Optical and quantum efficiency analysis of (Ag,Cu)(In,Ga)Se2 absorber layers

(Ag,Cu)(In,Ga)Se
₂
thin films have been deposited by elemental co-evaporation over a wide range of compositions and their optical properties characterized by transmission and reflection measurements and by relative shift analysis of quantum efficiency device measurements. The optical bandgaps were determined by performing linear fits of (ahv)
²
vs. hv, and the quantum efficiency bandgaps were determined by relative shift analysis of device curves with fixed Ga/(In+Ga) composition, but varying Ag/(Cu+Ag) composition. The determined experimental optical bandgap ranges of the Ga/(In+Ga) = 0.31, 0.52, and 0.82 groups, with Ag/(Cu+Ag) ranging from 0 to 1, respectively. The optical bowing parameter of the different Ga/(In+Ga) groups was also determined.