How NREL Researcher Garry Rumbles Has Advanced Science Through Mentorship

Internationally Known for Photochemistry Breakthroughs, Rumbles Created a Culture of Innovation Within NREL

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Garry Rumbles is an internationally known scientist in solar photochemistry—and not just for his groundbreaking research on the fundamental underpinnings of organic solar cells, his oft-cited paper on excitons in nanosystems, or his tireless organizing of conferences and workshops advancing the foundational science behind solar energy conversion.

At the National Renewable Energy Laboratory (NREL), Rumbles is also well known for a different contribution: supporting the people in his field of research. In addition to publishing hundreds of papers in photochemistry, photophysics, and energy conversion during his 25 years at NREL, he nurtured the careers of many scientists, helping develop the next generation of researchers.

Rumbles counts his mentorship efforts as his biggest contribution to the laboratory.

Because Rumbles departed from the laboratory on Jan. 31 with an emeritus research fellow appointment, the NREL community can continue to benefit from his expertise and advice. His emeritus status is an appropriate cap on a career that included leadership of NREL’s Department of Energy (DOE) Office of Science Basic Energy Sciences core solar photochemistry program, promotion to NREL’s prestigious senior research fellow position, and election as a fellow of the American Association for the Advancement of Science and as fellow of the U.K.’s Royal Society of Chemistry.

“Garry has an incredible track record of innovative research, and his leadership of NREL’s Solar Photochemistry Program for 15 years has been paramount to our success and impact, as well as forging new science frontiers,” said Bill Tumas, associate laboratory director for Materials, Chemical, and Computational Science at NREL. “Garry has been an outstanding mentor to many, from graduate students to staff. His contributions to the NREL Director’s Postdoctoral Fellowship are also particularly noteworthy. I am grateful for Garry working so well with us on transition of leadership of the core solar photochemistry program.”

When Rumbles decided to retire, he announced it well in advance and then launched a new, transparent process for finding his replacement.

“It wasn’t about who has the most journal citations but rather who is the best leader of a group of highly performing researchers who all have their own ideas,” said Jao van de Lagemaat, the center director for chemistry and nanoscience at NREL. “The person in this role has to synthesize a research program that’s consistent with NREL’s mission, what DOE needs, and what is at the forefront of the science in this area.”

Van de Lagemaat said the proof in Rumbles’ collaborative methods showed up in the three-year review with DOE’s Office of Science Basic Energy Sciences Solar Photochemistry Program last year. “The feedback from DOE was that they really appreciated the way we handled the leadership handoff,” he said. “I really do attribute this to Garry and how he structured the program and how he handed off leadership.”

Rumbles created a culture that led to better science, said Jeff Blackburn, who has taken Rumbles’ place as the lead principal investigator for NREL’s Solar Photochemistry Program.

“One of the biggest takeaways I’ve learned from Garry is that the people come first,” Blackburn said. “If you take care of the people and make sure the people doing the science feel engaged and supported, that leads to everyone doing their best work.”

Breaking Ground in Organic Light-Emitting Diodes

Rumbles grew up in the countryside east of London, where his family worked on a farm not far from the North Sea. Few kids went on to college in his community, but he had a teacher early on who encouraged him to think scientifically, and he discovered that this was a field in which he could excel—even when there was more work to do on the farm.

“I took my exams to go to university in June, and I was driving the combine in July,” he said with a laugh.

After earning a bachelor’s degree in chemistry with electronics at the University of Southampton, Rumbles entered a Ph.D. program at the University of London, where he worked in the lab of Professor Sir George Porter, a renowned photochemist who won the Nobel Prize in chemistry in 1967 for his work on fast chemical reactions.

Rumbles completed his doctorate in 1984 and then took several postdoctoral positions, including two in California, where he met his wife, Lee, while windsurfing. He then settled into a position as a professor at Imperial College London, where his research broke new ground in describing the photophysics of polymer organic light-emitting diodes, showing for the first time that the devices could form excitons and emit light. Rumbles earned himself a name for some research firsts there as well, completing the first time-resolved fluorescence experiments with excitation using evanescent waves and marking the first observation of optical refrigeration in a fluid solution using molecular dyes.

But in the late ‘90s, he wanted a new challenge—and Lee wanted to be back in the United States. In 1999, he took a sabbatical from Imperial College to work in NREL’s photochemistry group, which was led by Arthur Nozik at the time.

“Garry was a very good scientist and an accomplished one,” said Nozik, now a senior research fellow emeritus at NREL. “In England, he had published some unique work just as he was applying here, which was using light to produce cooling in a system. Usually when you shine light on something it heats it up, but he found a way for it to cool, and this was an interesting effect.”

In 2001, Nozik hired him.

