This study presents a comprehensive numerical investigation into solid-state quantum dot solar cells (SSQDSCs) utilizing P3HT poly(3-hexylthiophene) as both a hole transport and absorber layer employing SCAPS-1D simulation software, the research explores the performance of cells composed of FTO (Fluorine-doped Tin Oxide) as the front contact, integrated with different metal oxides (Titanium dioxide (TiO2), zinc oxide (ZnO), and tin dioxide (SnO2), CdS (Cadmium sulfide )quantum dots, P3HT, and Pt (platinum )as the back contact namely Hybrid solar cell. The thickness of each layer is systematically optimized, and the influence of various CdS quantum dots sizes is thoroughly examined. The study also dived into the characterization of interface defects at the P3HT/CdS junction, involving modifications to the electron affinity of P3HT. Additionally, the impact of metal work function variations was also investigated analyzing at each case critical parameters such as open-circuit voltage (VOC), short-circuit current density (JSC), fill factor (FF), power conversion efficiency (PCE) and quantum efficiency. The results demonstrate that optimization of these parameters has the potential to elevate solar cell efficiency to 18%. These simulation findings offer valuable insights for comparative analysis and a deeper understanding of the challenges encountered in experimental research.