Solar photovoltaic cells are made of polycrystalline silicon. The process of developing those cells start with a very pure semiconductor polysilicon. It is processed from quartz, which is used heavily within the electronics industry. [1] , [2]

     Next, the polysilicon is melted by being heated to a temperature above the melting point. In order to create P-type semiconductor material, trace amounts of boron is added to the melted polysilicon. A block of silicon, also known as an ingot, is created in two different ways; one is to grow crystals from a seed crystal that originated from the melted polysilicon while the other is to cast melted polysilicon into a block. Each individual wafers are sliced from the ingots via wire saws before being cleaned as they are subject to the surface etching process. Once the wafers are cleaned, they become thin N-type semiconductor layers around the entire exterior cell surface by being placed into a phosphorus diffusion furnace. An anti-reflective coating is then placed at the top surface of the cell. Electrical contacts are marked on the top surface, which becomes a negative charge. On the positive (back) side of the cell, a conductive (aluminized) material is placed to restore the P-type properties of the back surface. This would later displace the diffused phosphorus layer. Before the cells become usable, it must be tested electronically to determine whether it works properly, based on the current output and electrical connection to other cells. This would then form cell circuits ready to be assembled. Below is a flow chart which shows the polysilicon manufacturing process. [1], [3]

Primary author: Amos Han

Editor: Apratim Mukherjee