Defect monitoring using scanning photoluminescence spectroscopy in multicrystalline silicon solar cell

Room-temperature scanning photoluminescence (PL) was applied to full-size as-grown and processed EFG wafers to investigate the evolution of low lifetime areas after different solar cell processing steps. PL mapping of the band-to-band PL intensity provides a means to identify low lifetime areas. In these areas we consistently observe an additional "defect" PL band with the maximum at about 0.8 eV attributed to dislocation networks. A simple approach of selectively monitoring the concentration of the defect centers is introduced. Consecutive solar cell processing steps gradually increase band-to-band and defect PL intensities due to lifetime upgrading. Concurrently, the rate of reduction of the defect concentration is much lower. We demonstrate here that PL approach offers a monitoring method for dislocations to characterize as-grown and processed multicrystalline Si.