A solar cell is any device that directly converts the energy in light into electrical energy through the process of photovoltaics.
The term “photovoltaic” comes from the Greek Word meaning “light”, and the name of the Italian physicist Volta, after whom the volt (and consequently voltage) are named. It means literally of light and electricity.
The photovoltaic effect was first recognized 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. 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. This milestone created interest in producing and launching a geostationary communications satellite by providing a viable power supply.
Russia launched the first artificial satellite in 1957, and the United States’ first artificial satellite was launched in 1958. Russian Sputnik 3, launched on 15 May 1958, was the first satellite to use solar arrays. This was a crucial development which diverted funding from several governments into research for improved solar cells.
Three generations of solar cells
Solar Cells are classified into three generations which indicates the order of which each became important.
At present there is concurrent research into all three generations while the first generation technologies are most highly represented in commercial production.
First Generation technologies involve high energy and labor inputs which prevent any significant progress in reducing production costs.
Single junction silicon devices are approaching the theoretical limiting efficiency of 33% and achieve cost parity with fossil fuel energy generation after a payback period of 5-7 years.
Second Generation (Thin Film)
Second generation materials have been developed to address energy requirements and production costs of solar cells. Second generation technologies are expected to gain in market share.
The most successful second generation materials have been cadmium telluride (CdTe), copper indium gallium selenide, amorphous silicon and micromorphous silicon.
Third generation technologies aim to enhance poor electrical performance of second generation (thin-film technologies) while maintaining very low production costs.
Current research is targeting conversion efficiencies of 30-60% while retaining low cost materials and manufacturing techniques.