Abstract
Covalent chromophore dimers having the required energetics can undergo intramolecular singlet fission (SF) in solution; however, in the solid state, intra- and intermolecular SF can compete. Here, the structure and excited-state dynamics of a linear terrylene-3,4:11,12-bis(dicarboximide) (TDI) dimer, TDI-Ph-TDI, in which the two TDI molecules are linked via one of their imide nitrogen atoms to a 2,5-di-t-butylphenyl spacer at its 1,4-positions are studied in solution and in thin films to understand the interplay between these two SF mechanisms. TDI-Ph-TDI undergoes slow intramolecular SF in toluene due to weak through-bond interactions and a lack of through-space electronic coupling. The TDI-Ph-TDI dimers in the films are π-stacked, allowing for through-space interactions between neighboring TDI moieties. As a result, TDI-Ph-TDI undergoes intermolecular SF two orders of magnitude faster than intramolecular SF. Using film-processing techniques, the SF dynamics can be modified. The (T1T1) states in the unannealed and thermally annealed films dissociate to form free triplet excitons, whereas a long-lived (T1T1) state with mixed charge-transfer character is observed in a chlorobenzene solvent vapor annealed film. Although intramolecular SF in TDI-Ph-TDI cannot compete with intermolecular SF, the structure of TDI-Ph-TDI has a strong influence on the possible film morphologies and the role of the charge-transfer state in SF.
Original language | English (US) |
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Pages (from-to) | 6999-7009 |
Number of pages | 11 |
Journal | Journal of Physical Chemistry C |
Volume | 125 |
Issue number | 13 |
DOIs | |
State | Published - Apr 8 2021 |
Funding
This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award DE-FG02-99ER14999 (M.R.W.). The authors thank Paige Brown for assistance in collecting optical data and Dr. Stephen A. Miller and the Northwestern University Laser and Electronics Design Core Facility for assistance on instrumentation. This work made use of the IMSERC at Northwestern University, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), the State of Illinois, and the International Institute for Nanotechnology (IIN).
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- General Energy
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films