Know Your Solar: Why Silicon? And How is Power Generated in a Solar Cell?

Silicon has four electrons in its outer shell. However, it has the capacity to hold eight. By sharing these four electrons with other silicon atoms and their four shell electrons, the capacity of eight is filled. When they combine with each other in this way, silicon atoms develop a strong, stable bond. This structure is known as pure, crystalline silicon.

Pure silicon is a poor conductor of electricity, as there are no electrons free to move about. In other words, the silicon is better off with impurities. To create these impurities, silicon is combined with something else.

When silicon combines with an element that has five electrons to share, such as phosphorus, a negative charge is created. Silicon can only take four of the five electrons. This leaves one free electron looking for a spot. These additional electrons are known as free carriers; they carry an electrical current.

When silicon is combined with an element that has three electrons, a positive charge is created. Boron is a material which suits this purpose. When silicon and boron are combined, holes are created. These silicon combinations and their differing charges are used to make solar panels. As photons come down from the sunlight and strike the silicon, it shakes everything up. The free electron that was hanging onto the silicon/phosphorus combination is now forced to the outer ring. From here, it gets sucked up to the outer ring of the silicon/boron combination. Direct current (DC) electricity is created that can be sent “directly” to a battery in a DC system or to an inverter for AC (household plug in the wall) power. An inverter connected to a battery makes for an easy do it yourself system.