Thursday, February 20, 2014

Photovoltaic plastic cells at its peak Researchers at the Fraunhofer Institute for Solar Energy Sys

Crystal Structure. Translation Symmetry And Bravais Lattices. Basis and unit cell. Classifying lattices: plastic symmetry in 2D. Symmetry operations. Two Dimensional Lattice Types. Classifying lattices: Symmetry in 3D. Projected Crystal Structures. Polonium, Po. Chromium, Nickel Cr, Ni. Cobalt Co. More Crystal Structures. Silicon. CsCl. NaCl. Zinc Blende
Photovoltaic plastic cells at its peak Researchers at the Fraunhofer Institute for Solar Energy Systems (FhG-ISE), Germany, have made their dream a reality sooner than expected. In January 2009 they beat a world record in the field of multi-junction solar cells with a conversion rate of 41.24%. But they think they can go further, thanks to solar cells equipped metamorphic plastic multijunction structures. It seems that the sun has not yet said its last word. Source: Fraunhofer ISE Conventional photovoltaic cells (PV) silicon single junction, enough to power our watches and calculators, are not very effective to convert the energy of the solar spectrum plastic into electricity. These industrial photovoltaic cells efficiently convert only 17% of this energy, while other components are up to 25%. Hence, research is focusing on the development of multijunction PV cells. These cells, being composed of different elements, such as gallium arsenide, indium phosphide and gallium or germanium may capture a wider range of solar energy. A multijunction structure is in principle plastic only the accumulation of single-junction cells, but different semiconductors plastic are applied, each of the joints becomes different bands of the solar spectrum, with higher performance. For a decade, the Fraunhofer plastic Institute developed metamorphic multijunction solar cells, semiconductor based groups III-V, suitable for converting sunlight into electricity. The preparation of any PV cell is made from a semiconductor pn junction (1). To get a better conversion rate accumulate cells of different materials, each possessing its own PN junction. In early 2009, the Fraunhofer Institute holds the world record with a cell composed of a germanium substrate coated with gallium arsenide, and a third layer of indium phosphide and gallium. According to Andreas Bett, head of the solar cell, the idea of increasing the effectiveness accumulation is not new, but the key has been to use the right technology, with high quality materials. The trick: metamorphic crystal growth All semiconductors are crystalline materials. These periodic structures are formed plastic by layers of atoms separated by a distance of the chemical element used itself, termed "lattice constant". The bottom layer of the "cake" here is germanium, and if other material is deposited on top, in principle has to be compatible with germanium, ie have the same lattice constant. High quality glass, which poses few problems when converting sunlight is then obtained. But if the lattice constant differs, however slightly, called local failures "dislocations" that greatly reduce the conversion rate occur. plastic Therein lies the trick of metamorphic growth Fraunhofer Institute, which brought about a specific FV inactive layer, called "intermediate layer", which are confined all crystal dislocations. plastic Above said intermediate layer each new material is deposited lattice constant, which gives the end a nearly flawless crystal. All the imperfections plastic are concentrated in an electrically inactive region of the solar cell, leaving the active portions clean. The metamorphic crystal growth using a wider field in IIIV semiconductor multijunction PV cells. For optimum performance, the solar spectrum is divided into three zones of equal size using appropriate materials with absorption properties. The combination of Ga0.35In0.65P and metamorphic materials Ga0.83In0.17As / Ge is well adapted, and that each of the subcells of the triple junction generates the same amount of electric current, an essential condition for improving the conversion efficiency . Set yourself again? Higher goals? It was the first attempt by the Fraunhofer researchers. In 2008 they had broken the European record for solar conversion, which rose from 37.6% to 39.7% in the space of three months. The development of triple junction cells was performed under the FULLSPECTRUM project, funded under the Sixth Research Framework Programme, launched in 2003. The scientists began their research with a yield of 32% to 35% on the date of completion of the project in September

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