Multidimensional spectroscopy on the microscale: Development of a multimodal imaging system incorporating 2D white-light spectroscopy, broadband transient absorption, and atomic force microscopy.

The dynamics of electronic transitions in solid-state materials are closely linked to microscopic morphology, but it is often challenging to simultaneously characterize their broadband spectral and temporal response with high spatial resolution. We present a combined coherent multidimensional spectroscopy and microscopy system using visible white-light supercontinuum pulses as a broadband light source. This system correlates ~nm scale sample morphology determined from atomic force topography measurements with broadband transient absorption hyperspectral images and ultrafast multidimensional spectra, all with a spatial resolution of ≤1 μm. We demonstrate the application of this technique to the mapping of spatial heterogeneity in the process of singlet fission within single microcrystals of an organic semiconductor material, TIPS-Pentacene. Here, we identify heterogeneity in the temporal and spectral response corresponding to presence of non-equilibrium molecular packing near edges and morphological defect structures.