Solar power has the reputation of being the cleanest type of energy, but to produce this also requires ultra-clean and highly efficient components made from cutting-edge ceramics.
Solar cells traditionally use a semiconductor wafer, or chip, to convert incoming sunlight and generate electrical power. Now there is a race to reduce the cost of solar-generated electricity to make it cheaper than power generated from fossil fuels. This means that manufacturers have to provide super-efficient photovoltaic cells.
Research has now moved from designing chips to fit inside a solar cell to examining layers of thin films of technical ceramics to create a hybrid cell. The advantage of this process is that it uses smaller amounts of materials, and the production process can be much simpler and faster than the very delicate procedure of slicing and dicing silicon chips.
Even the process of melting and crystallising silicon chips is fraught with problems, as impurities are able to enter the chip and reduce its effectiveness in the solar cells.
The thin film cell consist of layers of an amorphous silicon on either side of an organic layer made of fullerene – an isomorph of carbon with a crystal structure the shape of a football. All of the layers have a thickness of less than one micron.
This combination has the advantage of converting infrared radiation from sunlight as well as the visible light into electrical power. A simple silicon film solar cell will only convert the green and blue wavelengths of the visible spectrum into electricity.
Another method of improving photovoltaic cell efficiency is to deposit a thin film of technical ceramics on the surface of the cell to replace the silicon chip. The deposition of thin film technical ceramics is not a new process. It has been used on all manner of electrical devices, from low-emission glass to flat-screen televisions.
Now manufacturers are experimenting with other materials such as copper indium alloys and cadmium telluride.
The procedure starts by melting the solid material in a ceramic crucible until it vaporises. This vapour in turn is deposited on a non-reactive substrate. The crucible itself has to be made from a non-reactive ceramic such as boron nitride.
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