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Writer's pictureThe Solar Journey

S208: "TOPCon of the Class" with Oliver Schultz-Wittmann

Updated: Nov 28



Season 2, Episode 8: Oliver Schultz-Wittmann, Holosolis

This week on The Solar Journey, Torsten speaks with Oliver Schulz-Wittmann, CTO of Holosolis, a veteran of the solar technological development. With a career spanning innovative startups, major R&D projects, and important roles in solar manufacturing, Oliver has seen a lot!

From humble beginnings analyzing samples for radioactivity post-Chernobyl during his time in civil service, Oliver is currently leading plans to establish a 5 GW solar cell and module manufacturing facility in France. He shares insights into the challenges and opportunities in scaling European solar production and also dives into the evolving role of intellectual property in the solar industry, as well as why he believes nuclear energy cannot compete with the speed, cost, and scalability of renewables.


Drawing from his extensive experience in navigating technological development, market shifts, and startup environments, he reflects, "Just focus on the things you can do. And when you have something, if there's value in it, there will be a way to apply it, to use it. So don't get distracted from all the noise around you."


An inspiring listen for anyone interested in scaling businesses or driving change in renewable energy manufacturing – this conversation is brimming with thoughts on innovation, perseverance, and the future of clean energy in Europe and beyond.

🎧 Listen to the full episode here.

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Show Notes:

  • Lessons from scaling PV startups and early-stage tech

  • Why IP is becoming a central issue in solar innovation

  • Oliver’s thoughts on the limitations of nuclear energy

  • The journey from a student at the Fraunhofer ISE to founding TetraSun and beyond

  • How timing and market conditions shape the success of new technologies

  • Holosolis’ ambitious plans to drive European solar manufacturing


Transcript

[00:00:00.380] - Torsten

My guest today on The Solar Journey is a part of the leadership team behind an ambitious plan to establish a 5 gigawatt of solar cell and module making in France. Oliver Schulz-Wittmann, CTO of Holosolis. Hi, Oliver.


[00:00:17.910] - Oliver

Hi, Torsten.


[00:00:18.750] - Torsten

You've had a long and varied career in PV photovoltaics, including founding a startup technology company that has had a successful exit. You've worked in R&D for a major manufacturer, and also on two occasions for the Fraunhofer ISE here in Germany, one of the most well-known institutes in this PV space. All that along with founding your own PV production consultancy. So you've had a very diverse and interesting journey. So we'll reflect on your first steps on your solar journey in a brief time.


But first, let's address what's a pretty hot topic at the moment. That's TOPCon technology. You were a co-founder at TetraSun until it was acquired by First Solar in 2013. In July this year, First Solar announced that it was investigating whether TetraSun patents were being violated by TOPCon manufacturers. What is your take on that move? We all know that First Solar is definitely not producing TOPCon today, right?


[00:01:23.890] - Oliver

I don't have any different information. Let me put it that way. If you look that maybe they go into a four terminal tandem, maybe your bottom cell would be TOPCon-based, which would not be a surprise. So who knows? So I don't have any deeper insights than you have.


[00:01:42.620] - Torsten

At the time, I don't remember it being explicitly said, but TetraSun was deploying TOPCon technology, right? Was it TOPCon?


[00:01:50.090] - Oliver

Well, it's something nowadays you would call TOPCon. So that's true. But I think the technology has been, from a physicist point of view, been around before and maybe had a different name or no name at all. What it was is a thin, passivating oxide and a dope polycrystalline silicon layer on top. So is that TOPCon? Is that Polo? Is that whatever? I don't know. It depends. We didn't call it TOPCon at the time, and I think it predates when the term TOPCon was coined. So yes, but nowadays you would call it TOPCon.


