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High-Efficiency, Self-Concentrating Nanoscale Solar Cell



Inventors Alex Zettl (l) and Jeff Grossman (r) have developed a portfolio of nanoscale solar cells which promise increased efficency. Dr. Zettl has been working in nanotechnology since 1991 and has over 150 publications in the field.
  • Fabricating highly efficient nano-solar cells
  • Enhancing efficiencies of existing solar cells


  • Permits self-focusing broadband or multi-gap absorption efficiencies
  • Maximizes the useful absorption of incidental light
  • Propagates light in any direction
  • Captures and recycles photons that slip through thin layers of silicon
  • Allows the reception and capture of multiple wavelengths across the solar spectrum
  • Streamlines the manufacturing and installation process


While solar cells have the potential to provide clean energy for a large portion of the earth's population, no one technology has provided the right combination of high-efficiency and low-cost. For example, conventional solar cells are designed to absorb light through an antireflective layer, and through a layer of silicon, to convert light into electricity. However, some of this light exits the device without generating electricity.

To address this problem, Alex Zettl and Jeffrey Grossman of Berkeley Lab have created a self-focusing, highly efficient solar cell/concentrator device based on photonic principles. The invention can be used to make novel photonic crystal solar cells or to increase the efficiency of existing solar cells.

Unlike solar cell manufacturing methods in use today, the invention makes it possible to design even higher efficiency solar cell devices made of conventional materials, such as silicon, cadmium-tellurium, indium-gallium-nitrogen, or cadmium-selenium. When photonic nanocrystals made of these materials are modified during fabrication, they can be customized to function as any one of a number of parts of a functioning solar cell all within a single nanoscale unit. These parts include a photovoltaic region that converts sunlight into electricity; a photonic crystal area that reflects and absorbs light; or a sophisticated, nanoscale wavelength sorter that pairs wavelengths with a coupler tuned to the desired frequency.

This ability to sort wavelengths of incoming sunlight makes it possible for the broadband-capable device to self-focus within a specific range of wavelengths and to capture and use photons that would otherwise not be utilized by a standard solar cell. As a whole, this innovative structure makes it possible for the Berkeley Lab photonic crystal solar cells to absorb a broad wavelength region across the solar spectrum and to achieve light absorption close to 100%.

The invention offers versatile construction options that can enhance thin-film, solar-powered devices. These constructions include a vertically layered, three-dimensional structure or a planar, two-dimensional design. Industry further benefits from the invention's streamlined assembly, which requires only a single series of steps and simplifies the fabrication and installation process for hybrid solar cell/concentrator devices.


  • Published Patent Application PCT/US2009/058544 available at Available for licensing or collaborative research.

To learn more about licensing a technology from LBNL see


Wagner, L., and J.C. Grossman, "Light-Induced Defects in Amorphous Silicon Solar Cells," submitted to Physical Review Letters (2008).



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