Characterization of (AgCu)(InGa)Se-2 Absorber Layer Fabricated by a Selenization Process from Metal Precursor

In this paper, the effects of Ag-alloying in the selenization of metal precursors to form (AgCu) (InGa)Se-2 are investigated. Metal precursors with different structures were prepared by sputtering from Cu0.77Ga0.23, Ag, and In targets. The phases and the composition of the precursor films were evaluated by X-ray diffraction, scanning electron microscopy (SEM), and energy dispersive X-ray spectrometry. The addition of a Ag layer between the Mo and Cu-Ga-In layers resulted in much less islanding of In-rich phases than typically observed in sputtered Cu-Ga-In films. Selenization at 475 degrees C of Ag-containing precursors resulted in better adhesion than precursors without Ag. After the selenization reaction, Ag and Cu were uniformly distributed through the film, although Ga remained near the back of the film, as was observed in precursors without Ag. A (AgCu)(InGa)Se-2-based solar cell with 13.9% efficiency was demonstrated.