Science Friday - The Promise Of Perovskite Solar Panels

Episode Date: August 14, 2024

Solar holds great promise as a clean energy solution, as the sun is an incredibly abundant resource, and panels can be placed unobtrusively on roofs and in fields. And solar panel technology has advanced quite a bit over the past few decades: panels have become less expensive, more efficient, and more widely used. Panels also generally fare well, considering that they’re outside in inclement weather year after year.Recent advancements with perovskite solar cells—a type of cell whose name refers to the structure of a compound it contains—have many clean energy enthusiasts excited. Perovskite solar cells are a thin, flexible technology that can even be painted onto a structure and conduct electricity. Much of the work on these has been conducted at the National Renewable Energy Laboratory (NREL) based in Golden, Colorado.At Science Friday Live in Boulder, Colorado, Ira sat down with two solar experts from NREL, Dr. Joseph Berry and Dr. Laura Schelhas, to discuss perovskite solar cell advancements and the future of this clean energy technology.Transcripts for each segment will be available after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Solar panels are pretty impressive, but just how impressive are they? Is it possible that solar panels could use moonlight to power? It's Wednesday, August 14th, and you're listening to Science Friday. I'm sci-fry producer Kathleen Davis. If you've been following the clean energy sector for a while, you'll know that solar panels have advanced tremendously over the past decades. And we see them more often, too, on roofs, in fields. Last month at Science Friday Live in Boulder, Colorado, Ira spoke to two researchers

at the cutting edge of solar panel technology. Let's take a listen. I got to tell you, this week I've been driving all through Colorado, and I've noticed something really interesting that I was very happy to see, and that was a lot of solar panels sprouting up. Yeah, I mean, if you listen to the show, you know I'm a huge fan of solar energy. I have solar panels on my roof, And if you've had your eyes on the solar industry for as long as I have been watching it, you know that solar technology has come a long way and it is rapidly changing.

They've become more efficient, they're less expensive, and that's what we're going to talk about now. And lucky for us, we have a lot of groundbreaking work on solar energy done right here in Colorado. So joining me to talk about the new research on solar panels are my guest, Dr. Joseph Berry, senior research scientists at the National Renewable Energy Laboratory in Golden, Colorado. That's, yeah, welcome to Science Friday.

And Dr. Laura Schellis, senior scientist also at NREL, isn't how we say it? Yeah, National Renewable Energy Laboratory. Welcome to Science Friday. Also, I remember when that was established your center, going back into the 70s. That's another thing to talk about. But for now, let's talk about over the years, Joe. You've been in this industry just a little bit, maybe like 25 years, something like that. I've been at NREL for now a little better than what.

I'm coming up on 18, I think. Yeah. So you've seen some changes coming. Tell me about the changes that you have seen over the years. I mean, there are some technologies that we deploy today that, like what you have on your house. They've been around for a long, long time. There are other technologies that have come up to try to, you know, do it cheaper, better, faster, that have had a little bit of challenges to make it to market and maybe, you know, have receded from prominence.

And, you know, it's been kind of a cycle and churn of kind of new technologies trying to basically break through and enter into the market. So I've seen, yeah, I don't know, half a dozen different technologies kind of come and two of them have really stuck around, I would say. Two of them? Two of them. Do I have to pry it out of you? Silicon and Cat Tell are the two big ones that. are deployed at multiple gigawatt scale. So that's what's on most people's roofs,

and that's what's in most utility scale power plants. Let's talk about solar panels, even the ones that I can talk from personal experience on my roof. They don't last forever, do they? What's the life expectancy? It can vary. Warranties are increasing now, so you're seeing warranties pushing over 30 years.

30 years? Yeah, which is insane. Because if you think about the lifetime of a car, right, which sees a lot of the same stress as a solar panel. How long? My roof is not going to last that long. Exactly. So it's astonishing to me that you can create something this cheap,

and it sees the sun, hail, rain, hot hole. And it keeps it all off of my roof too. Right, it just keeps trucking. Yeah. Right? It's kind of amazing. So we should expect that you should change them now if one's on the market every 20 years?

It depends. So I think rooftop probably 20, 25 years. And then with utility, it can be even longer. but with climate change, sometimes you don't get a chance because maybe a hurricane comes through or hail. That's kind of hard to prevent breaking the panel. Yeah, and I was surprised when I was doing research on this. I always thought, you know, let's have a south-facing roof,

but they said the west-facing roof was more efficient because that's the time you use it, need it most, right? I mean, you're raising another really interesting question. One of our other colleagues at NREL developed what they call the duck curve, right and if you look at energy and electricity usage throughout the day you get these spikes at the beginning and end of the day which is why citing something something that might that you would have thought would be suboptimal is actually the most impactful to your utility bill i know that the you two work on some cutting edge materials for solar panels joe let's talk about this thing called

peravskite what is that and why should we be excited about that well proscytes strictly speaking is a crystallographic structure, but if you think about any PV device or photovoltaic solar cell, it's made from a semiconductor and the different atoms that are in there form some structure. And so perovskites is a particular structure, and we use it as a shorthand for what we, what are technically metal halide perofskites. So these metal halide perofskites, when I started the lab, they were not a thing. Not a thing. They were not a thing.

