Relationship Between Minority Carrier Parameters and Solar Cell Characteristics of Electromagnetic Cast Polycrystalline Silicon

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.