Thursday, June 23, 2011

photovoltaic cells




Silicon is currently the most common material used to make photovoltaic cells. It is obtained by reduction from silica, comprising the most abundant in the crust and especially in sand or quartz. The first step is the production of silicon metal said, only 98% pure, made from pieces of quartz from pebbles or a vein deposit (the technique of industrial production can not be from the sand).

The solar grade silicon must be purified to more than 99.999%, which is obtained by converting silicon into a chemical compound to be distilled and then reprocessed into silicon.

Silicon is produced as a bar called "ingots" round or square. These ingots are then sawed into thin plates made to the square (if necessary) to 200 micrometers thick, which are called "wafers". After treatment to enhance doping elements (P, As, Sb or B) and thus obtain the silicon semiconductor type P or N, the wafers are "metallic" metal strips are embedded in the surface and connected to electrical contacts. After the wafers have become metallized photovoltaic cells.

The production of photovoltaic cells requires energy, and it is estimated that photovoltaic module should work about two to three years of its manufacturing technology to produce the energy that was needed to make (the module energy payback).

Manufacturing techniques and characteristics of major types of cells are described in the following three paragraphs. There are other cell types under consideration, but their use is almost negligible.

Materials and manufacturing processes are being ambitious research program to reduce cost of ownership and recycling of photovoltaic cells. The techniques of thin film substrates appear unmarked receive the votes of the emerging industry. In 2006 and 2007, growth in world production of solar panels has been hampered by lack of silicon, cells and prices have not fallen as much as hoped. The industry seeks to reduce the amount of silicon used. Monocrystalline cells increased from 300 to 200 microns thick and is thought now quickly reach 180 and 150 microns, reducing the amount of silicon and energy required, but also the price.

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