[00:02:29.110] - Torsten

We will come I'll get to that later on what is TOPCon and who invented it. Let's just briefly stay on the IP aspect of solar. There's also rumors, or it's half official, that Maxeon is also in IP discussions. With First Solar, Maxeon, and maybe others, there's apparently Chinese companies are building up a large portfolio now also in Europe and in the US regarding patents. I think perovskites is also an area where many, many, many patents have been filed. Oxford PV claims it has a huge portfolio in that sector and nobody should try to enter that business because they covered it all. So do you think that IP becomes a major aspect in the solar technology in the industry? Because it has not been really an important aspect in the past.


[00:03:23.420] - Oliver

Which is surprising, I think. I mean, if you look at other industries, I think IP is more on the forefront than it was in PV. Maybe it was about time that such things happened. Yeah, we will see how it plays out. I think now that also Chinese manufacturers try to enforce the patents they have. So that is maybe the new thing about it. So there have been patents, maybe lawsuits or at least infringement claims and so on before. I mean, Hanwha, I think, had one on the passivation with the aluminum oxide nitride stack. Maybe that was the first one.


[00:04:05.720] - Torsten

It felt odd back then, right? It felt odd. And now it seems to the number of cases just starts to rise in a big way, right?


[00:04:16.850] - Oliver

Yeah. It appears that maybe people are not that busy ramping anymore. So they have time to think about how else could we make money, how else could we protect our claim and our market position and these things. I may not be the best one to answer it.


What definitely I think is interesting is that the patents you're talking about, I mean, maybe not the one from First Solar, not the one from Maxeon, but the ones which now are showing up in the news. It's basically LG had filed for it 10 years ago. And 10 years later now, LG has exited the market, but it was sold to some companies. Then it was even like one patent was resold from one manufacturer to another one, which is used in order to sue the domestic Chinese competitor. So that is definitely new, I think. Let's see how this plays out. But then again, patents are usually really specific. So it may also spur some new ideas on how to do it differently and better. So from that perspective, I think it can always be a source of innovation.


[00:05:43.550] - Torsten

What is that patent about technology-wise?


[00:05:46.860] - Oliver

I think it's about some specific claims about how to treat the edges in, I would call it not traditional, but common TOPCon structure. It's what I read from the news. I mean, it's just these things.


[00:06:04.240] - Torsten

Speaking to Radovan Kopechek from ISC Konstanz a few weeks ago, here at The Solar Journey, he reported that the fear of IP infringement is one factor holding back some US manufacturers from deploying TOPCon. That's possibly one of the reasons why the build out of cell manufacturing capacity is pretty slow, which was also mentioned by Markus Beck at the latest EU PVSEC. What do you make of that?


[00:06:32.720] - Speaker 2

I think it could be. I mean, there's certainly also other things which slow down projects, like unexpended expenses for facilities, waiting for permits, maybe a lack of qualified workforce or whatever. So I think there's many things. Pinpointing it to someone who's raising claims of of of patents maybe as a single source would I think definitely be wrong.


[00:07:14.950] - Speaker 1

Yeah, you're totally right. I mean, these aspects you just mentioned, the availability of land factories, skilled labor was also mentioned in the EU PVSEC as one of the reasons for the slow growth of cell manufacturing capacity. Another aspect the race was financing, right? Apparently, it's difficult to raise private capital for building up the cell manufacturing, which require a lot more money than just a simple module line.


Before we move on, we always like to step back in time here at The Solar Journey to the early days of your solar journey. You studied physics in Hamburg, and then you did a PhD in University of Konstanz, where many solar scientists, engineers, spent their initial phase in their professional career. What was your personal attraction to physics?


[00:08:04.670] - Speaker 2

So after I left school, I went for like 15 months to do my civil service, which was a very regular day. So you were counting, clocking in in the morning and then clocking out in the afternoon, which was actually a pretty good time. But you know, Chernobyl was not that long after... I think it was '86, and I did my civil service in '94, so only eight years later. And there was still radioactivity to be found in playgrounds, in some food and everything. And part of my job was to go get some samples, have it analyzed in laboratories, and see whether you needed to maybe exchange the sand in a certain playground to have it safe for the kids.


