A method according to claim 7, wherein two or more images are obtained of photoluminescence produced with different illumination intensities, and said interpreting step comprises calculating the injection level dependence of the bulk minority carrier lifetime.ġ1. A method according to claim 8, further comprising the step of correcting said at least one image for the angular dependence of the transmission of a filter used for the long-pass filtering.ġ0. A method according to claim 7, wherein the photoluminescence emitted from said at least one side facet is long-pass filtered to strengthen the dependence of the normalised photoluminescence intensity on bulk minority carrier lifetime.ĩ. A method according to claim 1, wherein the normalised photoluminescence intensity is converted to bulk minority carrier lifetime data using a predetermined empirical relationship.Ĩ. A method according to claim 2, wherein two or more images are obtained of photoluminescence produced with different illumination intensities, and said interpreting step comprises calculating the injection level dependence of the bulk minority carrier lifetime.ħ. A system when used to implement the method according to claim 1.Ħ. A method according to claim 3, further comprising the step of correcting said at least one image for the angular dependence of the transmission of a filter used for the long-pass filtering.ĥ. A method according to claim 2, wherein the photoluminescence emitted from said at least one side facet is long-pass filtered to strengthen the dependence of the normalised photoluminescence intensity on bulk minority carrier lifetime.Ĥ. A method according to claim 1, wherein the normalised photoluminescence intensity is converted to bulk minority carrier lifetime data using a predetermined theoretical relationship.ģ. A method of conducting an analysis of a silicon ingot or brick, said method including the steps of: (a) exciting at least one side facet of said silicon ingot or brick to produce photoluminescence (b) obtaining at least one image of the photoluminescence emitted from said at least one side facet and (c) interpreting said at least one image to identify variations in effective and/or bulk minority carrier lifetime in said ingot or brick, wherein the step of interpreting said at least one image comprises normalising the photoluminescence intensity within said at least one image with regard to variations in the background doping density of said ingot or brick, to identify variations in effective minority carrier lifetime in said ingot or brick.Ģ. The methods may find application in solar cell manufacturing.ġ. The methods are particularly useful for bulk samples such as bricks or ingots of silicon, where information can be obtained over a much wider range of bulk lifetime values than is possible with thin, surface-limited samples such as silicon wafers. In another embodiment, the effect of background doping density is removed by calculating intensity ratios of two PL measurements obtained in different spectral regions, or generated by different excitation wavelengths. In another embodiment the effective lifetime is measured by another technique, enabling PL measurements to be analyzed in terms of background doping density. In one embodiment the background doping density is measured by another technique, enabling PL measurements to be analyzed in terms of effective minority carrier lifetime. Methods are presented for separating the effects of background doping density and effective minority carrier lifetime on photoluminescence (PL) generated from semiconductor materials.
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