Silicon solar panels are a passe, and new, high efficiency solar panels are being introduced in the market. Multi-junction photo-voltaic cells that have multiple p-n junctions are used in the manufacture of these cells. The purpose behind using more than one p-n junction is that a wide spectrum of light gets covered.
The materials used to manufacture solar cells primarily include germanium and gallium arsenide, while the research on use of indium phosphide is ongoing. Nanotechnology is an integral part of most of the research work carried out today and is also used in the research and development to make these panels more efficient.
Different semiconductors have their specific value of band gap energy. A semiconductor's band gap energy value allows it to absorb a certain light in an efficient way. That is why the choice of an appropriate semiconductor matters most in the application of this technology as maximum amount of energy has to be absorbed to make the solar cells efficient.
Molecular Beam Epitaxy
It is one of the techniques used in depositing single crystals on the substrate. This technique was developed in the 1960s in 'Bell Telephone Laboratories'. Alfred Y. Cho and J. R. Arthur were the ones who invented this technique. Single crystals are known for their unbroken edges.
As the name suggests, 'epitaxy' is the technique used for manufacturing these solar cells. In this process, a monocrystalline substrate is used and monocrystalline film is deposited on it. A high vacuum environment is required for conducting the process of molecular beam epitaxy.
The deposition rate of monocrystalline film in this method is very slow; it is less than 1000 nm per hour. The sublimation and condensation process of pure elements like arsenic and gallium is used to form wafers of these solar cells.
Metalorganic Vapor Phase Epitaxy
In metalorganic vapor phase epitaxy, a chemical reaction is used as opposed to the physical deposition technique used in molecular beam epitaxy. Chemical vapor deposition is the process used in metalorganic vapor phase epitaxy.
Metal hydrides and metalorganic compounds containing the necessary elements for manufacturing solar cells take part in a surface reaction. The pyrolysis process helps in the decomposition of these compounds and the pure elements are deposited on the substrate layer. The pressure maintained during this chemical process ranges from 2-100 kPa (Kilo Pascal).
Solar Panel Efficiency
The sunlight-to-electricity conversion efficiency is taken into account in determining whether a product is good enough to be used commercially. In the 1980s, the conversion rate was around 16%. Since then, solar panel efficiency has gradually increased. Today, this number has gone up to almost 40.7%.
Some companies in research and development of these modern solar panels claim to provide these equipment at an installation cost of $1-2 per watt. There are few companies in the market that offer solar panels with higher efficiency than traditional ones. The current installation cost is $3.14 per watt.