Stannous sulfide (SnS) was investigated as an absorbing layer for solar cells due to its suitable electrical and optical properties. Spiro-OMeTAD is commonly employed as a hole transport layer to enhance the performance of solar cells. The ZnS / SnS / Spiro-OMeTAD solar cell was designed and simulated by the wxAMPS software. The effects of the Spiro-OMeTAD hole transport layer on the properties of solar cells were mainly studied, namely the effects on open-circuit voltage, short- circuit current density, filling factor, photoelectric conversion efficiency and quantum efficiency. The results show that the open-circuit voltage of the ZnS / SnS / Spiro-OMeTAD solar cells increase to 0. 958 V and short-circuit current increase to 32. 96 mA/ cm2 when the Spiro-OMeTAD HTL is added. The fill factor and photoelectric conversion efficiency are 79. 26% and 25. 07% , respectively. The performance of the solar cells depends on the thickness of each layer, doping concentration, Gaussian defect state density, and temperature. The results demonstrate that the Spiro-OMeTAD, as a hole transport layer, is beneficial for enhancing various performance aspects of solar cells. Moreover, the ZnS / SnS / Spiro-OMeTAD exhibits a great potential as a photovoltaic device structure.