Abstract
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.
© 2014 Chinese Optics Letters
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