Advances position femtosecond stimulated Raman spectroscopy for new solid-state research

Femtosecond stimulated Raman spectroscopy (FSRS) is a chemically-specific vibrational technique that provides the ability to study structural dynamics during photoinduced processes on the ultrafast time scale. Despite its widespread use in structural dynamics and chemical mechanisms, its utilization with solid-state materials has been limited.

A new review by Cassabaum et al. highlights the potential and future challenges of FSRS in the realm of studying solid-state materials. The broad-reaching paper touches on electron-phonon coupling in crystals, long-range charge transport, mode-selective excitation and implications for nanoscale work.

Such advances push the field closer to more reliably studying the dynamics of photovoltaic and electronic devices, which largely rely on solid-state materials. A better understanding of these dynamics in solid-state electronics and photovoltaics will help researchers identify specific chemical structures responsible for various photoinduced charge transfer reactions.

“Our group and others have recently been using these ultrafast vibrational spectroscopies to examine dynamics in these materials on microscopic length scales,” said author Renee Frontiera. “We thought the field had advanced sufficiently such that a perspective article on the topic would be useful to a large number of researchers.”

Variants of FSRS spatially resolve portioning and energy loss as lasers interact with grain boundaries, defect sites and interfaces, allowing for label-free imaging below optical diffraction limits. Advances in mode-selective vibrational excitation have allowed researchers to “turn on and off” specific reaction pathways with certain nuclear motions.

Frontiera looks to continue her work in spatially-offset femtosecond stimulated Raman spectroscopy, a method for tracking exciton and charge transport across nanometer and micron length scales in photovoltaics. Additionally, she and her group are developing a label-free approach for biomedical imaging.

Source: “Femtosecond stimulated Raman spectro-microscopy for probing chemical reaction dynamics in solid-state materials,” by Alyssa A. Cassabaum, Kajari Bera, Christopher C. Rich, Bailey R. Nebgen, Siu Yi Kwang, Margaret L. Clapham, and Renee R. Frontiera, Journal of Chemical Physics (2020). The article can be accessed at https://doi.org/10.1063/5.0009976 .