Building Low-Cost, High-Efficiency Solar Cells (Text Version)

This is the text version for the "Building Low-Cost, High-Efficiency Solar Cells" video.

Aaron Ptak: III-IV solar cells are the best solar cells on the the planet...anywhere. They're high-efficiency...they're thin...they're light...they're flexible...they're the best you're gonna get. The problem is that they tend to be really expensive because of the way that they're manufactured.

Kelsey Horowitz: They're two to three orders of magnitude more expensive than incumbent technologies, like silicon or CdTe. They're just used in specialty applications that really need the performance, like space or some portable military applications.

Aaron Ptak: The incumbent manufacturing process for III-IV solar cells is pretty expensive. It's low throughput and uses some pretty expensive materials to make those solar cells. There's another growth technique called hydride vapor phase epitaxy that's been around for many decades. Actually, we call it our "brand new 50-year-old growth technique." It's well known to produce very high-quality materials, but what it's never been very good at is growing real devices, like solar cells, for example. We've been developing a new technique here called "dynamic HVPE" that allows us to make really high-efficiency devices.

Kelsey Horowitz: So, dynamic HVPE compared to the incumbent is much higher throughput because it's an inline, continuous system with really high deposition rates and it can also utilize the materials much more efficiently and use lower-cost input materials than the incumbent.

Aaron Ptak: In D-HVPE, we solve a lot of the problems for making devices by having two spatially separated growth chambers where we can move the substrate physically back and forth between the two chambers to build up high complexity devices. Right now at NREL, we have an R&D-scale reactor, where we can grow on a maximum wafer size of two inches. Our next step is to get bigger. We want to create a pilot production scale reactor where we can grow on multiple 6-inch wafers that will help us both prove out the technology, the remaining technical challenges, as well as create a reactor with much higher throughput.

Kelsey Horowitz: If we were able to get the cost of III-IV solar cells down, we'd be able to use them in a lot more portable applications, like unmanned aerial vehicles or portable power, as well as opening up new markets, like rooftop solar. Military applications are one really promising short-term application for this technology. Dynamic HVPE can create functional devices at really high speed with low material costs.

Aaron Ptak: What we're working on here is a way to drastically—and, by drastically, I mean about two orders of magnitude—reduce the cost of high-efficiency III-IV solar cells.