So I think that was part of this ambition to get rid of the need for nuclear. And that was maybe one driver. And also because that environment, there's many ways on where you can do it. But in this office atmosphere was a little dull. So I thought like, no, I need to go to university to have more freedom. And it was not very specific... physics is a very broad field. There's many things you can look into. For example, you can try to understand nuclear power a little bit better. You can also try to understand what are the alternatives of energy production. So that's what I found pretty interesting. And that's why I went to study physics afterwards.


[00:09:45.760] - Torsten

Many people now try to push a comeback of nuclear power. So you just mentioned Chernobyl. What do you make of that?


[00:09:54.830] - Oliver

Well, there's many things against it, I think. And from a very practical perspective, it's not going to be ready in time. And also it's way too expensive. And you generate waste, which you have no way of treating it, or no idea of where to store it. And so I think that's all rules it out on any front. I don't think it's the way to go. And especially if you have alternatives at hand, which are faster, cheaper, and benign, I wouldn't do it.


[00:10:32.470] - Torsten

You joined the University of Konstanz and the Fraunhofer ISE in the early phase of your career. So from 2000 to 2008, roughly. And then in that time, solar manufacturing was a vibrant place, particularly in Germany. What were your experience as a researcher while manufacturing here was so strong?


[00:10:57.070] - Oliver

When I started, it was people who were caught a rut – like, Oh, this may never work. So they had the projection, but not that many people believed in it. Nonetheless, it was, as you said, very vibrant. So you could just go to the lab as a student to print your cells and to measure them and to cover a lot of things. So it was not that specialized, I think. And it wasn't that many people at the time. So it was really interesting to see how all that was going.


And so I decided during my studies, I was spending a year at Imperial College in London, and that's where I had the chance to look a little left and right and figured out PV. That sounds like matching what I really like to do, because it's not necessarily only theoretical, but it's really applied science. And it would offer the chance to follow up on what I said. Okay, any bridge production, no need for nuclear. And so that would be a good match. And that's when I, after I returned, started doing some installations in Hamburg at a company where a 50 kilowatt project was the biggest ever at the time.


So that was pretty interesting. Then I decided, okay, to go to Fraunhofer and study that, do my diploma thesis over there. And then I stayed there. They offered me to also follow up with a PhD, try to make high efficiency cells in order to put it a challenge, do it on multi-crystalline silicon, which at the time, it was the dominant material, but of inferior quality. And so I spent three years investigating that. And we also had projects with the BP Solar at the time, Q-Cells as a German manufacturer at the time. So it was also offering a lot of opportunities to interact with people on developing stuff, and not only theoretically, but really hands-on and measuring it. And that was really good. And my affiliation with Konstanz was because of the professor, I mean, Fraunhofer cannot award PhD, so you needed to have a link to university. And this, however, is linked to University of Konstanz. So that was a great time.


[00:13:30.500] - Torsten

So how much do you think did your early experience in that vibrant industry affected your decision now in a way to take again responsibility at Holosolis?


[00:13:42.700] - Oliver

I think it's probably been a bit of a journey. I mean, I spent eight years at turnover leading the high efficiency group. Then I got married. And that changes your life. And we figured out, okay, do we want to stay or maybe explore some other area of the world. And then we spent a vacation in East Germany, checking out some places on which one would be the nicest. And then figured out, oh, maybe instead of going East, go West.


And so I was hired into a startup in California, which was a very interesting experience. They headhunted me. That's where I was exposed to a very new environment. It was interesting people and an interesting setting. I think with that specific company, it wasn't going that well. But I got to know a couple of people who had experience from the industry. Then I thought like, okay, I have some qualifications, some ideas. They do and they have that experience. And let's do something together. And that's when we decided to found TetraSun. It was four guys – that's how that name came along.


