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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
Author(s) -
Li Minghang,
Lin MingTe,
Chen WeiHsuan,
McDougald Roy,
Arvapally Ravi,
Omary Mohammad,
Shepherd Nigel D.
Publication year - 2012
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201127023
Subject(s) - quantum efficiency , oled , phosphorescence , triphenylamine , exciton , materials science , optoelectronics , diode , doping , electrical efficiency , photochemistry , chemistry , analytical chemistry (journal) , layer (electronics) , optics , nanotechnology , fluorescence , physics , organic chemistry , power (physics) , quantum mechanics
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/m 2 , and efficiency roll‐off of only 4% of the peak value at a useful brightness of 1000 Cd/m 2 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.