Photovoltaics

Photovoltaics (PV) refers to the renewable energy methods and technologies employed to convert any form of light, including sunlight (solar energy), into direct current (DC) electricity. Photovoltaics is capable of generating renewable electricity from the most abundant renewable energy source, sunlight, and is responsible for the annual global generation of gigawatt-hours (GWh) of electricity from gigawatts (GW) of globally installed capacity.

Individual PV installations generate watt-hours (Wh) to megawatt-hours (MWh) of electricity at 4% to 20% efficiency. Photovoltaics was founded through the discovery of the photovoltaic effect by Bell Telephone Laboratory researchers in 1954 using silicon wafers. In addition to common crystalline silicon PV, thin film PV has also been developed as a field of technology. The first applications of PV were for satellites and remote or “off-grid” power generation. Photovoltaics also found common application in calculators before becoming a grid-connected option for generating electricity on rooftops, building-integrated systems (BIPV), and utility-scale power plants. In the future, PV may be used to generate electricity from clothing, bags, consumer appliances and vehicles. Along with wind, hydroelectric, biomass and concentrating solar thermal power (CSP), photovoltaics is a leading renewable energy technology .

Through the photovoltaic effect, electrons in the semiconductor (photoactive) material are energized by photons from incident solar or simulated light and ejected to form a direct current and corresponding voltage. The most common semiconductive materials that have both exhibited the photovoltaic effect and are used for commercial photovoltaics manufacturing include crystalline silicon (both monocrystalline and polycrystalline [polysilicon]), germanium, gallium – arsenic compounds (gallium arsenide; GaAs), indium phosphorous compounds (indium phosphide; InP), other III-V compounds, cadmium telluride (CdTe), copper – indium – selenium (CIS; also including gallium – CIGS; also including sulfur – CIGSS), amorphous silicon (a-Si; aSi), microcrystalline silicon (m-Si, mc-Si, µc-Si), dyes, and organic semiconductive polymers. Photovoltaic technology is produced from either a crystalline silicon wafer (thick film; c-Si photovoltaics) or from deposited thin films (thin film photovoltaics).