Lead Free Solar Cells

The push for alternative energy sources got a big shot in the arm, as researchers at Northwestern University announced on May 5th, 2014, that they had discovered a replacement for lead as a light absorber and energy converter in solar cells. Most of today's solar cells are made from crystalline silicon. While silicon has proven very efficient as a solar energy to electricity converter, because it tends to be heavy, it can make miniaturization of solar cells more difficult.

In recent years, researcher have gone to other, light weight crystalline materials called perovskites. The most common and efficient perovskite until now has been lead. Lead is a toxic material, and scientists had worried about environmental hazards, should wide spread use of lead based solar cell technology become prevalent. But, researchers at Northwestern University believe that they have found a solution. Instead of lead, the researchers used tin.

The new solar cell consists of five layers of material that are only one to two microns thick, which is thinner than a human hair. The first layer consist of glass that allows the light in The second layer, made of titanium oxide, coats the glass and acts as a photo catalyst. The tin is added next and acts as the light absorber. The fourth layer consist of pyridine which serves to seal the cell and close the electric circuit. The fifth layer is made of gold which acts as a contact.

Tin has not only proven to be lighter than lead, it is also cheaper and therefore more cost efficient. The only draw back, at this time, is that lead peroskites have a 15% to 19% solar energy to electricity conversion rate while tin peroskites are just now approaching 6%. However, the use of lead peroskites began in 2009, so it is highly conceivable that those solar cells that use tin peroskites could reach that rate or higher in another 5 years or so. Couple that with the new solar cell's light weight and not only may we see them used to power homes, but we might see them used to power automobiles, and in other applications as well.