Universität zu Köln

Feser, Stephan and Meerholz, Klaus (2011). Investigation of the Photocross-Linking Mechanism in Oxetane-Functionalized Semiconductors. Chem. Mat., 23 (22). S. 5001 - 5006. WASHINGTON: AMER CHEMICAL SOC. ISSN 0897-4756

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Abstract

Oxetane-functionalized organic semiconductors have been used for fabricating multilayer OLEDs from solution and for lithographic patterning. These materials are commonly cross-linked photochemically by cationic ring-opening polymerization (CROP) in the presence of a photo-acid generator (PAG). Due to the sensitization of the reaction by the semiconductor itself, illumination leads to the photoinduced electron transfer (PET) from the PAG to the semiconductor. This in turn leads to besides the intended cross-linking - redoxchemical doping of the layers, which may have an important impact on the device performance. Until now, the exact quantities of this unintentional side reaction were unknown. In this study, we use organic field-effect transistors to investigate and quantify the mechanism of photosensitized cross-linking of oxetane-functionalized organic semiconductors. By comparing the compound of interest, for example, a derivative of the commonly used hole conductor triphenylamine dimer (TPD), with an almost identical, noncrosslinkable TPD-derivative and by using a quantitative oxidant in comparison with the PAG, we were able to quantitatively assign all possible reaction pathways. Furthermore, the experiments provide detailed information of the charge transport characteristics of doped cross-linked films. The charge-carrier mobility increases with the doping level by a factor of up to two. It turns out that the PAG induces a stoichiometric fraction of mobile charge-carriers of 2.5 x 10(-4). Finally, it is shown that thermal annealing of crosslinked films leads to controlled dedoping of the semiconductor.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Feser, Stephan UNSPECIFIED UNSPECIFIED UNSPECIFIED Meerholz, Klaus UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-485179
DOI:	10.1021/cm202327c
Journal or Publication Title:	Chem. Mat.
Volume:	23
Number:	22
Page Range:	S. 5001 - 5006
Date:	2011
Publisher:	AMER CHEMICAL SOC
Place of Publication:	WASHINGTON
ISSN:	0897-4756
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language LIGHT-EMITTING-DIODES; DIARYLIODONIUM SALTS; CHARGE-TRANSPORT Multiple languages Chemistry, Physical; Materials Science, Multidisciplinary Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/48517