Defects in the Absorber Layer and other layers of the interlayer in Cadmium Telluride (CdTe) cells are detrimental to their efficiency and stability, the present work will focus on investigating the effect of these defects on their electrical properties (I-V), this work was chosen to simulate solar cells using SCAPS-ID program. The solar cell consisted of Cadmium Telluride (CdTe) as an Absorber layer with a thickness of 0.25µm and a Windows layer (CdS:O) with a thickness of 0.025µm and Buffer Layer (Zn₂SnO₄) with a thickness of 0.05µm a Transparent Conduction Oxide (FTO) Layer with a thickness of 0.1µm and a Back Reflection layer (Cu₂Te) with a thickness of 0.1µm. The best results obtained were: {V_oc=0.85V, J_sc=38.07 mA/cm², FF=86.37%, h=28.07%}, the results showed that when the defect density of the Absorbent Layer varied from (1×10⁹cm^-3) to (1×10¹⁸ cm^-3) while keeping the other cell parameters unchanged, as well as the defect density for the rest of the layers of the solar cell it was observed that cell parameters were significantly reduced at high defect densities. Also, the defect intensity was changed in each of the Window Layer and the Back Reflection Layer separately, while keeping the rest of the parameters in the other layers the same. The density of defects in the interlayer was also changed while fixing the rest of the parameters, and the results were similar to what we obtained in the Absorption Layer, where with high concentrations of defects the cell parameters decrease significantly.