Solar cells are thin, wafer-like electricity-producing devices composed of various semiconducting materials that are arranged in various structures to produce solar cells for optimum performance. The material most commonly used is crystalline silicon. When light strikes the cell, a portion of its energy is transferred to the semiconductor. The energy causes electrons to begin moving and flowing freely.

Photovoltaic cells also have one or more electric fields that act to force electrons “freed” by light absorption to flow in a certain direction. This electron flow produces a current, and by placing metal contacts on the top and bottom of the solar cell, that current can be drawn off and used externally.

The electron flow forms the current, the cell’s electric field causes a voltage, and power is the product of the two. Now, since silicon is shiny, an antireflective coating is applied to the top of the cell to reduce reflection losses. Then, a glass cover plate protects the cell from the elements. Since a single PV cell typically produces 1-2 watts of power, they are connected to form modules, which is achieved by connecting several cells in a parallel series to create useful levels of voltage and current. They are then put in a frame with a glass cover and positive and negative terminals on the back.

These modules are then combined to form arrays of different sizes and power output.
The size of an array depends on factors such as the amount of sunlight that reaches a particular region and consumer demand. The modules of an array, which resemble a large ice cube tray, make up the majority of a photovoltaic system. This system can also include mounting hardware, power conditioning equipment, and batteries that store solar energy for use when the sun isn’t shining.

To be effective, PV systems also require structures that can hold them and point them toward the sun, as well as components that will “condition” the direct-current electricity by converting it to alternate-current electricity to be stored for later use, usually in batteries. These items are referred to as the balance of system (BOS) components. Combining solar modules with these elements ultimately creates an entire PV system that can be used to meet the growing demand for renewable energy sources.