MEI’s Pura wet processing system achieves breakthrough for ultra-pure polysilicon for solar cells

ALBANY, USA: MEI LLC has made a significant process breakthrough to create ultra-pure electronic-grade polysilicon ideal for manufacturing high efficiency photovoltaic (PV) solar cells and semiconductors.

MEI’s Pura wet processing system for polysilicon manufacturers achieves ultra-pure levels, dries tiny granular material—that prior to now was thought to be impossible to dry in large quantities—and reduces energy consumption over today’s wet processing and drying systems by 70-80 percent or more. Pura also saves valuable manufacturing floor space by reducing the wet process system footprint by more than 60 percent.

“By adopting the Pura wet processing system, manufacturers will reduce their costs and increase yield while obtaining a very high purity product,” said Dan Cappello, president and CEO, MEI LLC. “As part of Pura, we are also announcing our unique patent-pending FlashDry process.

"FlashDry is especially important for granular, fine and reclaimed scrap polysilicon because we can reduce surface contamination and preserve the purity level obtained during the wet processing stage. No one has ever achieved this outside of a lab in large quantities until now. MEI is already processing tons of test material. Independent testing quantifies the unprecedented purity and dryness we can obtain from any size polysilicon, from chunks to granules.”

The Pura wet processing system is unlike today’s conventional wet process systems, which have seen little or no innovation in decades. Conventional wet processes and drying techniques are extremely inefficient, consuming massive amounts of chemicals, water, and electricity for heated drying, not to mention valuable floor space.

The new Pura wet processing system encompasses MEI’s unique process IP (intellectual property) for etching, rinsing, and drying polysilicon, the key ingredient in manufacturing solar cells. Pura includes MEI’s patent-pending FlashDry cold dry process that eliminates the use of heat for drying polysilicon.

Pura targets manufacturing applications where high purity polysilicon and the ability to process all form factors is required. PV manufacturers often blend very fine granular material with large rock-like chunks to increase the charge weight of the crucibles used to make ingots for solar wafers. Adding the finer material to the crucible maximizes material use and reduces the handling time during this early, pre-wafer stage of solar cell manufacturing.

Pura combines MEI’s expertise in wet batch processing to create an ultra-pure polysilicon product, regardless of form factor, using a unique etch and rinse process combined with the company’s new FlashDry cold dry process. The result is less metallic contamination, less oxidation, and a measurably drier product. With the price of solar cells dropping, MEI’s process IP breakthroughs can reduce the manufacturer’s cost of ownership significantly.

Another unique benefit of working with MEI is software expertise. IDX, the company’s proprietary control software, provides access to process data from the Pura wet processing system. This allows engineers visibility into what is occurring in any tank or chamber.