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Solar cell

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A solar cell, or photovoltaic cell, is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.[1] It is a form of photoelectric cell, defined as a device whose electrical characteristics, such as current, voltage, or resistance, vary when exposed to light. Individual solar cell devices can be combined to form modules, otherwise known as solar panels. The common single junction silicon solar cell can produce a maximum open-circuit voltage of approximately 0.5 to 0.6 volts.[2]

Solar cells are described as being photovoltaic, irrespective of whether the source is sunlight or an artificial light. In addition to producing energy, they can be used as a photodetector (for example infrared detectors), detecting light or other electromagnetic radiation near the visible range, or measuring light intensity.

The operation of a photovoltaic (PV) cell requires three basic attributes:

  • The absorption of light, generating either electron-hole pairs or excitons.
  • The separation of charge carriers of opposite types.
  • The separate extraction of those carriers to an external circuit.

In contrast, a solar thermal collector supplies heat by absorbing sunlight, for the purpose of either direct heating or indirect electrical power generation from heat. A "photoelectrolytic cell" (photoelectrochemical cell), on the other hand, refers either to a type of photovoltaic cell (like that developed by Edmond Becquerel and modern dye-sensitized solar cells), or to a device that splits water directly into hydrogen and oxygen using only solar illumination.

Applications[]

Assemblies of solar cells are used to make solar modules that generate electrical power from sunlight, as distinguished from a "solar thermal module" or "solar hot water panel". A solar array generates solar power using solar energy.

History[]

The photovoltaic effect was experimentally demonstrated first by French physicist Edmond Becquerel. In 1839, at age 19, he built the world's first photovoltaic cell in his father's laboratory. Willoughby Smith first described the "Effect of Light on Selenium during the passage of an Electric Current" in a 20 February 1873 issue of Nature. In 1883 Charles Fritts built the first solid state photovoltaic cell by coating the semiconductor selenium with a thin layer of gold to form the junctions; the device was only around 1% efficient. Other milestones include:

  • 1888 – Russian physicist Aleksandr Stoletov built the first cell based on the outer photoelectric effect discovered by Heinrich Hertz in 1887.[3]
  • 1905 – Albert Einstein proposed a new quantum theory of light and explained the photoelectric effect in a landmark paper, for which he received the Nobel Prize in Physics in 1921.[4]
  • 1941 – Vadim Lashkaryov discovered p-n-junctions in Cu2O and Ag2S protocells.[5]
  • 1946 – Russell Ohl patented the modern junction semiconductor solar cell,[6] while working on the series of advances that would lead to the transistor.
  • 1954 – The first practical photovoltaic cell was publicly demonstrated at Bell Laboratories.[7] The inventors were Calvin Souther Fuller, Daryl Chapin and Gerald Pearson.[8]
  • 1957 – Egyptian engineer Mohamed M. Atalla develops the process of silicon surface passivation by thermal oxidation at Bell Laboratories.[9][10] The surface passivation process has since been critical to solar cell efficiency.[11]
  • 1958 – Solar cells gained prominence with their incorporation onto the Vanguard I satellite.

Space applications[]

Solar cells were first used in a prominent application when they were proposed and flown on the Vanguard satellite in 1958, as an alternative power source to the primary battery power source. By adding cells to the outside of the body, the mission time could be extended with no major changes to the spacecraft or its power systems. In 1959 the United States launched Explorer 6, featuring large wing-shaped solar arrays, which became a common feature in satellites. These arrays consisted of 9600 Hoffman solar cells.

By the 1960s, solar cells were (and still are) the main power source for most Earth orbiting satellites and a number of probes into the solar system, since they offered the best power-to-weight ratio. However, this success was possible because in the space application, power system costs could be high, because space users had few other power options, and were willing to pay for the best possible cells. The space power market drove the development of higher efficiencies in solar cells up until the National Science Foundation "Research Applied to National Needs" program began to push development of solar cells for terrestrial applications.

In the early 1990s the technology used for space solar cells diverged from the silicon technology used for terrestrial panels, with the spacecraft application shifting to gallium arsenide-based III-V semiconductor materials, which then evolved into the modern III-V multijunction photovoltaic cell used on spacecraft.

In recent years, research has moved towards designing and manufacturing lightweight, flexible, and highly efficient solar cells. Terrestrial solar cell technology generally uses photovoltaic cells that are laminated with a layer of glass for strength and protection. Space applications for solar cells require that the cells and arrays are both highly efficient and extremely lightweight. Some newer technology implemented on satellites are multi-junction photovoltaic cells, which are composed of different PN junctions with varying bandgaps in order to utilize a wider spectrum of the sun's energy. Additionally, large satellites require the use of large solar arrays to produce electricity. These solar arrays need to be broken down to fit in the geometric constraints of the launch vehicle the satellite travels on before being injected into orbit. Historically, solar cells on satellites consisted of several small terrestrial panels folded together. These small panels would be unfolded into a large panel after the satellite is deployed in its orbit. Newer satellites aim to use flexible rollable solar arrays that are very lightweight and can be packed into a very small volume. The smaller size and weight of these flexible arrays drastically decreases the overall cost of launching a satellite due to the direct relationship between payload weight and launch cost of a launch vehicle.[12]

