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Blue‐Light‐Emitting Oligoquinolines: Synthesis, Properties, and High‐Efficiency Blue‐Light‐Emitting Diodes
Author(s) -
Tonzola C. J.,
Kulkarni A. P.,
Gifford A. P.,
Kaminsky W.,
Jenekhe S. A.
Publication year - 2007
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.200600542
Subject(s) - oled , materials science , electroluminescence , quantum efficiency , chromaticity , photoluminescence , fluorescence , cyclic voltammetry , blue light , optoelectronics , photochemistry , common emitter , diode , electrochemistry , optics , chemistry , nanotechnology , electrode , physics , layer (electronics)
The synthesis, photophysics, cyclic voltammetry, and highly efficient blue electroluminescence of a series of four new n‐type conjugated oligomers, 6,6′‐bis(2,4‐diphenylquinoline) (B1PPQ), 6,6′‐bis(2‐(4‐ tert ‐butylphenyl)‐4‐phenylquinoline) (BtBPQ), 6,6′‐bis(2‐ p ‐biphenyl)‐4‐phenylquinoline) (B2PPQ), and 6,6′‐bis((3,5‐diphenylbenzene)‐4‐phenylquinoline) (BDBPQ) is reported. The oligoquinolines have high glass‐transition temperatures ( T g ≥ 133 °C), reversible electrochemical reduction, and high electron affinities (2.68–2.81 eV). They emit blue photoluminescence with 0.73–0.94 quantum yields and 1.06–1.42 ns lifetimes in chloroform solutions. High‐performance organic light‐emitting diodes (OLEDs) with excellent blue chromaticity coordinates are achieved from all the oligoquinolines. OLEDs based on B2PPQ as the blue emitter give the best performance with a high brightness (19 740 cd m –2 at 8.0 V), high efficiency (7.12 cd A –1 and 6.56 % external quantum efficiency at 1175 cd m –2 ), and excellent blue color purity as judged by the Commission Internationale de L'Eclairage (CIE) coordinates ( x = 0.15, y = 0.16). These results represent the best efficiency of blue OLEDs from neat fluorescent organic emitters reported to date. These results demonstrate the potential of oligoquinolines as emitters and electron‐transport materials for developing high‐performance blue OLEDs.