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18 November 2008


Sunovia and EPIR improve growth of single-crystal CdTe-on-Si for CPVs

Sunovia Energy Technologies Inc of Sarasota, FL and EPIR Technologies Inc of Bolingbrook, IL, USA (in which Sunovia has a stake) have made what they say are substantial improvements in their process for growing high-quality single-crystal cadmium telluride (CdTe) on silicon.

The achievement is the foundation for creating ultra-high-efficiency multi-junction solar cells with substantially lower costs than current multi-junction photovoltaic (PV) approaches, the firms claim. The process improvements involved increasing single-crystal growth rates by over 500%, allowing lower processing times per wafer and more PV cells per deposition chamber per day, increasing throughput and lowering costs.

The breakthrough should accelerate the demonstration of an initial 20MW manufacturing system for ultra-high-efficiency, low-cost solar cells. The firms believe that the system can be duplicated for much less than the typical cost for existing advanced solar cell manufacturing systems.

Further, deposition uniformity has been improved, with crystal quality distributions being reduced closer to the 55 arcsecond x-ray rocking curve width previously reported. Improving uniformity should make larger wafers and deposition chambers possible, helping to increase throughput and lower costs.

Sunovia and EPIR’s CdTe-on-Si technology is currently being funded and developed to produce high-sensitivity, long-wavelength infrared (IR) imaging technology with what is claimed to be much larger formats and substantially lower costs than existing technologies. The breakthroughs made in the development of IR technology are directly transferable to the production of high-efficiency, low-cost multi-junction PV cells.

The firms claim that their approach of growing high-quality II-VI semiconductor materials on low-cost large silicon wafers via EPIR’s high-throughput deposition (HTD) technology for concentrator photovoltaic (CPV) systems offers several advantages over current technologies. These include the following:

  • The II-VI material system offers many different opportunities for creating multi-junction cells that can effectively span the solar spectrum.
  • The use of active silicon growth substrates leverages micro-electronics industry technology to obtain large and low-cost, high-quality silicon wafers.
  • II-VI multi-junction solar cells in CPV systems use less than a thousandth of the cadmium and tellurium of their polycrystalline thin-film counterparts, avoiding concerns of environmental toxicity and raw material supply.
  • The HTD process does not use the highly toxic and flammable materials that III-V semiconductor deposition processes use, and hence does not require extensive and expensive safety systems, allowing faster capacity commissioning and regulatory approval.
  • The HTD process requires less than 20ft² per MW of production capability at an investment far less than the $1.5M/MW of current high-efficiency thin-film deposition systems.

See related items:

Sunovia and EPIR down-convert UV to visible light in transparent glass for enhanced PV efficiencies

Sunovia and EPIR collaborating with ETH Zurich on CdTe solar cells

Sunovia and EPIR complete Phase I solar cell and IR plant

Search: Sunovia CdTe solar cells