Evaluation of processing steps regarding lifetime of iron/copper contaminated mc Si wafers

Abstract

It is well known that gettering and passivation steps during solar cell processing enhance the minority charge carrier lifetime (here simply referred to as lifetime) in the silicon wafers. The purpose of this work is to study the influence of different solar cell processing steps on lifetime depending on the impurity level. Therefore neighboring wafers of standard multicrystalline as well as differently contaminated ingots were treated with various POCl3-diffusion and/or hydrogenation steps. The sequence of treatments is varied to check the effect of each processing step individually and to investigate if an individual processing step is less or more effective if another step was applied before. Afterwards these wafers were examined by microwave photoconductance decay measurements (μPCD). The gained results might be important for defect engineering and the development of an optimized solar cell process on cost effective and impurity-rich silicon material to reduce the detrimental impact of metal impurities on solar cell parameters.