In this paper, the wx-AMPS simulation software is used to model and simulate the antimony selenide (Sb ₂Se ₃) thin film solar cells. Three different electron transport layer models (CdS, ZnO and SnO ₂) are applied to the Sb ₂Se ₃solar 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 Sb ₂Se ₃solar cell first increases and then decreases with the increase of the χ _e-ETL. The lower χ _e-ETLcreates a barrier at the interface between the electron transport layer and the Sb ₂Se ₃layer, which can be considered as a high resistance layer, resulting in the increase of series resistance. On the other hand, when the χ _e-ETLis 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 Sb ₂Se ₃layer becomes weak with the value of χ _e-ETLincreasing according to the band structure of the Sb ₂Se ₃solar 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-ETLcan 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-ETLof the Sb ₂Se ₃solar cell. Moreover, based on the optimization of the χ _e-ETL, the enhancement of the Sb ₂Se ₃layer material quality can further improve the solar cell performance. In the case of removing the defect states of the Sb ₂Se ₃layer, the conversion efficiency of the Sb ₂Se ₃solar 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/cm ², V _oc=0.59 V, FF=80.40%). The simulation results show that the Sb ₂Se ₃thin film solar cells can obtain excellent performance with simple device structure and have many potential applications.