The electron transport layer (ETL) is linchpin in perovskite solar cells (PSCs). It offers potent and discriminatory electron elicitation, minute resistivity, and lofty strength along with optimal device performance. In this study combined DFT and SCAPS-1D framework are used to investigate the optimized designs of CH₃NH₃Pb(I_1-xCl_x)₃ organic-inorganic perovskite-based solar cells. The analysis of structural stability, mechanical strength and optoelectronic traits was done by employing first-principle calculations with three different exchange-correlation functionals for A₂SnO₄(A = Sr, Ba) Ruddlesden-popper (RP) compounds. SCAPS-1D was used to analyze device performance by employing different ETLs in PSC architecture. The structural analysis reveal that Sr₂SnO₄ possesses a more stable structure in tetragonal phase with space group I4/mmm (139) than Ba₂SnO₄. Mechanical stability is corroborated through the reckoning of elastic constants, with Sr-based RP perovskite showing better mechanical properties as compared to Ba-based RP perovskite enunciating it auspicious for device fabrication. Electronic properties, analyzed through the band structure (BS) and density of state (DOS), confirm the semiconducting nature of both materials, with indirect band gap of 4.59 eV (Ba₂SnO₄) and 4.21 eV (Sr₂SnO₄). The optical analysis has stipulated that both materials are found to be good absorbers of ultraviolet (UV) radiation. An optimized device FTO/Sr₂SnO₄/MAPb(I_1-xCl_x)₃/Cu₂O/Au is contemplated here with an open-circuit voltage (Voc) of 1.257 V, a short-circuit current (Jsc) of 23.06 mA/cm2, fill factors (FF) of 83.57 %, and a theoretical power conversion efficiency (PCE) of 24.25 %. Overall, our findings reveal that Sr₂SnO₄ RP material have promising and potential features as a novel ETL material for employment in organic-inorganic PSC as a source of renewable energy.