APPLICATIONS OF TECHNOLOGY:

• Low-cost power conversion
• Solar cells
• Power supply for consumer electronic

ADVANTAGES:

• Economical colloidal synthetic approach
• Low-temperature fabrication, at atmospheric pressure, no sintering needed
• Power conversion efficiency exceeds 1.6%, high carrier mobility
• Optimized bandgap for maximum absorption
• Can be adapted to plastic substrates, for flexibility and low cost
• Earth-abundant, nontoxic materials

ABSTRACT:

Paul Alivisatos, Cyrus Wadia, and Yue Wu of Lawrence Berkeley National Laboratory have developed photovoltaic cells that offer distinct advantages over current solar technology.   With a power conversion efficiency exceeding 1.6%, the new cells are produced using a novel approach - solution-phase colloidal synthesis of chalcocite (copper sulfide) nanocrystals.

The layered films of chalcocite and cadmium sulfide nanorods improve not only upon single-crystal and thin-film solar photovoltaic cells, but also on recent semiconductor nanostructure solar technology (e.g., all-inorganic, dye-sensitized, and hybrid nanocrystal-polymer composite solar cells). Semiconductor nanostructure solar cells typically have a relatively large bandgap of approximately 1.7 eV, whereas the Berkeley Lab hexagonal chalcocite nanocrystal films, which are spin-cast and monodispersed and have a bandgap of 1.26 eV, can make use of more of the solar spectrum. Moreover, they can be synthesized at temperatures as low as 150 degrees, without the need for high-temperature sintering or annealing, saving energy and substantially reducing manufacturing costs.

The nanocrystal films, on a substrate of glass, have excellent optical properties. The potential for transferring the technique to polymer substrates promises to further reduce costs for the manufacture of a lightweight, shock-resistant, and flexible power source that could be used in handheld consumer electronics.

STATUS:

• Published Patent Application PCT/US2009/035699 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:

• Wu, Y., C. Wadia, W. Ma, B. Sadtler, and A. Alivisatos, "Synthesis and Photovoltaic Application of Copper (I) Sulfide Nanocrystals," Nano Letters 8:2551-2555 (2008).
• Gur, I., N. Fromer, M. Geier, A. Alivisatos, "Air-stable all-inorganic nanocrystal solar cells processed from solution," Science 310:462-465 (2005).
• Yong, K., et al., "Shape control of CdS nanocrystals in one-pot synthesis," J. Phys. Chem. C 111 (6):2447-2458 (2007).
• Gill, W. and R. Bube, "Photovoltaic Properties of CU2S-CdS heterojunctions," Journal of Applied Physics   41:3731-3738 (1970).

REFERENCE NUMBER: IB-2511

SEE THESE OTHER BERKELEY LAB TECHNOLOGIES IN THIS FIELD:

• Streamlined Synthesis of Binary Nanorods for Power-Efficient Nanocrystal Devices IB-1940
• Controlled Assembly of Nanocrystal/Organic Composites IB-1941
• Nanocrystal Heterostructures for Biological Imaging and Electronic & Photonic Devices IB-1949