It seems like there's been a wave of news in the world of thin silicon and new approaches to crystalline silicon.
It's an obvious weak link and cost target in the solar value chain: silicon is the major cost component in silicon solar panels. Manufacturers spend a great deal of time and energy fabricating blocks of polysilicon, only to see up to half of that hard-earned material turned into sawdust in the wafer production step.
Thinner silicon -- and more efficient ways of slicing silicon or fabricating silicon wafers -- seems to be the solar meme du jour.
AstroWatt of Austin, Texas just announced the appointment of Curt Vass as CEO. Vass comes to the startup with 15 years of experience at Applied Material's silicon product division. According to the press release, "More recently, he has worked with a number of venture-backed companies in the solar area, including two Sequoia Capital funded companies." The two solar companies listed in the Sequoia Capital solar portfolio are Clean Cell and SunRun.
AstroWatt, funded by Austin Ventures and NEA, also just announced that Jeannine Sargent, the former head of Oerlikon, has become the Executive Chairman of the firm. And in a busy week at the startup, AstroWatt announced that the firm had produced a 13-percent-efficient champion cell using AstroWatt's SOM (Semiconductor-On-Metal) technology to create litho-less local back contact (LBC) hetero-junction solar cells.
AstroWatt, as reported by Ed Gunther, has developed a Semiconductor on Metal technology for creating thin silicon wafers. Gunther reports, "After partial processing, a monocrystalline silicon wafer is attached to an inexpensive, flexible 50 um metal foil also acting as the solar cell’s rear contact. Next, the foil, along with about 25 um of silicon, is exfoliated using a cleaving process. By reusing a 600 um wafer for multiple exfoliations, AstroWatt claims that “up to 4X [four times] reduction in substrate cost” is possible, and the metal substrate is crucial for wafer handling in existing equipment. AstroWatt also stated the theoretical peak silicon solar cell efficiency can be achieved with a 25 um silicon wafer thickness.
Dr. Dharmesh Jawarani, the co-founder of AstroWatt, will step down to the EVP, Engineering and Product Development position.
The company targets 20 percent efficiency while utilizing significantly less silicon.
Other startups innovating in this field include:
Silicon Genesis, known as SiGen promises kerf-free wafering via an implant-and-cleave process that is still in the early stages of development but could yield wafers with thicknesses down to 20 microns.
Ampulse claims that the firm’s "c-Si thin-film technology takes advantage of HW-CVD techniques to directly deposit a very thin layer of c-Si onto a uniquely textured and flexible metal substrate."
Bandgap Engineering has developed tunable methods for nano-structuring silicon. The firm claims that the absorption of nano-silicon is enhanced by up to several orders of magnitude over bare silicon over a wide range of wavelengths. This enables nano-silicon to absorb the light in the first four microns versus the top 50 to 100 microns that bulk silicon needs to absorb most of the light. This could impact cell efficiency and direct manufacturing cost -- and make for much thinner wafers.
Crystal Solar, recently profiled by Michael Kanellos, uses a vapor deposition process for making thin crystalline silicon wafers. The firm has made wafers measuring 50 microns thick in its labs and hopes to get down to 20 microns. Oceanshore Ventures is one of the firm's investors.
1366 Technologies has a "direct wafer" technology where molten silicon is directly converted into wafers, which can then be processed into thin solar cells.
Developing a new wafer technology and integrating it into an existing process chain is an enormous challenge. Evergreen Solar tried to revolutionize wafer technology with its string ribbon technology, but size incompatibility with their odd-shaped wafers proved daunting and the firm is still feeling the echoes of that misstep today.
Greentech Media's upcoming Solar Summit explores every stage of the solar value chain. Join us in Palm Springs next week.