Batteries Emotion: Multi-junction solar cell

Multi-junction solar cell

7 to 9 and July last year, in Freiburg, Germany (Freiburg) the Fraunhofer Institute for Solar Energy Systems (Europe's largest research center Fraunhofer-Gesellschaft 80 research institutes, one short FhG-ISE), the European record of solar cells increased by the 37.6% to 39.7%, after several efforts, and finally multi-junction solar cells a new world record - more than the U.S. Department of Energy Renewable Energy Laboratory (Department of Energy's National Renewable Energy Laboratory) 40.8% before.

Such a high efficiency multi-junction solar cell is mainly used to focus on photovoltaic systems (concentrating photovoltaic, referred to as CPV), direct conversion of sunlight as the sun, the source of power throughout the town. Will focus sunlight on a small (5mm) multi-junction solar cells, in solar energy equivalent to 454 can achieve 41.1% conversion efficiency, even in the higher energy 880 is still under solar irradiation measured 40.4%, the battery can be a wide use of sunlight intensity, and with more than 40% conversion efficiency.

Like the battery before the FhG-ISE, the new battery still use the deformation of the extension of the three junction structure and the lattice mismatch Ga0.35In0.65P/Ga0.83In0.17As / Ge (gallium indium phosphide and gallium indium arsenide deposited on Ge) layer structure. Compared with conventional solar cells, separation of the semiconductor material and there are no same lattice constant, we can only use the extension to combine the two layers of distortion, it is difficult to obtain high quality film, the other because of different between the two materials The lattice constant, combined prone to stress, resulting inserted row or other lattice defects.

By Frank, Dr. (Frank Dimroth) led group III-V Epitaxy and Solar Cells group, FhG-ISE to overcome the above difficulties and deficiencies limited to the electronic non-active zone, while the active area is relatively free of defects retained, which is to indispensable to achieve high conversion efficiency factor. "This is a good example and tell us how to use technological breakthroughs to control the crystallization of the semiconductor defects" Fraunhofer ISE's President Ike Weber (Eicke R. Weber), Dr. mentioned.

Multi-junction solar cell can be used in a variety of deformation of the extension group III-V compound semiconductors, the high efficiency of the battery structure formed by the appropriate materials can be divided into three bands of sunlight were to absorb. Researchers suggest that this is an important conclusion is that using a series of material connected to form the solar cell, its components will be the current minimum current that part to the limitations of the use of deformed extension of the battery Ga0.35In0.65P / Ga0.83In0.17As/Ge, can make the current matching, the complete output (multi-junction cell structure are produced close to three times the current of the battery), this is the battery can achieve high conversion efficiency of the important reasons.

Last year by the Fraunhofer ISE 37.6% conversion efficiency will be increased to 39.7% by adjusting the front-end structure of the metal thin wire has a lower contact resistance can pass large currents, therefore more suitable for concentrated solar constant of 300 ~ 600. Frank mentioned that the latest change in front of the metal thin battery is the graphics, and has a better quality film. In order for the technology and existing technology as a competitive, fast and feasible, Fraunhofer ISE in Germany Heilbronn (Heilbronn) of the Azur Space co-operation and technology transfer, also in Freiburg Concentrix Solar GmbH. "And the other focusing photovoltaic systems, our high efficiency solar cells is the most efficient way to reduce the cost of electricity" Fraunhofer ISE's Director, Dr Andrew Bate (Andreas Bett) mentioned. Fraunhofer ISE With the new battery to the goal of high conversion efficiency, a major step forward, and soon, the cost of photovoltaic power generation can compete with traditional power.

Dr Frank by changing the cell structure that will help make this type of battery has a long-term advantage, and to improve efficiency to 42 ~ 43%. Over the past 15 years, researchers at Fraunhofer ISE is committed to III-V family of multi-junction solar cell used in photovoltaic systems research focus from the beginning of the German Federal Ministry of Education (German Federal Ministry of Education and Research, referred to as the BMBF) for support Now while the German Federal Environment, Nature Conservation cum Nuclear Security Administration, Intelligent Energy Bureau (German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, called BMU) to provide financial aid, scholarships for doctoral students, the future will be faster and better results to share with the world.

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