Indium-doped mono-crystalline silicon substrates exhibiting negligible lifetime degradation following light soaking

Indium doping of Cz and CCz mono-crystalline silicon has been investigated as a means to reduce lifetime degradation after light soaking in wafers and cells. The lifetime degradation is due to the formation of a metastable boron-oxygen complex (B-O pairs) during incipient carrier injection and is proposed to be the mechanism responsible for light-induced degradation in p-type solar cells doped with boron. At higher resistivity (ρ > 2 ohm cm), it is possible to produce indium-doped wafers with reasonable lifetimes and which show negligible lifetime degradation after light soaking. However, at low resistivity (ρ ≤ 2 ohm cm), substrates contain a small fraction of un-ionized indium that does not contribute to base doping, but rather acts as a recombination center.