Research and industrial production[]

Research into solar power for terrestrial applications became prominent with the U.S. National Science Foundation's Advanced Solar Energy Research and Development Division within the "Research Applied to National Needs" program, which ran from 1969 to 1977,[13] and funded research on developing solar power for ground electrical power systems. A 1973 conference, the "Cherry Hill Conference", set forth the technology goals required to achieve this goal and outlined an ambitious project for achieving them, kicking off an applied research program that would be ongoing for several decades.[14] The program was eventually taken over by the Energy Research and Development Administration (ERDA),[15] which was later merged into the U.S. Department of Energy.

Following the 1973 oil crisis, oil companies used their higher profits to start (or buy) solar firms, and were for decades the largest producers. Exxon, ARCO, Shell, Amoco (later purchased by BP) and Mobil all had major solar divisions during the 1970s and 1980s. Technology companies also participated, including General Electric, Motorola, IBM, Tyco and RCA.[16]

See also[]

  • Anomalous photovoltaic effect
  • Autonomous building
  • Black silicon
  • Energy development
  • Electromotive force (Solar cell)
  • Flexible substrate
  • Green technology
  • Inkjet solar cell
  • List of photovoltaics companies
  • List of types of solar cells
  • Maximum power point tracking
  • Metallurgical grade silicon
  • Microgeneration
  • Nanoflake
  • Photovoltaics
  • P–n junction
  • Plasmonic solar cell
  • Printed electronics
  • Quantum efficiency
  • Renewable energy
  • Roll-to-roll processing
  • Shockley-Queisser limit
  • Solar Energy Materials and Solar Cells (journal)
  • Solar module quality assurance
  • Solar roof
  • Solar shingles
  • Solar tracker
  • Solar panel
  • Spectrophotometry
  • Theory of solar cells
  • Thermophotovoltaics

References[]

  1. ↑ Solar Cells. chemistryexplained.com
  2. ↑ "Solar cells – performance and use". solarbotics.net.
  3. ↑ Gevorkian, Peter (2007). Sustainable energy systems engineering: the complete green building design resource. McGraw Hill Professional. ISBN 978-0-07-147359-0.
  4. ↑ "The Nobel Prize in Physics 1921: Albert Einstein", Nobel Prize official page
  5. ↑ Lashkaryov, V. E. (1941) Investigation of a barrier layer by the thermoprobe method Archived 28 September 2015 at the Wayback Machine, Izv. Akad. Nauk SSSR, Ser. Fiz. 5, 442–446, English translation: Ukr. J. Phys. 53, 53–56 (2008)
  6. ↑ "Light sensitive device" U.S. patent 2402662 Issue date: June 1946
  7. ↑ "April 25, 1954: Bell Labs Demonstrates the First Practical Silicon Solar Cell". APS News. American Physical Society. 18 (4). April 2009.
  8. ↑ Tsokos, K. A. (28 January 2010). Physics for the IB Diploma Full Colour. Cambridge University Press. ISBN 978-0-521-13821-5.
  9. ↑ Black, Lachlan E. (2016). New Perspectives on Surface Passivation: Understanding the Si-Al2O3 Interface (PDF). Springer. p. 13. ISBN 9783319325217.
  10. ↑ Lojek, Bo (2007). History of Semiconductor Engineering. Springer Science & Business Media. pp. 120 & 321-323. ISBN 9783540342588.
  11. ↑ Black, Lachlan E. (2016). New Perspectives on Surface Passivation: Understanding the Si-Al2O3 Interface (PDF). Springer. ISBN 9783319325217.
  12. ↑ Garcia, Mark (31 July 2017). "International Space Station Solar Arrays". NASA. Retrieved 10 May 2019.
  13. ↑ The National Science Foundation: A Brief History, Chapter IV, NSF 88-16, 15 July 1994 (retrieved 20 June 2015)
  14. ↑ Herwig, Lloyd O. (1999). "Cherry Hill revisited: Background events and photovoltaic technology status". AIP Conference Proceedings. Vol. 462. p. 785. Bibcode:1999AIPC..462..785H. doi:10.1063/1.58015. {{cite book}}: |journal= ignored (help)
  15. ↑ Deyo, J. N., Brandhorst, H. W., Jr., and Forestieri, A. F., Status of the ERDA/NASA photovoltaic tests and applications project, 12th IEEE Photovoltaic Specialists Conf., 15–18 Nov 1976
  16. ↑ Reed Business Information (18 October 1979). The multinational connections-who does what where. Reed Business Information. ISSN 0262-4079. {{cite book}}: |author= has generic name (help)

Bibliography[]

External links[]

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