Microscopic Distributions of Defect Luminescence From Subgrain Boundaries in Multicrystalline Silicon Wafers

• Main Authors: Samundsett, Christian (Author), Sio, Hang C. (Author), Lai, Barry (Author), Li, Li (Author), Nguyen, Hieu T. (Contributor), Jensen, Mallory Ann (Contributor), Buonassisi, Anthony (Contributor), MacDonald, Daniel G (Contributor)
• Other Authors: Massachusetts Institute of Technology. Department of Civil and Environmental Engineering (Contributor), Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science (Contributor), Massachusetts Institute of Technology. Department of Mechanical Engineering (Contributor)
• Format: Article
• Language: English
• Published: Institute of Electrical and Electronics Engineers (IEEE), 2018-11-19T15:32:48Z.
• Subjects: Article
• Online Access: Get fulltext

 We investigate the microscopic distributions of sub-band-gap luminescence emission (the so-called D-lines D1/D2/D3/D4) and the band-to-band luminescence intensity, near recombination-active subgrain boundaries in multicrystalline silicon wafers for solar cells. We find that the sub-band-gap luminescence from decorating defects/impurities (D1/D2) and from intrinsic dislocations (D3/D4) has distinctly different spatial distributions, and is asymmetric across the subgrain boundaries. The presence of D1/D2 is correlated with a strong reduction in the band-to-band luminescence, indicating a higher recombination activity. In contrast, D3/D4 emissions are not strongly correlated with the band-to-band intensity. Based on spatially resolved, synchrotron-based micro-X-ray fluorescence measurements of metal impurities, we confirm that high densities of metal impurities are present at locations with strong D1/D2 emission but low D3/D4 emission. Finally, we show that the observed asymmetry of the sub-band-gap luminescence across the subgrain boundaries is due to its inclination below the wafer surface. Based on the luminescence asymmetries, the subgrain boundaries are shown to share a common inclination locally, rather than being orientated randomly.