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 language | American English |
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Pages (from-to) | 2387-2394 |
Number of pages | 8 |
Journal | Journal of Physical Chemistry Letters |
Volume | 14 |
Issue number | 9 |
DOIs | |
State | Published - 2023 |
NREL Publication Number
- NREL/JA-5900-84563
Keywords
- magnetic resonance
- ODMR
- photoinduced absorption
- singlet fission
- triplet pair