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High Efficiency Deep‐Blue Phosphorescent Organic Light‐Emitting Diodes with CIE x , y (≤ 0.15) and Low Efficiency Roll‐Off by Employing a High Triplet Energy Bipolar Host Material
Author(s) -
Maheshwaran Athithan,
Sree Vijaya Gopalan,
Park HoYeol,
Kim Hyein,
Han Si Hyun,
Lee Jun Yeob,
Jin SungHo
Publication year - 2018
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201802945
Subject(s) - phosphorescence , materials science , quantum efficiency , oled , common emitter , electroluminescence , optoelectronics , diode , carbazole , organic electronics , diphenylphosphine oxide , photochemistry , nanotechnology , layer (electronics) , chemistry , optics , fluorescence , physics , polymer chemistry , transistor , voltage , quantum mechanics
Recently, bipolar host materials are the most promising candidates for achieving high performance phosphorescent organic light‐emitting diodes (PHOLEDs) in order to maximize recombination efficiency. However, the development of host material with high triplet energy ( E T ) is still a great challenge to date to overcome the limitations associated with the present PHOLEDs. Herein, a highly efficient donor‐π‐acceptor (D‐π‐A) type bipolar host (4′‐(9H‐carbazol‐9‐yl)‐2,2′‐dimethyl‐[1,1′‐biphenyl]‐4‐yl)diphenylphosphine oxide ( m‐ CBPPO) comprising of carbazole, 2,2′‐dimethylbiphenyl and diphenylphosphoryl as D‐π‐A unit, respectively, is developed. Interestingly, a high E T of 3.02 eV is observed for m‐ CBPPO due to highly twisted conformation. Furthermore, the new host material is incorporated in PHOLEDs as emissive layer with a new carbene type Ir(cb) 3 material as a deep‐blue emitter. The optimized devices show an excellent external quantum efficiency (EQE) of 24.8% with a notable Commission internationale de l'éclairage ( x , y ) ≤ 0.15, (0.136, 0.138) and high electroluminescence performance with extremely low efficiency roll‐off. Overall, the above EQE is the highest reported for deep‐blue PHOLEDs with very low efficiency roll‐off and also indicate the importance of appropriate host for the development of high performance deep‐blue PHOLEDs.