In an interview with PV -Magazine At the end of 2022, Radovan Kopecek, the co-founder and director of the ISC Konstanz of Germany, predicted that solar modules built with cells based on both-sided contacted technology, such as Topcon panels, are possibly driven out of the market by PV modules based on Returned (BC) designs by 2028, with the first strong market volumes of BC technologies that will be between 2025 and 2028.
More than two years after that interview, Kopecek believes more than ever that the prospects he outlined at the time are currently taking shape, especially in the light of the fact that large BC modulemakers such as Longi and Aiko have recently announced surprising shipping results. “Both Longi and Aiko are convinced that the scenario that I predicted can come out even in 2027,” Kopecek told PV -Magazine. “I would rather stick to my Outlook 2028.”
Roadmap
Kopecek states that the PV industry is switching from Pure Topcon products to BC designs that may be combined with Topcon itself, or other regular technologies such as Perc or Heterojunction. “Topcon means that only the back of the cells have contacts or selective contacts of the carrier, while BC Technologies, which lead the module card and are the future I am talking about, have all contacts passivated,” he explained. “The next step can be a shift from Pure Topcon to a false Topcon technology in combination with BC.”
“Topcon can be improved by placing passivating contacts at the front, which is called ‘double poly’. However, this is more complex than what can be done for BC, where manufacturers only have to print the fingers on the front very shallow. The logical consequence is therefore to go to BC, especially to bifacial BC modules, for the market for utility scale, “Kopecek added. “The implementation of alternative metallization, such as copper (CU) or aluminum (already), is also much simpler on the back without cannibalization of the front efficiency.”
According to Kopecek, the processes for the production of BC cells and modules were more complicated in the past. “ISC Konstanz initially started working together with the Chinese manufacturer Spic and we have developed how module technology can be further improved, at Stringer level. What was really important in the past four years was that companies such as Spic, Aiko and Longi were involved in the development of individual processes. It is very important to produce BC panels with standard string processes. “
Equipment
Another important step in the absorption of BC products at an industrial level was the development of new, fast lasers. “A simple LAser Improved Contact Optimization (Leco) Or a laser for selective emitters is not fast enough, “said Kopecek. “Moreover, it is crucial to develop cheap P-plus poly layers. At the moment we have been dropped off at ISC Konstanz, for example, Poly -Laagen and then we implement doping with board differential. However, an intrinsic P-plus poly layer would be extremely beneficial for the production process. This is expected to take place in the next two years and will be a breakthrough, because it will have a positive effect on both performance and costs. “
Kopecek also explained that, for BC cell production, the in-situ Doping in P-Plus Poly layers deposited via Plasma-improved chemical vapor deposits (PECVD) has already improved considerably, which will make the entire production process faster and is able to make higher transit at the same costs. The processing of P-moored poly layers is more complicated due to the low solubility of drill in silicon, which is also the reason why Topcon Tech is based on n-type material with the passivating N-movers at the rear. However, P-doted polysilicon will be developed at high speed and will be used more effectively in the future.
In terms of power conversion ultimate, ISC Konstant researchers say that silicon solar cells with one junction are now approaching their theoretical limits, with cells and modules that approach 27% and 25-26% respectively. “But the most important thing is that BC cells can reach almost the same bifacility speed as topcon cells,” Kopecek added. “The common conviction is that bifaciality and BC do not go well together, but this is not true. Topcon has a fully covered rear due to an absorbent N-type poly-layer, while BC has P-Plus and N-Plus areas, in some cases also with some unlawed areas that are favorable. There is more shade due to the metallization than in Topcon, but the Emitter for BC Tech is located on the back, which contributes to a higher internal quantum efficiency (IQE). If we consider all the advantages and disadvantages, the bifacial factor can almost be identical to that of Topcon, which is around 0.8. “
Cost
BC products are still more expensive than topcon products, although the price increase between the two technologies has been considerably reduced in the past year. “But in terms of costs per watt it will be lower in the future,” Kopecek confirms. “That requires the use of a new BC -Supply Chain exactly as we have seen for Topcon. This is how it worked for all solar technologies in the past and should also be for BC in 2028. “
At the moment he estimates that the BC technology of ISC Konstanz is 30% more expensive than Topcon. “But we will soon be 15-20%,” he added.
The current global production capacity of BC modules is approximately 50 GW and, according to Kopecek, can even reach 1 two by 2030. “By 2028, PureCon and BC can have a 50:50 share in the market,” he emphasizes. “By that time, most manufacturers can decide to go to BC, although a rapid transition is not easy to reach. It may not be a simple conversion of a production technology to another, as we have seen from Perc to Topcon. Chinese manufacturers prefer to buy brand new equipment, this is how they usually act, and a transition may require two to four years. “
With regard to the geographical distribution, Kopecek noted that India is still switching from PERC to Topcon, while China will soon be able to see a shift from Topcon to BC. “In the future, China will, as always, be the fastest in the transition to new PV technologies. It will then be followed by India and at the last stage of the United States, “he emphasizes.
Tandem
Looking ahead, Kopecek is of the opinion that BC applications can have in three or four-terminal tandem solar cells, although two-terminal designs so far seem to be the preferred solution through both research and industry.
“However, I also expect that the large GW commercialization of Tandem -Zonnemodules will not take place until 2030 to 2035,” he said. “The current producers such as Oxford PV serve nichem markets and a real breakthrough can only come with GW scale factories. But if two-term-minimum tandem will be the winning technology, we still have the Topcon technology that can easily be used with this design. If successful, Tandem can be the next disruptor. I would not see a problem to go to Topcon production again. ‘
Standards
Standardization is another step in the scenario described by Kopecek. “In this respect, I believe that acceptable standardization levels can be achieved in 2026,” he says. “At the moment everything must be more or less standardized. In the beginning, Topcon was also divided into many different paths and then it became standard. The companies that are active in the BC domain still follow different routes and next year it must be clear to everyone, what the direction will be. “
Standardization is also desirable when it comes to naming the contact technologies. Before newcomers such as Spic, Longi or Aiko Solar, it was usually mentioned by the interchangeable contact (IBC) and it was usually associated with cell technology developed by Maxeon in Singapore, now part of the Chinese TCL Zhonghuan. “We also gave the IBC label to our first Zebra sun cells, which have no passivating contacts,” Kopecek explained. “However, IBC is too expensive, also because of the plate. Now we have moved to Poly Zebra, which is based on Topcon with BC design and is produced via screen prints. “
The industry is currently taking refuge in the XBC definition, which means that different types of cells may have different letters before the usual BC acronist, such as All-back contact (ABC) for Aiko and Hybrid Passivated Back Contact (HPBC) for Longi. “BC, however, should be the only definition we look ahead, we work in this direction in workshops and conferences,” said Kopecek. “We tried to call it tunnel back contact (TBC) for a while, but we decided that BC is a much simpler solution.”
Patent
Although Topcon and BC manufacturers seem to be more exposed to potential patent problems, Kopecek is convinced that the current scenario, in which different production giants will sue each other about mainly topcon designs, will not lead to poor surprises for BC modulemakers.
“The patents on the back contact technologies will expire in 2028, although not completely, which means that everyone of this year can produce BC products without having to buy a license,” Kopecek emphasized. “The technology was patented almost 20 years ago by Sunpower/Maxeon and the most critical patents will end in three years. That is why I believe that 2028 will be a turning point for this technology, because capacities can be scaled up quickly. “
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