TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The transparent conductive oxide (TCO) contact layer comprises indium tin oxide (ITO), aluminum doped zinc oxide (AZO), cadmium stannate, zinc indium oxide (Zn2In2O5), indium-tin-zinc oxide (In2-x-ySnxZnyO3), cadmium oxide or gallium oxide. The first conductivity type semiconductor layer(s) comprises a p-type copper indium selenide based alloy material absorber layer; and the second conductivity type semiconductor layer(s) comprises a n-type cadmium zinc sulfide, cadmium telluride, cadmium sulfide, zinc sulfide, or zinc magnesium oxide semiconductor layer. The first conductivity type semiconductor layer comprises a p-type copper indium gallium selenide absorber layer. The second conductivity type semiconductor layer comprises an n-type cadmium sulfide semiconductor layer; and the TCO contact layer comprises an AZO layer which has a higher resistivity at the first surface than at the second surface. The AZO layer has a constant aluminum content of 1.5-4 wt.% as a function of thickness. The oxygen concentration at the first surface of the AZO layer is 36-40 atom%. The oxygen concentration at the second surface of the AZO layer is 28-35 atom%. An ITO layer is located on the second surface of the AZO layer. Preferred Method: Forming the first conductivity type semiconductor layer(s) comprises forming a p-type copper indium selenide (CIS) based alloy material absorber layer; and forming the second conductivity type semiconductor layer(s) comprises forming a n-type cadmium zinc sulfide, cadmium telluride, cadmium sulfide, zinc sulfide, or zinc magnesium oxide semiconductor layer. Forming the first conductivity type semiconductor layer(s) comprises forming a p-type copper indium gallium selenide absorber layer. Forming the second conductivity type semiconductor layer comprises forming a n-type cadmium sulfide semiconductor layer; and forming the TCO contact layer comprises forming an AZO layer which has a higher resistivity at the first surface than at the second surface and which has a constant aluminum content in a range of 1.5-4 wt.% as a function of thickness.