Thursday, October 29, 2009

Guest Lecture - Ronald Roedel

The important part of the lecture was about structure of the solar cells and its operation. The main thing was about optical radiation which got absorb by the solar cells and the result creates active charged particle then particles will transferred by the solar.

Basically photons get collected by sunlight which we can call it "packets" of the sun energy. When solar cells were hit by photons the huge mass are get absorbed or reflected the quantity of high-energy photons will blow right away but most of the time they are get absorbed or reflected. While absorbing happened to a photon its energy is transported to a semiconductor. When an adequate amount of energy is transported the atom can run away from its regular position to the different position. Meanwhile the electron makes a hole to shape. Each photon with sufficient energy will usually give a way one electron plus one hole.

Each solar cell has three different and energetic layers. First “a top junction layer (made of the N-type semiconductor) second an absorber layer (which called the P-N junction) and third a back junction layer (made of the P-type semiconductor)”. But what is the P-N junction? In the P-N junction the cell includes its individual built-in electric field. This electric field offers the voltage which is necessarily to power electrons and holes by light absorption to run in their own instructions. In fact, it will direct the electrons to the N-type area, and the holes to the P-type area. Whether we offer an outer current path, electrons will run from side to side this pathway to their original area to join with holes the electric field send there. The electron surge offers the current and the electric field make a voltage. With both current path and voltage we can produce power.

Part of the lecture was about The Doping Model, The Fermi level (the chemical potential) and power and efficiency in the solar cell. About efficiency based on my research on the internet triple-junction compound solar cell can gain more efficiency than other product-around 35.8%. It is not similar to other silicon-based solar cells which normally used in solar panels for the home or office buildings. This product made from compounds “including indium and gallium”. Compound solar cells usually used on space satellites and they are costly to make.

Solar cells have three different generations. First Generation is “Silicon, second generation is Thin Film Structures which included Amorphous Silicon, III-V Solar Cells, II-VI Solar Cells, I-III-VI2 Solar Cells and organic Solar Cells and the third generation is Structures that exceed the single PN-junction thermodynamic conversion limit”.

The conclusion of the lecture was more concentrated on the Silicon. It is clear that the Silicon is the best and it will be the best for ever. Also second generation of solar cells provide a miniature competition to Silicon however this is momentary and third Generation of the solar cells are hardly challenging to make itself to the better position but technologically it is not possible.

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