How solar cells are made

Adjusted for inflation, solar modules cost $96 a watt in the mid-1970s and as little as 20 cents in 2020.

stations: 5
things upstream: 34
raw sources: 15
steps from the ground: 7

The short version

A solar cell is a thin silicon wafer with a p-n junction made by diffusing a thin n-type layer into the face of a lightly p-type wafer. A coating cuts reflected light, and metal contacts are printed on the faces. Cells made this way produce about half a volt each, and crystalline silicon makes up 95% of the market.

Saw thin wafers

Ingots of silicon are sliced into wafers. Square wafers for solar are 100 to 200 mm across and 100 to 500 micrometers thick.

Goes in
Silicon wafer
Diffuse the junction layer

The wafers are lightly p-type already. A hot diffusion of n-type dopants into the front face forms a p-n junction a few hundred nanometers below the surface, which pushes freed electrons in one direction when light hits.
Coat against reflection

An anti-reflective coating goes on the front, so the cell absorbs light instead of bouncing it back.
Print the metal contacts

Fine metal lines on the sunny face collect current, and a contact layer goes on the back.

Goes in
Silver Aluminum
Test and sort cells

Each cell is flashed with light and sorted by its output, so cells wired together later are well matched.