Solar Panel System GuideA thin-film solar panel uses a thin layer of light absorbing material laid on glass, plastic, or metal. The main types are cadmium telluride, copper indium gallium selenide, and amorphous silicon. This page sources its facts from EnergySage and the U.S. Department of Energy.
The three main thin-film materials
EnergySage names cadmium telluride, or CdTe, as the most widely manufactured type of thin-film panel. It describes amorphous silicon, or a-Si, as non-crystalline silicon applied to glass, plastic, or metal, and copper indium gallium selenide, or CIGS, as a semiconductor made from four elements.
On efficiency, EnergySage reports that CdTe modules reach up to 19.7 percent module efficiency, while residential CIGS and amorphous silicon options have efficiencies of 11 to 16 percent.
Cadmium telluride, the leading thin-film technology
The Department of Energy states that CdTe solar cells are the second most common photovoltaic technology after crystalline silicon, representing 21 percent of the U.S. market and 4 percent of the global market in 2022. It describes CdTe modules as mature and reliable products with efficiencies higher than 19 percent.
The Department of Energy also notes a cost and carbon advantage. CdTe modules reached one dollar per watt in 2009, and CdTe module production requires six times less carbon dioxide than silicon.
CIGS thin-film cells
The Department of Energy explains that although laboratory scale CIGS cell efficiencies have exceeded 20 percent, commercial CIGS modules typically have efficiencies between 12 and 14 percent.
The department describes how the material is tuned. Substituting gallium for indium raises the bandgap from about 1.04 electron-volts for copper indium diselenide films to about 1.68 electron-volts for copper gallium diselenide films. High efficiency CIS and CIGS devices use molybdenum as the back contact.