CIS Solar Cells

Copper indium selenide (CIS) solar cells are a precursor to copper indium gallium selenide (CIGS) cells. In fact, the acronym CIS is sometimes used interchangeably with CIGS. The two types of cells are very similar in makeup. CIS cells have achieved conversion efficiencies greater than 14 percent, but CIGS cells have done even better and thus currently receive more attention from solar manufacturers.

CIS cells are a type of thin-film solar cell. They consist of two semiconductor layers. The top layer acts as a window, allowing sunlight to penetrate to the lower layer (made up of CIS) that absorbs the light. That light generates electrons upon absorption, which are herded into an electric current to produce usable electricity. The same description can be used for CIGS cells. The only difference is the addition of gallium to the equation.

CIGS cells are in fact a combination of copper indium selenide and copper indium gallium selenide semiconductors. When gallium is added to the mixture, it increases the optical band gap of the solar cell, allowing more sunlight to be absorbed. Another reason for the use of gallium is its availability relative to indium, which is widely used in producing flat screen monitors. Still, much more indium is used than gallium in CIGS cells because beyond a certain point, the more gallium used, the lower the cell efficiency due to gallium lowering the short-circuit voltage of the cell.

CIS solar cells (non-gallium) are currently in production in Germany by Wuerth Solar. But while CIGS solar cells exhibit considerably higher cell efficiencies, expect the use of gallium to increase and expect to hear less about CIS solar cells.

Monocrystalline Solar Cells / Amorphous Silicon Solar Cells / Gallium Arsenide Solar Cells / CIGS Solar Cells / Polycrystalline Solar Cells / Copper Indium Selenide Solar Cells