Photo cells are a key link in creation of solar batteries. As a rule, solar batteries consist of silicon with various extent of crystallization. Therefore, looking at separate cells of photo cells of the solar battery it is possible to see that they have various colors and shades. Some elements have coloring from dark blue to black, others, blue with parts of crystals etc. Color of a cell depends on the production technology and a used material.
Structure of a standard photo cell
Photo cells are, as a rule, carried out from semi-conductor materials connected among themselves, forming a potential barrier. Their work is based on the phenomenon of p-n of transition arising under the influence of sunlight. Photons, getting on a photo cell to a semiconductor zone with bigger width of the forbidden zone, "beats out" electrons which begin movement to a zone N, and then having passed through a chain (loading) contact positive charges (holes). As a result of movement of electrons the potential difference, or tension is formed. The single-crystal photo cell consists of an integral crystal of flint. It is characterized by high efficiency, as a rule, 18-22 %, and the high price. It has characteristic dark color. A photo cell from single-crystal silicon the Solar battery on the basis of single-crystal photo cells Photo cells from polycrystalline silicon. Production of polycrystalline silicon occurs at slow cooling silicon расплава. These elements are characterized by efficiency in a range of 14-18 %. Smaller value of efficiency speaks existence in a crystal of polycrystalline silicon of the areas separated by granular borders which interfere with more high efficiency of elements. However the price of such elements is lower. Usually polycrystalline photo cells possess dark blue color with accurately expressed crystals of silicon. Photo cells from polycrystalline silicon Photo cells from amorphous silicon represent the thinnest layers of silicon received by a dusting in vacuum on glass, plastic or a foil from high-quality metal. These elements are characterized by low efficiency in a range of 6-10 % and considerable the lowest price. Usually such solar elements have blankly grayish color, visible crystals of flint are absent. Photo cells from amorphous silicon the Image of a silicon photo cell this the first that the solar battery occurs to the majority of people at the mention of a word. This results from the fact that a few years ago silicon as raw materials for the photo-electric industry, made nearly 100 % of the market. Today the situation considerably changed. Silicon as the construction block of the solar battery gives way in the market to new technologies called «thin-film solar cells» more and more. In this technology photo cells are made of very thin layer of the semiconductor. There are more progressive technologies which have been completely deprived of classical semiconductors. To classify these technologies entered concept of generation of photo cells. The first generation of photo cells is classical silicon elements with traditional p-n transition which the majority of us means solar photo cells by a word. As a rule, it is plates from pure single-crystal or polycrystalline silicon in thickness of 200-300 microns. They are characterized by high efficiency (17-22 %) and high prime cost. Now market share about 82 %. The second generation of photo cells as is based on use of p-n of transition, however do not use crystal silicon as the main material. The following materials are usually used: Telluriya, cadmium (CdTe), copper mix, India, gallium, selenium (CIGS) and amorphous silicon. As a rule, the thickness of a layer of the semiconductor absorbing light makes from only 1 to 3 microns. Process of production of such photo cells is more automated and has considerably smaller prime cost. The main lack of the second generation of elements is smaller efficiency, than elements of the first generation which fluctuates depending on technology from 7-15 %. Now market share about 18 %. the panel on a basis tellurid-cadmium of photo cells the Third generation of photo cells also treat thin-film technologies, however they are deprived of the habitual concept p-n of transition, therefore and uses of semiconductors. Now this generation includes various technologies, however the main direction is photo cells on the basis of organic polymeric materials. Advantage of photo cells of the third generation is low prime cost and simplicity of manufacturing. The main obstacle in a way of promoting is low efficiency which does not exceed 7 %. %. Now the market share of the third generation of elements does not exceed 0,5 % the Solar panel of the third generation It should be noted that the main tendency of development of generations of solar photo cells consists in decrease in prime cost of energy sometimes to the detriment of efficiency. Let’s show schematically the main stages in development of photo-electric modules. development of generations of photo cells