Key takeaways:
NexWafe’s epitaxial process grows silicon wafers directly from gas, avoiding ingot growth and sawing steps associated with mainstream Cz production route
The approach enables thinner wafers with low oxygen content and showed comparable cell performance to Cz wafers in HJT processing
The technology is being scaled through a pilot and an early commercial production plan is already in progress
The mainstream silicon wafer manufacturing process in the PV industry involves multiple energy-intensive steps: producing polysilicon from metallurgical-grade silicon, crystallizing it into ingots using the Czochralski (Cz) process, and finally sawing the ingots into wafers. This last step also results in material loss, commonly referred to as kerf loss.
NexWafe, a Germany-based startup and a spin-off of Fraunhofer ISE, developed a solution to avoid some of the above-mentioned steps to directly grow silicon wafers from the gas. Frank Siebke, Co-founder and Senior VP Business Development of NexWafe, presented the company’s approach of producing silicon wafers using a direct gas-to-wafer process, at the TaiyangNews High-Efficiency Solar Technologies 2025 Conference.
Siebke’s presentation focused on reducing material use and energy consumption through epitaxial wafer growth compared to conventional wafer production, while also enabling thinner wafers and new design possibilities for both space and terrestrial PV applications.
He began by explaining the limitations of today’s mainstream Czochralski (Cz) wafer production route, which involves multiple high-temperature, energy-intensive steps and results in significant silicon loss. NexWafe’s method uses a reusable seed wafer, on which a porous release layer is created. A new silicon layer is then grown epitaxially in an atmospheric pressure chemical vapor deposition (APCVD) reactor, after which the grown wafer is detached and the seed wafer is reused. The company reported successful growth of wafers ranging roughly from 50 to 180 µm, highlighting that the process allows high material utilization and makes ultra-thin wafers easier to produce.
Siebke also discussed the material characteristics of these epitaxial wafers, branded EpiNex. Since the wafers are grown from the gas phase rather than from molten silicon, oxygen incorporation is very low. This results in a more uniform structure without the ring patterns typically seen in Cz wafers. He shared results from thermal stability studies showing that the epitaxial wafers maintained minority-carrier lifetime even after thermal cycling representative of TOPCon processing, while conventional wafers showed some degradation. The wafers were also tested in a commercial heterojunction (HJT) cell line, achieving efficiencies of around 24.4%, comparable to reference Cz wafers processed under the same conditions.
He also emphasized the absence of saw damage with NexWafe’s EpiNex wafers and avoiding saw damage etching in contrast to its Cz counterpart. For space applications, thin HJT cells produced on these wafers were tested for radiation exposure in collaboration with research partners, showing comparable or improved radiation stability compared with conventional wafers. Lightweight mini-module demonstrations suggested that thinner wafers could significantly improve power-to-weight ratios, which is a key metric for low earth orbit (LEO) satellites and high-altitude platform systems (HAPS).
Looking ahead, he described how epitaxial growth could enable engineered wafers rather than just acting as a replacement for Cz wafers. Because doping can be controlled during growth, resistivity can be precisely tailored, and doping gradients or intrinsic layers could be integrated into the wafer itself. Simulations conducted with academic partners suggested that such structures could help improve cell efficiency, particularly for TOPCon architectures, without adding complex downstream processing.
On the manufacturing side, Siebke outlined the company’s progress in scaling the technology. Early reactor designs demonstrated feasibility but did not meet the quality requirements for high-efficiency cells, leading to the development of a second-generation APCVD system. A major focus has been on achieving strong thermal homogeneity inside the reactor, which is critical for crystal quality and low thickness variation. According to the results presented, large-area deposition of approximately 1 m² has been demonstrated, with good resistivity uniformity and very low impurity levels.
In terms of commercialization, NexWafe has established a pilot line in Freiburg and is building its first commercial facility in Bitterfeld, Germany, targeting an initial capacity of around 50 MW. The first phase will focus on thin wafers for space applications, with production targeted for 2027, while the line will also be used to qualify products for terrestrial PV markets. In the longer term, NexWafe plans to scale it up to GW levels through partnerships, including collaboration with Reliance in India and agreements linked to US manufacturing expansion.
Siebke also addressed the cost competitiveness of EpiNex wafers by stating that at a GW-scale, the process is expected to become cheaper than conventional Cz wafer production, mainly due to higher silicon utilization and fewer energy-intensive steps. He also noted that the process is compatible with various cell technologies, including TOPCon, back-contact, and HJT, as wafer thickness and resistivity can be adjusted to meet customer requirements.
The full presentation titled Epitaxial Wafers – Powering Future of Energy Generation can be accessed here.