Back Contact Solar Module Manufacturing Capacity Could Reach 1 TW by 2030, Says Tech Expert

Radovan Kopecek, an expert in back-contacted (BC) solar cell and module technologies, recently spoke with pv magazine about the manufacturing costs, efficiency, and technical challenges associated with BC technology. He predicts that the global manufacturing capacity for BC solar modules could reach 1 terawatt (TW) by 2030, positioning BC products as a mainstream technology in the industry. Kopecek noted that 2028 will be a pivotal year for this technology as many critical patents associated with it will expire.

In a late 2022 interview with pv magazine, Kopecek, co-founder and director of Germany’s ISC Konstanz, suggested that solar modules utilizing cells based on two-sided contacted technology, like TOPCon panels, could be supplanted by BC-designed modules by 2028. He anticipates that substantial market volumes for BC technologies will begin to emerge between 2025 and 2028. Now, more than two years later, Kopecek is increasingly confident in this outlook, particularly given the surprising shipment results recently announced by major BC module manufacturers like Longi and Aiko. “Both Longi and Aiko believe that the scenario I predicted could materialize as early as 2027,” Kopecek shared. “However, I prefer to stick to my 2028 forecast.”

Roadmap

Kopecek asserts that the photovoltaic (PV) industry will gradually transition from pure TOPCon products to BC designs, which could be integrated with TOPCon or other mainstream technologies such as PERC and heterojunction. He explained that while TOPCon technology features passivating contacts on only the rear side of the cells, BC technologies—which are currently leading the market—utilize passivated contacts on all sides. “The next step could involve moving from pure TOPCon to a hybrid version that combines TOPCon with BC technology,” he elaborated.

Kopecek also discussed potential improvements to TOPCon by adding passivating contacts to the front side, referred to as “double poly.” However, he noted that this approach is more complex compared to BC technology, where manufacturers can simply print the fingers on the front side very shallowly. He emphasized that the logical progression is towards BC, especially bifacial BC modules, for utility-scale applications. Additionally, the adoption of alternative metallization methods, such as copper or aluminum, is much simpler on the rear side without compromising front-side efficiency.

Equipment

A significant factor in the adoption of BC products at an industrial scale has been the development of new, faster lasers. Kopecek pointed out that traditional laser-enhanced contact optimization (LECO) and lasers for selective emitters are not rapid enough. He emphasized the need for cost-effective p-plus poly layers and indicated that ISC Konstanz is currently depositing poly layers and implementing doping through boron diffusion. He expects that intrinsic p-plus poly layers will be developed within the next two years, which would be a breakthrough, positively impacting both performance and costs.

Furthermore, Kopecek noted that improvements in in-situ doping for p-plus poly layers deposited via plasma-enhanced chemical vapor deposition (PECVD) have enhanced the BC cell production process, increasing speed and throughput without raising costs. The challenge with processing p-doped poly layers lies in the low solubility of boron in silicon, which is why TOPCon technology relies on n-type materials. However, advancements in p-doped polysilicon are progressing rapidly and are expected to be utilized more effectively in the future.

Power Conversion Efficiency

In terms of power conversion efficiency, researchers at ISC Konstanz report that single-junction silicon solar cells are nearing their theoretical limits, with cells and modules approaching efficiencies of 27% and 25-26%, respectively. “Importantly, BC cells may achieve a bifaciality rate comparable to that of TOPCon cells,” Kopecek remarked. He challenged the common belief that bifaciality and BC technology are incompatible, explaining that while TOPCon features a fully covered rear side with an absorbing n-type poly-layer, BC technology incorporates both p-plus and n-plus regions, sometimes with undoped areas that can be advantageous. Although metallization can cause more shadowing in BC than in TOPCon, the rear-side emitter contributes to a higher internal quantum efficiency (IQE), making the bifacial factor nearly identical to that of TOPCon, which is approximately 0.8.

Cost Considerations

Currently, BC products are more expensive than TOPCon products, although the price gap has significantly narrowed in the past year. Kopecek asserts that in terms of cost per watt, BC technology will be cheaper in the future. “This requires the establishment of a new BC supply chain, similar to what we have seen with TOPCon,” he explained. He estimates that ISC Konstanz’s BC technology is currently 30% more expensive than TOPCon, but expects this difference to decrease to 15-20% soon.

The current global production capacity for BC modules stands at about 50 gigawatts (GW), with Kopecek predicting it could reach 1 TW by 2030. He believes that by 2028, both pure TOPCon and BC technologies may share the market in a 50:50 ratio. “By then, many manufacturers are likely to transition to BC, though achieving this shift may not be straightforward,” he cautioned. The transition from one production technology to another is not always simple, as evidenced by the shift from PERC to TOPCon. Kopecek noted that Chinese manufacturers often opt to invest in brand-new equipment, which can prolong the transition period by two to four years.

Geographically, Kopecek mentioned that India is still moving from PERC to TOPCon, while China may soon shift from TOPCon to BC. “Historically, China has been the fastest to adopt new PV technologies, followed by India and, lastly, the United States,” he asserted.

Future Prospects

Looking ahead, Kopecek sees potential applications for BC technology in three- or four-terminal tandem solar cells, though two-terminal designs currently remain the preferred choice among researchers and industry professionals. “However, I anticipate that large-scale commercialization of tandem solar modules will not occur until 2030 to 2035,” he stated. Current producers, such as Oxford PV, are focused on niche markets, and substantial breakthroughs may only materialize with the establishment of GW-scale factories. If two-terminal tandem technology emerges as the dominant solution, Kopecek believes that TOPCon technology could easily be integrated.

Standardization and Patents

Standardization will also play a crucial role in the future of BC technology. Kopecek predicts that acceptable levels of standardization may be achieved by 2026. “At that point, we should have a more uniform framework. Initially, TOPCon was also divided into many variants before it became standardized. Currently, companies in the BC sector are exploring various paths, and by next year, it should be clear which direction will prevail.”

Standardization is also necessary for naming these back-contact technologies. Traditionally, the term interdigitated back-contact (IBC) was primarily associated with cell technology developed by Maxeon, now part of TCL Zhonghuan. “We initially labeled our first ZEBRA solar cells as IBC, though these have no passivating contacts,” Kopecek explained. “IBC has become too costly, mainly due to plating. We have since shifted to poly ZEBRA, which is based on TOPCon with a BC design and produced through screen printing.”

Currently, the industry is adopting the xBC definition, which allows different types of cells to have various prefixes before the BC acronym, such as all-back-contact (ABC) for Aiko and hybrid passivated back contact (HPBC) for Longi. “However, in the future, we aim for ‘BC’ to be the singular definition,” Kopecek stated. “We previously considered tunnel back-contact (TBC) but agreed that ‘BC’ is a simpler term.”

Despite the potential patent challenges faced by TOPCon and BC manufacturers, Kopecek remains optimistic that the current legal disputes among major manufacturers regarding TOPCon designs will not negatively impact BC module makers. “The patents on back-contact technologies will begin to expire in 2028, allowing everyone to manufacture BC products without needing to purchase a license,” he emphasized. “The technology was patented nearly 20 years ago by Sunpower/Maxeon, and the most critical patents will lapse in just three years. I believe 2028 will be a turning point for this technology, enabling rapid capacity scaling.”