Solar Cell: The Energy of the future environment-friendly

Technical share info (translated & edited from Chem-Is-Try.org)

Energy is one of the words that have a very wide meaning, as there is no activity on the natural highway of this move without energy and that is why one of his professors said in Japan that almost all disputes in the world, have a seizure on the energy source.

In general, energy sources are categorized into two parts, namely non-Renewable Energy and Renewable Energy. Energy sources including fossil groups is that It is the first major event in the world using this convention energy.

Around eight years old when dozens of experts in India to offer an alternative source of energy that is used in many developed countries, namely nuclear, much debate and dis-agreement occurred a long counter work plan so that the use of energy sources that are considered very dangerous. Among the proposals that many mare proposed that is why we do not using solar energy source. Indeed, there is no doubt that the solar cell is a source of energy environment-friendly and very promising in the future, as there is no pollution produced during the process of energy conversion, and many more sources of energy available in nature, the sun, especially in tropical countries such as Indonesia, which receives the sun throughout the year.

Fundamental problems in solar cell technology is a very low efficiency in the solar energy into electrical energy, which so far the highest efficiency can be achieved no more than 20%, and that in laboratory scale. Therefore, it is in developed countries, research on the solar cell is the attention which is very large, especially with the issues of clean environment ranted.

From light into electricity

A simple solar cell consists of a continuation of semi conductor which type p and n (PN Junction Semi conductor), which struck down if the sun will occur electron flow, electron flow nah this is referred to as a flow of electric current. While the structure of the solar cell is as shown in image 1.

Figure 1. Lamella structure of the solar cells in general

The main conversion sun's energy into electricity is the absorber, however, each layer is also very influential on the efficiency of solar cell. The sun consists of various types of waves electromagnetic that the spectrum can be seen on the image 2. Therefore, the absorber is expected here as much as you can absorb solar radiation derived from sunlight.

Figure 2. Radiation spectrum sun

More detail can be explained again that the sun consists of a photon-photon, if the override surface of solar cell material (absorber), it will be absorbed, reflected or be missed only (see figure 3), and only photons with certain energy level that will be exempt the electron from atomic bond, so that electric current yield. Level of energy is called energy band-gap which is defined as the amount of energy required for removing the electron from the covalent bond, so that there electric current flow. To removes electron from covalent bond, energy photons (HC / v must be greater or less than the energy band-gap. If the energy of the photons is too large in the energy band-gap, then the extra energy will be amended in to heat form in solar cells. Therefore it is very important in solar cells to set the material used, namely to modify the molecular structure of the semi conductor that is used.

Figure 3. Radiative transition of solar cell

Of course, that the efficiency of solar cell can be higher then the photons coming from the sun can be absorbed as much as a large number, then the reflection and re-mobilization and increase conductivity of material.

To be able to make so that photons can be absorbed as much as many, then the absorber must have an energy band-gap with a wide range, making it possible to be able to absorb the sun's energy that have very diverse it. One of the many materials that are examined is known CuInSe2 is one of the direct Semi conductor.

So many benefits from the solar cell as described above is not polemic does not stop and simply, there is indeed correct that the solar cell during the process of change of energy there is no pollution produced, but it has us calculate how much pollution that have been generated in the production process, small compared to the resulting efficiency. Now the challenge here is how to increase efficiency, which of course will impact the economic value.