<p>In this study, as part of stable and greener alternatives, a lead-free Cs-based halide double perovskite solar cell (PSC) has been extensively studied with configuration of FTO/ZnOS/Cs₂AgBi_1-xSb_xBr₆/Cu_xO/Au by means of SCAPS-1D software. Here, ZnOS and Cu_xO has been proposed as electron transport layer (ETL) and hole transport layer (HTL). Both materials are non-toxic, have exceptional charge extraction efficiency, superior thermal stability, elevated carrier mobility and greater surface passivation properties, making it a promising alternative for PSCs with high performance and higher stability. The proposed structure was optimized by fine-tuning of thickness, bulk defect densities, and the shallow uniform donor and acceptor densities of the absorber, as well as impact of the properties of charge carrier transport layers, and the interfacial defect densities. The optimized PSCs exhibited excellent performance metrics with power conversion efficiency (PCE) = 23.81%, open circuit voltage (V_OC) = 1.46&#xa0;V, short circuit current (J_SC) = 18.12 mAcm⁻², and fill factor (FF) = 89.88%. Moreover, the performance of the proposed optimized PSCs was tested under the real environment via changing the light intensities. A deterioration of the performance with respect to lessening of incident light was recorded, which was anticipated. Furthermore, the study explored that a serious detrimental impact on QE due to the increase of bulk defect density. Further, the effect of ETL’s donor density on the C-V and M-S plots was analyzed and found that perovskite-ETL interface is well-matched which could help in enhancement of the PCE and elevate the stability of the PSC. The findings of the study imply that the ZnOS and Cu_xO are compatible with proposed halide double perovskite and can efficiently extract the charge carriers from the absorber layer. We believe that the finding of this study will aid in the fabrication of highly efficient and cost-effective Pb-free perovskite solar cells in the future.</p>