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Investigation of Solution-Processed Ultrathin Electron Injection Layers for Organic Light-Emitting Diodes

Stolz, Sebastian and Scherer, Michael and Mankel, Eric and Lovrinčić, Robert and Schinke, Janusz and Kowalsky, Wolfgang and Jaegermann, Wolfram and Lemmer, Uli and Mechau, Norman and Hernandez-Sosa, Gerardo (2014):
Investigation of Solution-Processed Ultrathin Electron Injection Layers for Organic Light-Emitting Diodes.
In: ACS Applied Materials & Interfaces, ACS Publications, pp. 6616-6622, 6, (9), ISSN 1944-8244,
[Online-Edition: http://dx.doi.org/10.1021/am500287y],
[Article]

Abstract

We study two types of water/alcohol-soluble aliphatic amines, polyethylenimine (PEI) and polyethyleni-mine-ethoxylated (PEIE), for their suitability as electron injection layers in solution-processed blue fluorescent organic light-emitting diodes (OLEDs). X-ray photoelectron spectroscopy is used to determine the nominal thickness of the polymer layers while ultraviolet photoelectron spectroscopy is carried out to determine the induced work-function change of the silver cathode. The determined work-function shifts are as high as 1.5 eV for PEI and 1.3 eV for PEIE. Furthermore, atomic force microscopy images reveal that homogeneous PEI and PEIE layers are present at nominal thicknesses of about 11 nm. Finally, we solution prepare blue emitting polymer-based OLEDs using PEI/PEIE in combination with Ag as cathode layers. Luminous efficiency reaches 3 and 2.2 cd A−1, whereas maximum luminance values are as high as 8000 and 3000 cd m−2for PEI and PEIE injection layers, respectively. The prepared devices show a comparable performance to Ca/Ag OLEDs and an improved shelf lifetime.

Item Type: Article
Erschienen: 2014
Creators: Stolz, Sebastian and Scherer, Michael and Mankel, Eric and Lovrinčić, Robert and Schinke, Janusz and Kowalsky, Wolfgang and Jaegermann, Wolfram and Lemmer, Uli and Mechau, Norman and Hernandez-Sosa, Gerardo
Title: Investigation of Solution-Processed Ultrathin Electron Injection Layers for Organic Light-Emitting Diodes
Language: English
Abstract:

We study two types of water/alcohol-soluble aliphatic amines, polyethylenimine (PEI) and polyethyleni-mine-ethoxylated (PEIE), for their suitability as electron injection layers in solution-processed blue fluorescent organic light-emitting diodes (OLEDs). X-ray photoelectron spectroscopy is used to determine the nominal thickness of the polymer layers while ultraviolet photoelectron spectroscopy is carried out to determine the induced work-function change of the silver cathode. The determined work-function shifts are as high as 1.5 eV for PEI and 1.3 eV for PEIE. Furthermore, atomic force microscopy images reveal that homogeneous PEI and PEIE layers are present at nominal thicknesses of about 11 nm. Finally, we solution prepare blue emitting polymer-based OLEDs using PEI/PEIE in combination with Ag as cathode layers. Luminous efficiency reaches 3 and 2.2 cd A−1, whereas maximum luminance values are as high as 8000 and 3000 cd m−2for PEI and PEIE injection layers, respectively. The prepared devices show a comparable performance to Ca/Ag OLEDs and an improved shelf lifetime.

Journal or Publication Title: ACS Applied Materials & Interfaces
Volume: 6
Number: 9
Publisher: ACS Publications
Uncontrolled Keywords: polyethylenimine, polyethylenimine-ethoxylated, injection layers, photoelectron spectroscopy, OLEDs, printed electronics
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Surface Science
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 26 Feb 2015 09:49
Official URL: http://dx.doi.org/10.1021/am500287y
Identification Number: doi:10.1021/am500287y
Funders: We acknowledge financial support for the projects NanoPEP (FKZ 13N12127) and MORPHEUS (FKZ 13N11705) of the Leading-Edge Cluster Forum Organic Electronics managed by InnovationLab GmbH within the Strategy for Germany of the , Federal Ministry of Education and Research., We furthermore acknowledge the German Federal Ministry of Education and Research for financial support via the project MESOMERIE (FKZ 13N10721).
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