Solar Cell History & Timeline
Photovoltaics History and Timeline
Economics of PV
PV Environmental Impacts
Photovoltaics Pros & Cons
PV Companies, Industry Associations, Research Institutes
The timeline of solar cells begins in the 1800s when it is observed that the presence of sunlight is capable of generating usable electrical energy. Solar cells have gone on to be used in many applications. They have historically been used in situations where electrical power from the grid is unavailable.
The term "photovoltaic" comes from the Greek word “phos” meaning "light", and "voltaic", meaning electrical, from the name of the Italian physicist Volta, after whom the measurement unit volt is named. The term "photo-voltaic" has been in use in English since 1849.
The photovoltaic effect was first recognised in 1839 by French physicist Alexandre-Edmond Becquerel. However, it was not until 1883 that the first solar cell was built, by Charles Fritts, who coated the semiconductor selenium with an extremely thin layer of gold to form the junctions. The device was only around 1% efficient. Russell Ohl patented the modern solar cell in 1946 (U.S. Patent 2,402,662, "Light sensitive device"). Sven Ason Berglund had a prior patent concerning methods of increasing the capacity of photosensitive cells. The modern age of solar power technology arrived in 1954 when Bell Laboratories, experimenting with semiconductors, accidentally found that silicon doped with certain impurities was very sensitive to light.
This resulted in the production of the first practical solar cells with a sunlight energy conversion efficiency of around 6 percent. Russia launched the first artificial satellite in 1957, and the United States' first artificial satellite was launched in 1958 using solar cells created by Peter Iles in an effort spearheaded by Hoffman Electronics. The first spacecraft to use solar panels was the US satellite Explorer 1 in January 1958. This milestone created interest in producing and launching a geostationary communications satellite, in which solar energy would provide a viable power supply. This was a crucial development which stimulated funding from several governments into research for improved solar cells.
In 1970 the first highly effective GaAs heterostructure solar cells were created by Zhores Alferov and his team in the USSR.  Metal Organic Chemical Vapor Deposition (MOCVD, or OMCVD) production equipment was not developed until the early 1980's, limiting the ability of companies to manufacture the GaAs solar cell. In the United States, the first 17% efficient air mass zero (AM0) single-junction GaAs solar cells were manufactured in production quantities in 1988 by Applied Solar Energy Corporation (ASEC). The "dual junction" cell was accidentally produced in quantity by ASEC in 1989 as a result of the change from GaAs on GaAs substrates to GaAs on Germanium (Ge) substrates. The accidental doping of Ge with the GaAs buffer layer created higher open circuit voltages, demonstrating the potential of using the Ge substrate as another cell. As GaAs single-junction cells topped 19% AM0 production efficiency in 1993, ASEC developed the first dual junction cells for spacecraft use in the United States, with a starting efficiency of approximately 20%. These cells did not utilize the Ge as a second cell, but used another GaAs-based cell with different doping. Eventually GaAs dual junction cells reached production efficiencies of about 22%. Triple Junction solar cells began with AM0 efficiencies of approximately 24% in 2000, 26% in 2002, 28% in 2005, and in 2007 have evolved to a 30% AM0 production efficiency, currently in qualification. In 2007, two companies in the United States, Emcore Photovoltaics and Spectrolab, produce 95% of the world's 28% efficient solar cells.
Four generations of solar cells
The first generation photovoltaic cell consists of a large-area, single-crystal, single layer p-n junction diode, capable of generating usable electrical energy from light sources with the wavelengths of sunlight. These cells are typically made using a diffusion process with silicon wafers. First-generation photovoltaic cells (also known as silicon wafer-based solar cells) are the dominant technology in the commercial production of solar cells, accounting for more than 86% of the terrestrial solar cell market.
The second generation of photovoltaic materials is based on the use of thin epitaxial deposits of semiconductors on lattice-matched wafers. There are two classes of epitaxial photovoltaics - space and terrestrial. Space cells typically have higher AM0 efficiencies (28-30%) in production, but have a higher cost per watt. Their "thin-film" cousins have been developed using lower-cost processes, but have lower AM0 efficiencies (7-9%) in production and are questionable for space applications. The advent of thin-film technology contributed to a prediction of greatly reduced costs for thin film solar cells that has yet to be achieved. There are currently (2007) a number of technologies/semiconductor materials under investigation or in mass production. Examples include amorphous silicon, polycrystalline silicon, micro-crystalline silicon, cadmium telluride, copper indium selenide/sulfide. An advantage of thin-film technology theoretically results in reduced mass so it allows fitting panels on light or flexible materials, even textiles. The advent of thin GaAs-based films for space applications (so-called "thin cells") with potential AM0 efficiencies of up to 37% are currently in the development stage for high specific power applications. Second generation solar cells now comprise a small segment of the terrestrial photovoltaic market, and approximately 90% of the space market.
