Towards 20 GW

The world's largest solar trade fair SNEC 2021 showed a spurt in n-type TOPCon technology. Jolywood, the long-time TOPCon advocate as well as several leading suppliers known for their gigantic p-PERC capacities unveiled new TOPCon products. Jolywood struck a chord regarding several topics –  technology progress and production expansion to a 2-digit GW level at 3 production sites in China. TaiyangNews talked to Jia Chen, Deputy General Manager of Jolywood, about the current status of its TOPCon manufacturing, its future plans and technology insights.

 TaiyangNews: Jolywood is somewhat special in two aspects – a leading backsheet supplier expanding into cell manufacturing; and then when the PV world was focusing on p-type, especially PERC, Jolywood was among the handful of companies to pursue the path of n-type. So first, why the decision as a world-leading backsheet manufacturer to expand into cell/module manufacturing?

Jia Chen: At Jolywood, improving PV technology is front and center in our constant endeavor to help the industry further reduce the levelized cost of energy. When we started, the PV industry was really booming and is still a rapidly progressing industry. We have seen the pace of installations pick up rapidly across the globe, and we strongly believe that trend will continue for the foreseeable future. At Jolywood, our belief has always been that the technology is the engine for this improvement. And this improvement in technology comes on the back of improvements in all the materials, such as backsheets, ribbons, etc.

Also, cell technology is one of the key factors that can push the levelized costs of energy of PV technology lower so that more and more people around the world can enjoy this renewable and green energy. For this reason, our founder decided to focus on the cell manufacturing side, especially the high efficiency n-type. As you can see, Jolywood is not making any PERC cells, but has been pushing on n-type cells over the past 5 years, no matter how difficult it was.

 TaiyangNews: Can you walk us through your thought process behind moving into n-type – both IBC and n-PERT, rather than jump onto the p-type PERC bandwagon?

Jia Chen: Yes. When Jolywood chose the path of n-type in 2016, it was not as popular it is now. Our founder's in-depth research showed that n-type solar cells have the potential to reach much higher efficiency. Firstly, the material itself is much superior compared to the incumbent p-type, meaning that the modules can deliver much higher power and, as a result, reduced levelized cost of energy. Additionally, n-type holds the advantage over p-type in almost every aspect, be it bifaciality, degradation or reliability. So we're now seeing our conviction in n-type as the way of the future coming true.

Having said that, I must also emphasize that the journey has not been an easy one. When we started, benefits of n-type were hardly acknowledged. A lot of our customers did not believe that modules can generate electricity from the rear side, let alone the benefits such as low temperature coefficient and no degradation. Multiple departments of the company, especially the marketing, sales and technical teams, had to work very hard to put the data in front of the customers to convince them on how a solar project can benefit from these advantages.

TaiyangNews: What is your current cell/module production capacity for TOPCon / IBC – and what are your expansion plans?

Jia Chen: The current TOPCon production capacity of Jolywood is 2.1 GW. We are planning to add 1.5 GW in Taizhou, Jiangsu Province and 16 GW in Shanxi Province.

TaiyangNews: When did you decide to upgrade from PERT to TOPCon – and why?

Jia Chen: It was sometime in 2018, and there were a couple of reasons, the first being that PERT is very similar to p-PERC both in terms of cell efficiency and potential. We know that making n-type cells involves higher costs. So if the cell efficiency is comparable, and the cost is higher, there's no advantage for us as well as for our customers. It meant that we had to upgrade our technology. As part of this, we did a very detailed loss analysis of our cell architecture. The key losses for our n-PERT cells were at the contact region or at metallization. To solve this problem, we decided to improve the contact region. It was a time when TOPCon was very hot in academia and was exactly what we had been looking for, as TOPCon is about passivating contacts. On top, we just need one additional step for upgrading n-PERT to TOPCon, implying the investment costs are also low, while the efficiency potential is huge. So going to TOPCon was a no- brainer.

TaiyangNews: Jolywood is currently leading the industry in terms of TOPCon capacity and experience. What are your most important learnings during this journey?

Jia Chen: As I mentioned earlier, it hasn't been easy. It is always difficult to bring a new technology to commercial production, and TOPCon is actually very specific. We had to establish the entire supply chain by ourselves, be it equipment, materials or other process consumables. TOPCon industrialization started only 3 or 4 years ago – that too with Jolywood and few others in the lead. This means that the key mass production knowhow was not available across the industry. So we had to connect the dots one after the other and were the first to make all this effort on how to integrate different processing tools and materials. And yes, we are very proud of the rich experience we've gained during this rather tough journey.

TaiyangNews: A few other companies have also tried the TOPCon approach but were not able to get into high volume production or have given up altogether. What do you think went wrong with the others? And how has Jolywood managed to overcome these issues?

