Abstract A novel dopant-free ZnS/p-Si heterojunction solar cell with WO3 thin films as hole-selective contact was fabricated using thermal evaporation method. The obtained maximum power conversion efficiency (PCE) of 10.94% is the highest recorded value for ZnS/p-Si heterojunction solar cells, to the best of our knowledge. The transfer line matrix (TLM) measurements indicate that the contact between WO3 thin films and p-Si is ohmic behavior, with a contact resistivity (ρc) of 12.7 mΩ cm2. The forming mechanism of the ohmic contact behavior between WO3 thin films and p-Si was explained from the aspect of energy band. A power-loss analysis based on the ZnS/p-Si heterojunction solar cell was carried out for the first time. The results reveal that shading loss, NIR parasitic absorption, and base collection loss occupy the main optical loss pathways, while the bulk resistance of the undoped ZnS thin films and the finger contact resistivity are the most limiting series-resistance components. Minority-carrier lifetime measurments of p-Si, which was passivated with polystyrenesulfonate (PSS) thin films, indicate that the poor quality of p-Si is likely responsible for the shunt-resistance loss. Based on the power-loss analysis, several optimization strategies are proposed.