(Left) Silicon wires with match heads and (right) light absorption profile of a single match-head wire at 587 nm absorption. Credit: Image courtesy of the Center for Integrated Nanotechnologies
Crystal growth on a nano/microscale level produces “match-head”-like, 3D structures that enhance light absorption and photovoltaic efficiency. This is the first large structure grown on a nanowire tip and it creates a completely new architecture for harnessing energy. Match-head semiconductor nanowires focus incident light for greater overall efficiency. The match heads are naturally formed during the wire-growth process, which can be applied to various materials and structures for photonic and optoelectronic devices.
Enhanced light absorption and efficient, photogenerated carrier collection are essential characteristics of highly efficient solar cells. Nanowires with embedded radial junctions are promising building blocks for highly efficient photovoltaics because of their ability to achieve these two characteristics. Controlled silicon crystal growth on the tops of silicon wires creates a match-head structure which is a light concentrator.
Light absorptance was increased by 36% and photovoltaic efficiency was increased by 20%. Because the match-head crystal is naturally grown and minimizes surface energy, this technique is applicable for a wide range of materials and device architectures to boost performance. The ability to control the shape of the nanostructure is essential for manufacturing next-generation semiconductor devices eg photodetectors and light emitters. http://science.energy.gov/bes/highlights/2015/bes-2015-11-f/
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