If you’ve ever watched television or read by the light of a fluorescent lamp, you, like billions of other people on the planet, have benefitted from the physical properties of substances called phosphors.
Most of us take them for granted or don’t even realize they are there, but they convert otherwise invisible energy into (usually) visible light by glowing when energized.
Without them, television screens and fluorescent lights would not function, but you might be surprised to know that phosphors have other, more high-tech, applications.
Research conducted at UTSA by Dr. Ajith Kumar and graduate student Madhab Pokhrel promises to improve technologies such as solar energy, commercial product authentication, medical testing and many others. Kumar has developed a phosphor that is more sensitive to infrared (IR) frequencies than any other known phosphor.
The implications of his research go beyond the applications themselves. Not only does the research have the potential to improve the technologies mentioned and more, it does so at a lower cost in terms of energy used. Since IR energy takes less energy to produce than higher frequency energy, such as ultraviolet (UV), IR energy production is most cost-effective and more efficient—in other words, it’s greener.
According to Kumar, more than half of the solar energy that strikes a solar cell is wasted because the currently used material responds only to limited bandwidths of energy. Kumar says the use of a highly efficient phosphor such as his would extend the range of frequencies that solar cells could use to produce energy, becoming much more efficient than what current technology allows. With the world trying to transition from finite to sustainable energy sources, this type of development can be groundbreaking.
In the field of commercial product authentication—or the prevention of counterfeiting—the use of highly-efficient phosphors like Kumar’s has even wider applications.
Counterfeiting and stealing intellectual property drives up the cost of many commercial goods. It costs industries and the public some $200 billion annually, according to ipwatchdog.com. Phosphors are being used increasingly to make counterfeiting harder to get away with. According to Dr. Kumar, they are used in everything from paper money, to cigarettes, to blue jeans.
For example, phosphors are woven in very specific patterns into the fabric of certain brands of blue jeans to distinguish them from their illegitimate counterparts.
“By adjusting the composition and selecting the suitable emission color of interest, we can design phosphors that show thousands of well-defined spectral features, and that is the major property utilized in the authentication process,” Kumar said. “When we design an authentication material for a specific product, we also design a specific (usually IR-sensitive) sensor that can detect [specific hidden features inside the material] for that specific emission color.”
IR-sensitive phosphors are much more difficult to detect than the commonly used UV-sensitive phosphors.
“So, simply by shining the IR laser or LED from the sensing device we can (detect the hidden) features coded inside the material,” Kumar said.
IR-sensitive phosphors can also be used in certain medical testing procedures that require a dye contrast. According to Kumar, this lessens the need to use higher frequency energy, like x-rays, that are more harmful to patients and require much higher levels of energy to operate.