Science of Solar How Solar Cells Work

Stick out one of your arms and spin around in a circle. On a sunny day, this circle – about 2 square meters – contains enough solar energy to power your home. That’s a lot of potential!

Converting the sun’s power into electricity is a challenge that science has been working to solve since the late 1800’s. The first solar cell converted only 2% of the energy into power. Today, the solar cells used on rooftops can convert roughly 20% of the sun’s energy. In the lab, scientists have been able to capture up to 40%!

How do we capture this energy?

The best way to directly convert light to power is a solar cell.

A solar cell — or solar battery — is a sandwich of two silicon layers. The top layer is overloaded with too many electrons as (-) Type-N Silicon. The bottom layer is underloaded with too few electrons as (+), Type-P Silicon.

Because of the imbalance between the top and bottom layers, the electrons naturally want to move between the layers to restore balance.

When sunlight hits the electron, it’s a jolt of energy that motivates the electron to move. Now free and energized, the electrons in the negative (-) layer can jump through a wire to the underloaded positive (+) layer. This movement between negative and positive is a electric current.

This circulation of electrons is electricity!

Silicon and Solar

Pure silicon
Quartz Beach Sand (silicon + oxygen)

Over the years, many inventors have used different technology and materials to harness solar energy – including elements like Selenium (Se), Germanium (Ge), and Silicon (Si). Today, Silicon is the basis for most modern solar cells.

Silicon was ignored in electronics for many years because it’s properties were unique. Unlike other materials, it was not good at “insulating” electricity or a “conducting” electricity. However, it turned out to be excellent at doing both simultaneously; This is called a semi-conductor.

Silicon is the primary material used for solar cells. Most solar energy is generated using this element because:

  • It’s available! Silicon is the second most abundant element on earth.