MatSE Ph.D. student receives NASA fellowship to study solar cells

A materials science & engineering Ph.D. student will have the chance to elevate his research through a NASA fellowship.

Adrian Birge’s research involves growing single crystal thin films of compound semiconductors using molecular beam epitaxy. The thin films of III-V semiconductors, comprised of elements from columns three and five of the periodic table, are grown using a technique called Molecular Beam Epitaxy (MBE). MBE works by directing beams of high-purity elements towards a heated crystal substrate, where it is energetically favorable for them to form bonds and grow high-quality films.

“They’re useful for optical and electronic devices, like lasers or high-speed transistors, but they’re also really good for solar cells because of their good optical properties,” he said.

Birge also noted that many in his research group have grown high-efficiency solar cells devices that directly convert sunlight into electricity, which are commonly used on space satellites or spacecraft.

Through the NASA Space Technology Graduate Research Opportunity, Birge will have the chance to make improvements to solar cells’ performance in space. Specifically, he is working on multijunction solar cells, a stack of three or more solar cells that absorb different wavelengths, or energies of light, to maximize power.

While all three sub-cells experience degradation, the bottom sub-cell of that stack, indium gallium arsenide (InGaAs), degrades more than the other two while in space.

“That’s because there’s a lot of really high-energy particles flying around—mostly protons and electrons - the majority of which are ejected from the sun and then trapped in Earth’s magnetic field,” Birge explained.

These particles also surround other planets in high concentrations, making this work equally important for satellites and spacecraft visiting other planets.

The main focus of this research is radiation exposure. Birge’s proposed project involves making that bottom cell “radiation hard” so that it does not degrade as quickly from radiation.

“When you have a satellite out in space, this sub-cell will just degrade over time from constantly getting hit by these particles. And that increases the overall cell degradation,” he said.

Birge will use the NASA fellowship's funding to continue his research and access public laboratories around the country. The fellowship officially begins in mid-August but he has already been hard at work on this project.

“I have made progress just making these InGaAs solar cells. No fancy structures to make it more radiation hard but I’ve made several iterations of these bulk solar cells,” said Birge. “I’m making great progress making high-efficiency InGaAs solar cells as baselines for future radiation studies.”

Birge is finishing his second year working as a graduate student assistant with HMNTL Director Larry Lee. He said he would love to be a professor after he gets his Ph.D. He served as a teaching assistant in undergraduate school and wishes to do so in the fall.

“I really enjoy teaching and I really enjoy research,” said Birge. “It’s rewarding to see other people succeed and know that you helped them reach their goal. Obviously, it’s through their hard work that they reached their goals, but it feels really satisfying to know that you enabled them to reach their potential.” 

Birge also said teaching others helps him improve his own understanding of the material. His energy for teaching was inspired by many caring teachers throughout his education journey, but there were a couple educators who stood out to him. He said his high school AP calculus teacher, Mr. Brandenburg, was a truly high-energy personality.

“It was like 8:30 a.m. and he’s coming in yelling, ‘Let’s learn!’ And he had an obsession with yams. For some reason, he would use them to make all these analogies. So just kind of his high energy and passion for learning I found really inspiring and really engaging," he said. 

However, he said he does not think he would “go as wild as he did.”

Another teacher showed him the importance of empowerment in the classroom - his undergraduate physics professor, Margaret Koker. He recalled a time when he was having a bad day and not leading a discussion like he normally would have.

“She just said if this is how you want to be learning today, that’s totally fine,” said Birge. “I just want to check in and make sure that you’re okay with that. She wanted to make sure I wasn’t feeling overpowered or spoken over by my partner.” 

He said she was open and validating and made him feel seen, which he hopes to emulate in the future.

This fellowship is a step towards making that dream come true and contributing to the research field.

“I’m just so honored to have received this fellowship,” he said. “It’s a culmination of a lot of hard work, both in my research and in the proposal I wrote. And I’m really proud that I was able to receive this, but also just incredibly honored that the reviewers at NASA saw some potential in me to do good research."