Wide-bandgap (AgCu)(InGa)Se2 absorber layers deposited by three-stage co-evaporation

Wide-bandgap (AgCu)(InGa)Se₂ absorber layers with Ga/(In+Ga) = 0.8 were deposited by a three-stage co-evaporation process using varying Se incident flux and stage-one substrate temperature. Films exhibited preferential (204)/(220) orientation and a Ga-deficient notch near the surface, both characteristics analogous to previously reported Cu(InGa)Se₂ films deposited using the same process. Increasing Se-to-metals molar flux ratio from Se/M ≈ 5 to Se/M ≈ 20 reduced process variability, but did not result in an overall improvement in device performance. Reducing stage-one substrate temperature from T_SS = 550 to T_SS = 400°C also did not affect device performance. Consistent with earlier results, Ag incorporation improved wide bandgap device efficiencies from η ≈ 8% with no Ag to η ≈ 12% with Ag/(Ag+Cu) = 0.75.