Efficiency of solar cells

June 12, 2009

Firstly, let’s understand what a solar cell is. Simply put, it is a device that converts sunlight into electricity, through the photovoltaic effect. Sometimes, lots of solar cells are assembled to make solar modules, solar panels, or even photovoltaic arrays. Those solar cells that can generate electricity with a higher efficiency than the usual or conventional solar cells are called high efficiency solar cells. These are more efficient because of their electrical output per incident energy, that is, watt/watt. Constant research is going on, to increase the efficiency of solar cells.

In 2002, Sheffield Hallam University reported research that they had achieved the highest efficiency for solar cells, based on thin films of CdTe – 18%. However, NREL, the renewable energy research institute, had achieved 19.9% for solar cells, which were based on copper indium gallium selenide thin films. Of course, there are other ways to increase the efficiency of solar cells. For instance, there could be surface restructuring in order to reduce reflection loss. The cell surface would be constructed in the form of a pyramid, this would mean that incoming light would hit the surface many times. The new material used could be cadmium terruride (CdTe), copper indium selenide (CuInSe²) or even gallium arsenide (GaAs)

Also, various semiconductor materials (suited to various spectral ranges) could be arranged on top of each other, this is would help the scientist to use a wide spectrum of radiation. Another possible method is to use mirror and lens systems – which would focus higher light intensity on the solar cells. In this method, there is direct radiation. In the MIS Inversion Layer Cells method – a p-n junction does not produce the inner electrical field, but it is produced by the junction of a thin oxide layer, to a semiconductor. Light absorption could be increased and highly improved by using electrochemical liquid cells with titanium dioxide and electrolytes and dye.

Solar cells could be today’s answer to eliminating the harmful and poisonous side-effects of fossil fuels. However, there is a cost involved, and it is rather high. Some think that it is a luxury, rather than a necessity to save the environment. There are many ongoing projects which aim to increase the efficiency of solar cells. One such project in Germany aims to optimize the growth of silicon nanorods on inexpensive substrates. Cost-friendly substrates like glass or synthetic foil are being used. Nanorods that have the ability to act as good light-traps are being produced, these capture the light effectively, and transform it into electricity.

There is an urgent need to find more ways to generate electricity through solar cells, and therefore to make them more efficient.

The University of Delaware has been instrumental in its efforts by creating a high-performance crystalline silicon solar cell platform. The combined solar cell efficiency is a record breaking 42.8 percent. It’s particular important since it is at approximately 20 times magnification, at low concentration. It has high portability, so one can use it on a laptop computer.


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