<p>The cesium tin chloride (CsSnCl₃) is an attractive absorber material for lead-free perovskite solar cells, whose performance is yet to be unlocked as the present fabrication method involves various types of defects in the device. The targeted study focused on a variety of different layer structures for ETLs (electron transport layers), such as TiO₂ (titanium dioxide)/C60 (fullerene) bilayer and TiO₂ (for comparison), combined with different HTLs (hole transport layers). The selected HTLs for the study were CBTS (copper barium thiostannate), Cu₂O (copper (I) oxide), Spiro-OMeTAD (2,2′,7,7″-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene), MoO₃ (molybdenum trioxide), NiO (nickel oxide), and WSe₂ (tungsten diselenide). It is demonstrated that WSe₂ and TiO₂/C60 are the top materials out of all HTL and ETL materials, correspondingly. Thus, the ITO/TiO₂/C60/CsSnCl₃/WSe₂/Au is the optimal structure of the PSC. In this work, SCAPS (Solar Cell Capacitance Simulator)-1D modeling was used to explore the bilayer ETL of inorganic CsSnCl₃–PSC for efficiency enhancement. In planar PSCs, the optimization of electron–hole pair extraction and recombination at the ETL/perovskite interface secures high performance. An effective strategy is enhancing the TiO₂/perovskite interface by inserting a 5 nm ultra-thin layer (UTL) of C60. The bilayer structure TiO₂/C60 shows the advantages of high electron extraction and reduced interfacial recombination, which are attributed to better energy level alignment and effective defect passivation. We thus pay special attention to several possible elements meant to enhance the device performance. All included are absorber thickness, defect density in the absorber layer, doping densities across all layers, electron affinity of HTL, interfacial defect densities on both sides of ETLs and HTL, capture cross-section in the absorber layer, back metal contact, and operating temperature. The performance metrics, after this optimization, are V_oc (open-circuit voltage) = 1.3679 V, J_sc (short-circuit current density) = 26.33 mA/cm², FF (fill factor) of 91.38%, and PCE (power conversion efficiency) of 32.92%. These promising results from this study may be relevant for further efficiency improvements in an in-depth analysis of the mechanisms for electron transport in CsSnCl₃–PSCs. Finally, it was able to be represented that these interfacial bilayers enhanced the photovoltaic properties and overall performance of PSC significantly. Therefore, this full simulation opens avenues toward research on cost-effective, highly efficient, and lead-free perovskite-based solar cells toward a sustainable, environment-friendly, and pollution-free future.</p>