Organic light-emitting devices (OLEDs) with stable white light emitting were fabricated by usingexciton adjusting layer (EAL) inserted between dual emitting layers (EMLs). Three charge transportmaterials with different characteristics were chosen as EAL, including4,7-diphenyl-1,1′-phenanthroline (Bphen), N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD)and N,N′-dicarbazolyl-3,5-benzene (mCP). Device structure was given as: ITO/NPB (30 nm)/mCP:(t-bt)_2Ir(acac) (2 nm, 4 wt.%)/EALs/ mCP: Firpic (12 nm, 10 wt.%)/Bphen (35 nm)/Mg: Ag (100 nm).The results showed that, compared with device without EAL, the devices employed EAL yielded highdevice performance as well as favorable luminescence property and stable white emission. For thedevice with mCP EAL, the maximum brightness of 24700cd/m~2 and current efficiency of 14.5 cd/Awere obtained, while the CIE coordinates of device changed from (0.33, 0.35) to (0.35, 0.36) with thebias voltage increasing from 5 V to 12 V. It was suggested that by incorporating EAL in OLEDs, thecharge carrier recombination zone was broadened, and the balance of electron-hole was improvedbetween EMLs.
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