Many solar technologies have been, and continue to be, developed to harness energy from the Sun, an essentially unlimited source of free and environmentally friendly energy. One such technology—photovoltaic (PV) cells—converts sunlight into electricity without producing the harmful emissions that are a by-product of burning fossil fuels in traditional power plants. Typical PV cells are composed of several layers: two different layers of silicon, a metal backing, an antireflective coating, and metal conductor strips. As solar radiation hits the silicon, the energy knocks electrons loose from the silicon atoms; the free electrons then flow out of the cell along the metal conductor strips as electrical current.

PV cells are usually packaged in modules or panels, which are then connected to one another in arrays. PV cells have a variety of applications, from personal electronic devices (such as calculators, cell phone chargers, and bicycle lights) to utility-scale electricity generation at a power plant. Spacecraft and satellites also utilize PV cells to supply energy while in space. Other common uses on the ground include powering road signs, emergency telephones, streetlamps, and driveway lights. PV panels can also be installed to produce environmentally friendly electricity for homes and buildings. Homeowners who install PV systems in homes that are grid connected can sell their excess power to the grid. In addition, PV systems can provide electricity to rural areas that do not have access to the electrical grid.

The materials and manufacturing techniques used to make PV systems are expensive. High production costs, then, have kept the technology from becoming widely implemented. Despite incentives such as subsidies and tax credits, homeowners still have to pay significant initial costs. However, even though there may be higher initial costs to purchase and install a PV system, the system may pay for itself through fuel savings over the lifetime of its use. Furthermore, alternative materials and new technologies are being developed with the aim to reduce costs. For example, thin-film solar cells use less materials than traditional solar cells. These solar cells consist of a thin layer of semiconductor material applied to a supporting material such as glass, plastic, or metal. The reduction in materials needed to make these cells results in a reduction of cost. Researchers are also working on developing nanoparticles that can convert sunlight to electricity. This technology could possibly be used in something like a "solar paint."

Another limiting factor for PV systems is efficiency. Conventional PV cells convert into electricity only about 15 percent of the light that strikes them. At low efficiencies, larger arrays are needed to generate an adequate amount of electricity, and that means higher cost. Advances in PV technology aim to improve efficiency while also keeping production costs low.

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