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Fermi level positioning in organic semiconductor phase mixed composites: The internal interface charge transfer doping model

Mayer, Thomas and Hein, Corinna and Mankel, Eric and Jaegermann, Wolfram and Müller, Mathis M. and Kleebe, Hans-Joachim (2012):
Fermi level positioning in organic semiconductor phase mixed composites: The internal interface charge transfer doping model.
In: Organic Electronics, Elsevier Science Publishing, pp. 1356-1364, 13, (8), ISSN 15661199, [Online-Edition: http://dx.doi.org/10.1016/j.orgel.2012.03.028],
[Article]

Abstract

Photoemission data, taken on co-sublimed films and on bilayers of the prototypical small molecule semiconductor CuPc and p-type dopants TCNQ or WO3 show similar electronic trends that have to be interpreted by phase separation of the dopant within the matrix material forming a phase mixed composite. High resolution TEM micrographs for CuPc:WO3 co-deposited films clearly prove such phase separation. Therefore the doping models developed for singly dispersed dopant molecules cannot be applied. For the mechanism of the doping induced variations of the host matrix Fermi level in such phase mixed semiconductor:dopant composites we propose the internal interface charge transfer doping model. According to this model the Fermi levels of two mixed phases align at the internal interfaces and the doping limit is defined by the work function difference of matrix and dopant minus the potential drops induced by dipole formation at the internal matrix/dopant interfaces. It is shown that the magnitude of the internal interface dipole potential drops may be estimated from the dipoles measured at matrix/dopant bilayer interfaces and that the maximum dopant induced Fermi level shift may be estimated from the difference of work functions measured on thick films of matrix and of dopant, minus a mean value for the interface dipole.

Item Type: Article
Erschienen: 2012
Creators: Mayer, Thomas and Hein, Corinna and Mankel, Eric and Jaegermann, Wolfram and Müller, Mathis M. and Kleebe, Hans-Joachim
Title: Fermi level positioning in organic semiconductor phase mixed composites: The internal interface charge transfer doping model
Language: English
Abstract:

Photoemission data, taken on co-sublimed films and on bilayers of the prototypical small molecule semiconductor CuPc and p-type dopants TCNQ or WO3 show similar electronic trends that have to be interpreted by phase separation of the dopant within the matrix material forming a phase mixed composite. High resolution TEM micrographs for CuPc:WO3 co-deposited films clearly prove such phase separation. Therefore the doping models developed for singly dispersed dopant molecules cannot be applied. For the mechanism of the doping induced variations of the host matrix Fermi level in such phase mixed semiconductor:dopant composites we propose the internal interface charge transfer doping model. According to this model the Fermi levels of two mixed phases align at the internal interfaces and the doping limit is defined by the work function difference of matrix and dopant minus the potential drops induced by dipole formation at the internal matrix/dopant interfaces. It is shown that the magnitude of the internal interface dipole potential drops may be estimated from the dipoles measured at matrix/dopant bilayer interfaces and that the maximum dopant induced Fermi level shift may be estimated from the difference of work functions measured on thick films of matrix and of dopant, minus a mean value for the interface dipole.

Journal or Publication Title: Organic Electronics
Volume: 13
Number: 8
Publisher: Elsevier Science Publishing
Uncontrolled Keywords: Phase mixed organic–organic semiconductors, Phase mixed inorganic–organic semiconductors, Internal interface charge transfer doping
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Earth Science
11 Department of Materials and Earth Sciences > Earth Science > Geo-Material-Science
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Surface Science
Zentrale Einrichtungen
Exzellenzinitiative > Clusters of Excellence > Center of Smart Interfaces (CSI)
Exzellenzinitiative
Exzellenzinitiative > Clusters of Excellence
Date Deposited: 26 Nov 2013 12:11
Official URL: http://dx.doi.org/10.1016/j.orgel.2012.03.028
Identification Number: doi:10.1016/j.orgel.2012.03.028
Funders: We would like to acknowledge our cooperation partners Peter Erk and Jaehyung Hwang from BASF., The experiments have been performed within the OPEG project funded by the German Ministry of Education and Research BMBF.
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