Direct probe of the nuclear modes limiting charge mobility in molecular semiconductors

Thomas F. Harrelson; Varuni Dantanarayana; Xiaoyu Xie; Correy Koshnick; Dingqi Nai; Ryan Fair; Sean A. Nuñez; Alan K. Thomas; Tucker L. Murrey; Michael A. Hickner; John K. Grey; John E. Anthony; Enrique D. Gomez; Alessandro Troisi; Roland Faller; Adam J. Moulé

doi:10.1039/C8MH01069B

Direct probe of the nuclear modes limiting charge mobility in molecular semiconductors†

Thomas F. Harrelson,

^a Varuni Dantanarayana,^b Xiaoyu Xie,^c Correy Koshnick,^d Dingqi Nai,

^a Ryan Fair,^e Sean A. Nuñez,^f Alan K. Thomas,^g Tucker L. Murrey,

^d Michael A. Hickner,^f John K. Grey,

^g John E. Anthony,

^h Enrique D. Gomez,

^e Alessandro Troisi,

^c Roland Faller

^a and Adam J. Moulé

*^ab

Author affiliations

* Corresponding authors

^a Department of Chemical Engineering, University of California, Davis, CA, USA
E-mail: amoule@ucdavis.edu

^b Department of Chemistry, University of California, Davis, CA, USA

^c Department of Chemistry, University of Liverpool, Liverpool, UK

^d Department of Materials Science and Engineering, University of California, Davis, CA, USA

^e Department of Chemical Engineering, Pennsylvania State University, University Park, PA, USA

^f Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA, USA

^g Department of Chemistry & Chemical Biology, University of New Mexico, Albuquerque, NM, USA

^h Department of Chemistry, University of Kentucky, Lexington, KY, USA

Abstract

Recent theories suggest that low frequency dynamic intramolecular and intermolecular motions in organic semiconductors (OSCs) are critical to determining the hole mobility. So far, however, it has not been possible to probe these motions directly experimentally and therefore no unequivocal and quantitative link exists between molecular-scale thermal disorder and macroscale hole mobility in OSCs. Here we use inelastic neutron scattering to probe thermal disorder directly by measuring the phonon spectrum in six different small molecule OSCs, which we accurately reproduce with first principles simulations. We use the simulated phonons to generate a set of electron–phonon coupling parameters. Using these parameters, the theoretical mobility is in excellent agreement with macroscopic measurements. Comparison of mobility between different materials reveals routes to improve mobility by engineering phonon and electron–phonon coupling.

Materials Horizons

Direct probe of the nuclear modes limiting charge mobility in molecular semiconductors†

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Direct probe of the nuclear modes limiting charge mobility in molecular semiconductors

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