Third-generation photovoltaics are proposed to be very different from the previous semiconductor devices as they do not rely on a traditional p-n junction to separate photogenerated charge carriers. For space applications quantum well devices (quantum dots, quantum ropes, etc.) and devices incorporating carbon nanotubes are being studied - with a potential for up to 45% AM0 production efficiency. For terrestrial applications, these new devices include photoelectrochemical cells, polymer solar cells, nanocrystal solar cells, Dye-sensitized solar cells and are still in the research phase.
A hypothetical 'fourth-generation' of solar cells may consist of composite photovoltaic technology, in which polymers with nano particles can be mixed together to make a single multispectrum layer. Then the thin multispectrum layers can be stacked to make multispectrum solar cells more efficient and cheaper based on polymer solar cell and multijunction technology used by NASA on Mars missions. The layer that converts different types of light is first, then another layer for the light that passes and last is an infra-red spectrum layer for the cell—thus converting some of the heat for an overall solar cell composite. Current research is being conducted under a DARPA grant to determine if this technology is viable. Companies working on fourth-generation photovoltaics include Xsunx, Konarka Technologies, Inc., Nanosolar, Dyesol and Nanosys. Research is also being done in this area by the USA's National Renewable Energy Laboratory.
US685957 : Rays falling on insulated conductor connected to a capacitor; the capacitor charges electrically
1839 - Alexandre Edmond Becquerel observes the photoelectric effect via an electrode in a conductive solution exposed to light.
1873 - Willoughby Smith finds that selenium is photoconductive.
1877 - W.G. Adams and R.E. Day observed the photovoltaic effect in solid selenium, and published a paper on the selenium cell. 'The action of light on selenium,' in "Proceedings of the Royal Society, A25, 113.
1883 - Charles Fritts develops a solar cell using selenium on a thin layer of gold to form a device giving less than 1% efficiency.
1887 - Heinrich Hertz investigates ultraviolet light photoconductivity.
1887 - James Moser reports dye sensitised photoelectrochemical cell.
1888 - Edward Weston receives patent US389124, "Solar cell", and US389125, "Solar cell".
1894 - Melvin Severy receives patent US527377, "Solar cell", and US527379, "Solar cell".
1897 - Harry Reagan receives patent US588177, "Solar cell"..
1901 - Nikola Tesla receives the patent US685957, "Apparatus for the Utilization of Radiant Energy", and US685958, "Method of Utilizing of Radiant Energy".
1902 - Philipp von Lenard observes the variation in electron energy with light frequency.
1904 - Albert Einstein publishes a paper on the photoelectric effect. Wilhelm Hallwachs makes a semiconductor-junction solar cell (copper and copper oxide).
1913 - William Coblentz receives US1077219, "Solar cell".
1914 - Sven Ason Berglund patents "methods of increasing the capacity of photosensitive cells".
1916 - Robert Millikan conducts experiments and proves the photoelectric effect.
1918 - Jan Czochralski, a Polish scientist, produces a method to grow single crystals of metal. Decades later, the method is adapted to produce single-crystal silicon.
1920s - Solar water-heating systems, utilizing "flat collectors" (or "flat-plate collectors"), relied upon in homes and apartment buildings in Florida and southern California.
1932 - Audobert and Stora discover the photovoltaic effect in Cadmium selenide (CdSe), a photovoltaic material still used today.
1946 - Russell Ohl receives patent US2402662, "Light sensitive device".
1948 - Gordon Teal and John Little adapt the Czochralski method of crystal growth to produce single-crystalline germanium and, later, silicon.
1950s - Bell Labs produce solar cells for space activities.
1953 - Gerald Pearson begins research into lithium-silicon photovoltaic cells.
1954 - Bell Labs announces the invention of the first modern silicon solar cell. Shortly afterwards, they are shown at the National Academy of Science Meeting These cells have about 6% efficiency. The New York Times forecasts that solar cells will eventually lead to a source of "limitless energy of the sun".
1955 - Western Electric licences commercial solar cell technologies. Hoffman Electronics-Semiconductor Division creates a 2% efficient commercial solar cell for $25/cell or $1,785/Watt.
1957 - AT&T assignors (Gerald L. Pearson, Daryl M. Chapin, and Calvin S. Fuller) receive patent US2780765, "Solar Energy Converting Apparatus". They refer to it as the "solar battery". Hoffman Electronics creates an 8% efficient solar cell.
