Quintet-triplet mixing determines the fate of the multiexciton state produced by singlet fission in a terrylenediimide dimer at room temperature

Michelle Chen, Matthew D. Krzyaniak, Jordan N. Nelson, Youn Jue Bae, Samantha M. Harvey, Richard D. Schaller, Ryan M. Young, Michael R. Wasielewski

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)

Abstract

Singlet fission (SF) is a photophysical process in which one of two adjacent organic molecules absorbs a single photon, resulting in rapid formation of a correlated triplet pair (T1T1) state whose spin dynamics influence the successful generation of uncorrelated triplets (T1). Femtosecond transient visible and near-infrared absorption spectroscopy of a linear terrylene-3,4:11,12-bis(dicarboximide) dimer (TDI2), in which the two TDI molecules are directly linked at one of their imide positions, reveals ultrafast formation of the (T1T1) state. The spin dynamics of the (T1T1) state and the processes leading to uncoupled triplets (T1) were studied at room temperature for TDI2 aligned in 4-cyano-4′-pentylbiphenyl (5CB), a nematic liquid crystal. Time-resolved electron paramagnetic resonance spectroscopy shows that the (T1T1) state has mixed 5(T1T1) and 3(T1T1) character at room temperature. This mixing is magnetic field dependent, resulting in a maximum triplet yield at ∼200 mT. The accessibility of the 3(T1T1) state opens a pathway for triplet–triplet annihilation that produces a single uncorrelated T1 state. The presence of the 5(T1T1) state at room temperature and its relationship with the 1(T1T1) and 3(T1T1) states emphasize that understanding the relationship among different (T1T1) spin states is critical for ensuring high-yield T1 formation from singlet fission.

Original languageEnglish
Pages (from-to)8178-8183
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume116
Issue number17
DOIs
Publication statusPublished - 2019

Keywords

  • Electron paramagnetic resonance
  • Singlet fission
  • Spin state

ASJC Scopus subject areas

  • General

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