And I think that was the experience of building up something from scratch and having ideas and being able to push it through, if you can. It was a really great time I had. I mean, we followed through with building a line and selling it to first order and everything. Now, 25 years later, I've applied some learnings that I've acquired over the years here in this setting and am doing it in Europe and doing it on a larger scale... it's like the outcome of the years before all of them.


[00:16:08.450] - Torsten

So when you look back at the early times at TetraSun, what did you learn about developing an early stage PV technology? And how have you applied it then at your later roles and now also at Holosolis?


[00:16:24.200] - Oliver

One of the things is you can't control timing.


[00:16:28.760] - Torsten

What do you mean by that? It's just the time until you have achieved.


[00:16:33.440] - Oliver

No, I mean, like the market conditions, for example. So is it good time, bad time? What are the policy conditions? What is the silver price, going up and down? So we developed this technology and including copper plating, which at the time seemed like a really brilliant move because silver was getting way too expensive. But by the time we had accomplished, which I think having it done after four years of having an idea, to being able to build a production line for a very new technology is pretty short.


However, then there was no need because that scarcity of silver was gone, the printing had improved. Nonetheless, maybe the environment changes and your idea is really good or not. And we were expecting a wave and then wanted to ride that wave, but that wave never came.


So this copper plating technology, we were the only ones doing it. And this didn't help, to get high throughput tools from a beta tool. So all these things. But then certain things were really good, the ability to do it within First Solar. So First Solar made that strategic move to acquire a silicon technology, which usually you wouldn't expect.


So you couldn't build your case in order to be bought by the leading thin film company. Things sometimes just happen. And what one can do is be ready when the time comes. And so that you can control. But the timing outside, you can't control. Just focus on the things you can do. And when you have something, if there's value in it, there will be a way to apply it, to use it. So don't get distracted from all the noise around you.


[00:18:38.450] - Torsten

You just mentioned copper plating, and there's the Australian company called SunDrive, who now drives copper plating. What do you think is the role of this technology in the next years? And does it play a role here at Holosolis?


[00:18:57.140] - Oliver

So I think reducing the amount of silver and copper is a need for two reasons. One is just the sheer amount needed in order to get this industry to terawatt scale. So we cannot just multiply current use. And replacing it by copper is like a natural move. Is plating the right way to do it? Is it a printing technology based on copper? Is it a mix? There are silver-coated copper particles. There's a low temperature approach, there's a high temperature approach. So probably one of those or another one we haven't really thought of yet is going to come along and do it. I think it's great to have at least one which is demonstrated that you can do it and that it works. So that's really good.


It may not be optimum, if you think about simplicity of the process and applying something on the wafer and then etching it off. It's not the ideal solution if you think about what would be ideal. So that's maybe what's difficult and things like ghost plating and adhesions and stuff. So it's always been difficult. And depending on whether you have a new approach in order to make it better, I think will make you have a chance to to succeed, or maybe then it's just been a very good idea, but not taking over the mainstream market.


[00:20:40.170] - Torsten

First Solar then acquired TetraSun. You met all the milestones and all was good, and you were setting up a manufacturing line in Malaysia, I think it was. And then First Solar stopped the project, right? What can you tell us about it? Because now TOPCon is the mainstream technology. From today's perspective, why did First Solar stop it? Can you share more information?


[00:21:06.690] - Oliver

So first of all, at the time, I think had four business segments and had enough cash to push forward and invest into their technology and business development. And I think they needed to decide, okay, do we spread it and move forward with all the technologies? Or do we focus on exactly one thing? This is where we put all our effort. This is where we really want to focus and become the leader. And they decided for the latter.


And so they divested of three other business units, and that was including us. So they decided to go for large area cadmium tellerite modules and really just doing the modules, not the EPC, not the maintenance and O&M, and not the silicon part. I I think if you look at where they are today, it probably proves them right.


