In this paper, the wx-AMPS simulation software is used to model and simulate the antimony selenide (Sb₂Se₃) thin film solar cells. Three different electron transport layer models (CdS, ZnO and SnO₂) are applied to the Sb₂Se₃ solar cells, and the conversion efficiencies of which are obtained to be 7.35%, 7.48% and 6.62% respectively. It can be seen that the application of CdS and ZnO can achieve a better device performance. Then, the electric affinity of the electron transport layer (χ_e-ETL) is adjusted from 3.8 eV to 4.8 eV to study the effect of the energy band structure change on the solar cell performance. The results show that the conversion efficiency of the Sb₂Se₃ solar cell first increases and then decreases with the increase of the χ_e-ETL. The lower χ_e-ETL creates a barrier at the interface between the electron transport layer and the Sb₂Se₃ layer, which can be considered as a high resistance layer, resulting in the increase of series resistance. On the other hand, when the χ_e-ETL is higher than 4.6 eV, the electric field of the electron transport layer can be reversed, leading to the accumulation of the photon-generated carriers at the interface between the transparent conductive film and the electron transport layer, which could also hinder the carrier transport and increase the series resistance. At the same time, the electric field of Sb₂Se₃ layer becomes weak with the value of χ_e-ETL increasing according to the band structure of the Sb₂Se₃ solar cell, leading to the increase of the carriers' recombination and the reduction of the cell parallel resistance. As a result, too high or too low χ_e-ETL can lower the FF value and cause the device performance to degrade. Thus, to maintain high device performance, from 4.0 eV to 4.4 eV is a suitable range for the χ_e-ETL of the Sb₂Se₃ solar cell. Moreover, based on the optimization of the χ_e-ETL, the enhancement of the Sb₂Se₃ layer material quality can further improve the solar cell performance. In the case of removing the defect states of the Sb₂Se₃ layer, the conversion efficiency of the Sb₂Se₃ solar cell with a thickness of 0.6 μm is significantly increased from 7.87% to 12.15%. Further increasing the thickness of the solar cell to 3 μm, the conversion efficiency can be as high as 16.55% (J_sc=34.88 mA/cm², V_oc=0.59 V, FF=80.40%). The simulation results show that the Sb₂Se₃ thin film solar cells can obtain excellent performance with simple device structure and have many potential applications.