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The electroluminescent characteristics of blue organic light-emitting diodes (BOLEDs) fabricated with doped charge carrier transport layers are analyzed. The fluorescent blue dopant BCzVBi is doped in an emissive layer, hole transport layer (HTL) and electron transport layer (ETL), respectively, to optimize the probability of exciton generation in the BOLEDs. The luminance and luminous efficiency of BOLEDs made with BCzVBi-doped HTL and ETL increase by 22% and 17% from 11,683 cd/m2 at 8.5 V and 6.08 cd/A at 4.0 V to 14,264 cd/m2 at 8.5 V and 7.13 cd/A at 4.0 V while CIE coordinates of (0.15, 0.15) of both types of BOLEDs remained unchanged. The electron mobility of BCzVBi is estimated to be 1.02×10−5 cm2/Vs by TOF.

In this Letter, blue phosphorescence organic light-emitting diodes (PHOLEDs) employ structures for electron and/or hole confinement; 1,3,5-tris(N-phenylbenzimiazole-2-yl)benzene is used as a hole confinement layer and tris-(phenylpyrazole)iridium [Ir(ppz)3] is utilized for an electron confinement layer (ECL). The electrical and optical properties of the fabricated blue PHOLEDs with various carrier-confinement structures are analyzed. Structures with a large energy offset between the carrier confinement and emitting layers enhance the charge-carrier balance in the emitting region, resulting from the effective carrier confinement. The maximum external quantum efficiency of the blue PHOLEDs with the double-ECLs is 24.02% at 1500 cd/m2 and its luminous efficiency is 43.76 cd/A, which is 70.47% improved compared to the device without a carrier-confinement layer.

We fabricate white phosphorescent organic light-emitting diodes (PHOLEDs) with three dopants and double emissive layer (EML) to achieve color stability. The white PHOLEDs use FIrpic dopant for blue EML (B-EML), and Ir(ppy)3:Ir(piq)3 dopants for green:red EML (GR-EML) with N,N.'-dicarbazolyl-3, 5-benzene (mCP) as host material. Thicknesses of B-EML and GR-EML are adjusted to form a narrow recombination zone at two EML's interface and charge trapping happens in EML according to wide highest occupied molecular orbital and/or lowest unoccupied molecular orbital energy band gap of mCP and smaller energy band gap of dopants. The total thickness of both EMLs is fixed at 30 nm in the device structure of ITO (150 nm)/MoO3 (2 nm)/N,N'-diphenyl-N,N'-bis(l-naphthyl-phenyl)-(l,l'-biphenyl)-4, 4'-diamine (70 nm)/mCP:Firpic-8.0% (12 nm)/mCP:Ir(ppy)3-3.0%:Ir(piq)3-1.5% (18 nm)/2',2',2''-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (30 nm)/8-hydroxyquinolinolato-lithium (2 nm)/Al (120 nm). White PHOLED shows 18.25 cd/A of luminous efficiency and white color coordinates of (0.358 and 0.378) at 5000 cd/m2 and color stability with slight CIEXY change of (0.028 and 0.002) as increasing luminance from 1000 to 5000 cd/m2.