WARF Patents Cost and Energy-Efficient Schottky Barrier Photovoltaic Cells Using Carbon Nanotubes as Photoconducting Material-Licensing Opportunities Available

University of Wisconsin-Madison researchers have developed a cost- and energy-efficient photovoltaic cell that uses carbon nanotubes as the photoconducting material. Unlike semiconductor materials, carbon nanotubes absorb different spectra of light depending on the diameter and chirality of each tube. A variety of nanotube sizes and chiralities can be used within a photovoltaic array to significantly increase the efficiency over current technologies.

The carbon nanotube Schottky barrier photovoltaic cell earned the Wisconsin Alumni Research Foundation (Madison, WI) United States Patent 7,645,933 (January 12, 2010).

Inventors UW-Madison Materials Science and Engineering Professor Max Lagally, Professor Mark Eriksson, Todd Narkis, and Matt Marcus developed the patented carbon nanotube Schottky barrier photovoltaic cells and methods and apparatus for making the cells. The photovoltaic cells include contacts made from a first contact material which contact through photoconducting carbon nanotubes bridges to a second contact material.   

A Schottky barrier is formed at the interface between the first contact material and the carbon nanotubes while at the interface between the second contact material and the carbon nanotubes, a Schottky barrier for the opposite carrier is formed, or a small, or no Schottky barrier is formed. It is the Schottky barrier asymmetry that allows the photo-excited electron-hole pairs to escape from the carbon nanotube device.

The invention also includes a novel method of manufacturing the nanotube array. Normally, nanotubes are grown with a catalyst and preserved in a fluid, which the end user must go through several steps to remove. The nanotubes described here can be grown and then directly attached to the array surface.

Because large numbers of nanotubes are needed to generate current efficiently, they are attached in a dense, but random arrangement. After the nanotubes are deposited on the surface, the metallic contacts from which the current is gathered are applied in a uniform grid over the nanotubes.

KEY BENEFITS

• Significantly higher efficiency than current technologies


• Relatively inexpensive to manufacture


• Potentially able to compete with commercial sources for generating power


• Carbon nanotubes are flexible and may be placed on a polymer support to reduce production costs


• Avoids the need for expensive silicon processing environments


• Useful to power a variety of devices, including computers, mobile phones, calculators, and watches


• Useful to generate power in a power grid

For current licensing status, please contact Wisconsin Alumni Research Foundation team at licensing@warf.org or phone 608.262.4924.

Organosilicon Electrolyte and Carbon Nanotubes Make More Power Supercapacitors

Wisconsin Alumni Research Foundation (Madison, WI) reveals a more powerful electrochemical double-layer capacitor using organosilicon electrolytes and carbon nanotubes in U.S. Patent 7,612,985. University of Wisconsin inventors Viacheslav V. Dementiev, Robert C. West, Robert J. Hamers and Kiu-Yuen Tse say the electrolytes can provide improved supercapacitors, and improved electrodes and separators for use in capacitors and batteries. They could be used in electric and hybrid-electric vehicles, satellites, wind generators, photovoltaics, copy machines, high power electronic household appliances, electric tools, electric power generation, and electric distribution systems.

Lingzhi Zhang, Robert West and Viacheslav Dementiev have also developed lithium batteries using pure polysiloxane electrolytes. When compared to the carbonate electrolyte, the polysiloxane electrolyte proved to be superior in every way. In a test to simulate the batteries' life spans, the two batteries are charged and discharged repeatedly. The battery using the carbonate electrolyte failed after 500 cycles, which is equivalent to approximately two years of use. Results from this same test show a projected lifetime of over twelve years for the battery using the polysiloxane electrolyte. This increase is a direct result of polysiloxane's superior electrochemical stability. Furthermore, silicone electrolytes are nonflammable, environmentally benign and nontoxic, all of which are necessary for the battery to be implantable in the human body.

Quallion already uses the electrolytes developed at UW-Madison in new lithium batteries that power an implant device called the Bion. This device is a neurostimulator capable of alleviating many of the debilitating symptoms of epilepsy, strokes, Parkinson's disease and spinal cord injuries. The Bion is only 18 millimeters long and three millimeters in diameter. It is implanted using a hypodermic needle near the point where a nerve connection has been broken. The neurostimulator relays electrical signals from one side of the severed nerve to the other, effectively bridging the gap.