Mode-Specific Vibrational Analysis of Exciton Delocalization and Structural Dynamics in Conjugated Oligomers

Woojae Kim, Shinya Tahara, Hikaru Kuramochi, Satoshi Takeuchi, Taeyeon Kim, Tahei Tahara, Dongho Kim

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


Exciton delocalization in organic semiconducting polymers, affected by structures at a molecular level, plays a crucial role in modulating relaxation pathways, such as charge generation and singlet fission, which can boost device efficiency. However, the structural diversity of polymers and broad signals from typical electronic spectroscopy have their limits when it comes to revealing the interplay between local structures and exciton delocalization. To tackle these problems, we apply femtosecond stimulated Raman spectroscopy in archetypical conjugated oligothiophenes with different chain lengths. We observed Raman frequency dispersions of symmetric bond stretching modes and mode-specific kinetics in the S1 Raman spectra, which underpins the subtle and complex interplay between exciton delocalization and bond length alternation along the conjugation coordinate. Our results provide a more general picture of exciton delocalization in the context of molecular structures for conjugated materials.

Original languageEnglish
Pages (from-to)16999-17008
Number of pages10
JournalAngewandte Chemie - International Edition
Issue number31
Publication statusPublished - 2021 Jul 26


  • bond length alternation
  • exciton delocalization
  • femtosecond stimulated Raman
  • torsional relaxation


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