High efficiency orange-red phosphorescent organic light emitting diodes based on a Pt(II)-pyridyltriazolate complex from a structure optimized for charge balance and reduced efficiency roll-off

We report a high power efficiency (PE) of 44.7 ± 0.5 lm/W, high external quantum efficiency (EQE) of 19.7 ± 0.1% at 500 Cd/m2, and efficiency roll‐off of only 4% of the peak value at a useful brightness of 1000 Cd/m2 from orange‐red emitting, organic light emitting diodes featuring 1,1‐bis[(di‐4‐tol...

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Bibliographic Details
Published in:Physica status solidi. A, Applications and materials science Applications and materials science, 2012-01, Vol.209 (1), p.221-225
Main Authors: Li, Minghang, Lin, Ming-Te, Chen, Wei-Hsuan, McDougald Jr, Roy, Arvapally, Ravi, Omary, Mohammad, Shepherd, Nigel D.
Format: Article
Language:English
Subjects:
charge balance
exciton confinement
phosphorescence
power efficiency
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Summary:We report a high power efficiency (PE) of 44.7 ± 0.5 lm/W, high external quantum efficiency (EQE) of 19.7 ± 0.1% at 500 Cd/m2, and efficiency roll‐off of only 4% of the peak value at a useful brightness of 1000 Cd/m2 from orange‐red emitting, organic light emitting diodes featuring 1,1‐bis[(di‐4‐tolylamino)phenyl]cyclohexane (TAPC) as the hole transport layer/electron blocking layer, an emissive layer consisting of 65% bis[3,5‐bis(2‐pyridyl)‐1,2,4‐triazolato]platinum(II) (Pt(ptp)2) doped into 4,4′‐bis(carbazol‐9‐yl)triphenylamine (CBP), and 1,3,5‐tris(phenyl‐2‐benzimidazolyl)‐benzene (TPBI) as the electron transport layer (ETL). Based on a comparison of these structures with devices that did not incorporate an electron/exciton blocker and devices featuring N,N′‐dicarbazolyl‐3,5‐benzene (mCP) as the electron/exciton blocking layer, we ascribe the high efficiency and low efficiency roll‐off to better charge balance, and enhanced confinement of excitons and the recombination zone to the emissive layer.
ISSN:1862-6300
1862-6319
DOI:10.1002/pssa.201127023