A solar cell or photovoltaic cell is a device comprising semiconductor (usually silicon) functioning as diodes. When these diodes are illuminated, an electrical current goes in the diode reverse direction. Each individual cell generates a relatively low voltage; therefore there are series of the solar cells connected in solar panels. One can also connect in parallel solar cells in order to increase the current.
One can generally divide the solar panels into two groups:
- solar panels with crystalline solar cells;
- thin film solar cells.
Crystalline cells are most prevalent today as they have a higher efficiency than thin film cells. They consist of silicon that has been doped with various substances for desired functioning.
The crystalline cells can also be divided into two types:
- polycrystalline or multi-crystalline cells;
- mono-crystalline cells.
College students writing there research paper on the topic have to learn that solar cells have historically been expensive and have mostly been used in places not reached by the grid, such as summer houses, satellites, and lighthouses. The price of solar cells has, however, dropped sharply between 2000 and 2012 as a result of advances in technology and the expansion of production capacity in the world. As prices have dropped, the market has grown by an average of 40% since 2000 and by the end of 2011, there were approximately 64 GW of PV capacity installed in the world, of which 98% consisted of facilities connected to various national electricity systems.
The solar cell has many uses and is used for example also for charging smartphones, tablets, and laptops.
A solar cell is a type of photo diode. The solar cell is composed of two layers: the P-layer and N-layer. The most abundant element in the solar cell is silicon, which has four valence electrons. The N-layer is then doped with a substance with five valence electrons, such as phosphorus and the P-layer is doped with a substance having three valence electrons, such as boron. Electron concentrations is therefore different on both sides of the contact layer.
Diffusion then leads to electrons migration in the N-layer across the P-layer. The N-doped layer becomes positively charged, and the P-doped layer becomes negatively charged, with a strong electric field therebetween.
In the dark, there are no free electrons. But there comes a photon from the sunlight and it emits its energy to the electron and the photon has enough energy, for the electron to get excited. When the electron ends up in the electric field between the layers, swept it to the positively charged N layer, where it can be discharged into an external circuit (power line).
There is photovoltaic drop in efficiency due to the temperature rises. It has been found that it is relatively simple to use passive cooling and thus reduce the losses when the temperature increases.
You should look through free sample research papers on solar cells, if you have small or no experience in the field.
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