Certainly on a personal level, it's a little sad that after you've accomplished what you promised and everything was working well, not being given the ability to drive it to scale. They were always pretty good strategic thinkers and trying to help some individuals to find their way. I have to say, it's still a very good relationship right after and until today. This is how life goes, how business goes – make a decision and then follow through. They are excellent in doing that.


[00:22:45.220] - Torsten

What do you think is the secret sauce of First Solar? Because it's a singularity in the PV market. They are basically the only thin film company. They've been doing it for decades now and they seem to to be able to protect their market. It's strange because 95% of basically everything is silicon except for First Solar. It's usually said that silicon is so strong because everybody's working on it. And they proved that somehow you can have your own secret and also grow and keep your business profitable.


[00:23:24.160] - OIiver

I think it's amazing for the reasons you just stated, because it's a huge task. If you even have to do the fundamental research on a scientific level, either do it yourself or fund it, especially and just for you. So as compared to the overall drive, they're probably also good in shaping the policies around them. So that's part of being a big company and having the right people and the knowledge on how to do it.


Overall, I think it's good if there's not only a single idea out there on how you can do stuff. I think it pushes the silicon technology. Silicon technology pushes them to next level and so on. So I think it's a good thing for both technologies to be around, and especially like these thin film ideas and equipment ideas and analysis, characterization – physics is now probably playing a role again in perovskites.


[00:24:41.760] - Torsten

I do want to come back to TOPCon and the original versions of it. There's a battle, let's say, a discussion going on, on who invented TOPCon, right? So according to many, it's the throne of ISE, where you worked for quite some time. Then in a way, I guess, Tetra took it to a level hidden by certain patents, maybe. But then there's others groups which claim their contribution, including Martin Green from from UNSW.


Where do you see the truth in this? As someone who was so early and heavily involved in the evolution or the development of the TOPCon technology? Or maybe it's not a single place. There wasn't a single place or a specific group or a single individual who invented. Maybe it's just a mix of different separate inventions which now results in a architecture which is called TOPCon by the world.


[00:25:42.690] - Oliver

Success is many fathers and mothers, especially later on once it's proven to be successful. Some people try to put a claim in it, and may others decide on rightfully so or not. But if you look at the origins of having a silicon surface, having a silicon oxide, and doped polycrystalline silicon compound on top, performing exactly that to produced combination, yet being conductive. That's been around in the late '70s, so early '80s.


[00:26:23.690] - Torsten

Outside solar also, you mean?


[00:26:26.000] - Oliver

Yes. But you look at the bond structure, it's published in, I think, a 1979 Frank Graph paper. And then the group at Stanford, Dick Swanson and others, they have applied it for concentrated IBC cells, so the small ones for concentration, and found a way to get excellent performance from it. And I think this is also the origin of the nowadays called Maxeon patents, right? So then TetraSun found a way to develop a slightly different structure with a different manufacturing process, which is why it's novel and inventive. And then there's others looking at it and coming to another idea on how to do it. But I think the principle behind has been around before. And claiming it just because like an MIS contact is also having a very similar bond structure to be the inventor of it is... Well, if people think they need to do it, they can do it and others will judge. I may not be the judge on that.


[00:27:36.560] - Torsten

So one thing is inventing something and the other part is then scaling it up, bringing it into production, into mass production. I think it's quite amazing how, again, Chinese manufacturers have made these huge strides in scaling the TOPCon technology. How have these manufacturers been able to develop that technology so quickly? And bring it into volume production?


[00:28:03.070] - Oliver

There was and there still is always a need to innovate to improve the efficiency. I think it came at a time when basically the the PIRC structure was almost optimized out. So no further efficiency improvements on the horizon. And then something else comes along, which offers the potential to improve the pessimization, which was now called TOPCon technology. This together with the trend to gigafabs, which basically resulted in a lower cost of ownership. So I think those things came together.


