Abstract: Electron transport layer-free semi-transparent perovskite solar cells have excellent prospects for tandem solar cells.In this work, the electron transport layer-free semi-transparent perovskite solar cells were simulated using SCAPS software to analyze the key factors for device performance enhancement.The simulation results revealed that to obtain a high-performance device, the work function of front transparent conductive oxide (TCO) should be below 3.5 eV, and the work function of back TCO should be higher than 4.9 eV.Meanwhile, the defect density of perovskite layer should be reduced to below 1×10¹⁵ cm^-3.In addition, the defect density of states at the interfaces of TCO/CH₃ NH₃ Pb(I_0.775 Br_0.225)₃ and CH₃NH₃Pb(I_0.775Br_0.225)₃/Spiro-OMeTAD should be controlled to less than 1×10¹⁶ and 1×10¹⁹ cm^-3, respectively.