Singlet fission (SF) is a spin-allowed process in which a singlet exciton, 1 (S 1 S 0 ), within an assembly of two or more chromophores spontaneously down-converts into two triplet excitons via a multiexciton correlated triplet pair state, 1 (T 1 T 1 ). To elucidate the involvement of charge transfer (CT) states and vibronic coupling in SF, we performed 2D electronic spectroscopy (2DES) on dilute solutions of a covalently linked, slip-stacked terrylene-3,4:11,12-bis(dicarboximide) (TDI) dimer. This dimer undergoes efficient SF in nonpolar 1,4-dioxane and symmetry-breaking charge separation in polar dichloromethane. The various 2DES spectral features in 1,4-dioxane show different pump wavelength dependencies, supporting the presence of mixed states with variable 1 (S 1 S 0 ), 1 (T 1 T 1 ) and CT contributions that evolve with time. Analysis of the 2DES spectra in dichloromethane reveals the presence of a state having largely 1 (T 1 T 1 ) character during charge separation. Therefore, the 1 (T 1 T 1 ) multiexciton state plays an important role in the photophysics of this TDI dimer irrespective of solvent polarity.
ASJC Scopus subject areas
- Colloid and Surface Chemistry