Highly power efficient organic light-emitting diodes based on p-doped and novel n-doped carrier transport layers

摘要

The power efficiency of organic light-emitting diodes was significantly improved by introducing a novel n-doping (4 ' 7-diphyenyl-1, 10-phenanthroline: 33 wt% 8-hydroxy-quinolinato lithium) layer as an electron transport layer and a p-doping layer composed of 4,4 ',4 ''-tris (3-methylphenylphenylamono) triphenylamine (m-MTDATA) and tetrafluro-tetracyano-quinodimethane (F-4-TCNQ) as a hole transport layer. Hole-only and electron-only devices were demonstrated to observe an improvement in the conductivity of the transport layers. With this strategy, we demonstrated that the power efficiency was enhanced by similar to 100%, luminous efficiency was enhanced by similar to 54% while driving voltage was reduced by 32% as compared with the control device. We obtained a power efficiency of 4.44 Lm W-1, which is the best value so far reported for tris (8-hydroxyquinolinato) aluminium (Alq(3))-based emitters. This improvement was ascribed to the improved conductivity of the transport layers and to the better charge balance in the emission zone.