How solar cells work?

First, we will look at hydro dams. Hydro dams are gigantic solar cells.

The sun shines on water. Some water molecules absorb photons and gain enough energy to jump out of water. They rise to the sky, fall down as rain, and some of them end up in a lake circled by the dam. Then water flows down the dam to generate electricity.

Solar cells are diodes. They contain PN junctions, which are energy dams.

The sun shines on solar cells. Some electrons absorb photons and gain enough energy to jump over the dam, or the PN junction. Then those high energy electrons flow over the wires to form electric currents, doing all kinds of works.

Semiconductors do all sorts of communication works. Solar cells generate electricity from light. LED generate light from electricity. All these devices are based on silicon. All are based on PN junction. 

In periodic table, silicon is in the same group of carbon, the backbone of life. It is right below carbon. In constructing PN junction, the P (positive) junction uses B, left to the group of carbon and silicon, the N (negative) junction uses P, right to the group of carbon and silicon. So B is in group three. Silicon is in group four. P is in group five.