode device. The enhanced properties of the device with such a multilayer cathode are considered to the improved balance of electron/hole injection in the emitting layer.