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Layer Cross-Fading at Organic/Organic Interfaces in OVPD-Processed Red Phosphorescent Organic Light Emitting Diodes as a New Concept to Increase Current and Luminous Efficacy

Published online by Cambridge University Press:  31 January 2011

Florian Lindla ,
Manuel Boesing ,
Christoph Zimmermann ,
Frank Jessen ,
Philipp van Gemmern ,
Dietrich Bertram ,
Dietmar Keiper ,
Nico Meyer ,
M. Heuken  and
Holger Kalisch
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Florian Lindla
Affiliation:
[email protected], RWTH Aachen University, Institut für theoretische Elektrotechnik, Aachen, Germany
Manuel Boesing
Affiliation:
[email protected], RWTH Aachen University, Institut für theoretische Elektrotechnik, Aachen, Germany
Christoph Zimmermann
Affiliation:
[email protected], RWTH Aachen University, Institut für theoretische Elektrotechnik, Aachen, Germany
Frank Jessen
Affiliation:
[email protected], RWTH Aachen University, Institut für theoretische Elektrotechnik, Aachen, Germany
Philipp van Gemmern
Affiliation:
[email protected], Philips Technologie GmbH, Aachen, Germany
Dietrich Bertram
Affiliation:
[email protected], United States
Dietmar Keiper
Affiliation:
[email protected], United States
Nico Meyer
Affiliation:
[email protected], AIXTRON AG, Aachen, Germany
M. Heuken
Affiliation:
[email protected], RWTH Aachen University, Institut für theoretische Elektrotechnik, Aachen, Germany
Holger Kalisch
Affiliation:
[email protected], United States
Rolf H. Jansen
Affiliation:
[email protected], United States
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Abstract

The current and luminous efficacy of a red phosphorescent organic light emitting diode (OLED) with sharp interfaces between each of the organic layers can be increased from 18.8 cd/A and 14.1 lm/W (at 1,000 cd/m2) to 36.5 cd/A (+94%, 18% EQE) and 33.7 lm/W (+139%) by the introduction of a layer cross-fading zone at the hole transport layer (HTL) to emission layer (EL) interface. Layer cross-fading describes a procedure of linearly decreasing the fraction in growth rate of an organic layer during deposition over a certain thickness while simultaneously increasing the fraction in growth rate of the following layer. For OLED processing and layer cross-fading organic vapor phase deposition (OVPD) is used. The typical observation of a roll-off in current efficacy of phosphorescent OLED to higher luminance can be reduced significantly. An interpenetrating network of a prevailing hole and a prevailing electron conducting material is created in the cross-fading zone. This broadens the recombination zone and furthermore lowers the driving voltage. The concept of layer cross-fading to increase the efficacies is suggested to be useful in multi-colored OLED stacks as well.

Keywords

organicsemiconductingphysical vapor deposition (PVD)
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1154: Symposium B – Concepts in Molecular and Organic Electronics , 2009 , 1154-B05-07
Copyright
Copyright © Materials Research Society 2009

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References

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