Will bifacial IBC be the ‘final’ crystalline silicon product?

Since co-founding ISC Konstanz in the mid-2000s, Kopecek has never been one to shy away from making assertions about the future direction of PV technology. Back in 2012, for example, few shared his belief, frequently expounded in this publication and our sister journal, Photovoltaics International, that bifacial technology was the way forward for solar PV, offering huge scope for driving down the levelised cost of solar power.

Since that time, Kopecek has been the driving force behind the Bifi Workshop, a technical conference series that, as the name suggests, was first conceived to offer others in the bifacial community a platform for discussing a technology that the naysayers believed would never take off.

“When we started with the bifacial workshop in 2012, nobody believed in bifaciality because aluminium back surface field [the prevailing technology at the time] was not bifacial,” Kopecek explains. “But we said, the next step is PERC, and this will be bifacial.”

Despite their confidence in the technology, Kopecek and the other bifacial believers still faced “many hurdles” in bringing the technology into the market. “It wasn’t only the technology change, but you also have to convince PVsyst [the PV simulation software platform] to implement bifacial function into the simulations, and they were not interested because they said there is no bifacial market, why should we do that? So this was the first chicken and egg.”

First bifacial, now back contact bifacial

Twelve years on, the bifacial argument has been conclusively won. But the BiFi Workshop is still going strong, having apparently lost none of its vigour despite the ubiquity of the technology it first championed.

Next week, the event travels to Zhuhai, China, for its second leg of the year. Under discussion will be bifacial back contact technology, which Kopecek insists will be the ultimate evolution of c-Si technology.

As before with bifaciality, the industry is split in its belief in the extent to which back contact will become a dominant technology in the future. “There are still people that that do not believe that IBC will come on utility-scale, and that will be the major topic of the workshop: that if IBC will come on the utility-scale, of course, it has to become bifacial as well, because you cannot have a utility-scale PV system without bifaciality anymore,” Kopecek explains.

He says the workshop will begin with a discussion between “IBC believers and IBC doubters” on the question of “will bifacial IBC really enter the utility-scale or not”.

“I will have a strong opinion that it’s clear that it will happen,” Kopecek laughs. “But also, there will be some people who say, ah, we still have some doubts, because this depends on the timeline of tandem [perovskite], and then maybe two-terminal tandem. But the major topic of the workshop will be to show the progress of IBC technology and how we have made it in the last years to be more efficient and lower cost.”

On this, Kopecek says his belief in IBC is based on the fact all the processes for a large-scale transition to the technology are more or less “ready”. “There is only one process that still has to be developed to make the IBC really very mature and to be superior to TOPCon and that’s the p-type poly, which is not very easy. But many people are working on it and it will be certainly developed, and that’s how you can make it low cost,” he explains.

As with other significant shifts in c-Si technology – from aluminium back surface field to PERC and from PERC to TOPCon – large-scale change happened when the technology was ready and equipment standardised. “So, for example, from aluminium back surface field to PERC, it was the aluminium oxide that was, at the time, not developed. But when aluminum oxide kicked in, the PECVD, then the change was done. And from PERC to Topcon, it was the polysilicon development…then the switch was possible. And the same thing will happen to IBC as well. The switch will go quite fast.”

Believers and sceptics

In the IBC believers camp are companies such as LONGi, which has nailed its colours firmly to the back contact mast through products such as its recently launched Hi-MO 9 module, and AIKO, which is co-hosting the BiFi workshop. On the sceptic side, Kopecek says, are heavyweight players such as Trina and Q Cells, which instead are looking to alternatives such as TOPCon-based perovskite-silicon tandem technologies as the industry powerhouses of the future.

“The community is split now, half, half,” says Kopecek. Companies in the non-believer camp, Kopecek believes, are of this mindset because they tried IBC in the past “and failed”. “Why did they fail? Because the passivating contact technology was not ready yet, right?”

The other central tenet of their belief in a non-IBC future – that other, perovskite-based technologies will prevail – Kopecek believes will only happen over a much longer timescale than it would take for the industry to achieve meaningful increases in back contact-based efficiencies.

“This will happen maybe in, I would say even in 10 years from now because it’s not mature yet. This will be really a big revolution, if tandem can be produced at a huge gigawatt scale, [and] will take a long time.”

On the other hand, Kopecek says crystalline silicon is still on a fast learning curve that offers the opportunity for significant efficiency gains within a shorter timeframe. “At the moment, we are at the average module efficiency of 22.5 or 23%. And we can still reach close to 26%, to improve 1.3% or 1.4 every year over the next five or six years.”

‘Perovskite populists’

Given c-Si’s apparent scope for further improvements, Kopecek is dismissive of what he terms “perovskite populists”—those who believe that as-yet-uncommercialised perovskite-based or “niche” thin-film PV technologies rather than their c-Si counterparts will drive the energy transition: “There are some big boys now of perovskite and thin film – I sometimes call them perovskite populists – already saying that the product is ready, that we must go perovskite.”

Kopecek is of the opposite persuasion. He references an article he and colleagues have been working on for future publication arguing that it will be crystalline silicon rather than “revolutionary innovations” that will prevail.

“I am quite sure that perovskite will not drive our energy transition,” he says. “You know that [perovskites] will be out there, and they will be used for different applications, but they will still remain, as thin film always was, in a niche market.”

To justify this assertion, Kopecek reiterates his point about crystalline silicon being on a fast learning curve that, over the next five to seven years, will yield significant efficiency gains.

“Then we will hit the rooftop; this will be the ultimate crystalline silicon solar cell [and] PV will become completely unbeatable,” Kopecek says. “Within five years from now, PV, with storage, will become the lowest cost electricity source globally.”

In that same timeframe, Kopecek says, the industry will achieve a full production capacity of 3TW a year. “In short, we don’t need any hocus pocus like perovskite, as many people are saying, to reach our CO2 two emission goals. So crystalline silicon will be until 2050 the driver of our energy transition.”

Whether or not Kopecek’s latest prophecy turns out to be true will be for time to tell. But given his past form, you’d be brave to bet against it.

PV Tech is a media partner of the BiFi PV Workshop 2024 Zhuhai. For details, click here.