Singlet Fission via an Excimer-Like Intermediate in 3,6-Bis(thiophen-2-yl)diketopyrrolopyrrole Derivatives

Catherine M. Mauck, Patrick E. Hartnett, Eric A. Margulies, Lin Ma, Claire E. Miller, George C. Schatz, Tobin J. Marks, Michael R. Wasielewski

Research output: Contribution to journalArticle

79 Citations (Scopus)

Abstract

Singlet fission (SF) in polycrystalline thin films of four 3,6-bis(thiophen-2-yl)diketopyrrolopyrrole (TDPP) chromophores with methyl (Me), n-hexyl (C6), triethylene glycol (TEG), and 2-ethylhexyl (EH) substituents at the 2,5-positions is found to involve an intermediate excimer-like state. The four different substituents yield four distinct intermolecular packing geometries, resulting in variable intermolecular charge transfer (CT) interactions in the solid. SF from the excimer state of Me, C6, TEG, and EH takes place in SF = 22, 336, 195, and 1200 ps, respectively, to give triplet yields of 200%, 110%, 110%, and 70%, respectively. The transient spectra of the excimer-like state and its energetic proximity to the lowest excited singlet state in these derivatives suggests that this state may be the multiexciton 1(T1T1) state that precedes formation of the uncorrelated triplet excitons. The excimer decay rates correlate well with the SF efficiencies and the degree of intermolecular donor-acceptor interactions resulting from stacking of the thiophene donor of one molecule with the DPP core acceptor in another molecule as observed in the crystal structures. Such interactions are found to also increase with the SF coupling energies, as calculated for each derivative. These structural and spectroscopic studies afford a better understanding of the electronic interactions that enhance SF in chromophores having strong intra- and intermolecular CT character.

Original languageEnglish
Pages (from-to)11749-11761
Number of pages13
JournalJournal of the American Chemical Society
Volume138
Issue number36
DOIs
Publication statusPublished - Sep 14 2016

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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