In singlet fission (SF), one high energy singlet (S) exciton is converted to two lower energy triplet (T) excitons which, if separated quantitatively, can lead to a doubling of the photocurrent in a solar cell. The need for efficient solar energy harvesting has boosted the general interest in SF including the impact of intermolecular geometry and coupling of the involved chromophore pair.^[1]

In this communication, we will present a bichromophore in which two TIPS-pentacene heads are linked to a crown ether backbone as shown in Figure A. The interchromophore conformation can be controlled by either the solvent-dependent intramolecular aggregation or by a structural change of the crown ether due to cation binding. Transient absorption from femtosecond to microsecond and from UV to NIR (Figure B) is paired with molecular dynamics simulation. This allows the interchromophore geometries to be linked with the rate of singlet fission as well as the fate of the generated triplet pair.

We will show that triplet pairs can be spectrally and kinetically differentiated according to their coupling and that the formation of free, separated triplet pairs depends on geometrical fluctuations of the system.

[1] Millicent B. Smith, Josef Michl, Chemical Reviews, 2010, 110 (11), 6891–6936.