Multicrystalline silicon is the most used materialfor the production of silicon solar cells. The quality of the asgrown material depends on the quality of the feedstock andthe crystallization process. Bulk impurities, crystal defectslike dislocations and of course the grain boundaries determinethe material quality and thus the solar cell conversionefficiency. Therefore minority carrier lifetime measurementsare often done to characterize the material quality. Butthe measured values are from limited use because it is knownthat the solar cell process itself can dramatically change theminority carrier lifetime and the solar cell efficiency. In orderto obtain more detailed information of the behaviour ofdifferent defect types additionally high-resolution LBIC(light beam induced current)-measurements have been done.Since LBIC needs a pn-junction for photocurrent generationthe LBIC technique has been combined with the a-Si/c-Siheterojunction cell process, which makes it possible tomanufacture solar cells even from as cut wafers withoutchanging the material quality. With this combination ofmeasurement and preparation techniques it was possible toanalyze the influence of the diffusion process and the firingprocess on the behaviour of the three different defect types: grain boundaries, dislocation networks and bulk impurities.