In this study, the conversion efficiency (CE), open-circuit voltage (VOC) and short-circuit current density (JSC) of wurtzite InxGa1-xN/ZnSnN2 core/shell quantum dot (QD) solar cells are studied by using the detailed balance model. The effects of strain and external electric field have been considered. The results show that with the increase of the core size, the VOC increases, while the JSC and CE decrease. With the increase of shell size or In content, the VOC decreases, while the JSC and CE increase. In addition, our calculations show that the band gap of QD increases due to strain, which leads to an increase of the VOC, but decreases of the CE and JSC. By contrast, the situation is opposite under the effect of external electric field.