Why are solar cells blue in colour?

Solar silicon wafers appear blue? To be precise, solar cells appear blue, and they are polycrystalline solar cells, while monocrystalline solar cells are usually black.

The reason why they are blue or black is because that colour is the effect of the Anti-reflected Coating (anti-reflective coating). Solar panels mainly absorb photons around the green wavelength of visible light, while solar panels are blue, which means that the light reflected is of the blue wavelength. Black is, of course, neither reflective. So black is best, blue is second best.

There is currently a pigmented sensitised solar cell, which is a cell in which pigment and electrolyte are added between two substrates with transparent electrodes on a glass or plastic substrate. With this technology, transparent cells and cells of various colours can be manufactured. None of these cells are very efficient, but they are cheaper than silicon ones.

A necessary step in the cell production process is PECVD, the purpose of which is to coat the surface of the silicon wafer with an anti-reflective film (silicon nitride) to reduce light reflection, the thickness of the coating is about 80um, due to the optical properties of the silicon nitride film makes its surface blue.