Cullen grew up in Madison, Wisconsin, and studied chemical engineering at Stanford University. His research interests focus on characterizing and engineering emerging semiconductors to enable cheaper and more efficient solar cells. A 2020 Goldwater Scholar, he has conducted research on perovskite solar cells at the National Renewable Energy Laboratory as well as at Stanford. Outside of the lab, Cullen can be found playing the harpsichord, Nordic skiing, or mountain biking. As a Marshall Scholar, he will pursue a PhD in Physics at the University of Cambridge