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Graduate 3MT® finalist exploring next-generation solar power

From left, Professor Steve Ringel and Daniel Lepkowski.A finalist in the recent Three Minute Thesis Competition (3MT®) at The Ohio State University, graduate student Daniel Lepkowski discovered his passion for engineering early on.

(Watch Lepkowski's presentation here)

“It’s in my blood,” he said. “Both of my parents were engineers at Texas Instruments, so from a young age my brothers and I were always encouraged to explore engineering.” 

Lepkowski continues to explore while earning his Ph.D. in electrical and computer engineering under ECE Professor Steve Ringel.

What Lepkowski finds most fascinating is how technology advances, not by leaps and bounds, but incremental and carefully examined steps.

It’s this thought process he hopes to take away from his work at Ohio State.

“(ECE) requires this unique blend of knowledge, critical thinking and problem solving that isn't as prevalent in other professions. On top of that, the opportunity to shape the future of technology is really cool and appealing to me,” Lepkowski said.

The annual 3MT® competition hosted by Ohio State's Institute for Materials Research (IMR) allows graduate students to communicate their engineering passion to a wider audience. Lepkowski made it to the top six presenters out of a pool of 30 graduate students who participated. The finals were held during the recent 2019 OSU Materials Week hosted by IMR and its Materials and Manufacturing for Sustainability Discovery Theme focus area. 

Lepkowski's research proposal, “Innovative Pathways to >30% Efficient Solar Cells,” addresses the cost and efficiency of advanced solar power. It also won Best Paper Award during the week.

“Over 90% of solar cells used today are made of silicon, one of the most abundant and well-understood materials systems currently known,” Lepkowski said. 

However, in terms of efficiency, scientists have reached the limits of silicon capabilities. 

“So, what is the next technology that’s going to take us beyond our current limitations into this realm of high efficiency photo voltaics?” he said.

Lepkowski proposes III-V multi-junction solar cells, which apply crystals made of multiple materials absorbing various colors of sunlight. The crystals are produced in a lab by stacking individual atoms through a process called epitaxy – and yes, it’s super expensive. NASA expensive.

His research proposes combining the low cost of silicon with the high efficiency of these crystals by building them on top of silicon to form the III-V multi-junction structure. Scientifically, it's akin to putting gold plating on an inexpensive ring. 

The next challenge, he said, is dealing with the spacing between the atoms of these lab crystal junctions, which causes defects.

“That’s where my work comes in – to reduce the density of these defects and understand the effect of the defects on our cell performance,” Lepkowski said. “It’s my belief that this technology is the future in low cost, efficiency solar cells.”

Since his time at Ohio State, the efficiency rate has gone from 13.3 to 21.8 percent.

“We have a clear pathway, with reduction in defect density, up to 31 percent. This is a really important benchmark as 32 percent is already identified as making commercialization of this technology achievable. With the appropriate scalability and reductions in costs of the substrate, we can achieve 33 cents per watt, which is roughly one-third of current solar cell technology," he said.

Lepkowski’s ultimate goal after graduation is to find a career in the semiconductor industry, allowing him to help shape the future of technology. 

Either way, he said, the skills he is developing at Ohio State allow him to keep exploring wherever he chooses to go. 

Learn more about the 2019 OSU Materials Week and the 3MT finalists here. 

Story by ECE/IMR Communications Specialist Ryan Horns (