Nature of the Interfaces Between Stoichiometric and Under-Stoichiometric MoO3 and 4,4′-N,N′-dicarbazole-biphenyl: A Combined Theoretical and Experimental Study

Authors

  • Theodoros A. Papadopoulos,

    1. School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400, USA
    Current affiliation:
    1. Institut de Physique, Université de Liège, B-4000, Liège, Belgium
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  • Jens Meyer,

    1. Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA
    Current affiliation:
    1. Philips Research, Weisshausstrasse 2, D-52066 Aachen, Germany
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  • Hong Li,

    1. School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400, USA
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  • Zelei Guan,

    1. Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA
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  • Antoine Kahn,

    1. Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA
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  • Jean-Luc Brédas

    Corresponding author
    1. School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400, USA
    • School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400, USA.

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Abstract

A combination of density functional theory and experimental measurements via ultraviolet and X-ray photoelectron spectroscopies is used to explore the nature of the interface between the stoichiometric molybdenum trioxide (MoO3) or its under-stoichiometric counterpart with oxygen vacancies, and an organic hole-transport layer represented by 4,4′-N,N′-dicarbazole-biphenyl (CBP). Upon adsorption of CBP, special attention is paid to i) the appearance of gap states and the reduction of the molybdenum oxide surface, and ii) the evolution of the work function. Very good agreement is found between theory and experiment. The near alignment of the CBP highest occupied molecular orbital with the Fermi level and the conduction band edge of molybdenum oxide points to facile hole collection or injection.

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