CIGSe

CIGSe refers to copper indium gallium selenide, Cu(In,Ga)Se2, a p-type chalcopyrite semiconductor used as the absorber layer in thin-film solar cells. The gallium content varies to adjust the bandgap, enabling a tunable range from about 1.0 eV (indium-rich) to around 1.7 eV (gallium-rich). This tunability allows optimization for single-junction and tandem photovoltaic applications.

CIGSe has a high optical absorption coefficient, enabling thin absorber layers often only a few hundred nanometers thick. It can be deposited on large-area substrates with relatively low-temperature processing and is compatible with flexible, lightweight, or textured surfaces. Common fabrication routes include co-evaporation of copper, indium, gallium, and selenium, sputtering followed by selenization/annealing, or emergence of solution-based approaches. Sodium incorporation from surrounding glass can improve grain size, crystallinity, and device performance.

In a typical solar cell, the CIGSe absorber is deposited on a back contact such as molybdenum on glass or flexible foil, followed by a heterojunction partner layer (commonly a CdS buffer with a ZnO or related window layer, though Cd-free alternatives exist). This results in a standard n-i-p or p-n-like junction configuration. Variants use alternative buffer layers such as Zn(O,S) or In2S3, and different window layers to improve transparency and stability.

Performance and status: laboratory records for CIGSe solar cells have exceeded 23% efficiency, with commercial and pilot-scale modules generally reported in the high teens to low 20s percent range. CIGSe is recognized for strong photoresponse, potential flexibility, and relatively simple handling of large-area deposition, making it a prominent technology in thin-film photovoltaics. Ongoing research focuses on composition control, environmental considerations, and scalable manufacturing.