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We demonstrate the multiple quantum well (MQW) structures with the charge control layers (CCLs) to produce highly efficient red phosphorescent organic light-emitting devices (OLEDs). Various triplet quantum well devices from a single to five quantum wells are realized using wide band-gap hole and electron transporting layers, narrow band-gap host and dopant materials, and CCLs. Triplet energies in such MQW devices are confined at the emitting layers. The maximum external quantum efficiency of 14.8% with a two quantum well device structure is obtained. The described MQW device concept has been proposed to be very useful to future OLED display and lighting applications. [ABSTRACT FROM AUTHOR]

Using an Ir(ppy)3 metal complex doped in 4,4′4″-tris(N-carbazolyl)-triphenylamine hole and bis[2-(2-hydroxyphenyl)-pyridine]beryllium electron transport host materials, simple three layer green phosphorescent organic light-emitting devices comprising double emissive layers have been fabricated. A low driving voltage value of 3.3 V to reach a luminance of 1000 cd/m2 and maximum current- and power-efficiency values of 58.7 cd/A and 65.1 lm/W, and maximum external quantum efficiency (EQE) value of 18.6% are reported in this device. EQE exceeding 15% over a wide range of current density from 0.03 to 25 mA/cm2 is noticed. We demonstrate a low roll-off current efficiency value of 12% at a luminance of 10 000 cd/m2 in a highly efficient simple double emissive layer device, imperative to high brightness applications. [ABSTRACT FROM AUTHOR]

Using a narrow band-gap fluorescent host material, bis(10-hydroxybenzo[h] quinolinato)beryllium complex, efficient red phosphorescent organic light emitting diodes (PHOLEDs) comprising two layers have been reported. Significantly low driving voltage of 4.5 V to reach a luminance of 1000 cd/m2 is reported in this simple structure PHOLEDs. The current and power efficiencies of bilayered red PHOLED are 9.66 cd/A and 6.90 lm/W, respectively, promising for low power display and lighting applications. [ABSTRACT FROM AUTHOR]

We present a highly efficient green phosphorescent device comprising only of two organic layers. A host material bis[2-(2-hydroxyphenyl)-pyridine]beryllium having a good electron transporting and energy transfer characteristics, and a wide band gap hole transport material N,N′-di(4-(N,N′-diphenyl-amino)phenyl)-N,N′-diphenylbenzidine lead to the fabrication of a simplified high efficiency device. The driving voltage value of 3.3 V to reach a luminance of 1000 cd/m2 is reported. The maximum current- and power-efficiency values of 38.30 cd/A and 46.60 lm/W are demonstrated in this device. Results reveal a practical way to fabricate highly efficient truly bilayer organic devices for trouble-free manufacturing processes. [ABSTRACT FROM AUTHOR]

The authors studied the current-voltage characteristics of the organic superlattices of an ITO/1,3,5-tris-(3-methylphenylphenylamino) triphenylamine (m-MTDATA) (5 nm)/[m-MTDATAand 4,7diphenyl-1,10-phenanthroline (Bphen)]4/Bphen (5 nm)/LiF/Al. The thickness of m-MTDATA was varied from 3 to 7 nm with the fixed Bphen thickness at 3 nm. The current-voltage characteristics of the organic superlattice show a peak and a valley between 3 and 8 V when the thickness of m-MTDATA is 7 nm, which is due to the resonant tunneling currents. It is found that there is no luminance by the resonant tunneling currents. [ABSTRACT FROM AUTHOR]