Analysis of Intra-Grain Defects in Multicrystalline Silicon Wafers by Photoluminescence Mapping and Spectroscopy

Highly spatial resolved photoluminescence (PL) characterization of intra-grain defects in recent multicrystalline Si wafers for solar cells was performed. Comparison of band-edge PL intensity mapping with minority carrier lifetime mapping on a whole wafer showed that low PL intensity regions correspond to short lifetime regions. PL microscopic mapping revealed that micron-sized defects are present in these regions. We also confirmed that grain boundaries are not active recombination centers. Low-temperature PL spectra were investigated, and dislocation-related lines, D1–D4, were observed only in the defect areas. We consider that these defects are ascribable to dislocations decorated with heavy metals and responsible for great degradation of lifetime.