Knowledge of the full phonon spectrum is essential to accurately calculate the dynamic disorder (σ) and hole mobility (μh) in organic semiconductors (OSCs). However, most vibrational spectroscopy techniques under-measure the phonons, thus limiting the phonon validation. Here, we measure and model the full phonon spectrum using multiple spectroscopic techniques and predict μhusing σ from only the Γ-point and the full Brillouin zone (FBZ). We find that only inelastic neutron scattering (INS) provides validation of all phonon modes, and that σ in a set of small molecule semiconductors can be miscalculated by up to 28% when comparing Γ-point against FBZ calculations. A subsequent mode analysis shows that many modes contribute to σ and that no single mode dominates. Our results demonstrate the importance of a thoroughly validated phonon calculation, and a need to develop design rules considering the full spectrum of phonon modes.
|Number of pages
|Journal of Physical Chemistry Letters
|Published - Jun 23 2022
Bibliographical noteFunding Information:
This research was supported by the Department of Energy, Basic Energy Sciences, Award DE-SC0010419, including salary for D.V., M.D., L.S.R.C., and A.J.M. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The INS spectrum was measured at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory, partly supported by LLNL under Contract DE-AC52-07NA27344. J.E.A. was supported by the National Science Foundation, under cooperative agreement No. 1849213. T.N. and A.T. acknowledge the financial support from ERC (PoC grant No. 403098).
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ASJC Scopus subject areas
- Materials Science (all)
- Physical and Theoretical Chemistry