Spatially Offset Femtosecond Stimulated Raman Spectroscopy: Observing Exciton Transport through a Vibrational Lens

Siu Yi Kwang, Renee R. Frontiera

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

To design better molecular electronic devices, we need a strong understanding of how charges or excitons propagate, as many efficiency losses arise during transport. Exciton transport has been difficult to study because excitons tend to be short-lived, have short diffusion lengths, and can easily recombine. Here, we debut spatially offset femtosecond stimulated Raman spectroscopy (SO-FSRS), a three-pulse ultrafast microscopy technique. By offsetting the photoexcitation beam, we can monitor Raman spectral changes as a function of both time and position. We used SO-FSRS on 6,13-bis(triisopropylsilylethynyl) pentacene, a well-studied organic semiconductor used in photovoltaics and field-effect transistors. We demonstrated that the fast exciton and free charge carrier transport axes are identical and observed that exciton transport is less anisotropic by a factor of ∼3. SO-FSRS is the first technique that directly tracks molecular structural evolution during exciton transport, which can provide roadmaps for tailor-making molecules for specific electronic devices.

Original languageEnglish (US)
Pages (from-to)4337-4344
Number of pages8
JournalJournal of Physical Chemistry Letters
Volume11
Issue number11
DOIs
StatePublished - Jun 4 2020

Bibliographical note

Funding Information:
This research was supported through funding by the U.S. Department of Energy, DE-SC0018203. The authors thank Dr. Christopher Rich for helpful discussions when writing this paper.

Publisher Copyright:
Copyright © 2020 American Chemical Society.

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