Solar cell technology has advanced rapidly in recent years. Corporations, universities and research institutions have been busy searching for ways to make solar cells less costly, easier to produce and more efficient at generating electricity. As a result, today's solar (or photovoltaic) cells are a far cry from the bulky and inefficient panels of just a few years ago.
Most of the research into solar cells has focused on the materials used to make the cells. Here is an overview of recent advances and discoveries in solar cell technology.
Thin-film Solar Cells
Conventional solar cells are made from wafers of polycrystalline silicon. Typically, these wafers are about 200 to 260 microns thick. (260 microns is equal to about one-hundredth of an inch.) In contrast, thin-film solar cells usually measure about 1 micron deep.
Thin-film cells are commonly made of semiconductors like amorphous silicon (also known as a-Si), copper indium gallium diselenide (CIGS), or cadmium telluride (CdTe). Because these cells use extremely small amounts of semiconductor and little or no silicon, they are significantly less expensive to produce.
Although thin-film solar cells are not as efficient as those made of crystalline silicon, their lower manufacturing costs make them an attractive choice for future solar installations.
Printable Solar Cells
Imagine a solar cell that can be printed onto a thin, flexible material via a process similar to that used by an ink-jet printer. Someday, this might be the way the public creates its own solar cells for home applications.
Printable solar cells are made by mixing electrically conducting polymers with buckyballs. When the polymer absorbs sunlight, it releases electrons. These electrons are trapped by the buckyballs. A conductor carries away the electrons, thus producing electricity.
In 2007, researchers at the New Jersey Institute of Technology developed printable solar cells using carbon nanotubes as condutors. Other companies have successfully used titanium dioxide instead of buckyballs.
However, printable solar cells have a serious drawback: They are highly susceptible to damage from heat, dust and oxygen. Manufacturers are working on methods to hermetically seal the cells.
Dye-sensitized Solar Cells
Dye-sensitized solar cells convert sunlight to energy the way plants do. To make this kind of solar cell, a nanometer-size film made of titanium dioxide is coated with a dye. The dye is similar to compounds found in nature, such as chlorophyll, and is connected to an electrolyte. When sunlight strikes the dye, electricity flows from the film to the electrolyte.
Dye-sensitized solar cells are about half as efficient as crystalline silicon solar cells. However, they are made from inexpensive and abundant materials. According to one university's estimate, they are expected to cost just one-tenth of the price of a silicon solar panel.
Thanks to these and other exciting developments in solar cell technology, large-scale applications of solar power are on the horizon. In a few more years millions of people the world over will be generating their own electricity from the sun's free and plentiful energy.
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