Recombination parameters of lifetime-limiting carrier-induced defects in multicrystalline silicon for solar cells

In p-type multicrystalline silicon solar cells, carrier-induced degradation (CID) can cause up to 10% relative reduction in conversion efficiency. Although, a great concern has been drawn on this degradation in the photovoltaic community, the nature of this degradation is still yet unknown. In this contribution, the recombination parameters of the responsible defect causing this degradation are extracted via temperature and injection dependent lifetime spectroscopy. Three wafers from three different ingots were processed into cell precursor and lifetime structures for the study. Similar defect recombination parameters were obtained for all samples. Two candidates for the defect energy level were identified: E_t − E_i = −(0.32 ± 0.05) eV or E_t − E_i = (0.21 ± 0.05) eV in the lower and upper bandgap halves, respectively. The capture cross section ratios were found to be k = 56 ± 23 or k = 49 ± 21 for the lower and upper bandgap halves, respectively. Contrary to previous studies, these parameters have been extracted for the responsible defect of CID, without making assumptions regarding the defect energy level. The result allows to model and to predict the impact of this defect on the solar cell efficiency.