Available Technologies: Streamlined Synthesis of Binary Nanorods for Power-Efficient Nanocrystal Devices

APPLICATIONS OF TECHNOLOGY:

Solar cell devices
Light-emitting diodes (LEDs)
Microscale and nanoscale electronic devices

ADVANTAGES:

Lowers manufacturing costs
Improves electricity-generating efficiency of nanocrystal-based solar cells
Can be used with many micro- and nano-electronic applications
Simplified, solution-phase fabrication
Tunable composition of materials and optoelectronic properties
Enhances and is compatible with existing methods for fabricating nanocrystal-based devices

ABSTRACT:

Nanorods--rod-shaped nanocrystals--are valued for their potential to substantially lower the manufacturing costs of certain electronic devices, such as solar cells; however, the power efficiencies of nanocrystal-based solar cells have been much lower than those of conventional silicon solar cells. Paul Alivisatos and Bryce Sadtler of Berkeley Lab have discovered a way to enhance the synthesis of semiconducting nanorods, which can greatly improve the efficiency of nanocrystal solar cells, light-emitting diodes (LEDs), and other microscale and nanoscale electronic devices, and simultaneously lower manufacturing costs compared to silicon-based technology.

The inventors have found a way to convert cadmium-sulfide (CdS) nanorods in solution, to binary nanorod heterostructures made of CdS-Cu2S, by means of a partial cation exchange reaction. The new method is particularly useful for making Type II heterostructures, whose coupled electronic band structures make them well-suited for use in nanocrystal-based electronics, such as solar cells; it may also allow solar cells to approach efficiencies close to theoretical limits, which conventional methods have failed to achieve. Existing nanocrystal-based devices use either nanocrystal-organic polymer blends or bilayers of two different types of semiconductor nanocrystals, which do not allow a well-controlled interface or connection between a device's components. In contrast, the binary nanorods produced by this new method possess a strong, well-connected interface (known as an "epitaxial interface") between the two materials. This well-connected interface improves the flow of electrical current through nanocrystalline solar cell material, into the electrodes, to power an electrical device.

The Berkeley Lab method promises to simplify the manufacturing process for the micro- and nano-electronics industries, by using solution-phase processing, while also enabling better control over the composition and properties of materials during synthesis. For example, the inventors have shown that the spectral regions of solar energy absorbed by the nanorods can be controlled by their relative proportions of CdS and Cu2S materials, which in turn affect the amount of electrical current produced by a device. Thus, it is possible to adjust the binary nanorod's optoelectronic properties, or the extent by which binary nanorods absorb and emit light, making them useful for broad optoelectronic applications. The ability to control a material's composition and optoelectronic properties can also lower batch manufacturing costs, by producing devices of the same nanomaterial proportions and properties, and resulting in fewer fabrication errors.

STATUS:

Published Patent Application PCT/US2009/037952 available at www.wipo.int. Available for licensing or collaborative research.

To learn more about licensing a technology from LBNL see http://www.lbl.gov/Tech-Transfer/licensing/index.html.

FOR MORE INFORMATION:

Sadtler, B., Demchenko, D.O., Zheng, H., Hughes, S. M., Merkle, M.G., Damen, U., Wang, L.P., Alivisatos, A. P., "Selective Facet Reactivity during Cation Exchange in Cadmium Sulfide Nanorod," Journal of the American Chemical Society 2009, 131, 5285-93.

REFERENCE NUMBER: IB-2490

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