Enhanced Tunnel Junction for Improved Performance in Cascaded Solar Cells
BACKGROUND: Solar energy created through photovoltaics is finding increasing interest as an alternative power source for domestic and industrial use. The amount of power generated by a solar cell array is limited to the amount of solar cell area. In order to increase power delivery, the efficiency of the solar cells has to be increased. Many techniques, like the multi quantum-well (MQW) approach increases the efficiency of the cells but also increase the costs exponentially. Hence to make solar cells widely used, we need a cheaper and efficient solar cell.
DESCRIPTION: Researchers at the University of California, Santa Barbara have developed an enhanced tunnel junction for use in cascaded or multi-junction solar cells. The new tunnel junction provides a dramatically increased tunneling current density, effectively reducing the barrier thickness. High currents can pass across the barrier with a low voltage drop, improving the overall efficiency of the solar cells. Testing on an AlGa0.3As0.7/GaAs cascaded photovoltaic using this novel tunnel junction yielded a tandem cell with voltage 97% of ideal. The new tunnel junctions are easy to create and do not require significant increases in processing time or material costs.
* "Increased efficiency in multijunction solar cells through the incorporation of semimetallic ErAs nanoparticles into the tunnel junction" J. M. O. Zide, A. Kleiman-Shwarsctein, N. C. Strandwitz, J. D. Zimmerman, T. Steenblock-Smith, and A. C. Gossard A. Forman, A. Ivanovskaya, and G. D. Stucky, Applied Physics Letters, APRIL 2006
University of California
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