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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

Intensity of the defect luminescence at 1,250 nm in the BSF. The intensity is clearly increased at the right side of the BSF, which indicates a higher defect density here. This could cause the low lifetimes at the interface between BSF and silicon bulk.
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Figure 6: Intensity of the defect luminescence at 1,250 nm in the BSF. The intensity is clearly increased at the right side of the BSF, which indicates a higher defect density here. This could cause the low lifetimes at the interface between BSF and silicon bulk.

Mentions: Figure 5b shows the effective Shockley-Read-Hall lifetime along a linescan. Lifetime values greater than 200 ns mean that the lifetime is solely limited by Auger recombination under the measurement conditions. At the interfaces between BSF and aluminum contact and BSF and silicon bulk we detected low SRH lifetimes. While this may be caused by the high surface recombination at the aluminum contact, the nature at the second interface is less clear. Therefore, we investigated this area with μPLS and showed an increased defect luminescence at 1,250 nm in this area (Figure 6), which is an indication for a higher defect density in this area, which could cause the drop in lifetime. Defect luminescence at 1,250 nm was observed in previous experiments on multicrystalline silicon at recombination active defects [6]. A more detailed analysis of the BSF can be found in [18].


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)

Intensity of the defect luminescence at 1,250 nm in the BSF. The intensity is clearly increased at the right side of the BSF, which indicates a higher defect density here. This could cause the low lifetimes at the interface between BSF and silicon bulk.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Intensity of the defect luminescence at 1,250 nm in the BSF. The intensity is clearly increased at the right side of the BSF, which indicates a higher defect density here. This could cause the low lifetimes at the interface between BSF and silicon bulk.
Mentions: Figure 5b shows the effective Shockley-Read-Hall lifetime along a linescan. Lifetime values greater than 200 ns mean that the lifetime is solely limited by Auger recombination under the measurement conditions. At the interfaces between BSF and aluminum contact and BSF and silicon bulk we detected low SRH lifetimes. While this may be caused by the high surface recombination at the aluminum contact, the nature at the second interface is less clear. Therefore, we investigated this area with μPLS and showed an increased defect luminescence at 1,250 nm in this area (Figure 6), which is an indication for a higher defect density in this area, which could cause the drop in lifetime. Defect luminescence at 1,250 nm was observed in previous experiments on multicrystalline silicon at recombination active defects [6]. A more detailed analysis of the BSF can be found in [18].

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