Science → Solar Cells → 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.