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Mode‐Specific Vibrational Analysis of Exciton Delocalization and Structural Dynamics in Conjugated Oligomers
Author(s) -
Kim Woojae,
Tahara Shinya,
Kuramochi Hikaru,
Takeuchi Satoshi,
Kim Taeyeon,
Tahara Tahei,
Kim Dongho
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202102168
Subject(s) - delocalized electron , exciton , raman spectroscopy , chemical physics , conjugated system , context (archaeology) , relaxation (psychology) , spectroscopy , materials science , femtosecond , molecular vibration , chemistry , polymer , molecular physics , photochemistry , physics , condensed matter physics , optics , organic chemistry , psychology , paleontology , social psychology , laser , quantum mechanics , biology
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 S 1 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.