Cullen Chosy ’21 has been named a 2021 Marshall Scholar. Chosy is an honors thesis student studying chemical engineering and perovskite solar cells.

Chosy, the only Stanford recipient, will join 45 other American college students for graduate-level study at U.K. institutions in a field of study of their choosing. Applauded for his ambition by his professors, mentors and friends, Chosy plans on traveling to the University of Cambridge this fall to pursue a Ph.D. in physics. 

Chosy found an early role model through his older sister Madeline, a third-year chemistry Ph.D. student, with whom he would “tag along learning science” as the middle child in a homeschooled family from Madison, Wisconsin. During his free time, he ventured into Nordic skiing and mountain biking — two activities that Chosy believes instilled a strong sense of climate advocacy in him. 

Chosy’s first interaction with solar cell research came during high school when he took a general chemistry class at the University of Wisconsin and received hands-on experience in a college lab building a dye-sensitized solar cell from crushed blackberries. 

In the fall of his freshman year, Chosy took an introductory seminar course called CHEMENG 31N: “When Chemistry Meets Engineering” with associate chemical engineering professor Matteo Cargnello, which Chosy said was “a big experience that set [him] on the path to study chemical engineering.” 

Toward the end of the quarter, Chosy had the opportunity to make gold nanorods. He used electron microscopes to capture images of these rods — an experience that Chosy credits as an eye-opener to the field of chemical engineering. He dove deeper into his interest in investigating uses for perovskite solar cells and methods to improve its efficiency, a research niche that ultimately made him a strong Marshall Scholarship candidate four years later.

The Marshall Scholarship, which finances awardees’ graduate degrees in the United Kingdom, was created in 1953 by the United Kingdom to “retain and strengthen its close association with its ally, the United States.” For the 2021 selection process, eight regional committees around the United States selected students in higher education based on the criteria of “academic merit, leadership, and ambassadorial potential.” 

During his graduate education in England, Chosy hopes to further his solar cell research with the University of Cambridge’s Stranks Lab, a lab that he previously worked with to complete a project related to his honor’s thesis. 

His senior thesis, titled “Stabilizing Metal Halide Perovskites for the Atomic Layer Deposition of Tin Oxide Contact,” focuses on “applying atomic layer deposition to develop more stable contact layers in perovskite solar cells.”

“Perovskite solar cells offer several significant advantages over the conventional silicon cells found on rooftops today,” Chosy said. “Perovskites promise greater efficiencies at converting sunlight to electricity, lower costs and lightweight and flexible modules that are easier to install.”

As an undergraduate, Chosy excelled through his involvement with the Stanford Energy Club. After working with Cargenello for a full year after his freshman fall, he was accepted for an internship at the National Renewable Energy Laboratory (NREL) in Colorado, where he conducted perovskite solar cell research with professor Mike McGehee. 

During his junior year, Chosy transitioned from NREL to Stanford’s Bent Research Group, led by Professor Stacey Bent. Since the Bent lab previously collaborated with McGehee on multiple innovations, Chosy said he experienced a smooth transition while experimenting with perovskite solar cells.

Bent applauded Chosy’s continued work on solar cell research and his honors thesis. 

“Exceptional, thoughtful, and fearless, Chosy has carried out a challenging research project with enthusiasm and perseverance,” Bent said. “Cullen [Chosy] is absolutely deserving of a Marshall Scholarship.”

Chosy approached his Marshall Scholarship application with a “very specific focus,” concentrating on his applications to Oxford and Cambridge since they “have a super strong track record of innovation with perovskites,” which he called a “natural fit.”

Chosy recounted receiving a call from a Marshall Scholarship representative the day after his Friday interview: “It was definitely quite the moment,” he said. “Throughout this long process, I was trying not to focus too much on the outcomes.” 

Elaine Thornburgh, a lecturer in the music department and Chosy’s harpsichord teacher, met him during his Admit Weekend. Since inviting him to play the harpsichord at Stanford that day, she has become one of his closest mentors, witnessing both the musical and scientific sides of Chosy. 

“I’m not at all surprised,” Thornburgh said in response to Chosy winning the Marshall Scholarship. Describing him as “enthusiastic, curious, and affable,” Thornborugh said that his love for the harpsichord provides him with “clarity of thought,” an essential quality for a chemical engineer.

She highlighted Chosy’s willingness to help her with anything, ranging from harpsichord repairs to technical assistance, a trait Thronborugh described as “rare and special.”

Jimmy Raiford, a fifth-year chemical engineering Ph.D. student who has worked alongside Chosy on researching new solar technology, emphasized Chosy’s “well-roundedness” and skills to “adapt and be flexible” and characterized him as “a really bright guy…who stood out to me from the beginning.” 

It was clear early on when Chosy first joined the Bent Research Group that their collaboration dynamic “was partnership rather than a mentor-mentee relationship,” Raiford said. 

Matthew Dardet ’21, Chosy’s longtime roommate, described Chosy as an industrious and protean scientist who also takes time to enjoy the outdoors and ponder the world’s greatest mysteries.

“We would stroll around campus at night and have conversations with each other, talking about ideas, science, philosophy, politics, and predictions on the future, Dardet said. “Chosy is definitely a great person to be around, both as a roommate and friend to have intellectual engagements with.”

Contact Tom Quach at tomquach ‘at’ stanford.edu.