And in an oversupply situation, it's often that, even if you have a very low price tag on a module, if it is of a lower bin, you can't sell it, no matter what the price. So there's really a need to get the highest module bin out. And this was one way to do it. And it was based on semiconductor type and established processing equipment from the industry. So first, aluminum BASF, then PERC, then the change to TOPCon with high temperature. And people were just familiar with it. You know how to build the facilities, you know how to operate it. You can build larger furnaces. But you don't have to invent an entirely new one.


So I think all this together made it possible. Plus, the strategic support or drive or push from Chinese government, in this case, pushed it forward and made this to scale. So I think it was a good timing for the technology to be available. It was ready when the time was right, which from a technology perspective, was good luck on timing.


[00:30:06.410] - Torsten

You mentioned that very early in our conversation, that sometimes you need the right externalities to be successful. In a way, you could say TOPCon and the conditions in China were just ripe to bring that technology to volume manufacturing. Let's turn to Holosolis. Exciting plans. Holosolis is planning to set up 5 gigawatts of cell and module manufacturing to France. What's the status of the plans? When are you holding the first cell in your hands with, I don't know, 25% efficiency or more?


[00:30:43.680] - Oliver

Hopefully more and hopefully sooner. Like always, right? So we've identified the site and we've bought the site, so we know where we are building it. We've submitted the building permits. There's a lot of environmental and public debates and all that stuff going on. And that takes a long time. We've started early and we're keeping the schedule and we're getting a lot of good support from the governments on all levels, from the local region up to national, so that's really good support we see. And for European and possibly French levels, it's be going quickly. So that is all good. If everything goes well, maybe in early January or February, we will have the permits.

And then, in principle, you could start building.


And there's the question of getting enough funding in order to do it. So we're talking about hundreds of millions of dollars at a giga scale, which I think is necessary in order to get the economies of scale and in order to make it a useful addition to the reindustrialization of Europe. So that is a hurdle. And depending on how activity plays out, how quickly that goes. We can start sometime next year, then build a module building, build a cell building, equip it, and so on.


[00:32:30.150] - Torsten

So that was very much on the operational side of things, right? We talked about technology and your plans now to establish a manufacturing capacity. When you step back a little, that's my classic final question. What do you think does it take to get solar to the next level beyond the small bumps on the operational side? Everybody has a different outlook onto the future – what's important? To make it more attractive, cheaper, used more widely?


[00:33:13.830] - Oliver

I think it is already the cheapest technology. It is readily available. You can combine it with the storage. It provides you energy as electricity, which is a very high and very useful form of energy compared to heat, where you cannot do that much with it. But from electricity, you can do many things, everything. And so from that perspective, I think PV has already accomplished what it was set out to do some 25 years ago. So I think that is really great.


Now, keep spreading it, not having it monopolized and making it even more available to countries and industries that are hungry for energy. And I mean, this is not only like other areas of the world. But we have lots of industrial processing which requires energy, and you can supply it with electricity or then, turn it from electricity into a mechanical force or into heat, if that's what you need. And so all that has not really happened yet. So I think this is yet to come.


And so the application side, how to use it, how to store it? Maybe seasonal storage is one of the challenges. And for PV manufacturing, keep spreading it, making us resilient against the the humps and bumps potentially coming from political interferences.


So I think this is the task. I think the size is good, the cost point is really good, and the technology is matured. So saving that and getting it steadily across all industries and across the world for everyone who wants to use it. I think that would be the next level. And keep pushing forward and showing that this is the best option to go forward. And then you don't need to talk about banning things. And that is a natural choice within the system because people are eager to do it.


[00:35:52.350] - Torsten

You're doing exactly that, making it worldwide available by building that new FAB in France. Oliver, it's been a pleasure. I appreciate very much that you took the time for coming onto the The Solar Journey.


[00:36:06.260] - Oliver

Thanks for having me. Bye, Torsten.

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