6.+Silicon+Solar+Cell+Manufacturing

6.+Silicon+Solar+Cell+Manufacturing - April 14th, 2008 6....

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1 1 6. Manufacture of Silicon Solar Cells Brian E. Hardin Michael D. McGehee April 14 th , 2008 Recommended courses: EE212 Integrated Circuit Fabrication Processes with Prof. Plummer
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2 2 Today we focus on a very specific solar PV technology 90% of current PV market
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3 c-Si and mc-Si are made using similar processes. Multicrystalline Silicon (mc-Si) Produced via directional solidification. Crystalline Silicon (c-Si) Can be made with CZ or FZ processes.
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4 4 Si PV Processing (1) Quartz Metallurgical Grade Si (mg-Si) Solar Grade Silicon (SoG-Si) mc-Si c-Si (Siemens Process) (Directional Solidification) (CZ growth) (wafer sawing mc-Si and c-Si) To be discussed. Previously discussed.
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5 5 wafer processing PV Cell fabrication Module BOS + Installation (wafer sawing mc-Si and c-Si) (wafer doping, surface etching, electrode deposition etc.) PV cell interconnects + bypass diodes, encapsulation, etc. To be discussed Previously discussed. Si PV Processing (2)
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6 6 Metallurgical Grade Silicon Si is the 2nd most abundant element in the earth’s crust. Metallurgical grade Si (mg-Si) is made by heating sand in a furnace. SiO 2 + 2C→ Si + 2CO 1 million metric tons/yr of mg-Si is made for steel and aluminum mg-Si is 98-99 % pure. No shortage of mg-Si! Energy efficient process Lots of (very bad) impurities
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7 Siemens Process for Electronic Semiconductor Grade (eg-Si) and Solar Grade Si (SoG-si) Si + 3HCl → SiHCl 3 + H 2 Multiple fractional distillations are used to make the SiHCl 3 99.9999999% pure. The SiHCl 3 is exposed to a heated Si rod. SiHCl 3 + H 2 Si + 3HCl This process consumes a lot of energy.
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8 8 Si PV Processing (1) Quartz Metallurgical Grade Si (mg-Si) Solar Grade Silicon (SoG-Si) mc-Si c-Si (Siemens Process) (Directional Solidification) (CZ growth) (wafer sawing mc-Si and c-Si) To be discussed. Previously discussed.
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9 Making Single Crystal Ingots: Czochralski Growth (CZ) The semiconductor grade Si is melted with the dopant (B). A seed crystal is then slowly pulled from the melt. Oxygen dopes (~10 18 /cm 3 ) Si ingot because the quartz crucible is partially dissolved.
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6.+Silicon+Solar+Cell+Manufacturing - April 14th, 2008 6....

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