Investigation of conventional and pregettered multicrystalline silicon cells in terms of lifetime, diffusion length and defects

Diffusion lengths of minority carriers (L) are generally obtained by the SPV method. The method requires knowing the optical absorption coefficient α(λ), which depends on the stress strength and cannot be locally well determined. It is necessary to ascertain the mutual consistency of the local L measurements with that of lifetime τ and to correlate the local variations of L and τ with the presence of structural defects. Local measurements were made using arrays of small N⁺P mesa diodes realized in conventional and phosphorous pregettered solar cells. The lifetime was obtained from the small signal photovoltage decay and by the recovery time. An agreement is generally found for the variations of L and τ, especially for the phosphorous pregettered cells, in which the values of L and τ are higher due to a decrease of intragrain defect recombination strength. Discrepancies between L and τ, suggest the presence of local stresses