This work investigates the optical performance of the lead-free Cs3Sb2Br9-based perovskite solar cell (PSC) for the n-i-p and p-i-n structures by using the Transfer Matrix Method (TMM). The Cs3Sb2Br9-based n-i-p and p-i-n structures utilize Spiro-OMeTAD and PEDOT:PSS as the hole transport layer (HTL) and TiO2 and PCBM as the electron transport layer (ETL), respectively. The total absorption and the total reflection along with the generation and recombination rates for both structures are studied. It is shown that there is good absorption and poor reflection for the p-i-n structure as compared to the n-i-p structure which is due to the closer refractive index of the Cs3Sb2Br9 (absorber) layer and the HTL for the p-i-n structure. In addition, for the n-i-p structure, the generation rate is slightly high and the recombination rate is marginally low thus the net generation rate is high as compared to the p-i-n structure. This may be due to the longer optical path of incident sunlight into the absorber layer for the n-i-p structure. Finally, the influence of the optical current density by varying the thicknesses of the absorber layer, ETL, and HTL are analyzed. It concludes that the n-i-p structure expresses higher optical current density as compared to the p-i-n structure due to better carrier transportation by TiO2 instead of PEDOT:PSS. Moreover, TiO2 shows small changes in the optical current density by varying its thickness, whereas, PEDOT:PSS shows drastic variation in the optical current density by varying its thickness highlighting the poor carrier transportation of the top transport layer (PEDOT:PSS) for the p-i-n structure. Thus, it can be concluded from this work that the n-i-p structure exhibits superior optical performance with a maximum optical current density of 24.70 mA cm−2 and a maximum generation rate of 1.08 × 1022 cm−3 s−1. Thus, the n-i-p structure is advice for the excellent performance of the lead-free Cs3Sb2Br9-based PSC.