Regensburg 2007 – wissenschaftliches Programm

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

SYOE 8: Poster Session SYOE

SYOE 8.31: Poster

Dienstag, 27. März 2007, 18:00–20:00, Poster B

Morphology and OFET properties of poly(3,3”’-didodecyl-[2,2’:5’,2”:5”,2”’]-quaterthiophene) (PQT-12) with different molecular weights — •Patrick Pingel¹, Achmad Zen¹, Burkhard Stiller¹, Dieter Neher¹, Sybille Allard², and Ullrich Scherf² — ¹Institute of Physics, University of Potsdam, Am Neuen Palais 10, 14469 Potsdam — ²Macromolecular Chemistry, University of Wuppertal, Gauß-Str. 20, 42097 Wuppertal

It is well-known that molecular packing in thin-film organic field-effect transistors plays a crucial role in determining their field-effect mobilities. Here, we used PQT-12, which tend to adopt a better planar conformation compared to well-known poly(3-hexylthiophene) (P3HT). Since it is well established for P3HT that the average chain length largely determines the OFET-properties, we investigated different molecular weight fractions of PQT-12 (M_w = 1,700 to 12,000 g/mol) regarding to morphology and transport. In contrast to findings on P3HT, the OFET mobilities were above 10⁻³ cm²/Vs also for the lowest molecular weight fraction and the smallest mobility (10⁻⁵ cm²/Vs) was found in the intermediate-M_w. Studies of the optical, thermal and structural properties of PQT-12 solid samples suggest that the fraction with the shortest chains forms highly-crystalline layers. We attribute this behaviour to the very narrow molecular weight distribution of this low molecular weight fraction. Apparently, the OFET properties of both PQT-12 and P3HT are similar in that the OFET mobility depends largely on the overall crystallinity of the semiconducting layer.