Boosting Solar Efficiency with Perovskite Tech

Welcome to ASME techcast, bringing you the innovators, the innovations and the issues that push the envelope of engineering. I'm Louise Poirier, senior editor at Mechanical Engineering magazine. Solar electricity generation is on the rise. In fact, the Federal Energy Regulatory Commission reported late last year that more new solar generating capacity would installed in the US in the first eight months of 2023 than any other renewable or fossil fuel based energy source. But imagine if the solar panels generating all of this power were able to capture even more energy. That's where perovskites are coming into play. Researchers have been investigating this nanomaterial for its ability to improve the efficiency of solar cells for years, and commercialization could be on the horizon. Joining us today to talk about perovskites and their potential here on Earth and even out in space is John Ionelli, president and founder of Calux, a company that is working toward commercializing the use of perovskites to make solar energy more powerful and cost effective. John began his career as a research scientist and went on to serve in lead technology and engineering roles at several major technology companies before founding Calyx in 2014 with the goal of improving the performance of crystalline silicone modules using nanomaterials. John, welcome to the show. Thank you. So, to kick things off, I would love to hear more about your personal journey and what inspired you to start Calyx. Sure, yeah. So I've been in technology pretty much my whole career, initially in semiconductors and optical devices and so on, and then got into Solar about 20 years ago now. And one of the things that, you know, know has always been an opportunity in solar is if trying to develop a very high efficiency solar cell. A lot of folks have tried, a lot of folks have made high efficiency solar cells, but to make a very high efficiency solar cell at a very low cost. And so we've looked at this for a very, very long time. I spent some time working at a venture capital firm and we were specifically looking for ideas that would lead to this. And we came up with an approach and a technology that we thought was very viable and really had a good future to it. And so what we did was, you know, from that, from that venture capital firm, found some initial investment, started Calox and launched Calex about 10 years ago. And so, you know, from, from day one, you know, our thesis has been to develop a high efficiency solar cell that is at a cost, at least on parity, if not even cheaper on a dollar per watt basis than existing silicon cells in the market. And that continues to be our thesis, and that's what we're achieving in the product that we're getting ready to roll out. Absolutely. Now, I understand that product involves perovskites. I'm kind of curious to learn more about them myself. So how are they making solar energy more powerful and cost effective? And you know, why perovskites instead of other materials? Sure. No, great question. So, you know, if you look at the sort of the incumbent technology in solar cells, it has been silicon for many, many years and continues to largely be silicon based solar cells. There are some other technologies, cadmium telluride, which for solar has pioneered, but you know, outside of that, silicon has the lion's share of the market. And the, the efficiencies of silicon solar cells creeps up each year, but very, at a very, very low rate. You know, we're talking maybe a few tenths of a percent improvement each year in efficiency. And those improvements are sort of slowing down. You know, we're, we're slowly approaching sort of the ultimate performance of what silicon can ever achieve. So the, the approach that we always took was to develop what's called a tandem solar cell. Essentially, it means putting two solar cells in series or one on top of the other. And, and this works beautifully in terms of giving high efficiency if you have the right materials, but again, the right material that can be manufactured at a very low cost with, you know, abundant sort of readily available precursors to make that material and so on. So our approach has been a tandem solar cell using silicon as the bottom cell. We didn't want to invent two new solar cells, so we've always have focused on using silicon as the bottom cell. So the real question has been, what is the right top cell material? And we looked at a variety of different materials, and some materials work very, very well, but they're very, very expensive. The materials are very inexpensive, but their performance is just nowhere near where it needs to be. And perovskites were really the one material that sort of emerged over the last seven to eight years that has shown a very, very low cost of manufacturing and very, very high performance. And the performance numbers just continue to get better and better each year. It's a much more sort of early stage material compared to silicon, which has been around for, you know, 50 years. But there's continues to be a lot of research in perovskites, and that's why we see the efficiencies getting better and better. So, you know, in short, perovskites are very inexpensive to manufacture and to overlay them on Top of a silicon cell in a tandem type structure, they sort of check all the boxes. They have the right electrical characteristics, the right optical characteristics, and you also use a very, very small amount of the perovskite material compared to silicon. So, you know, silicon cells are anywhere from 100 to 200 microns thick. Typical perovskite cell is less than 1 micron. So, you know, you're talking less than 100th the amount of material for a perovskite compared to a silicon cell. So it was really all of those aspects that have led us at Calox, as well as other folks in this space, to really focus on perovskites. Now, I'm curious, do you have a sense of the sort of the cost difference between silicone and perovskites at this point? It's a tough question to answer only because silicon prices continue to come down. Right. You know, one thing that silicon has done, again, it's, it's efficiency sort of creeps up very, very incrementally year over year. But it's, it's, you know, commercial cost have really have really continued to drop. Some of