Jia Chen: I don't think anything went wrong with them. Companies suspend or delay a project for different reasons. I can think of a few: different operating environments, capacity driven strategies; for example, companies might have high PERC capacities, a few would like to spend more time in evaluating the technology and wait till the technology is mature. So it all depends on the situation – the financial situation, the capacity, the beliefs or the strategies of a company. In my opinion, no company has failed so far, but rather have a different strategy and pace to realize the benefits of TOPCon technology.

As for Jolywood, we have always been solely focusing on TOPCon and making it better and better. TOPCon is our bread and butter, and we have had to push ourselves hard to be where we are and to
go further, gaining knowledge and expertise in the process.

TaiyangNews: From your experience, what are the 3 key features that will determine the success of TOPCon technology?

Jia Chen: First of all, it is the efficiency gap between PERC and TOPCon. Currently, the efficiency delta between these two technologies is 1% to 2% in the lab setting. And recently, a lot of companies including Jolywood have demonstrated efficiencies above 25% in the lab. It shows that adding one step of putting tunneling oxide and polysilicon layer can improve the cell efficiency and increase the module power. And with more and more efforts, we strongly believe that the non-silicon costs for TOPCon will be comparable to those of PERC.

Next would be the other factors impacting the levelized cost of energy. To offer TOPCon in a product form, we have had to put ourselves in the shoes of a project developer. Because it is very important for the customer how much power the module can generate in real-world conditions. The nameplate power is just indicative as the power is measured at STC, but the modules in the field operate at around 75 °C. So a low temperature coefficient proves very advantageous here. Another important aspect is the bifacial feature of a cell technology, where TOPCon certainly scores higher than PERC. The customer must be educated on such advantages of TOPCon that can help reduce the levelized cost of energy with more and more relative data.

And finally there is a need for more companies to join and cooperate for the development of TOPCon technology. It's boring when you're alone at a party. At Jolywood, we've always been vocal in inviting more people to join us on this TOPCon journey, all the while sharing our learnings to encourage others. We also appreciate full cooperation of our partners – equipment and material suppliers – without which TOPCon would have not reached where it is today. TOPCon requires different parts of the industry, value and supply chains to work together to accelerate the progress.

TaiyangNews: What are the main challenges with the technology today? What do you think will be the key challenges in 5 years?

Jia Chen: From a technology point of view, currently the TOPCon process flow is quite complex. You cannot use a very complex processing flow-based technology to compete with something very straightforward and lean. We, at Jolywood, have been working on this technology for the last
5 years and we have suffered a lot, especially from production issues. One of the key issues in production is that, given the lengthy process flow, we had a lot of yield issues, which we have been trying to solve over time. That's why we have been focusing our efforts in shortening the process flow to improve the yield and reduce costs. For example, last year, we announced Jolywood's J-TOPCon 2.0 with our POPAID technology, which focuses more on shortening the process flow than increasing
the yield. It is quite different compared to other companies that are mostly working on pushing the lab efficiencies higher. However, at Jolywood, most of the projects even at the R&D level are aimed at shortening the process flow, solving the yield issues and stabilizing the process. What we have achieved is quite commendable, but I think there is still room for improvement; we must further shorten the process flow or at least make the processing window wider, so that when TOPCon ramps up to a 10 or 20 GW level there are less issues in the production line.

The second factor from a technology point of view is that silver consumption for TOPCon is still higher compared to PERC. Our target is to make costs comparable to PERC; thus, we need to bring silver consumption on par with PERC. And to do so, we need to work closely with paste suppliers. At the same time, we also have to optimize our process to reduce silver consumption. When this happens, costs for TOPCon would be automatically very similar to those of PERC.

TaiyangNews: How long will it take before we see some of the global cell/module leaders follow you, transforming larger PERC capacities into TOPCon?

Jia Chen: I suppose it is already happening. A lot of mainstream tier-one companies with huge capacities have announced plans to develop TOPCon not just at an R&D level, but serious plans for production. There have also been some announcements of upgrading PERC lines to TOPCon. Overall, the situation is more optimistic compared to last year and I believe more and more companies will soon join the TOPCon party.

TaiyangNews: Are you happy with the current supply chain for TOPCon – production equipment, deposition technologies and metallization pastes?

Jia Chen: Firstly, I am very thankful to all the suppliers who are currently working on TOPCon, because the segment is quite small compared to PERC and the required R&D effort is high. I can imagine that the revenue they are generating from the TOPCon stream is not very profitable for them, which is why I am very grateful to all those who are active in this field.

Having said that, am I happy with the current supply? The answer is unfortunately not completely. There is a lot of scope. Paste is one example. As I mentioned earlier, paste consumption is still high. The losses incurred in the contacts region are still high, which has an effect on efficiency. Paste companies have to improve contact formation and reduce consumption. Boron diffusion is another process that needs optimization, which is a lengthy process involving high Capex and Opex.

