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Highly Efficient Blue Organic Light‐Emitting Diodes Based on 2‐(Diphenylamino)fluoren‐7‐ylvinylarene Derivatives that Bear a tert ‐Butyl Group
Author(s) -
Lee Kum Hee,
Kwon Young Soo,
Lee Jin Yong,
Kang Sunwoo,
Yook Kyoung Soo,
Jeon Soon Ok,
Lee Jun Yeob,
Yoon Seung Soo
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201100304
Subject(s) - electroluminescence , quantum efficiency , fluorene , oled , homo/lumo , dopant , materials science , luminous efficacy , photochemistry , photoluminescence , indium tin oxide , chemistry , doping , molecule , organic chemistry , optoelectronics , nanotechnology , polymer , layer (electronics) , composite material
Abstract Blue fluorescent materials with a 2‐(diphenylamino)fluoren‐7‐ylvinylarene emitting unit and tert ‐butyl‐based blocking units were synthesized. The photophysical properties of these materials, including UV/Vis absorption, photoluminescent properties, and HOMO–LUMO energy levels, were characterized and rationalized with quantum‐mechanical DFT calculations. The electroluminescent properties of these molecules were examined through the fabrication of multilayer devices with a structure of indium–tin oxide, 4,4′‐bis{ N ‐[4‐( N,N ‐di‐ m ‐tolylamino)phenyl]‐ N ‐phenylamino}biphenyl, 4′‐bis[ N ‐(1‐naphthyl)‐ N ‐phenylamino]biphenyl, and blue materials doped in 2‐methyl‐9,10‐di(2‐naphthyl)anthracene/tris(8‐quinolinolato)aluminum/LiF/Al. All devices exhibit highly efficient blue electroluminescence with high external quantum efficiency (3.20–7.72 % at 20 mA cm −2 ). A deep‐blue device with Commission Internationale de l’Eclairage (CIE) coordinates of (0.15, 0.11) that uses 7‐[2‐(3′,5′‐di‐ tert ‐butylbiphenyl‐4‐yl)vinyl]‐9,9‐diethyl‐2‐ N ‐(3,5‐di‐ tert ‐butylphenyl)‐2,4‐difluorobenzenamino‐9 H ‐fluorene as a dopant in the emitting layer showed a luminous efficiency and external quantum efficiency of 3.95 cd A −1 and 4.23 % at 20 mA cm −2 , respectively. Furthermore, a highly efficient sky‐blue device that uses the dopant 7‐{2‐[2‐(3,5‐di‐ tert ‐butylphenyl)‐9,9′‐spirobifluorene‐7‐yl]vinyl}‐9,9‐diethyl‐2‐ N,N ‐diphenylamino‐9 H ‐fluorene exhibited a luminous efficiency and high quantum efficiency of 10.3 cd A −1 and 7.7 % at 20 mA cm −2 , respectively, with CIE coordinates of (0.15, 0.20).