In this paper, an initial model based on a CIGS experimental device has been established. Afterwards, the conventional i-ZnO layer replaced by ZnO1-xSx or Zn1-yMgyO layers as window layer and the solar cell performance analyzed. The estimated optical bandgap (Eg) of Zn1-yMgyO material is linearly enhanced from 3.3 eV for pure ZnO to 4.1 eV for Zn0.6Mg0.4O. Also, Eg for ZnO1-xSx material is variable between 2.83 eV–3.76 eV that is wider than pure ZnO. The AlZnO/ZnO1-xSx/CdS/CIGS structure when 0.4 < x < 0.6 and the AlZnO/Zn1-yMgyO/CdS/CIGS structure when 0.055 < y < 0.2 are the proposed solar cells with 21.15% efficiency.