“Scariest time of my life,” Rumbles said of his move to NREL and the United States. “I was for all intents and purposes a tenured researcher at Imperial College. But it was one of the best things I ever did. I did new stuff, I became a different person, I did my research differently. Everything worked out better because I was thrown into that pit of uncertainty.”

The Mentor Creates the Next Mentor

Rumbles was an established scientist when he arrived at NREL, but when he looks back now, he realizes he still had some things to learn. He credits Nozik for prompting his own drive to mentor young researchers.

“Art Nozik became the mentor who reminded me that I needed mentoring,” Rumbles said. “I used to have an attitude toward it—I’d worked my way using my own ideas for so long that I thought it was the right way, and he taught me that my ideas could be better.”

Now, many of the scientists in the Solar Photochemistry Group have stories about the ways Rumbles helped them create their own paths to success—all as he was growing the group’s annual funding from $2 million to $4 million. Rumbles said he likes to tell researchers they should think about their careers as a long-term project. But Elisa Miller, a distinguished researcher at NREL and associate director of the Office of Science Basic Energy Sciences’ Center for Soft PhotoElectroChemical Systems (SPECS), noted that he also kept a long view of people’s careers himself.

“It’s like he has a roadmap of all of the people and where they’re going,” said Miller, who first met Rumbles when she was a graduate student at the University of Colorado Boulder. She was interested in coming to NREL for the Director’s Postdoctoral Fellowship, a prestigious program that Rumbles created and led for 10 years. The program pairs outstanding postdocs with NREL researchers, and Rumbles counts it among his proudest achievements. “He leverages people’s skills. It’s, ‘You communicate what’s best for you, and I’m going to help you get there.’”

Rumbles also championed the Renewable and Sustainable Energy Institute (RASEI), which created the opportunity for students like Miller to meet and work with NREL researchers. RASEI was formed in 2009, and it continues to enable joint appointments at NREL and the University of Colorado Boulder. Rumbles was a RASEI fellow from the program’s inception and has served as its associate director.

Staying the Course With Fundamental Science

Following its founding by Nozik and its growth under Rumbles, the Solar Photochemistry Program is now NREL’s longest-standing Office of Science Basic Energy Sciences core program. During his time with the program, Rumbles’ published output was immense, but he is especially proud of two achievements: his push to use a variant of microwave spectroscopy in his research, which led to NREL developing a unique, world-class suite of capabilities in spectroscopy, and his dogged pursuit of basic science research in photochemical processes in organic solar cells.

“There’d been a widely accepted point of view on how organic solar cells work, and he looked at that explanation and just was not satisfied,” said Obadiah Reid, an NREL researcher in solar photochemistry who has worked closely with Rumbles on organic photovoltaics. In addition to his position at NREL, he’s now an associate professor at RASEI and joint appointee of both institutions. “So much of the work we’ve been doing over the last 10 years is testing alternative hypotheses that would explain the phenomenon.”

Their early alternative hypotheses explored whether the Marcus formulation, a framework for describing photo-induced electron transfer in solution-phase molecular systems, could be applied to a different system: solid-state organic photovoltaics.

“He put forward this really nice conceptual framework for how the Marcus formulation can describe organic photovoltaics,” Blackburn said. “Both of those—microwave spectroscopy and the fundamentals of photoinduced charge transfer—are going to be hallmarks of the program long after Garry retires.”

Looking back, Rumbles is glad he did not drop important research to pursue trends, and he appreciates that the Office of Science shared his vision.

“The Office of Science wasn’t worried about current trends—they were worried about fundamental science,” Rumbles said, noting that organic photovoltaics research was out of fashion for about 10 years. “They anticipated it was going to become important again, and they didn’t want to lose their knowledge base.”

Sailing Toward New Horizons

Upon his departure, his NREL colleagues wished him well but acknowledged the loss of a mentor.

“I think one of the things that all of us are going to miss about Garry is the continuous stream of positive reinforcement,” Reid said. “Science is full of criticism, just in its structure. You’ve got reviews for papers, proposals, and we all give talks, and people are all about constructive criticism. It can lead to a negative-feeling environment, but one of the things Garry was really good at was always being positive and giving people positive reinforcement. He created a culture—a positive, collaborative one.”

If anyone needs his advice as an emeritus researcher, Rumbles is expecting to be nearby in the early months of his retirement, because it is too cold to sail. He has been sailing since he was 17, when he learned to pilot the winds on the North Sea. Once sailing season starts this year, he expects to spend a lot of time on his sailboat, which is currently moored in Connecticut.

But in the meantime, he and Lee plan to spend time with family. They have a daughter, Annie, and two sons, Peter and Daniel, plus two grandchildren and a third on the way.

“I’m looking forward to taking the grandchildren sailing,” Rumbles said. “They’ll hate it until they love it!”

Learn more about NREL’s research in solar photochemistry and basic energy sciences.