How PV cells are made?
Very pure semiconductor-grade polysilicon (99.9999999% purity) is required for the process of fabricating conventional single and polycrystalline silicon PV cells.
The semiconductor-grade polysilicon is melted and trace amounts of boron are added to create a P-type semiconductor material.
An ingot or block of silicon is formed by using any of the two methods: a) pure crystalline silicon ingot is grown by seeding crystal drawn from the molten polysilicon or b) by casting the molten polysilicon in a block, creating a polycrystalline silicon material.
Then individual wafers are sliced from the ingots using wire saws and subjected to a surface etching process.
Wafers are placed in a phosphorus diffusion furnace after cleaning, creating a thin N-type semiconductor layer around the outer surface of the cell.
Then an anti-reflective coating is applied to the surface of the PV cell, and electrical contacts are patterned on the top (negative) surface of the cell.
An aluminized conductive material is deposited on the surface of the back (positive) side of the cell, restoring the P-type properties of the back surface by displacing the diffused phosphorus layer.
Every single cell is then electrically tested, sorted based on current output, and electrically connected and assembled to other cells in circuits for in photovoltaic modules.
Thin Film PV: Thin-film PV modules are mass-produced by depositing ultra-thin layers of semiconductor material on a glass or thin stainless-steel substrate in a vacuum chamber. A laser-scribing process is used to separate and weld the electrical connections between individual cells in a module. Thin-film PV materials offer great promise for reducing the materials requirements and manufacturing costs of photovoltaic modules and systems.