Summary: Silicon cells are made from silicon wafers. Silicon wafers are in turn formed from polysilicon ingots.
You surely would have heard about solar cells. But did you know that the crystalline solar cells come from silicon wafers? Yes, wafers. So what are these wafers, how are they made and how are solar cells made from these wafers?
Silicon wafers are an intermediate product in the solar PV manufacturing process. These are made by slicing polysilicon ingots, usually by diamond tipped cutting saws.
A solar cell is made from a silicon wafer, which in turn is made from polysilicon ingots.
Wafers for use in solar PV systems are square in shape, and as of 2014, are as large as 200 mm and about 400 micrometer in thickness.
Each wafer will have a capacity of about 4-5 W.
Questions from the curious cat
Are the silicon wafers used for solar cells the same used to make computer chips?
Material-wise, the wafers used for solar cells are the same as those used for computer chips. The solar wafers used for making electronics is however more pure than the ones used for making solar cells.
Silicon wafers used in integrated circuits have a purity of “nine nines” 99.9999999%). As a solar cell does not the level of miniaturization that is present in integrated circuits, the purity requirements of wafers used in solar cells is 99.9999% to 99.99999% (6N to 7N).
What is the process by which wafers are made from ingots?
The starting point for silicon wafers is the polysilicon ingot. These ingots are sliced with a wafer saw. The result of this operation is a raw wafer, which is then polished. These polished wafers form the starting material for solar cells.
What is the size of a silicon wafer?
Silicon wafers used for making solar cells typically are square in shape, with about 200 mm each side. That makes them about 400 sqcm or about 65 sq inch. These are of course, average numbers.
What is the weight of a wafer?
A 200 mm size wafer will weight about 50 g.
What is the capacity of a wafer?
Commercially available silicon wafers currently (2014) have a wattage of 4-5 watts
How much do wafers cost?
Cost of wafers are of course a function of time. As of 2014, a silicon wafer that is about 4 W, is priced in the range US $1-1.3.
What are the machinery and equipment required to make wafers?
The main equipment that makes a silicon wafer from a polysilicon ingot is the cutting saw. These are high precision saws that incorporate an automated mechanism to slice wafers.
Some nice videos for you
Silicon wafer production video – really well done video, even without audio!
Excellent web resource
http://depts.washington.edu/chemcrs/bulkdisk/chem364A_spr05/handout_Silicon.pdf
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