For mono-Si wafers, 158.75mm full square will become the most adopted design by the second half of the year. Only a few manufacturers use wafers that are larger than this. LG and Hanwha Q Cells, for instance, use M4 wafers (161.7mm), while Longi is promoting 166mm wafers.
The state-of-art Full Square Mono Wafers have maximized the light exposure to the same level of multi wafer by expanding the square measure. The wafers are always fully square so that they fit the PV module in an optimal way.
1 Material properties
Property | Specification | Inspection Method |
Growth method | CZ | |
Crystallinity | Monocrystalline | Preferential Etch Techniques（ASTM F47-88） |
Conductivity type | N-type | Napson EC-80TPN |
Dopant | Phosphorus | - |
Oxygen concentration[Oi] | ≦8E+17 at/cm3 | FTIR (ASTM F121-83) |
Carbon concentration[Cs] | ≦5E+16 at/cm3 | FTIR (ASTM F123-91) |
Etch pit density(dislocation density) | ≦500 cm-3 | Preferential Etch Techniques（ASTM F47-88） |
Surface orientation | <100>±3° | X-ray Diffraction Method (ASTM F26-1987) |
Orientation of pseudo square sides | <010>,<001>±3° | X-ray Diffraction Method (ASTM F26-1987) |
2 Electrical properties
Property | Specification | Inspection Method |
Resistivity | 0.3-2.1 Ω.cm 1.0-7.0 Ω.cm | Wafer inspection system |
MCLT (minority carrier lifetime) | ≧1000 μs(Resistivity 0.3-2.1 Ω.cm) | Sinton transient |
3 Geometry
Property | Specification | Inspection Method |
Geometry | Full square | |
Wafer Side length | 158.75±0.25 mm | wafer inspection system |
Wafer Diameter | φ223±0.25 mm | wafer inspection system |
Angle between adjacent sides | 90° ± 0.2° | wafer inspection system |
Thickness | 180 ﹢ 20/﹣10 µm; 170﹢ 20/﹣10 µm | wafer inspection system |
TTV (Total thickness variation) | ≤ 27 µm | wafer inspection system |
4 Surface properties
Property | Specification | Inspection Method |
Cutting method | DW | -- |
Surface quality | as cut and cleaned, no visible contamination, (oil or grease, finger prints, soap stains, slurry stains, epoxy/glue stains are not allowed) | wafer inspection system |
Saw marks / steps | ≤ 15µm | wafer inspection system |
Bow | ≤ 40 µm | wafer inspection system |
Warp | ≤ 40 µm | wafer inspection system |
Chip | depth ≤0.3mm and length ≤ 0.5mm Max 2/pcs; no V-chip | Naked eyes or wafer inspection system |
Micro cracks / holes | Not allowed | wafer inspection system |
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