Solar industry icon: ‘This group of people is not going to be thwarted’

From the magazine

Thanks for making the time to speak with me. What is your official title these days?

I’m retired. Isn’t that what you’re allowed to be?

Absolutely it is, particularly with all that you’ve achieved. And congratulations on this recent IEEE Award. What do you see as the significance of this award?

What I like about this award is that the impetus came from my students. I’m so proud of them, and for them to get together and do this means a whole lot to me.

Looking at the PV industry in 2025, it does appear that back-contact is poised to move into the mainstream – and potentially become the predominant technology in 2027 or 2028. As the inventor of the technology, how do you feel about that?

You really think that? Wow, I don’t know.

Well, we saw the transition from aluminum-back surface cell technology to PERC [passivated emitter rear cell] relatively quickly, and then PERC to TOPCon [tunnel-oxide passivated contact]. And it does seem that the industry is ready for a transition to back-contact, with manufacturers like Aiko and Longi both pursuing the technology now.

I have to say that I think it is going to be a ‘battle royale’ between heterojunction, TOPCon and IBC. And it’ll be fun to watch. It is one of those things that is like, in the best Socratic sense, if you assigned me one of those I could tell you exactly why it is going to win and why the others are doomed to fail. Pick any one and I could do the same thing.

HJT and TOPCon are both applicable to back-contact architectures – is that right?

Yeah, and in fact all the modern back-contact cells use some sort of HJT-type structure, including at SunPower. When we first came out with Gen3, one of the amusing things looking back on it is that we didn’t want anybody to know that we were using tunnel-oxide poly [TOPCon]. And that’s why we called it “passivated contact.” But it wasn’t long before anybody who knew what they were doing figured out what it was.

It really didn’t slow any of our competitors down. And I think an interesting point, which I’ve been writing up, is that there was an almost unexpected importance of efficiency. The way relatively modest efficiency differences can swing production and billions of dollars of assets. We certainly saw that with the aluminum back-surface field demise and then with the TOPCon taking over from PERC. And now the question is what’s next. Of course I have a sentimental favorite in that race.

Now we’re talking about 350 GW of installations, potentially, in China alone this year and 90 GW in May – a single country, a single month. How would you have reacted if someone had told you that when you were drawing the first diagrams of the first back-contact cell in the 1970s?

Well, I got my first research contract at Stanford in 1973 and we started working on IBC cells shortly thereafter. I never expected that IBC cells would become a serious flat-plate technology, but it was all for high-concentration PV, where you could afford expensive processes.

Along that same thread, almost nobody within the industry felt that wafered silicon would be the ultimate winner in this. At that time, you either joined the concentrating silicon group or the thin-film PV crowd. And that is where most of the research funding went.

To fast forward to today, the fact that not only did wafered silicon win, but it actually became cheaper than conventional energy – I can’t help thinking, ‘how did this happen?’ When I try to make sense of it, and look to other industries and technologies to look for a difference, the real difference is that at the time of the oil crisis in 1973 and 1976, it brought a dedicated group of individuals into the PV community that were in it for the long haul, were dedicated, diligent and smart. And what is underhyped in terms of its importance was the international conferences that we had. At these conferences the international community would get together every six months for a time – once in Europe, once in the United States, and once in Asia – and it really promoted a sense of community, a shared vision, and a sense that we’re all in this and working together. Some of us made what looked like great choices to go into thin film, and they were casualties. But nonetheless it was a shared community.

As you mention, the oil crisis had a major impact on how things developed – under US Presidents Nixon and then Carter, providing funding for solar R&D. Fast forward to today, and we are seeing cuts to NREL under President Trump. How do you react to that?

I think it’s needless on the part of the administration. It is not well thought out. But on the other hand it is typical of the whole progress of what has come to be known as the “solar coaster.” When I got in and Carter was in office, a lot of other people got into PV, and into the research community and started their careers. When Reagan came in, the budget got sliced dramatically – from something like $160 million a year to $20 million. As a result quite a few people had to go back to their day jobs, which generally meant the chip industry.

But the mission survived and that is just one of many, many ups and downs as we go through this. It has been like this ever since the beginning. And while it seems silly and painful, it doesn’t give me any sense of foreboding or gloom that the administration is going to be able to stop us. This group of people is not going to be thwarted by the political climate, that’s for sure.

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