LAUSR

The Ag-Cu-In-Ga (ACIG) material system has been investigated over a composition range used for reaction to form (Ag,Cu)(In,Ga)Se2 thin films for photovoltaic application. ACIG thin films were sputter deposited from Ag 0.77Ga0.23, Cu0.77Ga0.23, and In targets using different layer sequences with Ag/(Cu + Ag) and (Ag + Cu)/(Ga + In) ratios fixed at 0.25 and 0.90, respectively. The most uniform morphology was achieved with a Ag-Ga layer followed by a layer with co-sputtered Cu-Ga and In. Varying the sputtering sequence for stacked layers resulted in dissimilar morphologies and structural phases. X-ray diffraction analyses revealed that Ag-Ga and In layers intermix to form the (Ag,Cu)In2 phase in all Ag-containing samples except one with a Ag-Ga/Cu-Ga/In sequence. In addition, precursors were shown to be unstable during storage at room temperature, where a secondary (Ag,Cu*)In2 phase with higher Cu content formed. Finally, phase composition of the precursors annealed at 300°C was characterized.