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Micro-spectroscopy on silicon wafers and solar cells.

Gundel P, Schubert MC, Heinz FD, Woehl R, Benick J, Giesecke JA, Suwito D, Warta W - Nanoscale Res Lett (2011)

Bottom Line: This is demonstrated on micro defects in multicrystalline silicon.In comparison with the stress measurement by μRS, these measurements reveal the influence of stress on the recombination activity of metal precipitates.With the aim of evaluating technological process steps, Fano resonances in μRS measurements are analyzed for the determination of the doping density and the carrier lifetime in selective emitters, laser fired doping structures, and back surface fields, while μPLS can show the micron-sized damage induced by the respective processes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstr, 2, 79110 Freiburg, Germany. paul.gundel@ise.fraunhofer.de.

ABSTRACT
Micro-Raman (μRS) and micro-photoluminescence spectroscopy (μPLS) are demonstrated as valuable characterization techniques for fundamental research on silicon as well as for technological issues in the photovoltaic production. We measure the quantitative carrier recombination lifetime and the doping density with submicron resolution by μPLS and μRS. μPLS utilizes the carrier diffusion from a point excitation source and μRS the hole density-dependent Fano resonances of the first order Raman peak. This is demonstrated on micro defects in multicrystalline silicon. In comparison with the stress measurement by μRS, these measurements reveal the influence of stress on the recombination activity of metal precipitates. This can be attributed to the strong stress dependence of the carrier mobility (piezoresistance) of silicon. With the aim of evaluating technological process steps, Fano resonances in μRS measurements are analyzed for the determination of the doping density and the carrier lifetime in selective emitters, laser fired doping structures, and back surface fields, while μPLS can show the micron-sized damage induced by the respective processes.

No MeSH data available.


Related in: MedlinePlus

Measurements on multicrytalline silicon. (a) PL intensity I1 (left side) in comparison to a PL imaging measured lifetime (right side) of the same wafer. Both measurements are in good qualitative agreement. An excerpt in the white square is further analyzed in (b) In both images denuded zones of 100-μm width with higher lifetimes are visible around the dark grain boundaries. (b) Micro-photoluminescence lifetime map of the quantitative Shockley-Read-Hall lifetime. The map shows three grain boundaries with distinctively different recombination properties. The upper right grain boundary is almost recombination inactive and hardly visible, whereas the grain boundary on the lower right side is highly recombination active, which can be attributed to a strong metal precipitate decoration.
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Figure 8: Measurements on multicrytalline silicon. (a) PL intensity I1 (left side) in comparison to a PL imaging measured lifetime (right side) of the same wafer. Both measurements are in good qualitative agreement. An excerpt in the white square is further analyzed in (b) In both images denuded zones of 100-μm width with higher lifetimes are visible around the dark grain boundaries. (b) Micro-photoluminescence lifetime map of the quantitative Shockley-Read-Hall lifetime. The map shows three grain boundaries with distinctively different recombination properties. The upper right grain boundary is almost recombination inactive and hardly visible, whereas the grain boundary on the lower right side is highly recombination active, which can be attributed to a strong metal precipitate decoration.

Mentions: After demonstrating the applicability of μRS and μPLS on technological structures, we continue with measurements on defects in multicrystalline silicon. For this, a 1 × 1 cm2 wafer is measured with micro-photoluminescence lifetime mapping. The PL intensity I1 with the large diameter is compared in Figure 8a to a PL imaging measurement. PL imaging is used here only for comparison and is explained in [19]. The images show a good qualitative agreement, even though μPLS measures under high injection and PL imaging measures in the low injection regime. This is due to the fact that high and low injection lifetimes are both proportional to the inverse defect density [20]. This highlights the usefulness of μPLS for the characterization of solar cells, which are typically working under low injection conditions. These results are discussed in detail in [7].


Micro-spectroscopy on silicon wafers and solar cells.

Gundel P, Schubert MC, Heinz FD, Woehl R, Benick J, Giesecke JA, Suwito D, Warta W - Nanoscale Res Lett (2011)

Measurements on multicrytalline silicon. (a) PL intensity I1 (left side) in comparison to a PL imaging measured lifetime (right side) of the same wafer. Both measurements are in good qualitative agreement. An excerpt in the white square is further analyzed in (b) In both images denuded zones of 100-μm width with higher lifetimes are visible around the dark grain boundaries. (b) Micro-photoluminescence lifetime map of the quantitative Shockley-Read-Hall lifetime. The map shows three grain boundaries with distinctively different recombination properties. The upper right grain boundary is almost recombination inactive and hardly visible, whereas the grain boundary on the lower right side is highly recombination active, which can be attributed to a strong metal precipitate decoration.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211253&req=5

Figure 8: Measurements on multicrytalline silicon. (a) PL intensity I1 (left side) in comparison to a PL imaging measured lifetime (right side) of the same wafer. Both measurements are in good qualitative agreement. An excerpt in the white square is further analyzed in (b) In both images denuded zones of 100-μm width with higher lifetimes are visible around the dark grain boundaries. (b) Micro-photoluminescence lifetime map of the quantitative Shockley-Read-Hall lifetime. The map shows three grain boundaries with distinctively different recombination properties. The upper right grain boundary is almost recombination inactive and hardly visible, whereas the grain boundary on the lower right side is highly recombination active, which can be attributed to a strong metal precipitate decoration.
Mentions: After demonstrating the applicability of μRS and μPLS on technological structures, we continue with measurements on defects in multicrystalline silicon. For this, a 1 × 1 cm2 wafer is measured with micro-photoluminescence lifetime mapping. The PL intensity I1 with the large diameter is compared in Figure 8a to a PL imaging measurement. PL imaging is used here only for comparison and is explained in [19]. The images show a good qualitative agreement, even though μPLS measures under high injection and PL imaging measures in the low injection regime. This is due to the fact that high and low injection lifetimes are both proportional to the inverse defect density [20]. This highlights the usefulness of μPLS for the characterization of solar cells, which are typically working under low injection conditions. These results are discussed in detail in [7].

Bottom Line: This is demonstrated on micro defects in multicrystalline silicon.In comparison with the stress measurement by μRS, these measurements reveal the influence of stress on the recombination activity of metal precipitates.With the aim of evaluating technological process steps, Fano resonances in μRS measurements are analyzed for the determination of the doping density and the carrier lifetime in selective emitters, laser fired doping structures, and back surface fields, while μPLS can show the micron-sized damage induced by the respective processes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstr, 2, 79110 Freiburg, Germany. paul.gundel@ise.fraunhofer.de.

ABSTRACT
Micro-Raman (μRS) and micro-photoluminescence spectroscopy (μPLS) are demonstrated as valuable characterization techniques for fundamental research on silicon as well as for technological issues in the photovoltaic production. We measure the quantitative carrier recombination lifetime and the doping density with submicron resolution by μPLS and μRS. μPLS utilizes the carrier diffusion from a point excitation source and μRS the hole density-dependent Fano resonances of the first order Raman peak. This is demonstrated on micro defects in multicrystalline silicon. In comparison with the stress measurement by μRS, these measurements reveal the influence of stress on the recombination activity of metal precipitates. This can be attributed to the strong stress dependence of the carrier mobility (piezoresistance) of silicon. With the aim of evaluating technological process steps, Fano resonances in μRS measurements are analyzed for the determination of the doping density and the carrier lifetime in selective emitters, laser fired doping structures, and back surface fields, while μPLS can show the micron-sized damage induced by the respective processes.

No MeSH data available.


Related in: MedlinePlus