A Safer Way to Coat Long-Lasting Solar Cells  

Technology Review has an article on a "Antireflective film which helps solar cells maintain their energy yield" - A Safer Way to Coat Long-Lasting Solar Cells.

In the solar photovoltaic market, even the smallest improvement in efficiency can have a meaningful impact on manufacturers' bottom line, which is why antireflective coatings are so important. These thin coatings, which cause solar cells to appear blue, maximize how much sunlight is absorbed and reduce surface defects that can lower performance.

However, the most popular coating method--the vapor deposition of a silicon nitride film using saline gas--comes with major risks. Silane can ignite when exposed to air; the gas is costly to transport, and silicon cell manufacturers must invest in special storage, ventilation, and other safety measures to prevent accidents. ...

Rohatgi and his team of researchers at Georgia Tech have spent the past 18 months working with Montreal-based Sixtron Advanced Materials on a new silane-free process for applying antireflective film to solar cells. During their work they discovered that the coating--a silicon carbide nitride material carrying the trade name Silexium--also reduces light-induced degradation by up to 88 percent.

Crystalline silicon wafers, which are usually doped with boron, also contain oxygen. When sunlight first hits a new cell it causes boron and oxygen to combine, resulting in a 3 percent to 5 percent degradation in cell efficiency. The researchers found that when the Silexium film is added, some of the carbon in the coating ends up diffusing into the bulk of the silicon wafer. They believe the carbon competes with the boron to make a bond with oxygen. Because there's less oxygen for the boron to bond with, light-induced degradation is largely avoided.