Liu, S. W.Sun, X. W.Demir, Hilmi Volkan2016-02-082016-02-0820122158-3226http://hdl.handle.net/11693/21221We demonstrated graded-host phosphorescent organic light-emitting diodes with high efficiency and reduced efficiency roll-off. The emissive layer of the graded host device consists of both electron and hole transport type hosts, 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBI) and 4,4-,4- tris(Ncarbazolyl) triphenylamine, respectively, with graded composition, and the phosphorescent red emitter bis(2-phenylquinoline) (acetylacetonate) iridium(III), which wasuniformly doped into the graded hostmatrix. The graded host device shows improved quantum efficiency and power efficiency with significantly reduced efficiency rolloff as compared to the unipolar-host and double layer heterojunction host devices.EnglishAcetylacetonatesDouble layersEmissive layersGraded compositionHole transportsHost devicesPhosphorescent organic light-emitting diodesPower efficiencyRed emitterTriphenyl aminesBenzeneHeterojunctionsIridium compoundsLight emissionLight emitting diodesPhosphorescenceEfficiencyArticle10.1063/1.37016852158-3226