Gallium arsenide solar cells are marked by high efficiency and high price. Due to these reasons, they have found most of their applications where such a high efficiency is required and the budget of the project allows their use.
Aerospace industry is the most important industry where these cells are being used extensively.
Efficiency of Gallium Arsenide Solar cells
These cells have efficiency as high as 29% during laboratory testing. But, since the conditions are different in real world, their efficiency drops somewhat but they can still show an efficiency of 20%. The greater efficiency in laboratory is mainly because a concentrated light source is used to calculate the efficiency there.
However, the reduction in performance in real world is also owing to a great many other factors. Multi junction or tandem gallium arsenide solar cells have the world record of 40.7% efficiency.
Advantages of Gallium Arsenide Solar cells
These cells are a great contender in solar cells industry especially where high efficiency is the preference. Following are the advantages which make these cells so popular
- The band width of Gallium Arsenide makes it perfectly suitable for single junction solar cells.
- It is much more effective than silicon solar cells. A few microns thickness will suffice for the purpose where hundreds of microns of silicon solar cells are used.
- Its absorption rate is very high.
- Its efficiency does not drop in high temperature zones.
- Gallium Arsenide solar cells are also considered suitable for outer space application because ultra violet and other kinds of radiations present beyond the earth cannot damage these cells.
Types of Gallium Arsenide Solar cells
These cells are classified as
- Single junction Gallium Arsenide Solar cells
- Multi junction Gallium Arsenide Solar cells
Formation of single junction Gallium Arsenide Solar cells
Gallium arsenide cells are formed by thin layers of single crystal material. These layers are deposited in series. Each layer is doped opposite to the layer next to it. Doping means addition of impurities to Gallium Arsenide to make it electrically conductive. If one layer is doped with positive particles the next will be doped with negative and so on.
Cost of Gallium Arsenide Solar cells
Gallium arsenide is quite expensive. An estimate shows that it costs about $10,000 per square meter. The substrate and GaAs should have very similar crystalline structure. But it is very costly to make substrate of GaAs. Efforts are being done to make reusable substrates.
Multi junction or tandem GaAs
These are the most modern and advanced solar cells. They have the world record of very high conversion efficiency. Actually, they are not made of just Gallium arsenide. They have many other compounds embedded in them like Germanium and Gallium Indium Phosphide. Research institutions, companies and universities are working to reduce the price of these cells. This combination is very useful since it absorbs a wide spectrum of sunlight and has very high conversion efficiency. These cells have been used in Mars Rover mission.