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Title: Seleno groups control the energy-level alignment between conjugated organic molecules and metals

Abstract

The charge injection from metallic electrodes into hole transporting layers of organic devices often suffers from deviations from vacuum-level alignment at the interface. Even for weakly interacting cases, Pauli repulsion causes an interface dipole between the metal and conjugated organic molecules (COMs) (so called “push-back” or “cushion” effect), which leads notoriously to an increase of the hole injection barrier. On the other hand, for chalcogenol self assembled monolayers (SAMs) on metal surfaces, chemisorption via the formation of chalcogen-metal bonds is commonly observed. In these cases, the energy-level alignment is governed by chalcogen-derived interface states in the vicinity of the metal Fermi-level. In this work, we present X-ray and ultraviolet photoelectron spectroscopy data that demonstrate that the interfacial energy-level alignment mechanism found for chalcogenol SAMs also applies to seleno-functionalized COMs. This can be exploited to mitigate the push-back effect at metal contacts, notably also when COMs with low ionization energies are employed, permitting exceedingly low hole injection barriers, as shown here for the interfaces of tetraseleno-tetracene with Au(111), Ag(111), and Cu(111)

Authors:
; ; ;  [1];  [2];  [3]; ;  [4];  [2];  [5];  [6]; ;  [2];  [1];  [7]
  1. Institut für Physik, Humboldt-Universität zu Berlin, 12489 Berlin (Germany)
  2. Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522 (Japan)
  3. (FUNSOM), Soochow University, Suzhou 215123 (China)
  4. Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen (Germany)
  5. (China)
  6. Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, BESSY II, 12489 Berlin (Germany)
  7. (Germany)
Publication Date:
OSTI Identifier:
22253649
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 1; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALIGNMENT; CHALCOGENIDES; CHEMISORPTION; CONTROL; DIPOLES; FERMI LEVEL; INJECTION; INTERFACES; PHOTOELECTRON SPECTROSCOPY; SILVER 111; TETRACENE; X RADIATION

Citation Formats

Niederhausen, Jens, Heimel, Georg, Wilke, Andreas, Rabe, Jürgen P., Duhm, Steffen, Institute of Functional Nano and Soft Materials, Bürker, Christoph, Schreiber, Frank, Xin, Qian, School of Physics, Shandong University, 27 Shanda Nanlu, Jinan 250100, Vollmer, Antje, Kera, Satoshi, Ueno, Nobuo, Koch, Norbert, and Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, BESSY II, 12489 Berlin. Seleno groups control the energy-level alignment between conjugated organic molecules and metals. United States: N. p., 2014. Web. doi:10.1063/1.4858856.
Niederhausen, Jens, Heimel, Georg, Wilke, Andreas, Rabe, Jürgen P., Duhm, Steffen, Institute of Functional Nano and Soft Materials, Bürker, Christoph, Schreiber, Frank, Xin, Qian, School of Physics, Shandong University, 27 Shanda Nanlu, Jinan 250100, Vollmer, Antje, Kera, Satoshi, Ueno, Nobuo, Koch, Norbert, & Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, BESSY II, 12489 Berlin. Seleno groups control the energy-level alignment between conjugated organic molecules and metals. United States. doi:10.1063/1.4858856.
Niederhausen, Jens, Heimel, Georg, Wilke, Andreas, Rabe, Jürgen P., Duhm, Steffen, Institute of Functional Nano and Soft Materials, Bürker, Christoph, Schreiber, Frank, Xin, Qian, School of Physics, Shandong University, 27 Shanda Nanlu, Jinan 250100, Vollmer, Antje, Kera, Satoshi, Ueno, Nobuo, Koch, Norbert, and Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, BESSY II, 12489 Berlin. 2014. "Seleno groups control the energy-level alignment between conjugated organic molecules and metals". United States. doi:10.1063/1.4858856.
@article{osti_22253649,
title = {Seleno groups control the energy-level alignment between conjugated organic molecules and metals},
author = {Niederhausen, Jens and Heimel, Georg and Wilke, Andreas and Rabe, Jürgen P. and Duhm, Steffen and Institute of Functional Nano and Soft Materials and Bürker, Christoph and Schreiber, Frank and Xin, Qian and School of Physics, Shandong University, 27 Shanda Nanlu, Jinan 250100 and Vollmer, Antje and Kera, Satoshi and Ueno, Nobuo and Koch, Norbert and Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, BESSY II, 12489 Berlin},
abstractNote = {The charge injection from metallic electrodes into hole transporting layers of organic devices often suffers from deviations from vacuum-level alignment at the interface. Even for weakly interacting cases, Pauli repulsion causes an interface dipole between the metal and conjugated organic molecules (COMs) (so called “push-back” or “cushion” effect), which leads notoriously to an increase of the hole injection barrier. On the other hand, for chalcogenol self assembled monolayers (SAMs) on metal surfaces, chemisorption via the formation of chalcogen-metal bonds is commonly observed. In these cases, the energy-level alignment is governed by chalcogen-derived interface states in the vicinity of the metal Fermi-level. In this work, we present X-ray and ultraviolet photoelectron spectroscopy data that demonstrate that the interfacial energy-level alignment mechanism found for chalcogenol SAMs also applies to seleno-functionalized COMs. This can be exploited to mitigate the push-back effect at metal contacts, notably also when COMs with low ionization energies are employed, permitting exceedingly low hole injection barriers, as shown here for the interfaces of tetraseleno-tetracene with Au(111), Ag(111), and Cu(111)},
doi = {10.1063/1.4858856},
journal = {Journal of Chemical Physics},
number = 1,
volume = 140,
place = {United States},
year = 2014,
month = 1
}