Dresden 2011 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 8: Poster: Organic Semiconductors
CPP 8.41: Poster
Monday, March 14, 2011, 17:30–19:30, P2
Temperature and Molecular Weight Dependent Structures In Poly(3-hexyl thiophene) — •Jens Balko1, Peter Kohn1, Ruth Lohwasser2, Michael Sommer2, Mukundan Thelakkat2, and Thomas Thurn-Albrecht1 — 1Institute of Physics, Martin-Luther-University Halle-Wittenberg, 06120 Halle, Germany — 2Applied Functional Polymers, Macromolecular Chemistry I, University of Bayreuth, 95440 Bayreuth, Germany
Poly(3-hexyl thiophene) (P3HT) is a common polymer semiconductor, often used as material or component in organic field effect transistors or solar cells. Despite of the extensive amount of work done on this material there are a number of important open questions concerning the structure and morphology. We performed temperature dependent scattering experiments on bulk samples of P3HT in order to elucidate the phase transitions taking place. We used chemically well-defined samples, i.e. with a very narrow distribution of molecular weights and a high degree of regiorregularity.
The measurements showed that all samples with molecular weights ranging from 5 to 34 kDa (GPC) exhibit a liquid-crystalline phase prior to melting during heating. The phase transitions also appear during cooling from the isotropic melt. While for lower molecular weight crystallization leads to the formation of extended chain crystals, around a molecular weight of 20 kDa chain folded crystals form, with the number of folds depending on the cooling rate. Moreover the close analysis of WAXS patterns allows us to estimate the degree of crystallinity.