Imagine buying solar cells for your home at Target. The research Eli Fahrenkrug is developing could make that a reality. His dissertation research has developed a process that could lead to mass produced, affordable solar energy, reducing the cost of manufacturing to the point that solar energy could be readily available and transform solar cells into a standard household purchase.
He describes, “In my first year, my advisor and I identified one of the major problems and barriers in solar energy. Specifically, materials like silicon are too expensive to manufacture for large scale solar implementation. The energy payback time for a silicon solar cell is 1-2 years of operation just to cover the energy cost of making it. We wanted to determine the physical origin of this long payback time and to find a way to decrease it. We identified the manufacturing process of silicon itself as one of the major barriers. Silica is really just sand and thus is earth abundant, but to transform it to silicon you need to heat it to 3,000 degrees, reduce and melt it down. We sought to change manufacturing process without using high temperatures. We’ve made a lot of progress and are pretty excited about it. Now, we can do this on tabletop in a beaker with a battery.”
Using abundant resources like metal oxides and water, the lab found they just needed a catalyst: “We discovered if we take a low melting point liquid metal, like gallium which melts in your hand, we can use it as a conventional electrode and as a solvent. If we pass current through the liquid metal, we can convert metal oxides dissolved in water into raw materials like silicon or germanium. The raw material then dissolves back into the liquid metal, eventually forming large crystals within the liquid metal. The liquid metal is a catalyst so is not used up, and we’re starting with some raw, abundant precursors without complex equipment. Conceptually, it’s the same process that’s used to make rock candy, except we’re using a liquid metal to make semiconductor crystals for solar cells. Using this process, we have been able to make many commercially relevant photovoltaic materials like silicon, germanium, and gallium arsenide. This strategy holds great potential for significantly decreasing the manufacturing cost. The next step is to refine the science and to partner with engineers to help us increase scalability of the technology.”
Eli came to Michigan to work with his advisor, Prof. Steven Maldonado, a young leader in the field of photovoltaics and energy conversion. He explains, “I was intrigued by the group’s work up to that point and was personally aligned with the thought of contributing to the energy crisis in some way. This is one of the biggest crises faced by our generation. I believe you have to pick where you think you can contribute the most. Solar is not going to solve everything but it will certainly contribute to satisfying rising global energy demands. In science, it is easy to get tunnel vision, but if you can see the impact of your work, it’s pretty motivating. I like to see that direct impact by working at the forefront of science and engineering.”
He feels a sense of urgency in engineering affordable renewable energy sources and finds many scientists incorporate this urgency into their process. He continues, “When you work in solar energy, you can conduct science for the sake of science, or you can seek to develop science that is tangible to the broader community. In cases of the latter, you start the research thinking: how can I do this science so that it is scalable, can be used, and can make an actual impact on society now?”
Eli will graduate in December and is currently finishing a final project involving the scaling process to take this from science in a beaker to large area thin film technology. The goal is to grow thin film semiconductors like silicon and germanium on 4 inch wafers. If successful, the technology could rival current manufacturing means.
Eli’s long term goal is to pursue a professorship in academia. He explains, “What I enjoy most is scientific creativity and academic freedom. An academic role is one of the only places you can do both. It’s also one of the few places where you can be paid to conceive and develop completely original ideas.” He plans to work as a postdoctoral fellow after which he’ll seek a tenure-track faculty position, although he wouldn’t mind taking his time, if he could: “I could stay forever and keep developing this science. As a senior grad student, you have the momentum and skillset to make those discoveries faster and you’ve developed a wisdom that fosters more efficient science. You can do it really fast. A postdoc will be just as exciting because I can explore a completely different facet of science with different researchers with the end goal of fusing all of my research experience into a unique platform as an independent researcher.”
Michigan has set the stage for this work and has been a wonderful training ground for this doctoral candidate: “From a research standpoint, U-M is unrivaled. It is so huge and there are so many people doing great things. Any possible science you can think of, there’s somebody on campus that’s an expert. If you’re looking for a tool that is esoteric, someone here has it. That can be a double edged sword in that at a massive university it can be hard to have that small lab feel and culture which is also important to breed good science, but that’s certainly not the case at all at Michigan.”
Renewable energy isn’t just a part of Eli’s scientific endeavor. An avid cycler, Eli rides everywhere, commuting seven miles to campus by bike each day, regardless of the weather. It’s good training, as he and his partner will spend eight days riding from San Francisco to San Diego this summer. He says, “We like to do self-supported tours. For our first leg from Canada to San Francisco, we took three weeks. We don’t have the same time for the second leg, so we have to really push through and do 90 miles each day.” Biking to campus will look pretty easy after that.”