Parallel triplet formation pathways in a singlet fission material

Nilabja Maity, Woojae Kim, Naitik A. Panjwani, Arup Kundu, Kanad Majumder, Pranav Kasetty, Divji Mishra, Robert Bittl, Jayashree Nagesh, Jyotishman Dasgupta, Andrew J. Musser, Satish Patil

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1 Citation (Scopus)

Abstract

Harvesting long-lived free triplets in high yields by utilizing organic singlet fission materials can be the cornerstone for increasing photovoltaic efficiencies potentially. However, except for polyacenes, which are the most studied systems in the singlet fission field, spin-entangled correlated triplet pairs and free triplets born through singlet fission are relatively poorly characterized. By utilizing transient absorption and photoluminescence spectroscopy in supramolecular aggregate thin films consisting of Hamilton-receptor-substituted diketopyrrolopyrrole derivatives, we show that photoexcitation gives rise to the formation of spin-0 correlated triplet pair 1(TT) from the lower Frenkel exciton state. The existence of 1(TT) is proved through faint Herzberg-Teller emission that is enabled by vibronic coupling and correlated with an artifact-free triplet-state photoinduced absorption in the near-infrared. Surprisingly, transient electron paramagnetic resonance reveals that long-lived triplets are produced through classical intersystem crossing instead of 1(TT) dissociation, with the two pathways in competition. Moreover, comparison of the triplet-formation dynamics in J-like and H-like thin films with the same energetics reveals that spin-orbit coupling mediated intersystem crossing persists in both. However, 1(TT) only forms in the J-like film, pinpointing the huge impact of intermolecular coupling geometry on singlet fission dynamics.

Original languageEnglish
Article number5244
JournalNature communications
Volume13
Issue number1
DOIs
Publication statusPublished - 2022 Dec

Bibliographical note

Funding Information:
N.M. acknowledges CSIR and IISc Bangalore for a Senior Research Fellowship. S.P. thanks support from the EPSRC project Strategic University Network to Revolutionize Indian Solar Energy-SUNRISE (EP/ P032591/1) and the Department of Science and Technology, New Delhi, for a Swarnajayanti Fellowship and SERB, IRHPA grant. J.N. thanks DST-SERB India for funding under the Ramanujan Fellowship scheme (RJN-187/2017) and the SciNet HPC Consortium, Compute Canada for the computational resources. N.A.P and R.B. acknowledge funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany´s Excellence Strategy—EXC 2008—390540038—UniSysCat. A.K. and J.D. acknowledge support from the Department of Atomic Energy (DAE), Government of India, under Project no. 12-R&D-TFR-5.10-0100.

Publisher Copyright:
© 2022, The Author(s).

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • General
  • Physics and Astronomy(all)

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