They weren't even even an idea for the most part. And they've come about kind of in the last, let's say, 12 to 15 years have really become, we can make these particular devices, at least at the lab scale, at higher efficiency than any other kind of comparable system. Really? How efficient are we talking about? So at lab scale, these can now do better than 26%. Wow. And we started out years ago just a few percent, right? There's actually a story about one of our colleagues that we could share. Tell you.

Yeah. one of our colleagues was approached with this Parasca technology at one point, and the efficiency was only like 2 or 3 percent, and they're like, yeah, no, we aren't interested in that until it's more efficient. And so it was a little bit later before some of the rest of us decided that, oh, well, we will look at it. And the really interesting thing about this besides how efficient it is, is Lori, you can actually paint this on a side of a building?

It's paintable? Yeah, so the panel's, you have on your roof are likely silicon. So that's a wafer. You have to pull this big bull and cut it and put it together. But what you'll see is our colleague just painting this on a conductive substrate and then the numbers changing on the volt meter. And so that's really the power being produced by the light we're just shining on it during that process. So the crystals align themselves on the right way as you're painting them? They don't have to be aligned. They just need to be crystallized. So there's some benefit maybe to them aligning, but they just have to form into that

crystal in Matrix, but it doesn't have to be a single crystal. It can just be kind of a hodgepodge of stuff, and you're off to the races. Wow. But you're in the silicon camp, aren't you, still? I am a all-hands-on-deck. I think... No cop out here. A little bit. No, honestly, I think for the energy transition, we need everything. And so I think that Parovskites represent a really new cool technology that's high efficiency and we certainly can make a lot of it but there's work to be done still so yeah and so you're still in the camp that we can make them

silicon more efficient and work with that well the cool thing is actually when you put these two together and so you can actually make your paravskite semi-transparent and then you can put it right on top of your silicon and make a tandem and so then you have the benefit of the silicon and the benefit of the Parovskite, and now you've just made a happy solar sandwich. This is one of the things that, you know,

I mentioned that there's technologies that have come and some that have gone. One of the reasons why the paroxychates are especially interesting is this thing that Laura has just highlighted, is the ability for proskites not only to be really efficient like we just talked about, but to really add value and overall efficiency to incumbent technology.

So we can take a silicon cell, and thermodynamics kind of, says that a silicon cell can only kind of be on the order of 30% efficient. Right. We can basically exceed that by pairing a perovskite with the silicon, right? Whoa. So you've reached the limit almost. You've almost beat the limit.

We can go beyond what we would call the conventional detailed balance limit for a single junction device. So that's a lot of words, but what that basically means is that we have to make compromises. If the sun was only one color, we could make an 80% efficient device really easily. But it's not one color, right? They're all, there's a full spectrum. And so that means that we have to make some compromises if we're just going to have a single device harvest that energy. And that's what we do for silicon. And it can still be very efficient.

But if you really want to get very, very high efficiencies, you got to have multiple cells that are optimized for each of the different sections of the spectrum. I got a question for you about that. But first, I want to tell our audience the mics are open if you want to get to the microphones and ask questions about solar cells, please do that. One question I have for you is that question itself about the broad spectrum. One of the parts of the broad spectrum that we don't see is infrared, the heat section, right? Couldn't solar cells be working at night when the heat is still out there if you can find a way to get the solar, you know, cells to do that?

So it's a little bit of a question about power density. So we do have some colleagues who are working on what we consider to be kind of thermal PV devices. But they're going to basically aim those devices, not at just, you know, general thermal radiation that you might capture and say a night vision camera. They're going to aim it at a really hot source. Right. And essentially use that like we would use the sun. Just the sun is a little bit more of a ubiquitous source that has high quality energy coming from it. at high density.

Yeah, and if you actually take the other end of the spectrum to UV, you can use that during the day. If you can collect the UV, it ends up being transparent. And now you can introduce things like solar windows that you can still see through. Wow, UV ultraviolet during the day. I mean, can the perovskite do there? You have to find another crystallized structure that is.

We're working on systems that will, in fact, target those parts of the spectra as well. But again, you know, in the context of solar, we're kind of stuck with the sun we got. And so we want... You know, yeah, right? But there's a whole lot of solar radiation coming on Earth, isn't there? But when we think about different sections, right, if we think about how much energy is really available in some of these other parts of the spectrum, there is energy available and we can't take advantage of it, but it's not where you get the biggest bang for your book.

