Light Induced Degradation in mc-Si Based on Compensated Silicon

Light induced degradation caused by boron-oxygen related defects in boron doped Czochralski silicon is known to considerably reduce the solar cell conversion efficiency upon initial use. In multicrystalline silicon the minority carrier lifetime is determined by grain boundaries, twins, dislocations as well as intentional and unintentional contaminants. In addition to metallic impurities such as iron, chromium and copper, which are known to degrade the lifetime under illumination, boron doped multicrystalline silicon also contains oxygen. With increasing quality of the silicon feedstock BO-related degradation is becoming an increasingly important factor limiting the lifetime in multicrystalline wafers. Using photoluminescence-imaging the light induced degradation in mc-Si wafers based on compensated silicon are studied. High resolution lifetime maps allow for a spatial evaluation of the degradation across wafers.