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.
* 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 fabricates 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, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland achieves 11% efficient energy conversion with dye-sensitized cells that use a photoelectrochemical effect.
* 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.
* 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. 
* 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.