Femtosecond stimulated Raman spectroscopy (FSRS) is a spectroscopic technique which probes changes in molecular structure on the ultrafast timescale of chemical reactions. We have integrated microscopy abilities into a standard FSRS system, which enable us to determine how heterogeneous regions of crystalline environments impact chemical processes, as well as to track the propagation of excited states through materials. The vibrational information afforded by Raman spectroscopic probing enables a clear determination of how structure impacts function. Here we detail two specific advances provided by FSRS spectro-microscopy. First, we use structural insights provided by FSRS probing of rubrene crystals to design derivatives which show increased rates and yields of singlet fission, a process which can increase the efficiency of organic photovoltaic devices. Secondly, we debut spatially offset FSRS, which can track structural contributions such as coherent phonon motion to exciton transport. Overall, these studies point to the utility of nonlinear vibrational probing in understanding how local environments can impact dynamics relevant to solar energy conversion.<b> </b>

Femtosecond stimulated Raman spectroscopy probes of singlet fission dynamics and exciton transfer

ACS Fall 2021

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