A solar cell includes a first electrode located over a substrate, at least one p-type semiconductor absorber layer located over the first electrode, the p-type semiconductor absorber layer comprising a copper indium selenide (CIS) based alloy material, an n-type semiconductor layer located over the p-type semiconductor absorber layer, an insulating aluminum zinc oxide layer located over the n-type semiconductor layer, the insulating aluminum zinc oxide having an aluminum content of 100 ppm to 5000 ppm and a second electrode over the insulating aluminum layer, the second electrode being transparent and electrically conductive. The insulating aluminum zinc oxide having an aluminum content of 100 ppm to 5000 ppm, may be deposited by pulsed DC, non-pulsed DC, or AC sputtering from an aluminum doped zinc oxide having an aluminum content of 100 ppm to 5000 ppm.