A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by using the photovoltaic effect. It is a type of photoelectric cell, a device whose electrical characteristics (such as current, voltage, or resistance) vary when it is exposed to light. Individual solar cell devices are often the electrical building blocks of photovoltaic modules, known colloquially as "solar panels". Almost all commercial PV cells consist of crystalline silicon, with a market share of 95%. Thin-film technologies account for a small share of the global photovoltaic module production. Cadmium telluride thin-film solar cells (CdTe) is the dominant thin-film technology by production volume, while other thin-film technologies include copper indium gallium selenide (CIGS), and amorphous thin-film silicon. The common single-junction silicon solar cell can produce a maximum open-circuit voltage of approximately 0.5 to 0.6 volts.
Photovoltaic cells may operate under sunlight or artificial light. In addition to producing solar power, they can be used as a photodetector (for example infrared detectors), to detect light or other electromagnetic radiation near the visible light range, as well as to measure light intensity.
The operation of a PV cell requires three basic attributes:
The absorption of light, generating excitons (bound electron-hole pairs), unbound electron-hole pairs (via excitons), or plasmons.
The separation of charge carriers of opposite types.
The separate extraction of those carriers to an external circuit.
There are multiple input factors that affect the output power of solar cells, such as temperature, material properties, weather conditions, solar irradiance and more.
A similar type of "photoelectrolytic cell" (photoelectrochemical cell), can refer to devices:
using light to excite electrons that can further be transported by a semiconductor which delivers the energy (like that explored by Edmond Becquerel and implemented in modern dye-sensitized solar cells)
using light to split water directly into hydrogen and oxygen which can further be used in power generation.
In contrast to outputting power directly, a solar thermal collector absorbs sunlight, to produce either:
direct heat as a "solar thermal module" or "solar hot water panel"
indirect heat to be used to spin turbines in electrical power generation.
Arrays of solar cells are used to make solar modules that generate a usable amount of direct current (DC) from sunlight. Strings of solar modules create a solar array to generate solar power using solar energy, many times using an inverter to convert the solar power to alternating current (AC).
Electric vehicles that operate off of solar energy or sunlight are commonly referred to as solar cars. These vehicles use solar panels to convert absorbed light into electrical energy to be used by electric motors, with any excess energy stored in batteries. Batteries in solar-powered vehicles differ from starting batteries in standard ICE cars because they are fashioned to impart power towards electrical components of the vehicle for a long durations.
The first instance of photovoltaic cells within vehicular applications was around midway through the second half of the 1900s. In an effort to increase publicity and awareness in solar powered transportation Hans Tholstrup decided to set up the first edition of the World Solar Challenge in 1987. It was a 3000 km race across the Australian outback where competitors from industry research groups and top universities around the globe were invited to compete. General Motors ended up winning the event by a significant margin with their Sunraycer vehicle that achieved speeds of over 40 mph. Contrary to popular belief, solar powered cars are one of the oldest alternative energy vehicles.
Cells, modules, panels and systems
Multiple solar cells in an integrated group, all oriented in one plane, constitute a solar photovoltaic panel or module. Photovoltaic modules often have a sheet of glass on the sun-facing side, allowing light to pass while protecting the semiconductor wafers. Solar cells connected in series creates an additive higher voltage, while connecting in parallel yields an additive higher current.