Emitting Species of Poly(3-hexylthiophene): From Single, Isolated Chains to Bulk

Title data

Raithel, Dominic ; Baderschneider, Sebastian ; de Queiroz, Thiago B. ; Lohwasser, Ruth H. ; Köhler, Jürgen ; Thelakkat, Mukundan ; Kümmel, Stephan ; Hildner, Richard:
Emitting Species of Poly(3-hexylthiophene): From Single, Isolated Chains to Bulk.
In: Macromolecules. Vol. 49 (2016) Issue 24 . - pp. 9553-9560.
ISSN 1520-5835
DOI: https://doi.org/10.1021/acs.macromol.6b02077

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Abstract in another language

The photophysical properties of films of alkyl-substituted polythiophenes are governed by a subtle interplay between intra- and interchain electronic couplings. The intramolecular properties, however, are still not entirely clear because polythiophenes possess a strong tendency to form π-stacked aggregate structures with appreciable interchain couplings. Here we employ low-temperature single-molecule photoluminescence spectroscopy on isolated regioregular poly(3-hexyl- thiophene), P3HT, chains with different, but well-defined molecular weights to reveal the intrachain properties of their emitting sites. We find that the inhomogeneous distribution function of the zero-phonon lines (ZPL) is very narrow (\textless480 cm−1, 60 meV), which indicates a low degree of torsional disorder of the P3HT backbone on length scales of the emitting sites (despite a large mean dihedral angle). Moreover, the single- chain ZPLs are exclusively located in the high energy tail of the corresponding spectrum of a disordered ensemble. Using concentration-dependent measurements in combination with time- dependent density functional theory, we show that this spectral shift stems from aggregation-induced partial planarization and concomitant electronic coupling between segments of neighboring P3HT chains.