Electrical & Electric

The Basics of Solar Cells

Solar Energy is Here to Stay  

Overview:

Converting solar energy to electricity via the photovoltaic cells is not entirely new. However, it is one of the most exciting and practical scientific discoveries in several hundred years. The use of solar power is far less damaging to the environment than burning fossil fuels and safer than nuclear power generation.

In comparison to other renewable energy resources such as hydro power, wind, and geothermal, solar energy is unmatched in terms of portability and flexibility. The sun shines sometimes and everywhere on most days and it is not likely to run out of energy for a few billion years.

These characteristics make solar power a key energy source as we move from fossil fuel dependency and toward a more sustainable and clean way to meet our energy needs.

The sunlight that powers solar cells travels through space at 186,282 miles per hour to reach the earth in about 8.4 minutes after leaving the surface of the sun. Although the solar energy that reaches the Earth's surface is reduced due to water vapor, ozone layer absorption, and scattering by free air molecules, there is still plenty of power to collect.

Using solar power in our homes, factories, offices, vehicles and personal electronics has become practical, economical, and will continue to increase in its importance to meet our energy needs.

Almost anyone can set up a solar panel and use solar power independent of the commercial electrical grid and other power sources. Batteries and super capacitors for the electronic devices that we use can be recharged by this natural and renewable energy resource. Solar power will cut down on pollution and make life better and safer for everyone.

A solar cell is a solid state semiconductor device that produces DC (direct current) electrical current when stimulated by photons. When the photons contact the atomic structure of the photovoltaic cell they dislodge electrons from the atoms. This leaves a void which attracts other free available electrons. If a PN junction is fabricated in the cell, the dislodged photons flow toward the P side of the junction. A PN junction is formed by joining P type and N type semiconductors together in very close contact.

The result of this electron movement induces a flow of electrical current which can be routed from the surface of the cell through electrical contacts to produce power.  The efficiency of a solar cell largely depends on its spectral response. The wider the spectrum of light that the cell can respond to (the spectral response), the more power can be generated.  

The reflectivity of the cell surface and the amount of light blocked by the surface electrodes on the front of the cell affect the efficiency of solar cells. An anti-reflective coating placed on cells and the use of very thin electrodes on the surface of cell faces help to reduce this loss of photonic stimulation. In terms of cell efficiency the hotter a cell gets, the less current it produces.

Because solar cells in use get very hot it is important to mount them in such a way that they are cooled as much as possible to keep current production at its maximum.

Silicon is used for solar cells construction, however this is changing as thin film technologies using gallium arsenide, cadmium telluride and copper indium diselenide will make them more efficient.

Solar energy is here to stay and as improvements are made in photovoltaic solar cell design they will become even more efficient and less expensive to construct and buy. In the next decade we can expect to see home solar cells on most residential house roofs.

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