Researcher Melissa Gish Bridges Chemistry and Physics To Improve Solar Energy Technologies

Researcher Melissa Gish Bridges Chemistry and Physics To Improve Solar Energy Technologies

Melissa Gish approaches physics and chemistry problems like puzzles: Control this or that variable, and work out how the jigsaw pieces fit together.

"I didn't really like biology because I felt like there were too many variables to adequately control," said Gish, a chemistry researcher at the National Renewable Energy Laboratory (NREL).

The journal Trends in Chemistry recently honored Gish in a special issuedesigned to highlight emerging leaders in chemistry who are innovating in their respective fields, as well as to celebrate Trends in Chemistry's fifth anniversary and Cell Press' 50^th anniversary.

That inclination toward controlling variables to chart a path to discovery led her from high school biology experiments on the breeding behavior of mosquitoes to majoring in chemistry in college. In her senior year, Gish studied quantum mechanics and worked in a physical chemistry lab-and that work led her to pursue a Ph.D. in experimental physical chemistry.

"The intersection of physics and chemistry just made sense to me in a way that other disciplines hadn't," she said. "It just clicked."

At the University of North Carolina at Chapel Hill (UNC), Gish immediately started working in ultrafast spectroscopy, where pulsed lasers are used to study ultrafast events after a system absorbs light-within solar energy research-and her renewable energy research interests then led her to NREL, first as a postdoctoral researcher and now as a chemistry researcher.

"NREL has world-class fundamental research and amazing physical chemists," she said, "so I could continue working with ultrafast spectroscopy and solar energy research."

Leading on Transient Spectroscopy

Gish began her work in transient spectroscopy-studying the properties of short-lived excited states of molecules and materials-at UNC and continues that work at NREL.

"We were studying dye-sensitized photoelectrosynthesis cells, which involved the absorption of light to kick off an electron transfer cascade that would lead to catalysis to generate solar fuels," she said. "These systems often had two-to-three-plus components, each with its own photophysics that needed to be parsed out with careful control experiments. These problems are puzzles-each puzzle is unique and fun to solve, with the added bonus of working toward new renewable energy technologies."

At NREL, Gish has become a leader in using transient spectroscopy to study pathways to more efficient solar cells and solar energy production and uncovering the photophysics of complicated molecular and materials systems, often connecting that information to photochemical reactions. Her work spans much of the periodic table, from organic molecules and polymers to transition and rare earth metal-organic complexes to silicon nanoparticles to semiconductor materials and more. Gish's recent investigations extend across the U.S. Department of Energy's (DOE's) Office of Science Basic Energy Sciences research portfolio at NREL and have targeted the short excited-state lifetimes of conjugated polymers, tuning of singlet fission at mesoporous interfaces, and development of a strategy to differentiate rare earth elements.

Gish is presently interested in connecting ultrafast photophysics on the very small scale-femtoseconds, picoseconds, and nanoseconds-to photochemical transformations on the seconds-to-hours time scale.

"Understanding the initial processes after light absorption that may affect the photochemistry or photocatalysis that happens many decades later can help us design better systems for solar energy harvesting or light-induced separations," Gish said. "I've been working on in situ methods to spectroscopically determine intermediates and products on longer time scales to connect the ultrafast experiments."

As she looks to the immediate future in her research, Gish is thinking about the photophysics of product selectivity in photocatalysis, in which solar energy is converted to chemical energy.

"To make usable, storable solar fuels, we need to be able to generate the product that we want-for example, methanol-and there's a lot we don't understand about how to drive solar fuel production and photocatalysis to the final product of our choosing," she said.

Gish's work extends to safety in the lab. She is a technical and safety leader for laser-based spectroscopy at NREL, stewarding several ultrafast laser systems and mentoring users of all experience levels in best safety practices for alignment, designing experiments, and operating systems to obtain high-quality data and rigorous data analysis. She has also played an integral part in NREL's Laser Safety Panel, helping improve the laser operator qualification process and defining the laser system supervisor's roles and responsibilities.

Supporting and Mentoring Others

Good leaders give back to their communities, and Gish gives back through mentorship and building community.

At NREL, Gish cofounded two employee resource groups for NREL staff: the Full Spectrum Network (LGBTQIA+ employees and allies) and the Postdoc and Graduate Student Network.

"My involvement in Full Spectrum and, in particular, my role in starting Pride Month events at NREL means a lot to me," Gish said. "What I'm most proud of is how the group has continued as I and the initial steering committee passed the torch to the current leadership. Running an employee resource group is a lot of work and requires a lot of dedication and passion, and it's amazing to see how each iteration of Full Spectrum continues our initial traditions and builds on them. For example, the annual Pride flag raising at the South Table Mountain Campus is something that started after my time and was extended to the Flatirons Campus this year."

Full Spectrum has helped bring together the LGBTQIA+ community at NREL and helped them feel seen and embraced.

"I think it's important for NREL to show LGBTQIA+ staff that our contributions are recognized and celebrated, which is a legacy I am proud of," Gish said. "I have had new employees reach out to me and say that our work in Full Spectrum and the visibility it has provided to LGBTQIA+ staff has influenced their decision to come work at NREL because of the safe space that has been created."

Gish is also proud of her work with the Postdoc and Graduate Student Network, where she mentors early-career researchers from undergraduate and graduate students to postdoctoral researchers.

"Postdocs and students are in a unique position where they are actively looking for their next job while producing high-quality scientific research and learning the advanced techniques we have here at NREL," she said. "We wanted the network to provide professional development opportunities, soft-skills workshops, and networking opportunities to alleviate some of that stress that these early-career folks feel. I have also had opportunities to mentor postdocs, grad students, and undergrads as a staff scientist.

"I really enjoy watching students and postdocs grow and become confident scientists," Gish continued. "As the NREL principal investigator of a Reaching a New Energy Sciences Workforce (RENEW) project in collaboration with Metropolitan State University of Denver, I've had the pleasure of mentoring undergraduate students with limited lab experience who are motivated and passionate about learning spectroscopy as well as what it is like to be a scientist and explore this career as an option."

Gish's RENEW project focuses on understanding spin dynamics of first row transition metal photosensitizers.

She is continuing her career trajectory by actively solving chemistry puzzles-developing spectroscopic capabilities to answer new questions about next-generation solar energy technologies-and building her portfolio as a principal investigator while mentoring and serving her community.

"Melissa has developed quickly into a key team member of several of our DOE Office of Science Basic Energy Sciences projects and was recently successful as an NREL principal investigator on a RENEW project focused on harnessing spin physics to drive photochemical reactions," said NREL's Andrew Ferguson, spectroscopy and photoscience group manager. "I have been particularly impressed by her resilience, exemplified by her response to the restrictions imposed by the COVID pandemic on her postdoctoral work; her vision to develop the spectroscopic tools to connect ultrafast photophysical processes to much slower photochemical reactivity; and her commitment to effective training and mentoring of early-career researchers. She is certainly worthy of recognition as an emerging leader in chemistry, and I am excited to see where her career goes from here."

Learn more about Melissa Gish's research and NREL's solar energy research.