CuGaSe2rich

CuGaSe2rich is a term used in materials science to describe copper gallium selenide–rich compositions within the Cu(In,Ga)Se2 family. It denotes regions of the Cu–Ga–Se quaternary system where gallium content is high relative to indium and copper, approaching the stoichiometry of CuGaSe2. These compositions are studied because gallium content strongly affects optical and electronic properties relevant to thin-film absorbers.

The dominant phase in CuGaSe2-rich materials is the chalcopyrite CuGaSe2 structure. The lattice is related to CuInSe2 but with Ga occupying the group-III site, which alters lattice constants and defect chemistry. The optical band gap increases with Ga content, with CuGaSe2 exhibiting a direct band gap around 1.7 eV, a value that influences device voltage and spectral response.

Fabrication of CuGaSe2rich absorbers typically uses thin-film deposition methods such as co-evaporation of Cu, Ga, and Se, or sputtering followed by selenization and annealing to form crystalline absorber layers. Precise control of Ga content is essential to avoid Ga-rich secondary phases like Ga2Se3 and to minimize phase segregation during growth and operation.

In solar cell applications, CuGaSe2-rich absorbers are explored to optimize the balance between band gap, open-circuit voltage, and current within Cu(In,Ga)Se2–based devices. Defect chemistry, including copper vacancies and gallium antisites, influences p-type behavior and compensation, as in related chalcopyrite absorbers.

See also: CuInSe2, CuGaSe2, CIGS solar cells.