Latest / The Manufacturing Podcast with Fexingo: Factories, Supply Chains, and Industrial Business / How a Swiss Factory Is Printing Transparent Solar Panels
Transcript
- Lucas: Luna, I want to start with a number that I think is genuinely surprising. By the end of this decade, the global market for building-integrated photovoltaics — solar panels that are literally part of a building's skin — is expected to hit roughly thirty-six billion dollars. Luna: That's a big number. But the technology has always struggled to get out of the niche, hasn't it? Most BIPV products are either ugly, inefficient, or both. Lucas: Exactly. And that's the problem a Swiss company called Insolight is trying to solve with a very specific manufacturing twist. They're printing transparent solar cells onto glass using a roll to roll process — think newspaper printing, but with photovoltaic ink. Luna: Wait — printing. Like, literal inkjet printing? Lucas: Essentially yes. Insolight uses a technique called slot-die coating, where a thin layer of photovoltaic material is deposited onto a flexible substrate or directly onto glass. The key material is a perovskite — a crystal structure that's incredibly efficient at converting light to electricity, and it can be dissolved into a liquid and printed. Luna: So we're talking about solar panels that look like tinted windows. You could put them on a skyscraper and nobody would even know they're generating power. Lucas: That's exactly the pitch. Their pilot line near Lausanne can coat about ten thousand square meters of glass per year right now. That's roughly the facade area of a large office tower. And they've already pre-sold eighty percent of their 2027 production to European building contractors. Luna: Pre-sold two years out. That suggests the contractors believe the product works. What's the efficiency looking like? Lucas: The transparent panels are around eight to ten percent efficiency — compared to roughly twenty percent for a conventional silicon panel. But remember, conventional panels are opaque. You can't put them on a window. So the relevant metric isn't efficiency per cell, it's energy yield per square meter of building surface. Luna: Right. And if you're covering a whole facade, you're capturing light that would otherwise just be glare or heat. Lucas: Exactly. Insolight's panels are about forty percent transparent — they look like slightly tinted glass. They block some infrared and UV, which actually reduces cooling load. So the building saves on air conditioning while generating electricity. Luna: Before we go deeper into the tech — and I want to — I have to say, this is exactly the kind of conversation that we're able to have because we don't run ads on this show. No sponsors, no pre-rolls, no mid-rolls about meal kits. If these episodes have helped you think differently about manufacturing or given you a concrete example to mention in a meeting, and you want to support that ad-free choice, the link is buy me a coffee dot com slash fexingo. Lucas: Yeah. It's a small thing that makes a big difference for us. And it keeps the show exactly what we want it to be. So — back to that printing process. Because the manufacturing method is really what makes this scalable, not just the chemistry. Luna: Right. So how does the roll to roll printing actually work in a factory setting? Lucas: So imagine a roll of flexible plastic or a sheet of glass moving through a series of coating stations. At each station, a precise amount of perovskite ink is deposited through a slot die — basically a narrow slit that spreads the liquid evenly. Then it goes through a drying oven and a laser patterning step that creates the electrical contacts. Luna: And this is all done at room temperature, or close to it? Lucas: The drying step needs moderate heat — maybe one hundred to one hundred fifty degrees Celsius. But compare that to conventional silicon wafer manufacturing, which requires temperatures over one thousand degrees and happens in a vacuum chamber. The energy input per panel is dramatically lower. Luna: So the factory footprint is smaller, the capital cost is lower, and you can ramp up production faster. Lucas: Exactly. Insolight's current line cost about eight million euros to set up. A comparable conventional solar fab would be ten times that. That's why startups can enter this space without needing a billion dollars upfront. Luna: But there has to be a catch. If it's cheaper to make and the material is abundant, why isn't everyone doing this? Lucas: The catch is durability and scale. Perovskites are notoriously sensitive to moisture and oxygen. Early perovskite cells degraded in hours. Insolight has developed an encapsulation layer — they seal the printed cell between two sheets of glass with a desiccant — that they claim gives a twenty-five year