Optical readout of singlet fission biexcitons in a heteroacene with photoluminescence detected magnetic resonance

Gajadhar Joshi, Ryan D. Dill, Karl J. Thorley, John E. Anthony, Obadiah G. Reid, Justin C. Johnson

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Molecular spin systems based on photoexcited triplet pairs formed via singlet fission (SF) are attractive as carriers of quantum information because of their potentially pure and controllable spin polarization, but developing systems that offer optical routes to readout as well as initialization is challenging. Herein, we characterize the electron spin magnetic resonance change in the photoluminescence intensity for a tailored organic molecular crystal while sweeping a microwave drive up to 10 GHz in a broadband loop structure. We observe resonant transitions for both triplet and quintet spin sublevel populations showing their optical sensitivity and revealing the zero-field parameters for each. We map the evolution of these spectra in both microwave frequency and magnetic field, producing a pattern of optically detected magnetic resonance (ODMR) peaks. Fits to these data using a suitable model suggest significant spin polarization in this system with orientation selectivity. Unusual excitation intensity dependence is also observed, which inverts the sign of the ODMR signal for the triplet features, but not for the quintet. These observations demonstrate optical detection of the spin sublevel population dictated by SF and intermolecular geometry, and highlight anisotropic and multi-scale dynamics of triplet pairs.

Original languageEnglish
Article number164702
JournalJournal of Chemical Physics
Issue number16
StatePublished - Oct 28 2022

Bibliographical note

Publisher Copyright:
© 2022 Author(s).

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


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