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

Effective intermediate electrode layers comprising of LiF(1nm)∕Ca(25nm)∕Ag(15nm) or LiF(1nm)∕Al(3nm)∕Au(15nm) were studied in stacked organic light-emitting devices (OLEDs). Stacked OLEDs with two identical emissive units consisting of NPB∕Alq3: C545T/BCP exhibited superior luminous efficiency-current density characteristics over conventional single-unit devices. At 20mA∕cm2, the luminous efficiency of the stacked OLEDs using the intermediate layers of LiF∕Ca∕Ag and LiF∕Al∕Au were about 19.6cd∕A and 17.5cd∕A, respectively, almost doubling that of the corresponding control devices, as expected.