these, we think, are real cost. You know, some of them, you know, sort of are artificial in the sense that there may be some subsidies behind these, these, you know, that are driving these very low cost numbers. And whether those subsidies are sustainable or not, that's a question. There are tariffs for certain countries that can inflate the effective cost of a silicon cell and so on. So it's tough to do a direct comparison, but we could certainly say the cost on a. And again, on a per watt basis. You normally talk about the solar cell cost of how many dollars per watt of generation. The cost of the, of the prospect cell is absolutely lower than the silicon cell. And again, what we compare is we compare a silicon cell by itself, which might be 21 to 22% efficient for a very good silicon cell today. And we compare that to a tandem, which is a perovskite over that silicon cell, which might be 27% efficient. So we see a large bump in efficiency. But on a per watt basis, the cost of our perovskite over silicon tandem is at least at parity on a dollar per watt basis. As the standalone silicon cell, you sort of get this efficiency bump and really pay no cost penalty on a dollar per watt basis. So that's really what's so attractive to the end users for this technology. Yeah, absolutely. Now, I understand you're looking at transferring this technology to other applications. You know, maybe in Space. Can you talk me through that? Sure, yeah, it's. And that's definitely, you know, much earlier stage, a little more premature than the terrestrial applications. But space in general is certainly sort of growing. A lot of this is because of some of the technology which is lowering payload costs and launch costs, a lot of that driven by folks like SpaceX. So the Space market in general is actually been pretty active recently. And there have always been, you know, solar generation, solar cells in space. The requirements there are a little bit different. And, you know, two of the big requirements are the, the actual weight of the solar cell material because, you know, they talk about numbers. Used to be about 40 to 50 thousand dollars per kilogram for launch cost. Those numbers now, again, depending upon a lot of specifics, are some probably down more in like the $15,000 to $18,000 per kg launch cost. So launch costs have come down, but they're still very, very large. So making the solar cell very lightweight can save quite a bit of money. And again, the perovskite uses a very, very small amount of material for the perovskite cell. So compared to other cell technologies, in theory, could be much lighter weight. And the other big requirement is that the cells have to be radiation resistant or radiation tolerant in space, much different than what they would have to, you know, be tolerant of, you know, here on the surface of the Earth. So things like high energy, whether it's high energy, proton or electron radiation, it's a different sort of technical requirement. It turns out that, you know, the Perovskites tend to be fairly radiation tolerant. And not only that, they, they, they exhibit essentially a healing behavior. So after they go through a temperature cycle, which they will typically go through once a day, there is really, we actually have, have measured and shown radiation healing through this temperature cycle. So there's a lot of, a lot of very interesting aspects about the perovskite cells that could make them very, very attractive for, for space applications. Again, it's the lightweight, it's the radiation tolerance, and certainly the high efficiencies are always good. You want to generate as many watts per kilogram that you put up there. So again, I think it's, you know, it's, it's something that we've looked at. It's something that other folks are starting to look at now in much earlier stage, I think, compared to the terrestrial, you know, opportunities, but certainly looks like a very real opportunity that perovskites could fit into. That'll be exciting to see grow over the coming years, for sure. Yeah. Yeah. Now I'm curious, are there any other emerging renewable energy technologies that you're seeing at the moment are that are really exciting you or inspiring you? Yeah, you know, I mean, the, you know, the couple big ones out there and they get a lot of press and, you know, justifiably so, you know, a lot of good, a lot of exciting things happening in energy storage and sort of from the storage side, what, what, you know, is fitting into that is, is hydrogen. So hydrogen, you know, is certainly getting a lot of good deserved press over the last few years. And what's interesting is, you know, on a lot of these other, you know, interesting technologies, for example, hydrogen, if you're, you know, if you're generating hydrogen with devices known as electrolyzers, you're looking to, if you really want to generate, quote, green hydrogen, you're going to want to run these electrolyzers with electrons that came from a, you know, a renewable energy generator. So you're looking for cheap green electrons is the, is the way folks like to describe it. And you know, things like perovskite solar cells fit, fit right into that very, very nicely. So being able to generate very, very low cost green electricity, which will then run other technologies for things like hydrogen electrolyzers and so on. So, you know, we're not playing in that space directly in terms of hydrogen generation, but we're sort of tangentially playing into that because we have a very nice solution for generating those green electrons which would then fuel those other technologies. Now, something else I'm curious to know your thoughts about is the role of mechanical engineers in leading the way to develop these kinds of new and emerging technologies. You know, can you talk me through that? Sure, yeah. I mean, you know, with really most of these technologies, you know, we see a lot of material science, a lot of electrical engineering, a lot of mechanical engineering, sort of almost. Regardless, you know, whether you're looking at battery technologies or thin film solar technologies like perovskites, we've specifically seen issues around, you know, where mechanical engineers have been very helpful around some of the thermal designs that go into these. So these are typically very, very thin layers in a perovskite