Public Abstract

DE-SC0023374: Identification of nuclear coordinates driving solar energy conversion processes using ultrafast Raman techniques

Award Status: Active

Institution: Regents of the University of Minnesota, Minneapolis, MN
UEI: KABJZBBJ4B54
DUNS: 555917996

Most Recent Award Date: 08/06/2024
Number of Support Periods: 3
PM: Roizen, Jennifer

Current Budget Period: 09/01/2024 - 08/31/2025
Current Project Period: 09/01/2022 - 08/31/2025
PI: Frontiera, Renee

Supplement Budget Period: N/A

Public Abstract

The overarching hypothesis for this research is that Raman spectroscopy can be used to guide the design of effective molecular-based solar energy conversion systems. Using molecules to transduce light into chemical or electrical energy involves fast processes which occur on highly multidimensional potential energy landscapes. By mapping out the relevant reaction coordinates and by distinguishing driving from spectator vibrational and vibronic modes, these investigations are intended to guide rational molecular design for improved performance. This fundamental research is based in the development and application of advanced Raman spectroscopic techniques to complex chemical systems with multiple nuclear coordinates contributing to the reaction trajectory. Specifically, these investigations aim to identify certain nuclear coordinates and vibrational coherences which can be rationally modified in order to improve function. This research will make use of the femtosecond stimulated Raman spectroscopy (FSRS) technique, which is capable of monitoring multidimensional structural changes in a range of chemical systems on an ultrafast timescale. Our group has made a number of technical advances to the femtosecond stimulated Raman spectroscopy technique, including incorporation of an optical microscope, development of spatially-offset femtosecond stimulated Raman spectroscopy, coherent control methods to identify driving from spectator modes, and development of methods to discriminate electronic from vibrational signatures. This research will make use of these technical advances to provide scientific insight into the optimal design of molecular systems for solar energy conversion and capture, including fundamental examination of ways to control electron transfer and transport. These investigations focus on photoinduced processes in systems that are challenging to model theoretically, as well as systems in which external parameters such as applied electric fields or coupling to cavity modes can be used as handles to change the potential energy surface and thus the reaction coordinate and trajectory. Based on understanding the role of specific nuclear coordinates in these systems, ultrafast mechanisms will be documented and design principles will be provided for improved performance. In Aim 1, we use coherent control techniques to identify which modes facilitate or hinder transport of photoinduced excited states and excitons. This research will be used to identify how molecular structure can be tuned in order to maximize extraction of solar generated charges in realistic environments. In Aim 2, investigations focus on how molecular states couple to cavity modes, mapping out the complex multidimensional potential energy landscapes of excitonic polaritonic system. This research will be used to identify coordinates which dictate how coupled molecules and cavities can be optimized for increased light-driven reactivity. In Aim 3, studies examine mechanisms of light-driven charge transfer and transport under applied bias, uncovering how specific nuclear coordinates couple to external electric fields. This research will be used to optimize photoelectrochemistry methods for molecular-based solar energy conversion by determining out how molecules react under bias. Taken together, this project will track vibrational motions and coherences in driving select photoinduced processes, enabling rational molecular design of efficient solar photovoltaic and photocatalytic systems.

The overarching hypothesis for this research is that Raman spectroscopy can be used to guide the design of effective molecular-based solar energy conversion systems. Using molecules to transduce light into chemical or electrical energy involves fast processes which occur on highly multidimensional potential energy landscapes. By mapping out the relevant reaction coordinates and by distinguishing driving from spectator vibrational and vibronic modes, these investigations are intended to guide rational molecular design for improved performance. This fundamental research is based in the development and application of advanced Raman spectroscopic techniques to complex chemical systems with multiple nuclear coordinates contributing to the reaction trajectory.

Specifically, these investigations aim to identify certain nuclear coordinates and vibrational coherences which can be rationally modified in order to improve function. This research will make use of the femtosecond stimulated Raman spectroscopy (FSRS) technique, which is capable of monitoring multidimensional structural changes in a range of chemical systems on an ultrafast timescale. Our group has made a number of technical advances to the femtosecond stimulated Raman spectroscopy technique, including incorporation of an optical microscope, development of spatially-offset femtosecond stimulated Raman spectroscopy, coherent control methods to identify driving from spectator modes, and development of methods to discriminate electronic from vibrational signatures. This research will make use of these technical advances to provide scientific insight into the optimal design of molecular systems for solar energy conversion and capture, including fundamental examination of ways to control electron transfer and transport.

These investigations focus on photoinduced processes in systems that are challenging to model theoretically, as well as systems in which external parameters such as applied electric fields or coupling to cavity modes can be used as handles to change the potential energy surface and thus the reaction coordinate and trajectory. Based on understanding the role of specific nuclear coordinates in these systems, ultrafast mechanisms will be documented and design principles will be provided for improved performance. In Aim 1, we use coherent control techniques to identify which modes facilitate or hinder transport of photoinduced excited states and excitons. This research will be used to identify how molecular structure can be tuned in order to maximize extraction of solar generated charges in realistic environments. In Aim 2, investigations focus on how molecular states couple to cavity modes, mapping out the complex multidimensional potential energy landscapes of excitonic polaritonic system. This research will be used to identify coordinates which dictate how coupled molecules and cavities can be optimized for increased light-driven reactivity. In Aim 3, studies examine mechanisms of light-driven charge transfer and transport under applied bias, uncovering how specific nuclear coordinates couple to external electric fields. This research will be used to optimize photoelectrochemistry methods for molecular-based solar energy conversion by determining out how molecules react under bias. Taken together, this project will track vibrational motions and coherences in driving select photoinduced processes, enabling rational molecular design of efficient solar photovoltaic and photocatalytic systems.