Abstract: As an important branch of photovoltaic industry, semitransparent solar cells have broad application prospects in photovoltaic building integration, car sunroofs and wearable electronic devices. Antimony selenide (Sb₂Se₃) has attracted much attention in the field of thin film solar cells in recent years because of its stable chemical properties, high abundance and suitable band gap. Ultra-thin Sb₂Se₃ solar cells with absorption layer thickness of 90-160 nm were prepared by near-space sublimation method. Firstly, the relationship between the transparency and microstructure of the ultra-thin Sb₂Se₃ light-absorbing layer and the film thickness is explored. It is found that the thin Sb₂Se₃ light-absorbing layer has a low crystallization degree, which leads to high carrier recombination and restricts the photoelectric performance of Sb₂Se₃ solar cells. Based on this, the Sb₂Se₃ absorption layer was treated by vacuum high-temperature annealing process. After 10 min of vacuum annealing at 290 ℃, the crystallization degree of ultra-thin Sb₂Se₃ absorption layer was significantly improved, and a diffraction peak of (221) appeared, representing the longitudinal growth of (Sb₄Se₆)_n molecular chain. At this time, the built-in voltage of the device is increased to 0.442 V, the carrier transmission time is shortened to 1.431 μs, which effectively inhibits the recombination of carriers, and the photoelectric conversion efficiency of the 110 nm thick semitransparent Sb₂Se₃ solar cell is significantly increased from the unoptimized 0.8% to 3.03%. The research results provide a feasible technical route for the optimization and future development of semitransparent Sb₂Se₃ solar cells.