What is the photovoltaic effect?

When photons from sunlight hit a semiconductor material in a solar cell, they knock electrons loose from their atoms. The cell is designed with two layers of silicon doped with different impurities, creating a positive and a negative side (a p-n junction). The electric field at the junction pushes freed electrons toward the negative side, creating a flow of electric current. This was first observed by French physicist Edmond Becquerel in 1839, and modern silicon solar cells were developed at Bell Labs in 1954. Today’s best commercial panels convert about 20 to 25 percent of sunlight into electricity.