Epitaxy, the Next Green Wave for PV

By?Davor Sutija, CEO of NexWafe

Solar industry stimulus initiatives and the need to rebalance the global solar photovoltaics (PV) supply chain are converging to accelerate the already fast-growing demand for solar energy technologies. To meet the 2050 net-zero energy goals set by the Paris Agreement, installed renewable energy capacity needs to increase to 630GW per year in 2030. Meeting these goals requires the PV industry to adopt new and disruptive means to increase output and improve both the quality and production efficiency of solar PV wafers. These requirements are possible by reducing the traditional amount of material consumed and wasted during wafer production, simplifying the process, delivering thinner wafers, and enabling higher solar cell efficiencies.

Traditional Czochralski (CZ) PV wafer production has long been an obstacle for future demand because of two inherent problems. The first problem is half of the silicon used is either lost or must be recycled; second, the sawing of ingots limits the achievable thinness of wafers and introduces mechanical damage. This is important because the current process is not consistent with the sustainability ethos; more than 50 percent of the energy used to make PV modules is used precisely in these steps.

Improving on traditional manufacturing methods requires a genuinely disruptive and promising solution: epitaxy. NexWafe’s epitaxy process avoids the use of polysilicon, minimizes silicon waste, and consumes 70 percent less energy than traditional CZ manufacturing processes. The process is simpler and requires fewer steps and materials. Epitaxy also allows for more tailored silicon wafers that have a consistent doping content, which is not possible with the more traditional production method.

NexWafe’s EpiWafer process starts with forming a fully detachable separation layer on top of a reusable monocrystalline seed wafer. This porous separation layer is then closed at its outermost surface to form a perfect template for the growth of a new monocrystalline wafer. The next step is thus the formation, directly from the gas phase, of an epitaxial wafer using an atmospheric chemical vapor deposition (CVD) process. The EpiWafer is then mechanically detached from the underlying seed wafer. NexWafe’s seed wafers are reusable – up to 50 times – to create more epitaxial wafers

The epitaxial wafers from this direct gas-to-wafer process are fully formed, completely eliminating the time- and energy-intensive process of ingot pulling and wasteful and potentially damaging sawing. A post-detachment treatment process ensures the new EpiNex wafers are free from any remnants of the seed substrate and are ready for use as a drop-in replacement for conventional Czochralski wafers in cell manufacturing.

Epitaxy is game-changing for PV because with one in-line process it creates optimal, thickness-customizable wafers that have unparalleled material properties that are expected to improve cell efficiencies while eliminating the material and energy waste of traditional processes. NexWafe’s proprietary methodology for higher-throughput, in-line silicon deposition is also more ecologically friendly and sustainable. Using far less silicon and fewer steps means the energy required to build the wafers drops significantly.

With epitaxy, the solar industry truly can evolve from a multi-step wafer production process to a simpler, greener process. The promises of the highly scalable epitaxy process have the potential to make solar cells lighter and easier to install with higher efficiencies, driving down cost to become more affordable for all.

If you’d like to learn more about NexWafe’s epitaxy and how we are addressing the PV market, reach out to us here.?