31605
2009
2009
eng
article
1
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Structural and electronic implications for carrier injection into organic semiconductors
We report on the structural and electronic interface formation between ITO (indium-tin-oxide) and prototypical organic small molecular semiconductors, i.e., CuPc (copper phthalocyanine) and alpha-NPD (N,N'-di(naphtalen-1-yl)- N,N'-diphenyl-benzidine). In particular, the effects of in situ oxygen plasma pretreatment of the ITO surface on interface properties are examined in detail: Organic layer-thickness dependent Kelvin probe measurements revealed a good alignment of the ITO work function and the highest occupied electronic level of the organic material in all samples. In contrast, the electrical properties of hole-only and bipolar organic diodes depend strongly on the treatment of ITO prior to organic deposition. This dependence is more pronounced for diodes made of polycrystalline CuPc than for those of amorphous alpha-NPD layers. X-ray diffraction and atomic force microscopic (AFM) investigations of CuPc nucleation and growth evidenced a more pronounced texture of the polycrystalline film structure on the ITO substrate that was oxygen plasma treated prior to organic layer deposition. These findings suggest that the anisotropic electrical properties of CuPc crystallites, and their orientation with respect to the substrate, strongly affect the charge carrier injection and transport properties at the anode interface.
http://www.springerlink.com/content/100501
10.1007/s00339-009-5336-6
0947-8396
allegro:1991-2014
10107932
Applied physics A : materials science & processing. - ISSN 0947-8396. - 97 (2009), 1, S. 1 - 9
Mauro Castellani
Ingo Salzmann
Philippe Bugnon
Shuwen Yu
Martin Oehzelt
Norbert Koch
Institut für Physik und Astronomie
Referiert
35157
2013
2013
eng
8
1-2
4
article
Nature Publ. Group
London
1
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Moderate doping leads to high performance of semiconductor/insulator polymer blend transistors
Polymer transistors are being intensively developed for next-generation flexible electronics. Blends comprising a small amount of semiconducting polymer mixed into an insulating polymer matrix have simultaneously shown superior performance and environmental stability in organic field-effect transistors compared with the neat semiconductor. Here we show that such blends actually perform very poorly in the undoped state, and that mobility and on/off ratio are improved dramatically upon moderate doping. Structural investigations show that these blend layers feature nanometre-scale semiconductor domains and a vertical composition gradient. This particular morphology enables a quasi three-dimensional spatial distribution of semiconductor pathways within the insulating matrix, in which charge accumulation and depletion via a gate bias is substantially different from neat semiconductor, and where high on-current and low off-current are simultaneously realized in the stable doped state. Adding only 5 wt% of a semiconducting polymer to a polystyrene matrix, we realized an environmentally stable inverter with gain up to 60.
Nature Communications
10.1038/ncomms2587
2041-1723
wos:2011-2013
1588
WOS:000318873900042
Neher, D (reprint author), Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany., norbert.koch@physik.hu-berlin.de; neher@uni-potsdam.de
Alexander von Humboldt Stiftung; Bundesministerium fur Bildung und
Forschung (BMBF project 'NEMO') [FKZ 13N10622]; DFG [SPP1355]
Guanghao Lu
James C. Blakesley
Scott Himmelberger
Patrick Pingel
Johannes Frisch
Ingo Lieberwirth
Ingo Salzmann
Martin Oehzelt
Riccardo Di Pietro
Alberto Salleo
Norbert Koch
Dieter Neher
Institut für Physik und Astronomie
Referiert
36192
2012
2012
eng
5
3
108
article
American Physical Society
College Park
1
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Intermolecular hybridization governs molecular electrical doping
Current models for molecular electrical doping of organic semiconductors are found to be at odds with other well-established concepts in that field, like polaron formation. Addressing these inconsistencies for prototypical systems, we present experimental and theoretical evidence for intermolecular hybridization of organic semiconductor and dopant frontier molecular orbitals. Common doping-related observations are attributed to this phenomenon, and controlling the degree of hybridization emerges as a strategy for overcoming the present limitations in the yield of doping-induced charge carriers.
Physical review letters
10.1103/PhysRevLett.108.035502
0031-9007
wos:2011-2013
035502
WOS:000299328500016
Salzmann, I (reprint author), Humboldt Univ, Inst Phys, D-12489 Berlin, Germany., ingo.salzmann@physik.hu-berlin.de; georg.heimel@physik.hu-berlin.de
DFG (Germany); JSPS (Japan); Austrian Science Fund (FWF) [P21094]
Ingo Salzmann
Georg Heimel
Steffen Duhm
Martin Oehzelt
Patrick Pingel
Benjamin M. George
Alexander Schnegg
Klaus Lips
Ralf-Peter Blum
Antje Vollmer
Norbert Koch
Institut für Physik und Astronomie
Referiert
39424
2015
2015
eng
58
63
6
1
53
article
Wiley-Blackwell
Hoboken
1
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Charge Transfer in and Conductivity of Molecularly Doped Thiophene-Based Copolymers
The electrical conductivity of organic semiconductors can be enhanced by orders of magnitude via doping with strong molecular electron acceptors or donors. Ground-state integer charge transfer and charge-transfer complex formation between organic semiconductors and molecular dopants have been suggested as the microscopic mechanisms causing these profound changes in electrical materials properties. Here, we study charge-transfer interactions between the common molecular p-dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane and a systematic series of thiophene-based copolymers by a combination of spectroscopic techniques and electrical measurements. Subtle variations in chemical structure are seen to significantly impact the nature of the charge-transfer species and the efficiency of the doping process, underlining the need for a more detailed understanding of the microscopic doping mechanism in organic semiconductors to reliably guide targeted chemical design.
Journal of polymer science : B, Polymer physics
10.1002/polb.23631
0887-6266
1099-0488
wos:2015
WOS:000346080500005
Koch, N (reprint author), Humboldt Univ, Inst Phys, Newtonstr 15, D-12489 Berlin, Germany., norbert.koch@physik.hu-berlin.de
Fatemeh Ghani
Andreas Opitz
Patrick Pingel
Georg Heimel
Ingo Salzmann
Johannes Frisch
Dieter Neher
Argiri Tsami
Ullrich Scherf
Norbert Koch
eng
uncontrolled
charge transfer
eng
uncontrolled
conducting polymers
eng
uncontrolled
doping
eng
uncontrolled
thiophene
Institut für Physik und Astronomie
Referiert