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18 October 2004 Increase the field-effect mobility of regioregular poly(3-hexylthiophene) by introducing fixed acceptor molecules
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It is well known of regioregular poly(3-hexylthiophene) (P3HT) to self-assemble on hydrophobic surfaces, because the regular arrangement of its side chains allows an efficient π-stacking of the conjugated backbones. This should be the reason for the very high reported field effect mobilities (0.2 cm2/Vs)1. We present an alternative approach to increase the field effect mobility and the transistor stability by introducing a strong acceptor dopant in the main chain of P3HT while preserving the regioregularity of the 3-hexylthiophene segments in the polymer chain. P3HTs with different contents of acceptor molecules which are fixed linked in the main chain of the polymer, were synthesized using the McCullough Grignard metathesis method. As acceptor unit has been integrated 9-dicyanomethane-fluorene. The introduced dopant amount has been varied in order to obtain an optimum between the processability of the polymers and the resultant transistor performance. The utilized organic field effect transistor (OFET) substrates with SiO2 gate dielectric were always pre-treated with a silylating agent (HMDS) to facilitate the self-organization properties of the polymers by hydrophobization of the SiO2 surface. The optimized doped structures showed higher field effect mobility by one order of magnitude compared to the conventional P3HT, (μFE~9 x 10-3 cm2/V.s for the doped compound vs. μFE~5 x 10-4 cm2/V.s for P3HT), combined with a marked current modulation with ON/OFF ratio of ~ 7 x 103 and a better operational stability of the resultant OFET-devices.
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Silvia Janietz, Dessislava Sainova, and Armin Wedel "Increase the field-effect mobility of regioregular poly(3-hexylthiophene) by introducing fixed acceptor molecules", Proc. SPIE 5522, Organic Field-Effect Transistors III, (18 October 2004);

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