Resolving the backbone tilt of crystalline poly(3-hexylthiophene) with resonant tender X-ray diffraction

Guillaume Freychet; Paul Chantler; Yuxuan Huang; Wen Liang Tan; Mikhail Zhernenkov; Nagaraj Nayak; Anil Kumar; Peter A Gilhooly-Finn; Christian B Nielsen; Lars Thomsen; Subhayan Roychoudhury; Henning Sirringhaus; David Prendergast; Christopher R McNeill

doi:10.1039/d2mh00244b

Resolving the backbone tilt of crystalline poly(3-hexylthiophene) with resonant tender X-ray diffraction

Mater Horiz. 2022 Jun 6;9(6):1649-1657. doi: 10.1039/d2mh00244b.

Authors

Affiliations

¹ NSLS-II, Brookhaven National Laboratory, Upton, NY 11973, USA.
² Department of Materials Science and Engineering, Monash University, Wellington Road, Clayton, Victoria, 3800, Australia. christopher.mcneill@monash.edu.
³ Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK.
⁴ Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
⁵ Department of Chemistry, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.
⁶ Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK.
⁷ Australian Synchrotron, ANSTO, 800 Blackburn Road, Clayton, Victoria, 3168, Australia.
⁸ The Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.

PMID: 35421883
DOI: 10.1039/d2mh00244b

Abstract

The way in which conjugated polymers pack in the solid state strongly affects the performance of polymer-based optoelectronic devices. However, even for the most crystalline conjugated polymers the precise packing of chains within the unit cell is not well established. Here we show that by performing resonant X-ray diffraction experiments at the sulfur K-edge we are able to resolve the tilting of the planar backbones of crystalline poly(3-hexylthiophene) (P3HT) within the unit cell. This approach exploits the anisotropic nature of the X-ray optical properties of conjugated polymers, enabling us to discern between different proposed crystal structures. By comparing our data with simulations based on different orientations, a tilting of the planar conjugated backbone with respect to the side chain stacking direction of 30 ± 5° is determined.