Effective intermediate layers for highly efficient stacked organic light-emitting devices

Effective intermediate electrode layers comprising of LiF(1 nm)/Ca(25 nm)/Ag(15 nm) or LiF(1 nm)/Al(3 nm)/Au(15 nm) were studied in stacked organic light-emitting devices (OLEDs). Stacked OLEDs with two identical emissive units consisting of NPB/Alq(3): C545T/BCP exhibited superior luminous efficiency-current density characteristics over conventional single-unit devices. At 20 mA/cm(2), the luminous efficiency of the stacked OLEDs using the intermediate layers of LiF/Ca/Ag and LiF/Al/Au were about 19.6 cd/A and 17.5 cd/A, respectively, almost doubling that of the corresponding control devices, as expected. (c) 2005 American Institute of Physics.