The relationship between minority carrier properties and solar cell characteristics of electromagnetic (EM) cast polycrystalline Si has experimentally been investigated. The minority carrier lifetime τ and diffusion coefficient D were evaluated by a novel dual mercury probe method. The solar cell characteristics, e.g., a conversion efficiency η were measured by fabricating experimental solar cells using the corresponding wafers. The wafer showing high-η (13.1%) has relatively high τ (av. 8.2 μs) with small variation of I) (av. 29.6 cm2/s). On the contrary, the low-η (11%) wafer shows low τ (av. 1.1 μs), including some inferior portions with very low τ of less than 0.5 μs. It is also shown that D drastically deteriorates with decreasing τ if τ is less than around 2 μs. To realize high efficiency polycrystalline solar cells, the wafers with high value of τ and without considerably low-τ portions are needed.