Solar Silicon Wafers 125mm & 150mm Psuedo Squares

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Thin Float Zone SIlicon for Solar Applications

monocrystal solar silicon wafers

Researchers have discovered that the thinner a silicon wafer is the more efficient.

Ask for Item#253540

 2” and 3” diameter, float-zone, Si(100), n-type 1-5 Ohm-cm 20 microns thick

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Solar Wafers with PN Junction

Researchers asks: I was just wondering whether the “Solar” products have a PN junction already (i.e. product ID 2920). If not, do you stock any products with a PN junction?

UniversityWafer Answer:

1) For solar application, P/N junction is typically made with a diffusion process. We do have a diffusion facility capable of creating junctions on wafers with diameter up to 4". Please let us know if you are interested in going into the project on a smaller diameter wafers.

2) We also have Si wafers with P/N junctions created by silicon on silicon epitaxial deposition method. Please ask for our inventory.

Solar Silicon Wafers

Summary of Solar Cell Production, and Limiting Efficiency of Silicon Solar Cell

Limiting Efficiency

It has been well established that the limiting efficiency of single crystals falls at about 29% [Swanson] this limit was established in the seminal work by Tiedje. In figure 1 we can see this limiting efficiency as a function of solar cell thickness. In this diagram, the peak efficiency is shown to be 29% with a thickness of just under 100µm.

Typical production solar cells achieve about 20% efficiency, while the best laboratory efforts have achieved about 25% [Swanson]. Green provides an excellent summary of the current progress of high-efficiency single-crystal silicon solar cells, and reconfirms the 29% limit established by Tiedje.

Production Process.

The process of manufacturing solar cells from single crystal p-type silicon wafers is detailed below.  This is the generalized method used based on a number of sources. It should be noted that different companies have different patented, and trade secret processes for each of these steps, but the steps remain the same.

Texturing:

After an initial cleaning procedure, the wafer is textured to create pyramid-like structures on the surface of the silicon. This causes incoming sunlight reflected off of one pyramid to bounce into other pyramids on the surface improving the overall sunlight absorption rate.

N doping (usually Phosphorous):

A variety of methods are used to dope the top surface of the P-type wafer to create N-type regions. This process (typically gas diffusion in a high-heat furnace) creates the critical p-n junction which forms the permanent electrical field.

 

Edge diffusion cleaning:

The doping process causes the phosphorous dopant to diffuse to the edges of the wafer, if this excess dopant was allowed to remain it would cause short circuiting between the positive and negative contacts of the solar cell. The excess dopant is removed by an acid-etching procedure.

Anti-reflective coating

The wafer is then given an anti-reflective coating, usually silicon nitride, to improve absorption.

 

Screen printing of front and rear surface contacts

In the final step of the production process, front and rear surface contacts are screen printed onto the surface of the wafer to create the positive and negative contacts of the solar cell. The solar cells are then ready to be wired together to create solar panels.

References

1.) Tiedje et al; Limiting Efficiency of Silicon Solar Cells: https://optoelectronics.eecs.berkeley.edu/ey1984ieeeed315.pdf

2.) M.A Green; Progress and outlook for high-efficiency crystalline silicon solar cells https://144.206.159.178/FT/957/22841/412931.pdf

3.) Swanson, R.M; Approaching the 29% limit efficiency of silicon solar cells

4.) Solar Cell production process https://www.photonics.com/Article.aspx?AID=40098

5.) Solar cell production video:  https://www.youtube.com/watch?v=TRATu_wEgAY

6.) Solar Cell production video: https://www.youtube.com/watch?v=fZ1SC-vUe_I

156 Mono Solar Cells

We have the following 156.75mm x 156.75mm +/-0.25mm substrates.

Dimension 156.75mm x 156.75mm + 0.25mm
Diagonal 210mm + 0.5mm (Round Chamfers)
Thickness 200um + 20um
Front Anisotropically texturized surface and dark silicon nitride anti-reflection coatings
  0.7mm silver busbars
Back local aluminum back-surface field
  1.7mm (silver/aluminum) discontinuous solderng pads
156mm x 156mm mono solar cell
monocrystalline solar wafer specs
mono crystal solar cell drawing
Production and Quality Control
Precision cell efficiency sorting procedures
Stringent criteria for color uniformity and appearance
Reverse current and shunt resistance screening
ISO9001, ISO14001, and OHSAS 18001 certificated
Calibrated against Fraunhofer ISE
Electrical Performance
Efficiency Code 216 215 214 213 212 211
Efficiency 21.6 21.5 21.4 21.3 21.2 21.1
  5.28 5.25 5.23 5.2 5.18 5.16
Max. Power Current 9.29 9.26 9.24 9.22 9.2 9.19
  9.76 9.73 9.72 9.69 9.67 9.66
Max. Power Voltage 0.568 0.567 0.566 0.564 0.563 0.562
  0.667 0.666 0.665 0.664 0.663 0.682
Efficiency Code 210 209 208 206 204 202
Efficiency 21 20.9 20.8 20.6 20.4 20.2
Power 5.13 5.11 5.06 5.03 4.98 4.94
Max Power Current 9.16 9.14 9.12 9.07 9.03 8.99
Short Circuit Current 9.64 9.62 9.6 9.56 9.52 9.49
Max Power Voltage 0.56 0.559 0.557 0.555 0.552 0.55
Open Circuit Voltage 0.661 0.66 0.658 0.656 0.654 0.652
Temperature Coefficients
Current Temp Coefficients 0.04%/C
Voltage Temp Coefficients -0.32%/C
Power Temp Coefficients -0.42%/C