A team of researchers from Australia's Royal Melbourne Institute of Technology (RMIT) created a new type of nanostructure called a nanocone. The new creation integrates the upside-down physics of topological insulators with the simpler plasmonics process, leading to a nanomaterial that has the ability to be used in combination with silicon-based photovoltaics in order to improve their light absorption.
Topological insulators are unique for their ability to act as insulators on the inside and conductors on the outside, and plasmonics use the density changes in electrons that are created with photons colliding with a metal surface. Using these two processes, the team created a plasmonic nanostructure with a core-shell that allows it to act as a topological insulator.
"This is the first time that a nanocone with intrinsically core-shell structure has been fabricated," said Min Gu, who led the research. "The nanocone has a topologically protected metallic shell and a dielectric [insulating] core. They do not need a particular fabrication method and the unique nanostructure has the intrinsic properties of topological insulators."
The new structure could bolster the light absorption of solar cells focusing incident sunlight onto silicon using the insulating core of the nanocones, which provide a very high refractive index that reaches the near-infrared frequency range. At the same time, its metallic shell ensures a strong plasmonic response and backward light scattering that doesn't exit the visible frequency range.
Integration of these nanocone arrays into silicon thin-film solar cells could boost light absorption of the cell by up to 15 percent in the ultraviolet and visible ranges.
"With the enhanced light absorption, both the short circuit current and photoelectric conversion efficiency could be enhanced," Gu said.
Increasing the effectiveness of silicon-based solar cells is a strong focus in the alternative energy movement, with the United States' National Renewable Energy Lab announcing earlier this year that they set the record for solar cell conversion of sunlight into electricity. The findings of Gu and colleagues might help these cells more effectively absorb sunlight and break this record in the future.
The team plans to continue their investigation, shifting their focus to plasmonics in other types of topological insulator nanostructures such as nano-spheres and nano-cylinders.
The findings were published in the March 25 issue of Science Advances.
