Post-Deposition Recrystallization of Chloride Treated Cu(In x Ga (1-x)) Se 2 Thin-Film Solar Cells

Conditions promoting the recrystallization of CuIn
_(1-x)
Se
₂
(CIGS) deposited by co-evaporation at 350°C were studied. Cu-rich and Cu-poor CIGS samples were annealed at 400°C and 550°C for 1 hour in the presence of alkali halide, In
₃
Cl, Cu
₂
Cl, SeCl
₄
, and Se vapors. Increases in grain size of greater than 10× were observed with In
₃
Cl with Se, Cu
₂
Cl with and without Se, and SeCl
₄
at 550°C. Smaller magnitude grain size increases resulted at 400°C. Film composition was influenced by the vapors present with In
₃
Cl enhancing the In content and Cu
₂
Cl enhancing the Cu content. Based on XRD analysis, the In
₃
Cl+Se treatment best preserves the CIGS structure while resulting in a large amount of grain growth.