Publication type: Article in scientific journal
Type of review: Peer review (publication)
Title: Dipolar doping of organic semiconductors to enhance carrier injection
Authors: Hofmann, Alexander J.L.
Züfle, Simon
Shimizu, Kohei
Schmid, Markus
Wessels, Vivien
Jäger, Lars
Altazin, Stéphane
Ikegami, Keitaro
Khan, Motiur Rahman
Neher, Dieter
Ishii, Hisao
Ruhstaller, Beat
Brütting, Wolfgang
et. al: No
DOI: 10.1103/PhysRevApplied.12.064052
Published in: Physical Review Applied
Volume(Issue): 12
Issue: 6
Issue Date: Dec-2019
Publisher / Ed. Institution: American Physical Society
ISSN: 2331-7019
Language: English
Subject (DDC): 530: Physics
Abstract: If not oriented perfectly isotropically, the strong dipole moment of polar organic semiconductor materials such as tris-(8-hydroxyquinolate)aluminum (Alq3) will lead to the buildup of a giant surface potential (GSP) and thus to a macroscopic dielectric polarization of the organic film. Despite this having been a known fact for years, the implications of such high potentials within an organic layer stack have only been studied recently. In this work, the influence of the GSP on hole injection into organic layers is investigated. Therefore, we apply a concept called dipolar doping to devices consisting of the prototypical organic materials N,N′-Di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) as nonpolar host and Alq3 as dipolar dopant with different mixing ratios to tune the GSP. The mixtures are investigated in single-layer monopolar devices as well as bilayer metal/insulator/semiconductor structures. Characterization is done electrically using current-voltage (I-V) characteristics, impedance spectroscopy, and charge extraction by linearly increasing voltage and time of flight, as well as with ultraviolet photoelectron spectroscopy. We find a maximum in device performance for moderate to low doping concentrations of the polar species in the host. The observed behavior can be described on the basis of the Schottky effect for image-force barrier lowering, if the changes in the interface dipole, the carrier mobility, and the GSP induced by dipolar doping are taken into account.
URI: https://digitalcollection.zhaw.ch/handle/11475/19630
Fulltext version: Published version
License (according to publishing contract): Licence according to publishing contract
Departement: School of Engineering
Organisational Unit: Institute of Computational Physics (ICP)
Appears in Collections:Publikationen School of Engineering

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