solar cell that are stacked on top of each other. When you look at how these devices have to operate over wide temperature swings, the different layers have different thermal expansion coefficients. There can be, there can be stress that's built up within some of these layers. Some of these layers could delaminate if those stresses are too large. And, you know, these are sort of specific problems that you Know, we've addressed just from a thin film solar point of view. And all of those, you know, play directly into, you know, into what's being into, into mechanical engineering skills on the space side of things as well. You know, their weight, as I mentioned, is very, very critical. So putting some of these designs together that are very, very compact and very, very lightweight is a, is a huge skill that's needed in terms of getting these perovskites, as well as any solar technology into the space environment. And then some of the other things too, is that we, we run these cells for, through reliability testing to, you know, one, simulate real world field conditions, be it various humidities that they'll encounter, various temperatures that they'll encounter. And then we also try to simulate the accelerated aging. So, so the cells, you know, we have to warranty a cell or a solar, solar panel for 20 years or 25 years, or, you know, whatever our data sheet warranty would be. We cannot age a cell for 25 years in order to prove that. So you go through accelerated aging tests. And a lot of these tests have a lot of mechanical engineering skills that have to be put both from deriving sort of the test, the test conditions, the test chambers, all of the engineering that goes around, how to actually design and instrument a lot of these reliability experiments that happen. So it's pretty fertile ground, not just for material scientists or electrical engineers, but definitely for mechanical engineers as well. Now, where do you see perovskite technology heading over the next, say, five years? What excites you about the near term and what kind of challenges do you see ahead? Yeah, I think, you know, a lot of folks have demonstrated very good performance. You know, Caleb's included in terms of absolute efficiencies. And I think those numbers will continue to get better and better like any technology, but the performance is certainly there. We have done a pretty good job in our end in terms of scaling this technology up. So, you know, we're not manufacturing very small laboratory size devices. We're manufacturing full 1 meter by 2 meter solar panels, perovskite on glass. So the scale up is something that we've undertaken here. And that's sort of, you know, the first introduction now into commercializing the technology, the reliability. If there was one Achilles heel early on in perovskites, it was probably the reliability. So how long will these devices last in the field? And can you prove that through things like this relia accelerated aging testing that I described earlier, or even just plain outdoor testing, which we have done quite a bit of here? Those reliability numbers are drastically improved over, if you just look back four or five years and I think those reliability numbers will continue to get better and better. Some of this is around how the devices are formulated. A lot of this is around how these devices are packaged. But we definitely see the reliability of these devices and these materials continuing to improve and hitting those numbers of be it a 20 year or 25 year warrantied module. I think, you know, there's a, there's a very clear path into getting these materials to those, those reliability numbers. But that's probably the, you know, the big focus. Again, incremental improvements in performance will always happen. Cost reductions will always happen as, as manufacturing yields get better and better and scaling continues to grow and then getting the reliability up to sort of the commercial level of where silicon panels are today. Right. So what's next for Calyx and for yourself? So we're, you know, we're excited that we're, you know, commercializing this technology now. Again, you know, as I said, we're, we're making full 1 meter by 2 meter perovskite on glass panels which are, you know, nominally the size of a, of a commercial, you know, what they call a 72 cell silicon sort of module format. So these are, these are commercial size panels, full perovskite on glass. And you know, we're making these now and we make them almost every day of the week. And it's exciting, it's exciting to see an actual commercial form factor, you know, for many years making smaller size devices, be it a 2 inch, a 6 inch and 8 inch size solar cell in the laboratory. Now to see full size 1 by 2 meter panels coming off a production line. So we're going to continue to scale the production line that we have here in the US and then you know, ideally be expanding out of here. And so, you know, that's, that's certainly going to occupy us for the, for the next couple of years. That sounds exciting and I'll be, I'll be glad to see where you guys go for sure. Now, any final thoughts you'd like to share with our listeners? No, I think we touched on most of the, you know, it's, it's an, it's an exciting solar technology. You know, there, there have been a lot of technologies that have tried to replace silicon and you know, be sort of the next big thing in solar. And you know, we've, we've taken a little bit of a different approach. We're not trying to replace silicon by any means. We're trying to. We're trying to augment it. So we put our perovskite down on top of a silicon cell, and we take a silicon cell from 21 or 22 up to 27% or higher. So, you know, we love silicon because that's the bottom cell in our tandem, and we think this is the right approach. So we're very excited. Absolutely. Yeah. Every incremental gain is so important in renewable energy, that's for sure. Absolutely. All right, well, I guess we'll have to call it there. Thank you so much for joining us today, John. Oh, my pleasure. Take care. If you'd like to learn more about Calyx, its technology, or what's new, visit klux. Com. And if you'd like to hear more conversations on a wide range of engineering topics, please subscribe to ASME TACAST on your podcast platform of choice. I'm Louise Poirier. Thanks for listening.