Ultrafast 2D White-Light (2DWL) and broadband transient absorption (TA) imaging are used to map the spatial variation in the electronic structure of individual TIPS-pentacene (TIPS-Pn) microcrystals. 2DWL cross-peaks resolve an electronic state located 70meV below the brightest singlet transition, placing it in resonance with the correlated paired triplet (T1T1) state. Based on imaging data and exciton calculations, we assign the spectral feature to a singlet state caused by defect molecules with near orthogonal orientation. This defect state is most prominent near crystal edges and deformations, but still can be found throughout the crystals at lower densities. Following singlet fission, similar TA kinetics are observed for both the defect and (T1T1) states. Accordingly, we find that the presence of these defects in the TIPS-Pn microcrystals alters the electronic structure providing locations for interconversion between entangled triplet and singlet states.

Spatial imaging of the molecular structures and energetics associated with singlet fission within single microcrystals using 2D white light and transient absorption microscopy

256th National Meeting (2018)

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