Right. All right. All right. All right. Let's see how much a bang for our buckling get in the audience. Let's go over here. Yes. Thank you. I love this stuff about the solar sandwich. I have really two questions. One is price. I know silicon's very inexpensive now, but I think maybe proskites are as well. And then I've heard proskites are very unstable. And I don't know if that's been solved. As far as price goes, right? If we think about the fundamental thing, what really causes things to be expensive, right? It ends up being the amount of energy we put into something.

Right. And silicon, it takes a lot of energy both to purify the material and then to, you know, get it into the right structure. We have a lot more of an entitlement to essentially lower that energy expenditure to make the material to begin with. Having said that, it's one thing to do it and it's, or have that entitlement, it's another thing to realize that entitlement. And, yeah, we're always trying to make everything cheaper, better, faster. But so are the people who make silicon, right? It's just a question how to get there. Yeah, and then the stability question, I think, is a really important one. When we think of silicon, it's silicon, and it's a rock, and it's really stable.

Parovskites, like Joe said, is this crystal structure that can be a non-stable material. When we first started working on it, it was. One of our colleagues tells this joke, the first time they made a little device, they had to run over to the tester to even get a measurement. now we have these sitting outside for months and even going on a year. So in terms of the material stability, will it just stay in that structure? We've made a lot of progress as a field. Field performance, reliability, and durability kind of factors in the whole module and everything else that's going on.

We're not there yet, but it is certainly promising what we're seeing. I mean, the one other thing I would say is that, you know, at a basic level, your photo will panel is not dissimilar from your cell phone. And if you put your cell phone out on your roof for 30 years, you wouldn't expect it to do terribly well. And that's the challenge we're trying to address. At the same time, when we walk into the lab, you know, on our research team, I'm involved in the stuff that's easy, right, which is you can walk into the lab, you can measure it, you can know what's efficiency. Laura's involved in the stuff that's really, really hard, which is what What measurement can you do in five minutes that will tell you where you're going to be in 30 years?

Yeah. And that's just kind of really demanding. Let's see what's demanding in the audience here. Yes, go ahead. Hi, so I learned how to drive in the 70s, and ever since then I've figured out, I imagined electric vehicles back in those days and solar powered, specifically solar powered electric vehicles. So this paint on technology seems very promising to literally paint.

a car with this product and it literally powers itself either on the fly or charges the battery. So tell me what your prediction is for that. Yeah. Could you charge the battery? I mean, getting the car to run, you need a lot of solar cells. But maybe trickle charging or something like that? There's certainly people looking at it. We see some folks looking at kind of putting it on the front of the car.

I think there's even been commercial product out where they've used it to power just like your seat heaters. and stuff like that. I think one of the challenges with getting a lot of power out of something on a car is one of the issues with solar is shade. There's ways that you can get around it,

but thin film technologies in particular do struggle with shading. And so if you have these really high efficient things that you can paint all over the place, but you're going under shady things all the time, it may short out your device. It's not impossible. It's just an engineering challenge

that we'd have to overcome. Right, but you could paint the top of a carport, you know, in a parking lot or something. And there are definitely carports that do this and employ silicon and things like that. I used to live in California, and they put in a new, beautiful carport at the mall with these glass glass modules. You could kind of see through them, and they were beautiful, maybe because I'm a nerd. But I thought they looked really cool. I'm with you on that one. Let's go over here, yes.

Is it possible that solar panels could use moonlight to power? Oh, I love that question. See, they always ask the best questions, the kids. And it does. It works. So we've looked... You can see some energy generation from moonlight in certain circumstances. So I used to work on some projects where we were doing a lot of long-term fitting of time series data of solar panels. and we kept seeing this weird stuff at night.

And my colleague, Bennett Myers, at Slack in California, figured out it was actually the moonlight that was causing a little bit of power generation. So, yeah. One way to think about it is that the moon is like a big reflector. The catch is that it's not reflecting kind of directionally at a particular target. It's diffuse reflection.

But that's still light, and if it's light, you can totally get it. My brother, who was a commercial photographer for many years, and he would actually meter a full moon. He says it's the same light as daylight on pavement on the street. That's how intense. You don't want to look through it with a telescope even, you know? And that's what science is all about, finding out these answers to these questions.

Yeah, well, I'm sorry we don't have any more time for questions, but thank you all for taking time to be with this day. Thank you both of you. Dr. Joseph Berry, senior research scientist, at NREL and Golden and Dr. Laura Schellis, senior scientist also at the National Renewable Energy Laboratory. Thank you for dropping by and telling us all about these new advances. And that's all the time that we have for now.

A lot of folks help make the show happen, including Diana Plasker. Beth Rami. Danielle Johnson. Santiago Flores. And many more. Tomorrow we'll talk about a crowd favorite topic, fossilized dinosaur poop. But for now, I'm Zy Frye producer Kathleen Davis. Have a great day.