APSTL Claims Crystalline Silicon Advance
Advanced Packaging & Systems Technology Laboratories LLC (APSTL, Scottsdale, Ariz.) says it is making progress on development of a thin crystalline silicon on substrate (TCSS) technology for production of photovoltaic (PV) cells at much lower costs than thick crystalline silicon wafers. The approach involves creation of a 50 micron layer of polycrystalline p+ silicon deposited on an aluminum substrate.
David Lammers, News Editor -- PV Society, 9/24/2008
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Advanced Packaging & Systems Technology Laboratories LLC (APSTL, Scottsdale, Ariz.) said it is developing a thin crystalline silicon on substrate (TCSS) technology for production of photovoltaic (PV) cells. The ultimate goal is to use the technique in a roll-to-roll process for silicon-based solar cells, reducing module costs by ~30%.
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| A cross section of 50 µm layer of polycrystalline p+ silicon deposited on an aluminum substrate. (Source: APSTL) |
“Unlike conventional processes to deposit thin films on substrates using various CVD techniques, the layer deposited by TCSS technology is crystalline, which is conducive to higher conversion efficiencies for solar cells,” said Dev Gupta, CTO. The approach deposits a thin layer of crystalline silicon on a metallic substrate. The process eliminates the saw loss incurred with ingots, and reduces the specific silicon consumption (g/Wp) up to 6×. The finished material can be singulated into square or rectangular wafers to replicate traditional thick polycrystalline silicon wafers, and will be compatible with current tooling for back-end processing to build the modules, Gupta said. “Ultimately continuous sheets of crystalline silicon on substrates to build large integrated PV panels will be possible.”
The company is not publicly disclosing much about how it achieves what it claims, Gupta said, other than saying the approach is driven by an understanding of imperfections in silicon and their effect on electron transport, as well as “the effect of deposition processes and crystal growth conditions on the creation of various defects.”
While unable to disclose its proprietary intellectual property, the technology development company laid out the rationale for the TCSS technology, saying that it will “extend reliable crystalline silicon technology into the &$2/Wp segment of PV modules, and at the same time provide it with panels 50% more space-efficient and more rugged compared to glass substrate-based thin-film technologies.”
Also, the TCSS approach could reduce the need for thick silicon wafers and the expensive polysilicon production infrastructure. Silicon wafers have a crystalline atomic structure which enables a conversion efficiency of ~15-22 %, nearly double that of current thin-film PV panels. However, the relatively thick crystalline silicon wafers, Gupta said, are made with an “archaic process.” The wafers need to be relatively thick for handling purposes, even though the crystalline silicon layer needs to be only ~80 µm thick for the maximum absorption of photons and conversion to electrons.
TCSS wafers may enable the silicon wafer-based PV manufacturing infrastructure to become more cost-competitive with the latest thin-film technologies, he said. The thin-film PV approaches require relatively costly deposition tools to deposit amorphous silicon, or the compound Cd-Te, CdS, CIS and CIGS films.
Besides the tooling costs, thin-film PV development “has been relatively slow for the more complex thin-film formulations, including compound semiconductors such as CIS and CIGS,” Gupta said. The thin-film vendors face “yet unresolved fundamental materials issues such as the impact of processing on non-uniformity, phase separation, and defects in the deposited films, with consequences on conversion efficiency,” he said.
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Mr. Varga :
The "new" aspect of this news is that this company is now showing crystalline silicon on a metallic substrate as evidenced by the atttached photograph. That is a first. Did not see any such evidence of "existence" of anything except verbiage at the website of your client ( aossolar ). The other website you referred to ( Nanogram ) had some computer animation but nothing "real". I think the scientific / technical community, as compared to promoters, prefers to see real data. You should ask those two companies to publish their results.
Rad Mexiula - 09-28-2008 9:31:00 CDT -
www.nanogram.com has a 30 micron crystalline silicon process with a fab under construction for PV, others such as www.aossolar.com claim 10 microns. And there are others. So I am a bit confused why this is NEWS?
Bo Varga - 09-26-2008 2:03:00 CDT
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