The passivation layers at the front of the cell are often referred as to the window layer because it must be transparent so as the solar cell has a high efficiency. In this work, numerical simulation has been proposed to study the effect of the AlGaAs gradual and normal windows on the cell sensitivity to the electron irradiation so as to passivate the solar cell. To expect the effect of gradual window layers, the J-V and P-V characteristics are confirmed better energy conversion performance of the illuminated solar cells after irradiation.The short circuit current J sc and the open circuit voltage V oc are evaluated for different electron irradiation fluencies. The results show how the gradual window layer improves resistance to electron irradiation through its own parameters.