Solar cell

Solar energy seems to be one of the most promising green energy in the future. We know that the sun is a powerful and huge resource, easily overpower the oil reserves in the current state. Solar energy usually is related to solar cell. This cell allows the conversion of light (usually sunlight in the context to be 'green' apposed the artificial or lamp light generated by fossil fuels) directly to electrical energy without an external voltage source. You may possibly seen the cells in different forms, such as modules from which the cells are framed together to form a larger pieces and arrays which are the combination of modules, usually used in power plants etc. Also worth to mention solar energy is applicable to almost everything as long as there is light, from the cells in a calculator to those installed on the roof top of a high rise building.

Now let's have a look at the mechanism of a solar cell. Silicon is widely used in solar cell due to its property, it has 14 electrons in 3 different shells with a electrical configuration of 1s2 2s2 2p6 3s2 3p2. To become stable, it will require another 4 electrons in the outer shell. A pure Si is not what we want because when it is in stable state, the conductivity is very low due to the absence of free electrons. As contrast to most cases in which impurities are to be avoided, to make things work like a charm, we add impurities into the Si, with a ratio of 1 in a million, this process is also known as doping. To get a P-type semiconductor, Boron is usually added. Boron has 3 outer electrons, hence an additional hole ( a positive charge) is created. In the contrary, Phosphorous is added to obtain an N-type semiconductor. Phosphorous has 5 valance electrons, but only 4 will bond with Si atoms, the other 1 will have no one to bond with and is left alone. When there is more electrons, an N-type material is produced as in the latter case.

to be continued...