Spatially resolved emitter saturation current by photoluminescence imaging

Heavily doped regions (in particular emitters) in silicon wafer solar cells are a major source of recombination which limits the open-circuit voltage, the short-circuit current and hence the efficiency. These regions are typically characterized by the emitter saturation current density, which is commonly calculated from the plot of the inverse effective lifetime (corrected for Auger recombination) as a function of minority carrier concentration. In this paper we present a simple spatially resolved emitter saturation current density measurement method which is based on photoluminescence imaging. The spatially averaged values obtained by the proposed method were found to be in a good agreement with the ones obtained by the standard photoconductance-based method. The application of the method to a selective emitter solar cell structure is demonstrated.