1958 - T. Mandelkorn, U.S. Signal Corps Laboratories, creates n-on-p silicon solar cells, which are more resistant to radiation damage and are better suited for space. Hoffman Electronics creates 9% efficient solar cells. Vanguard I, the first solar powered satellite, was launched with a 0.1W, 100 cm² solar panel.
1959 - Hoffman Electronics creates a 10% efficient commercial solar cell, and introduces the use of a grid contact, reducing the cell's resistance.
1960 - Hoffman Electronics creates a 14% efficient solar cell.
1961 - "Solar Energy in the Developing World" conference is held by the United Nations.
1962 - The Telstar communications satellite is powered by solar cells.
1963 - Sharp Corporation produces a viable photovoltaic module of silicon solar cells.
1964 - Farrington Daniels' landmark book, Direct Use of the Sun's Energy, published by Yale University Press.
1967 - Soyuz 1 is the first manned spacecraft to be powered by solar cells
1970 - First highly effective GaAs heterostructure solar cells are created by Zhores Alferov and his team in the USSR. 
1970s - Huge groundswell of public interest in solar energy use: photovoltaic and active and passive solar, including in architecture and off-grid buildings and home sites.
1971 - Salyut 1 is powered by solar cells.
1973 - Skylab is powered by solar cells.
1974 - Florida Solar Energy Center begins ].
1974 - J. Baldwin, at Integrated Living Systems, co-develops the world's first building (in New Mexico) heated and otherwise powered by solar and wind power exclusively.
1976 - David Carlson and Christopher Wronski of RCA Laboratories create first amorphous silicon PV cells, which have an efficiency of 1.1%.
1977 - The Solar Energy Research Institute is established at Golden, Colorado.
1977 - President Jimmy Carter installs solar panels on the White House and promotes incentives for solar energy systems.
1977 - The world production of photovoltaic cells exceeded 500 kW
1980 - The Institute of Energy Conversion at University of Delaware develops the first thin-film solar cell exceeding 10% efficiency using Cu2S/CdS technology.
1982 - Spherical solar cell was developed.
1983 - Worldwide photovoltaic production exceeds 21.3 megawatts, and sales exceed $250 million.
1984 - 30,000 SF Building-Integrated Photovoltaic [BI-PV] Roof completed for the Intercultural Center of Georgetown University. At the time of the 20th Anniversary Journey by Horseback for Peace and Photovoltais in 2004 it was still generating an average of one MWh daily as it has for twenty years in the dense urban environment of Washington, DC.
1984 - Amoco Oil pulled factory loan to takeover of Solarex Corporation factory in Frederick, Maryland.
1985 - 20% efficient silicon cell are created by the Centre for Photovoltaic Engineering at the University of New South Wales.
1986 - 'Solar-Voltaic DomeTM' patented by Lt. Colonel Richard T. Headrick of Irvine, CA most efficient architectural configuration for building-integrated photovoltaics [BI-PV] in existence where it increases output on acre footprint 4.5 times Hesperia, CA field array.
1988-1991 AMOCO/Enron used Solarex patents to sue ARCO Solar out of the business of a-Si, see
Solarex Corp.(Enron/Amoco)v.Arco Solar, Inc.Ddel, 805 Fsupp 252 Fed Digest.
1989 - Reflective solar concentrators are first used with solar cells.
1990 - The Cathedral of Magdeburg installs solar cells on the roof, marking the first installation on a church in East Germany.
1991 - Efficient Photoelectrochemical cells are developed; the Dye-sensitized solar cell is invented.
1991 - President George H. W. Bush directs the U.S. Department of Energy to establish the National Renewable Energy Laboratory (transferring the existing Solar Energy Research Institute).
1992 - University of South Florida fabricats a 15.89-percent efficient thin-film cell
1993 - The National Renewable Energy Laboratory's Solar Energy Research Facility is established.
1994 - NREL develops a GaInP/GaAs two-terminal concentrator cell (180 suns) which becomes the first solar cell to exceed 30% conversion efficiency.
1996 - The National Center for Photovoltaics is established. Graetzel, Polytechnique Fdrale de Lausanne, Lausanne, Switzerland achieves 11% efficient energy conversion with dye-sensitized cells that use a photoelectrochemical effect.
1996 - Solar Two, a test 10MW solar concentrator begins to operate.
