<p>In this work, lead-free quantum dot solar cell based on AgBiS₂-ZnS-ZnSe dual-shell quantum dots is thoroughly investigated via the SCAPS-1D numerical simulator. The proposed device structure consists of ITO/SnO₂/BaTiO₃ (polarized)/AgBiS₂-ZnS-ZnSe/Li: NiO_x/Au, where thin polarized BaTiO₃ interlayer is introduced to enhance charge separation and suppress interfacial recombination. The comprehensive optimization of significant device parameters, such as absorber thickness, acceptor concentration, defect density, transport layer thickness and doping, dielectric permittivity, and operating temperature, was performed to explain their influence on PV performance. The results reveal that absorber engineering combined with polarization assisted interface modification leads to substantial performance enhancement. The optimal absorber thickness of 400&#xa0;nm, acceptor density of 10¹⁶ cm^-3, and low defect density of 10¹³ cm^-3 significantly suppress bulk recombination. The insertion of an ultra-thin 4&#xa0;nm BaTiO₃ layer with high dielectric permittivity generates strong polarization induced internal electric field, improving carrier extraction and junction quality. The optimization of the SnO₂ electron transport layer and Li: NiO_x hole transport layer thicknesses and doping concentrations results in outstanding PCE of 28.43%, with V_oc of 1.075&#xa0;V, J_sc of 32.72&#xa0;mA/cm², and FF of 80.84%. Comparative analysis of the initial and final JV and QE characteristics confirms significant improvements in charge collection and recombination suppression. This study demonstrates that polarization engineering combined with dual-shell quantum dot absorber design is highly effective strategy for achieving high efficiency, environmentally benign quantum dot solar cells.</p>