We investigate the properties of N,N′-[(Diphenyl-N,N′-bis)9,9,-dimethyl-fluoren-2-yl]-benzidine (BF-DPB) as hole transport material (HTL) in organic light-emitting diodes (OLEDs) and compare BF-DPB to the commonly used HTLs N,N,N′,N′-tetrakis(4-methoxyphenyl)-benzidine (MeO-TPD), 2,2′,7,7′-tetrakis(N,N′-di-p-methylphenylamino)-9,9′-spirobifluorene (Spiro-TTB), and N,N′-di(naphtalene-1-yl)-N,N′-diphenylbenzidine (NPB). The influence of 2,2′-(perfluoronaphthalene-2,6-diylidene)dimalononitrile (F6-TCNNQ p-dopant) concentration in BF-DPB on the operation voltage and efficiency of red and green phosphorescent OLEDs is studied; best results are achieved at 4 wt. % doping. Without any light extraction structure, BF-DPB based red (green) OLEDs achieve a luminous efficacy of 35 .1 lm/W (74 .0 lm/W) at 1000 cd/m2 and reach a very high brightness of 10 000 cd/m2 at a very low voltage of 3.2 V (3.1 V). We attribute this exceptionally low driving voltage to the high ionization potential of BF-DPB which enables more efficient hole injection from BF-DPB to the adjacent electron blocking layer. The high efficiency and low driving voltage lead to a significantly lower luminous efficacy roll-off compared to the other compounds and render BF-DPB an excellent HTL material for highly efficient OLEDs.
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15 September 2014
Research Article|
September 18 2014
Alternative p-doped hole transport material for low operating voltage and high efficiency organic light-emitting diodes
Caroline Murawski;
Caroline Murawski
a)
1
Institut für Angewandte Photophysik, Technische Universität Dresden
, George-Bähr-Str. 1, 01062 Dresden, Germany
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Cornelius Fuchs;
Cornelius Fuchs
1
Institut für Angewandte Photophysik, Technische Universität Dresden
, George-Bähr-Str. 1, 01062 Dresden, Germany
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Simone Hofmann;
Simone Hofmann
1
Institut für Angewandte Photophysik, Technische Universität Dresden
, George-Bähr-Str. 1, 01062 Dresden, Germany
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Karl Leo;
Karl Leo
1
Institut für Angewandte Photophysik, Technische Universität Dresden
, George-Bähr-Str. 1, 01062 Dresden, Germany
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Malte C. Gather
Malte C. Gather
1
Institut für Angewandte Photophysik, Technische Universität Dresden
, George-Bähr-Str. 1, 01062 Dresden, Germany
2SUPA, School of Physics & Astronomy,
University of St Andrews
, North Haugh, St Andrews, KY16 9SS Scotland, United Kingdom
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a)
Author to whom correspondence should be addressed. Electronic mail: [email protected]
Appl. Phys. Lett. 105, 113303 (2014)
Article history
Received:
May 07 2014
Accepted:
September 08 2014
Citation
Caroline Murawski, Cornelius Fuchs, Simone Hofmann, Karl Leo, Malte C. Gather; Alternative p-doped hole transport material for low operating voltage and high efficiency organic light-emitting diodes. Appl. Phys. Lett. 15 September 2014; 105 (11): 113303. https://doi.org/10.1063/1.4896127
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