<p>Cs₂AgBiBr₆, a lead-free double perovskite, has garnered significant research interest due to its high stability, non-toxicity, and superior optoelectronic properties. Specifically, among the double perovskite solar cells (DPSCs), hydrogenated Cs₂AgBiBr₆-based solar cells exhibited the highest efficiency. However, unoptimized energy-band alignment with the charge-transport layers (CTLs) and unoptimized absorber thickness hinder the hydrogenated Cs₂AgBiBr₆-based DPSC from attaining its full photovoltaic (PV) performance. In this work, we design and optimize a lead-free, complete inorganic hydrogenated Cs₂AgBiBr₆-based DPSC using SCAPS-1D based numerical simulations. We explore various inorganic hole-transport layers (CuSCN, NiO_x, CuGaO₂, MoO₃, CBTS) and electron-transport layers (SrTiO₃, In₂S₃, Zn₂SnO₄, Cr₂O₃, ZnO_0.3S_0.7) to achieve ideal energy alignment in the DPSC heterostructure. To explore the full PV potential, we perform a step-by-step optimization of various parameters, including the absorber layer thickness and bulk defect density, the CTL materials, defect densities at the interfaces, the parasitic resistances, and the back contact material of the hydrogenated Cs₂AgBiBr₆-based DPSC. Results indicate that CBTS is the best hole-transport layer (HTL) when used with all electron-transport layers (ETLs) investigated in this work, resulting in power conversion efficiencies of 26.65%, 22.73%, 20.9%, 24.43%, and 23.38% with ZnO_0.3S_0.7, Cr₂O₃, Zn₂SnO₄, SrTiO₃, and In₂S₃, respectively. Overall, this work provides an insightful strategy for further optimization and fabrication of high-performance hydrogenated Cs₂AgBiBr₆-based DPSCs.</p>