Ultradots, Inc. (Menlo Park, CA) patented nano luminescent materials emit light in the visible range or the near infrared range and are targeted for security, anti-counterfeiting, solar energy and photonic devices applications. Luminescent materials and the use of such materials in anti-counterfeiting, inventory control, photovoltaic, photonic and other applications are described in U.S. Patent 7,641,815.
Since emitted light in the infrared range is not visible, the luminescent materials can be advantageously used to form covert markings for anti-counterfeiting applications.
The luminescent material exhibits photoluminescence having: (a) a quantum efficiency of at least 20 percent; (b) a spectral width no greater than 100 nm at Full Width at Half Maximum; and (c) a peak emission wavelength in the near infrared range, according to developers John Varadarajan, Mirna Resan, Fanxin Wu, William M. Pfenninger and Nemanja Vockic.
In the year 2000, the World Health Organization estimated that more than 7% of the world’s pharmaceuticals were counterfeit. In the United States alone, the loss to counterfeit drugs was estimated to be in the range of $2 billion. By 2005, the estimate of the world’s pharmaceutical supply chain loss was more than 10% of the world supply of drugs or $32 billion a year. Concerning less critical products in the supply chain of goods, the financial loss to counterfeit commodity products amounted to more than $500 billion and more than 7% of all trade in 2004
Although the nanodots have anti-counterfeiting and inventory control applications, the inventors contemplate that the luminescent materials can be used for a variety of other applications. In particular, the luminescent materials can have band gap energies, electrical conductivities, and other characteristics that render the luminescent materials desirable for a variety of optoelectronic applications, such as those related to photovoltaic devices, photoconductors, photodetectors, light-emitting diodes, lasers, and other devices that involve photons and charge carriers during their operation.
The luminescent materials can be advantageously used in photovoltaic devices as a solar down conversion material. In particular, the luminescent materials can absorb a wide range of solar wavelengths and convert the absorbed solar radiation into a peak emission wavelength.
The luminescent materials can be advantageously used in photovoltaic devices as a solar down conversion material. In particular, the luminescent materials can absorb a wide range of solar wavelengths and convert the absorbed solar radiation into a peak emission wavelength.
This peak emission wavelength can have an energy matched with (e.g., at or near) a band gap of a semiconductor material, such as silicon, within the photovoltaic devices. This down conversion process can increase a theoretical efficiency of a silicon photovoltaic device from 31% to 41%. Further enhancements in efficiency can occur with the use of solar down conversion concentrators, where the absorbed solar radiation from a large area is concentrated onto a small area of the semiconductor material.
