Impact of morphology on polaron delocalization in a semicrystalline conjugated polymer

Robert Steyrleuthner, Yuexing Zhang, Lei Zhang, Felix Kraffert, Benjamin P. Cherniawski, Robert Bittl, Alejandro L. Briseno, Jean-Luc Bredas, Jan Behrends

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

We investigate the delocalization of holes in the semicrystalline conjugated polymer poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene) (PBTTT) by directly measuring the hyperfine coupling between photogenerated polarons and bound nuclear spins using electron nuclear double resonance spectroscopy. An extrapolation of the corresponding oligomer spectra reveals that charges tend to delocalize over 4.0-4.8 nm with delocalization strongly dependent on molecular order and crystallinity of the PBTTT polymer thin films. Density functional theory calculations of hyperfine couplings confirm that long-range corrected functionals appropriately describe the change in coupling strength with increasing oligomer size and agree well with the experimentally measured polymer limit. Our discussion presents general guidelines illustrating the various pitfalls and opportunities when deducing polaron localization lengths from hyperfine coupling spectra of conjugated polymers.
Original languageEnglish (US)
Pages (from-to)3627-3639
Number of pages13
JournalPhys. Chem. Chem. Phys.
Volume19
Issue number5
DOIs
StatePublished - 2017

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