1998 - August and September University of New South Wales made premiere offering of on-line 'Advanced Photovoltaics Short Course'
1998 - Historic Joint Agency Rulemaking into the Role of the Utility Distribution Company [UDC] in Distributed Generation [DG] before the California Public Utilities Commission 98-12-015 and 99-10-025; California Energy Commission 99-DIST-GEN(1) and 99-DIST-GEN(2); California Oversight Board 99-1-A-DG
1999 - Total worldwide installed photovoltaic power reached 1000 megawatts.
President George W. Bush installed a 9 kW 'building-integrated photovoltaics' panel on the roof of a grounds maintenance building at the White House for the National Parks Service. Also installed were two solar water heating systems.
Photoelectrochemical cells are developed.
March California Governor Arnold Schwarzenegger proposed Solar Roofs Initiative for one million solar roofs in California by 2017.
June 1 Kansas Governor Kathleen Sebelius issued a mandate for 1,000 MWp renewable electricity in Kansas by 2015 per Executive Order 04-05
Kansas Solar Electric Co~operatives was established by Eileen M. Smith, M.Arch. to evolve 1,000 MWp Building-Integrated Photovoltaics [BI-PV] Solar Electricity in Kansas by 2018 via Kansas House Bill 2018 passed in 2003 by KS Representative Tom Sloan [K.S.A. Chapter 17]. Unique non-profit program to produce, install, monitor, maintain and manage grid-connected electricity sells for 10% solar electricity for Kansas by 2018. 
Polysilicon use in photovoltaics exceeds all other polysilicon use for the first time.
January 12 California Public Utilities Commission approved the California Solar Initiative (CSI), a comprehensive $2.8 billion program that provides incentives toward solar development over 11 years. 
January Kansas Solar Electric Co~operatives [K-SEC] announces Phase I Demonstration Program to produce, install, monitor, maintain and sell 100 kWp or 10,000 SF Building-Integrated Photovoltaics [BI-PV] in each county of Kansas by January 2009
April Kansas Solar Electric Buildings Registry announces first goal of 250 homes and 50 commercial rooftops compiled in list for each county of Kansas by January 2007
December 5 New World Record Achieved in Solar Cell Technology - New Solar Cell Breaks the “40 Percent Efficient” Sunlight-to-Electricity Barrier.
Investors begin offering free installation in return for a long term Power Purchase Agreement (PPA).
April 23 Start of construction of Nellis Solar Power Plant, a 15 MW PPA installation. 5 MW began operation on October 12, and the final third was completed in December
May The Vatican announced that in order to conserve Earth's resources they would be installing solar panels on some buildings, in "a comprehensive energy project that will pay for itself in a few years".
June 18 Google solar panel project begins operation.
July 30 New World Record Achieved in Solar Cell Technology - 42.8% efficiency achieved by University of Delaware.
December 18 Nanosolar ships the first commercial printed CIGS, claiming that they will eventually ship for less than $1/Watt. However, the company does not publicly disclose the technical specifications or current selling price of the modules.
List of energy topics
List of solar energy topics
PV financial incentives
Timeline of materials technology
Perreault, Bruce A.. Nikola Tesla's Radiant Energy system. Retrieved on 2008-01-16.
David C. Brock (Spring 2006). Useless No More: Gordon K. Teal, Germanium, and Single-Crystal Transistors. Chemical Heritage Foundation. Retrieved on 2008-01-21.
D. M. Chapin, C. S. Fuller, and G. L. Pearson (May 1954). "A New Silicon p-n Junction Photocell for Converting Solar Radiation into Electrical Power". Journal of Applied Physics 25 (5): 676-677.
Alferov, Zh. I., V. M. Andreev, M. B. Kagan, I. I. Protasov, and V. G. Trofim, 1970, ‘‘Solar-energy converters based on p-n AlxGa12xAs-GaAs heterojunctions,’’ Fiz. Tekh. Poluprovodn. 4, 2378 (Sov. Phys. Semicond. 4, 2047 (1971))]
Nanotechnology in energy applications, pdf, p.24
Nobel Lecture by Zhores Alferov, pdf, p.6
White House installs solar-electric system
United States Department of Energy (December 5, 2006). "New World Record Achieved in Solar Cell Technology". Press release. Retrieved on 2008-01-16.
Krauss, Leah (May 31, 2007). Solar World: Vatican installs solar panels. United Press International. Retrieved on 2008-01-16.
From 40.7 to 42.8 % Solar Cell Efficiency (July 30, 2007). Retrieved on 2008-01-16.
Nanosolar Ships First Panels. Nanosolar Blog. Retrieved on 2008-01-22.
Nanosolar - Products. Nanosolar.com. Retrieved on 2008-01-22.
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