lifetime. But that hasn't been proven yet in the field for this specific transparent product. Luna: So the building contractors are taking a leap of faith, essentially. Lucas: They're taking a calculated risk. Insolight has been operating pilot installations on their own building since 2023, and the degradation has been within acceptable limits. Plus, the pre-sale contracts include performance guarantees. If the panels drop below a certain output, Insolight replaces them. Luna: That's a strong signal. What about cost per watt? How does it compare to rooftop solar? Lucas: Right now, Insolight's transparent panels are expensive — roughly one euro per watt, compared to about twenty cents per watt for a conventional silicon panel. But you're not just buying electricity; you're buying a building material that also generates power. Architects are willing to pay a premium for a seamless aesthetic. Luna: And if you factor in the savings on cladding or glass that you would have installed anyway, the net cost is lower. Lucas: That's the argument. Insolight targets a payback period of five to seven years in southern Europe, where solar irradiance is higher. In Germany or the UK, it's more like eight to ten years. Still attractive for a building that will stand for decades. Luna: Who are their main competitors in this space? Lucas: There are a few. A company called Ubiquitous Energy in the US is doing something similar — they print transparent solar cells onto glass using a different organic material. Oxford PV in the UK is working on perovskite-on-silicon tandem cells that are opaque but highly efficient. And then there's Onyx Solar in Spain, which makes conventional amorphous silicon thin-film glass. Luna: But Insolight's bet is that printing perovskites at scale gives them a cost advantage that others can't match. Lucas: Exactly. They're planning a second line next year with five times the capacity. If that works, they'll be the first company to deliver truly transparent printed solar at a commercial scale. Luna: Let's talk about the bottleneck. What's the hardest part of the process? Lucas: The hardest part is uniformity. When you're coating a sheet of glass one point four meters by one point one meters, the perovskite layer has to be perfectly even across the entire surface. A variation of even a few microns creates hot spots that hurt efficiency and accelerate degradation. Luna: So it's a precision coating problem, not just a chemistry problem. Lucas: Exactly. Insolight spent two years tuning the slot-die parameters — the gap width, the flow rate, the substrate speed — to achieve consistent thickness. They also developed an in-line inspection system that uses optical sensors to catch defects in real time. If a panel has a flaw, it gets diverted before it reaches the encapsulation station. Luna: That sounds like a pretty sophisticated manufacturing line for a startup. Lucas: It is. They partnered with a Swiss automation company called Soudronic to build it. Soudronic normally makes high-speed lines for battery electrode coating, so they adapted that expertise for solar. Luna: Interesting. So there's technology transfer from battery manufacturing to solar. Lucas: Exactly. And that's a pattern we're seeing more and more — the same roll to roll equipment can be used for different energy products. It's one reason the capital cost is coming down. Luna: Where does Insolight go from here? Are they thinking about licensing their process? Lucas: They've said they're open to licensing the ink formulation and the process parameters to larger glass manufacturers. The idea is to become a technology supplier rather than just a panel maker. That would let them scale faster without building massive factories themselves. Luna: That makes sense. The glass industry is huge — companies like Saint-Gobain and NSG Group already have coating lines for low-E glass. Retrofitting those lines to print perovskite could be relatively straightforward. Lucas: Exactly. Insolight is in talks with two European glass manufacturers right now. If those deals close, we could see transparent solar glass on the market within three years at a price that competes with standard architectural glass. Luna: That would be a game-changer for urban energy generation. Imagine every new office building in a city like London or Tokyo generating some of its own power, silently, invisibly. Lucas: It's a compelling vision. The question is whether the durability data will hold up over the next five years. If it does, this could be one of the most impactful manufacturing innovations in the building sector. Luna: And if it doesn't, we'll have learned a lot about printing perovskites, which will feed into other applications. Lucas: That's the beauty of manufacturing R&D. Even the failures teach you how to do the next thing better.