Regensburg 2007 – scientific programme

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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices

SYOE 8: Poster Session SYOE

SYOE 8.103: Poster

Tuesday, March 27, 2007, 18:00–20:00, Poster B

Influence of the end cap chain length of Dn6T on OFET characteristics — •Benedikt Gburek, Torsten Balster, and Veit Wagner — International University Bremen*, P.O. Box 750 561, 28725 Bremen, Germany *Jacobs University Bremen as of spring 2007

Comparative in- and ex-situ studies have been performed on organic field-effect transistors (OFETs) with the oligomers dihexyl-sexithiophene (DH6T) and didecyl-sexithiophene (DD6T) as organic channel materials. These two end-substituted oligothiophenes with the same number of thiophene rings differ only by the length of their alkyl end-chains. While DH6T is one of the best-known materials in OFET research, the similar DD6T is a rather new and promising material due to the transition into a liquid crystal phase at 108 ^∘C. In this phase, DD6T is supposed to show larger crystals, thus offering better conduction properties.

The charge carrier mobility of DD6T shows a stronger increase with increasing temperature (49 % in 45 ^∘C) for room temperature grown films than DH6T. In addition, the slope of the DD6T mobility vs. temperature curves increases around 100 ^∘C, which corresponds to the transition into the liquid crystal phase. After cooling down of the sample, the mobility has the same value as before the thermal treatment, indicating a reversible phase transition. For room temperature deposited DD6T films, a lower charge carrier mobility (0.02 cm²/(Vs)) has been measured than for DH6T films (0.033 cm²/(Vs)). On the other hand, DD6T transistor characteristics exhibited higher stability upon exposure to air than those of DH6T.