A study on the dual emissions of organic light emitting devices

The color of light-emitting diodes is tunable by adjusting the dual emissions of two type of devices containing 2,3-bis(2′,N-dimethyl-3′-indolyl)-N-methylmaleimide. The first device, utilizing Alq3 (tris(8-hydoxyquinolinato)aluminum) as the electron transporting layer (ETL), displays yellow color which is invariant to applied bias. The second device, utilizing TPBI (2,2′,2″-(l,3,5-benzenetriyl)tris(l-phenyl-lH-benzimidazole) as ETL, displays a continuous change of color from orange to blue depending on the doping level as well as the applied bias. The different emitting characteristics can be rationalized by the variation of potential energy barriers at the interface between different layers, which control the movements of electrons as well as holes