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The Li3PO4/Al electrode: An alternative, efficient cathode for organic light-emitting diodes

Gassmann, Andrea and Melzer, Christian and von Seggern, Heinz (2012):
The Li3PO4/Al electrode: An alternative, efficient cathode for organic light-emitting diodes.
In: Synthetic Metals, 161 (23-24), Elsevier Science Publishing, pp. 2575-2579, ISSN 03796779,
[Online-Edition: http://dx.doi.org/10.1016/j.synthmet.2011.08.009],
[Article]

Abstract

In this contribution an alternative, efficient cathode for organic light-emitting diodes (OLEDs) is introduced consisting of a sub-nanometer thin lithium phosphate (Li3PO4) layer capped with aluminium. This cathode is competitive to the LiF/Al state-of-the-art cathode and performs equally well in small molecule and polymer OLEDs but yields a higher device lifetime. The functional principle of the Li3PO4/Al cathode is based on the in situ formation of a dipolar interface. Partly oriented AlPO4 dipoles are the reason for a potential drop at the interface and a work function lowering of about 500 meV. The work function of the Li3PO4/Al cathode is found to be comparable to the work function of calcium resulting in a promotion of electron injection. As the reaction products of the interface reaction are environmentally stable and chemically attached to the interface diffusion of these species into the organic layer is unlikely. This might be the reason for the observed enhanced device lifetime for devices with a Li3PO4/Al cathode.

Item Type: Article
Erschienen: 2012
Creators: Gassmann, Andrea and Melzer, Christian and von Seggern, Heinz
Title: The Li3PO4/Al electrode: An alternative, efficient cathode for organic light-emitting diodes
Language: English
Abstract:

In this contribution an alternative, efficient cathode for organic light-emitting diodes (OLEDs) is introduced consisting of a sub-nanometer thin lithium phosphate (Li3PO4) layer capped with aluminium. This cathode is competitive to the LiF/Al state-of-the-art cathode and performs equally well in small molecule and polymer OLEDs but yields a higher device lifetime. The functional principle of the Li3PO4/Al cathode is based on the in situ formation of a dipolar interface. Partly oriented AlPO4 dipoles are the reason for a potential drop at the interface and a work function lowering of about 500 meV. The work function of the Li3PO4/Al cathode is found to be comparable to the work function of calcium resulting in a promotion of electron injection. As the reaction products of the interface reaction are environmentally stable and chemically attached to the interface diffusion of these species into the organic layer is unlikely. This might be the reason for the observed enhanced device lifetime for devices with a Li3PO4/Al cathode.

Journal or Publication Title: Synthetic Metals
Volume: 161
Number: 23-24
Publisher: Elsevier Science Publishing
Uncontrolled Keywords: OLED, Electron injection, Li3PO4/Al, Interface reaction, Dipolar layer
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Electronic Materials
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 15 Nov 2013 09:12
Official URL: http://dx.doi.org/10.1016/j.synthmet.2011.08.009
Additional Information:

Conference Proceedings of Symposium N, E-MRS 2011 Spring Meeting, Nice, France

Identification Number: doi:10.1016/j.synthmet.2011.08.009
Funders: This work was supported in the framework of the OPAL 2008 project (BMBF 13N8995). , The authors thank the German Federal Ministry of Education and Research for the financial support.
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