Near-Infrared Absorption Features of Triplet-Pair States Assigned by Photoinduced-Absorption-Detected Magnetic Resonance

Ryan Dill, Gajadhar Joshi, Karl Thorley, John Anthony, Brian Fluegel, Justin Johnson, Obadiah Reid

Research output: Contribution to journalArticlepeer-review

4 Scopus Citations

Abstract

Singlet fission proceeds through a manifold of triplet-pair states that are exceedingly difficult to distinguish spectroscopically. Here, we introduce a new implementation of photoinduced-absorption-detected magnetic resonance (PADMR) and use it to understand the excited-state absorption spectrum of a tri-2-pentylsilylethynyl pentadithiophene (TSPS-PDT) film. These experiments allow us to directly correlate magnetic transitions driven by RF with electronic transitions in the visible and near-infrared spectrum with high sensitivity. We find that the new near-infrared excited-state transitions that arise in thin films of TSPS-PDT are correlated with the magnetic transitions of T1, not 5TT. Thus, we assign these features to the excited-state absorption of 1TT, which is depleted when T1 states are driven to a spin configuration that forbids subsequent fusion. These results clarify the disputed origin of triplet-associated near-infrared absorption features in singlet-fission materials and demonstrate an incisive general purpose tool for studying the evolution of high-spin excited states.
Original languageAmerican English
Pages (from-to)2387-2394
Number of pages8
JournalJournal of Physical Chemistry Letters
Volume14
Issue number9
DOIs
StatePublished - 2023

NREL Publication Number

  • NREL/JA-5900-84563

Keywords

  • magnetic resonance
  • ODMR
  • photoinduced absorption
  • singlet fission
  • triplet pair

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