Photovoltaic conversion generates electricity directly from sunlight. Certain materials have the property to produce electric flow when they are subjected to sufficient amounts of light. When formed into cells, they are called photovoltaic or PV cells. They are also sometimes called solar cells. Materials used in PV cells include silicon and more complex composites such as copper indium diselenide, cadmium telluride, and gallium arsenide.
PV cells convert light energy to electricity as follows:
When light strikes the cell, its energy is absorbed by the semiconductor and knocks loose electrons. The PV cells are designed with layers of slightly different materials that make the loose electrons flow in a specific direction. This is what creates an electric current. Metal contacts are placed at the edges of each cell allowing this current to be drawn off for external use.
For most uses, multiple PV cells are connected and combined into a module that contains dozens of cells held within a frame. The module is then covered with glass. Positive and negative terminals are connected to the contacts from outside the frame to direct the electron flow. Multiple modules can be combined into an array to obtain the amount of power desired at a specific installation. The electricity produced from PV cells is DC, or direct current, electricity. It can be used directly in a DC appliance, stored in batteries, or converted to alternating current (AC) with an inverter to operate AC appliances or for delivery into the electric grid.