Sunlight is composed of photons, or particles of solar energy. These photons
contain various amounts of energy corresponding to the different wavelengths of
the solar spectrum. When photons strike a photovoltaic cell, they may be
reflected, pass right through, or be absorbed. Only the absorbed photons provide
energy to generate electricity. When enough sunlight (energy) is absorbed by the
material (semiconductor), electrons are dislodged from the material's atoms.
Special treatment of the material surface during manufacturing makes the front
surface of the cell more receptive to free electrons, so the electrons naturally
migrate to the surface. When the electrons leave their position, holes are
formed. When many electrons, each carrying a negative charge, travel toward the
front surface of the cell, the resulting imbalance of charge between the cell's
front and back surface creates a voltage potential like the negative and
positive terminals of a battery. When the two surfaces are connected through an
external load, electricity flows.