Despite a sluggish forecast for the overall high-tech industry in 2009, nanomaterials for solar cells grew 47% in 2008 and is projected to grow another 44% in 2009, according to a report Market Outlook for Nanomaterials for Electronics Applications: Semiconductors, Solar, Displays. Sensors, RFID, Lighting recently published by The Information Network, a New Tripoli, PA-based market research company.
Copper Indium Gallium DiSelenide (CIGS) solar cells pushed the market as manufacturers such as NanoSolar, Global Solar, Daystar Technologies, IBM, Miasole, and Ascent Solar increased production. With efficiencies greater than 10%, well above amorphous silicon, manufacturers are developing unique deposition methods and substrates using nanomaterials.
“Competing with GICS are traditional crystalline and polycrystalline cells made with silicon wafers. On the horizon is a new nanomaterial that promises to cut solar cell prices,” noted Dr. Robert Castellano, president of The Information Network. “A privately held company, The Nanosteel Company, Inc., is currently developing a steel based on nanotechnology that would allow for a 60-micron diameter wire. When utilized by solar wafer manufacturers, it could drive down the price of solar, making crystalline and polycrystalline cells more cost effective at the system level than amorphous silicon cells.”
Silicon is the largest contributor to the cost of wafer-based cells, accounting for as much as 50% of the total. Cell cost, in turn, accounts for about half of the total cost of a photovoltaic system.
A key focus in the solar industry is the reduction of wafer thickness, and hence weight and material costs.
Silicon wafers are sliced by a wire saw from a large cylinder of silicon, called a boule, but there is material called kerf loss during the process. The amount of kerf loss is based on the diameter of the wire and the particle size of the silicon carbide abrasive slurry used to cut through the silicon.
The typical as-cut wafer thickness is 200 microns. The typical length of a silicon boule is 1.0 meter. If there was no kerf loss, 5,000 200-micron solar wafers would be produced, and at $6 per wafer it amounts to $30,000 worth of wafers.’
Currently, the standard wire diameter is 120 microns (based on tensile strength so that it doesn’t break during cutting) and the particle size of the abrasive is 8 microns. During the sawing operation, the surface of the solar wafer is also damaged by the abrasion of the SiC to a depth of about 11 microns for wire saw wafers. In the manufacture of solar wafers, a polishing operation is not performed as with semiconductor wafers. Therefore, the 11-micron damage on both sides of the wafer needs to be removed in an etching process after cleaning. As a result, only 2, 793, 200-micron thick wafers would be cut amounting to $16,758 and representing a total loss of 44% due to kerf.
Reducing the diameter of the wire from 120 microns to 60 microns will result in 60 microns less kerf for each wafer and result in 3,356 wafers produced. That equates to $20,136 in wafer revenues and a loss of only 32% due to kerf.
May not sound like much. But, in 2008 a total of 4,814 Megawatts of electricity was produced from solar wafers, up from 3,443 Megawatts in 2007 (there was an additional 810 Megawatts of thin film solar cells utilized that do not require silicon wafers). A solar wafer generates 4 watts. For the 4,814 Megawatts of electricity generated, a total of 1,204 million wafers were utilized. The total revenues for solar wafers alone at $6 each were $7.22 billion. And that is a big number. The savings of 12% in kerf loss using a 60-micron wire comes to $866 million.
The Information Network is a leading consulting and market research company addressing the semiconductor, LCD, HDD, MEMS, nano, and solar industries.