TaiyangNews: What do you think will be the global production capacity of TOPCon by end of this year, end of 2022 – and in 5 years?

Jia Chen: At the end of this year, we should have 5 to 10 GW of TOPCon capacity globally. Not only are other companies planning to ramp up their capacities, Jolywood alone will contribute a lot to this. As for next year, it really depends on how successful the other companies are with their plans. When the mainstream companies are successful, a lot will follow them. Then TOPCon could be huge. However, it also depends on the end-customer acceptance and supply chain development. Next year, it could be anywhere between 20 and 50 GW depending on several factors, including supply chain developments. I personally believe that it will ramp up very quickly.

TaiyangNews: Let's talk about bifaciality of the TOPCon structure. How important is bifaciality and do you see much potential for improvement?

Jia Chen: The bifacial approach facilitates generation of electricity from the rear side, increasing the energy yield of the solar PV system. And whether it's very important or relatively important really depends on the project itself. For example, Jolywood products are very popular in the Middle East because a lot of larger projects are situated in deserts. Here, the ground is very reflective, so bifacial technology makes a lot of sense – and that is also why Jolywood's products with a bifaciality of 80% are quite famous.

The potential for bifaciality improvement is a rather tricky question. Basically, bifaciality is the ratio of rear and front efficiency. If you just improve the front side of a cell, though there is improvement overall, it reduces the bifaciality. Similarly, improving the rear side alone makes the bifaciality higher, but that may not completely contribute to the actual improvement. As a cell maker, when we are trying to improve the cell's performance, we generally focus on the front side, because most of the light comes from the front side, thus it is very important. We want to improve the bifaciality, but not at the cost of front side efficiency.

TaiyangNews: What is your current average and champion cell efficiency?

Jia Chen: The current average efficiency of mass production exceeds 24% and maximum mass production efficiency is at 24.5%, while the champion cell reached 25.4%.

TaiyangNews: What do you think is the limit for the commercial average efficiency for TOPCon technology?

Jia Chen: The average efficiency in production can reach up to 25% in 1 year or 1.5 years. Currently, the biggest losses are on the front side, which means you have to implement a selective emitter scheme or even implement a passivating contacts structure also on the front side. However, none of these are very mature at the production level, so the potential is very high for TOPCon technologies. In case of any true breakthrough on the front side, the efficiency can be improved beyond 25% in production.

TaiyangNews: What is the main targeted application for your TOPCon modules – premium residential or even utility scale?

Jia Chen: TOPCon, with its high efficiency and higher module power, is highly suitable for residential applications. There is no doubt about it. However, we at Jolywood believe that if costs are low enough – of course not on par with PERC but very close – with all the other additional advantages of TOPCon, it is also very competitive for utility applications. And as we have emphasized in several conferences and announcements, we have successfully implemented the technology in the utility segment.

TaiyangNews: Can you elaborate on your TOPCon technology roadmap – and other cell technologies as you also work on IBC?

Jia Chen: As you know, we are in production with TOPCon and IBC and are well versed with the advantages of these two technologies. Our main production is in TOPCon. In the future, we may consider IBC or TOPCon + IBC, we call it the TBC structure. However, for all the single junction crystalline silicon solar cells, the ultimate efficiency limit is around 29%. We believe that with tandem structures, we can further improve the efficiencies. So, in the future, we would like to stack TOPCon with other structures, maybe perovskites, which seems promising.

TaiyangNews: Opting for TOPCon, why do you think you can beat HJT, the other potential successor for PERC?

Jia Chen: I know that the majority of the industry views TOPCon and HJT as rivals. But we, at Jolywood, never really think of HJT as competition. I don't know whether you're aware, we are actually trying to learn from the progress of HJT. POPAID is one example. In the end, be it TOPCon or HJT, all are passivated contacts, only the approaches are different. And there are always things that followers of each technology can learn from others. Both the technologies will lead to higher efficiencies. At the end of the day, it is the investor that has to decide on which way to go, and costs are going to play a major part in such decisions. It also depends if the project is an upgrade of existing PERC lines, while the situation might be slightly different for newcomers. So it is difficult to say who will win the race, as there may not be "one runway for these two technologies". They may even coexist and compete from time to time.

TaiyangNews: In 5 years, will we see Jolywood primarily be a backsheet company, like today, or will you primarily be a TOPCon cell/module producer – and why?

Jia Chen: As you may already know, as of H1/2021, we are the world's largest backsheet supplier and we have been leading in TOPCon technology. Ideally, I would say we would be leading in both streams, and it is not easy to give up either of the two.

TaiyangNews: Thank you for the interview.

On Nov. 15, on Day 1 (14-17:00 CET) of TaiyangNews' Solar Module Innovations Virtual Conference, Nicolas Zhu, Jolywood Sales Director Europe and America, will talk about High Efficiency TOPCon Modules for Rooftop and C&I Applications. Join us and register for free here.