Liquid Phase Deposition Print   PDF   E-mail  

Changing How Solar Cells Are Made

Natcore was formed to exploit technology, licensed from Rice University, that enables the controlled deposition of silicon dioxide and mixed silicon oxides onto a substrate from an aqueous solution at ambient temperatures and pressures. That technology is known as liquid phase deposition (LPD). We are the exclusive licensee.

One industry in which Natcore's LPD technology could yield very significant improvements in costs and efficiencies is photovoltaics. Photovoltaics is the technology of converting solar energy directly into electricity.

Silicon dioxide, or silica, is a fundamental building block in semiconductors, fiber optics and solar cells. It is an absolutely essential element in all these applications. It is currently deposited onto silicon through a process called thermal oxide growth.

Standard Silicon Solar Cell Cross-Section

Traditional solar cell manufacture involves an expensive chemical vapor deposition (CVD) method. CVD uses complicated, multi-million-dollar vacuum furnaces to grow the necessary anti-reflective (AR) thin-film coating on a silicon substrate. CVD also uses highly toxic and flammable silane and other dangerous chemicals, and requires silicon wafers of sufficient thickness to withstand the high-temperature firing. Thinner wafers often warp in this harsh environment.

Conversely, Natcore offers a liquid phase deposition (LPD), or wet chemistry, process that grows the AR coating in a relatively mild chemical bath at ambient temperatures. It uses low-cost equipment. It eradicates the need for silane and dramatically reduces energy requirements. By allowing for much thinner silicon wafers, it can lower silicon usage by more than 40%. It also enables the development of advanced materials and devices that would be destroyed during the standard thermal oxide growth process.

Moreover, LPD can utilize the waste materials from the initial production of the silicon wafers. And the effluents from the LPD process can be recycled or can be mixed with lime and sold to cement manufacturers for use in their production process.

LPD represents a potential breakthrough in cost that could spawn dramatic growth not only in solar energy but in other important markets as well. Because it requires no vacuum or high-temperature processing, for example, Natcore's film growth technology can enable low-cost production of planar lightwave circuits that are necessary in fiber optic networks.

Surface passivation [LINK TO NEWS RELEASE] is the icing on the LPD cake. Surface passivation is the process of filling the dangling atomic bonds at the surface of the solar cell. Successful passivation of the wafer surface is critical to enabling production of long-term, high-performance silicon solar cells.

In Natcore's refined LPD process, this necessary passivation is achieved using the same production steps normally applied to the solar cell to create its top and bottom metal contacts; no additional heating cycles are required. The synergistic nature of Natcore's technology with existing cell fabrication steps will greatly simplify the standard silicon solar cell manufacturing process.

Natcore's LPD process has been independently tested and validated in an industrial laboratory setting at Battelle Memorial Institute, one of America's most respected laboratories.

The technology is now ready to be tailored to specific applications. And while it has many exciting potential application, Natcore is currently focusing on the area where it will have the greatest impact: solar energy.

Natcore does not plan to manufacture solar cells. Instead, we plan to sell materials, deposition systems and licenses based on our technology to companies that do so.

Because the AR coating is the final step in solar cell manufacturing prior to contact formation, and because the LPD process will utilize simple, low-cost tubs and a proprietary cartridge system, it is expected that Natcore's process will fold easily into virtually any silicon cell production plant.

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