EXPERIMENTAL INVESTIGATION OF A FAST METHOD FOR MEASURING THE INTERSTITIAL IRON CONCENTRATION IN P-TYPE MULTICRYSTALLINE SI SOLAR CELLS

摘要

Recently, we proposed a fast technique for measuring the interstitial Fe_i concentration (C_(Fei.ΔSR)) in multicrystalline silicon solar cells. This so called ΔSR/SR-method is based on the characteristic injection-level dependence of the Shockley-Read-Hall carrier diffusion length in p-type Si governed by Fe_i. Only the short-circuit current densities of the solar cells at a single near infrared wavelength at 2 known light intensities are measured. In this work the obtained C_(Fei.ΔSR) is experimentally compared with C_(Fei.L), which is the Fe_i concentration determined by measurements of the diffusion length before and after the Fe_i is paired with the boron dopant. As a result, C_(Fei.ΔSR) is higher than C_(Fei.L), because other impurities than Fe_i, which also bring about an injection-level dependence of the carrier diffusion length, are often present in mc Si at significant concentrations. Nevertheless, the ΔSR/SR-method is well suited for qualitative tests for these kinds of impurities in total. Therefore, valuable information about possible contamination originating from the raw wafers or the cell production line can be obtained very fast.