Dresden 2017 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 55: Focus: Static and Dynamic Disorder Phenomena on the Transport in Organic Semiconductors I

CPP 55.8: Talk

Thursday, March 23, 2017, 12:45–13:00, ZEU 222

Impact of Polaron Delocalization on Electrical Transport in Conjugated Polymers — Robert Steyrleuthner, Felix Kraffert, and •Jan Behrends — Berlin Joint EPR Lab, Fachbereich Physik, Freie Universität Berlin, Germany

The degree of charge delocalization strongly influences the transport properties of organic semiconductors. However, accurately determining the spatial extension of polaron wave functions remains a challenge. Using electron nuclear double resonance (ENDOR) spectroscopy for measuring the hyperfine coupling between photogenerated polarons and bound nuclear spins, we investigate the delocalization of holes in the semicrystalline conjugated polymer PBTTT (Poly[2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene]). An extrapolation of the corresponding oligomer spectra reveals that charges tend to delocalize over 4.0 to 4.8 nm with delocalization strongly dependent on molecular order and crystallinity of the PBTTT polymer thin films.[1]

We further use ENDOR spectroscopy to measure the charge delocalization for a number of conjugated polymers with applications in optoelectronic devices. The results are compared to charge carrier mobilities obtained from time-of-flight measurements, and a correlation between polaron extension and carrier mobility will be discussed.

[1] R. Steyrleuthner, Y. Zhang, L. Zhang, F. Kraffert, B.P. Cherniawski, R. Bittl, A.L. Briseno, J.-L. Bredas and J. Behrends, Phys. Chem. Chem. Phys., 2016, DOI: 10.1039/c6cp07485e