Strategies for gaining share in the solar market (Part II)

NEW TRIPOLI, USA: Solar cell manufacturers must differentiate themselves during the slowdown in the solar cell market, according to a report: Opportunities in The Solar Market For Crystalline and Thin Film Solar Cells, recently published by The Information Network.

We wrote in Part I how solar manufacturers can differentiate their products, particularly during the economic slowdown.

We discussed increasing efficiency. For example, a local company (contact us for details) has developed a coating for amorphous and polycrystalline cells that can improve efficiency between 8 percent and 12 percent using non-vacuum techniques so that the cost is in the cents per watt range.

Tunable refractive indices make these materials excellent candidates for improving both thermal conductivity and absorption bandwidths. When these unique, novel coatings are coupled with nano-enhanced polymeric coatings, significantly improved durability and extended product life can be anticipated. UV resistance, resistance to optical crazing, and the effect of adverse weather and temperature conditions is also predicted. Films can be coated on any surface.

The other strategy for gaining share, which was mentioned in Part 1 and is discussed here, is to improve reliability:

Long life and low cost of ownership are of paramount importance if solar is to grow, particularly if there is to be a large acceptance at the residential level.

Manufacturing can introduce defects in solar cells that can result in low electron mobility (EM), electron traps and photo-degradation from UV light. These issues affect the efficiency and lifetime of solar cells and the importance of measuring electron mobility at the wafer and cell stage.

The lifetime of minority carriers has been widely identified to be the key material parameter determining the conversion efficiency of pn-junctions in silicon solar cells. Defects in the crystal lattice reduce the charge carrier lifetime and thus limit the performance of the solar cells.

Another major efficiency loss is due to impurities in the cell. These can be foreign atoms or molecules in the crystal lattice (including the dopant atoms), and provide sites where electrons and holes can recombine, thereby reducing the number of charged particles available to create an electrical current.

Lehighton Electronics (Lehighton, PA) is an example of a company that has developed a variety of tools to test and measure solar wafers. One tool can measure sheet resistance and resistivity to see if there is any subsurface damage. Another system can measure minority carrier lifetimes, while a third model can find traps in solar wafers.

Manufacturers and buyers of silicon wafers can benefit from knowledge about the quality of the product. Manufacturers can adjust growing parameters to minimize defect and impurity problems and buyers can evaluate product before going to the expense of turning them into solar cells.