>>could improve Med Imaging/ Cancer Rx’s + Increase Solar Cell efficency by 25 – 30%. Goal is to turn low-energy colors of light, such as red, into higher-energy colors, like blue/green. A traditional solar cell can only absorb light with energy above a certain threshold. Infrared light passes right through, its energy untapped. But if low-energy could be transformed into higher-energy light, a solar cell could absorb more.
UD’s College of Engineering’s A/Prof Matthew Doty said; “You can’t simply turn a red photon into a blue one, but you can combine the energy from two or more red photons to make one blue photon.” …”Photon upconversion” isn’t new but UD team’s approach is. They want to design a new kind of semiconductor nanostructure that will act like a ratchet. It will absorb 2 red photons, one after the other, to push an electron into an excited state when it can emit a single high-energy (blue) photon.
METHOD: they will develop new semiconductor structures with multiple layers of different materials, eg aluminum arsenide and gallium bismuth arsenide, each a few nm’s thick. This “tailored landscape” will control the flow of electrons into states with varying potential energy, turning once-wasted photons into useful energy. It could reach upconversion efficiency of 86%, a vast improvement over 36% efficiency of today’s materials. + amount of light absorbed and energy emitted could be customized for any apps, from ightbulbs to laser-guided surgery.
They used molecular beam epitaxy to make the nanostructures. They will be built by depositing layers of atoms one at a time. Each structure will be tested to see how well it absorbs and emits light, and results used to tailor the structure to improve performance.
They will also will develop a milk-like solution filled with millions of identical individual nanoparticles, each one containing multiple layers of different materials >> this will implement the photon ratchet idea. The team envisions a future upconversion “paint” that could be easily applied to solar cells, windows and other commercial products.
Biomed: Many diagnostic tests and med Rx’s, eg CT and PET scans to chemotherapy, rely on fluorescent dyes and drugs. Ideally, such payloads are delivered both at specific disease sites and times. The UD team aims to develop an upconversion nanoparticle that can be triggered by light to release its payload >> ie controlled release of drug therapies even deep within diseased human tissue while reducing the peripheral damage to normal tissue by minimizing the laser power required. http://www.udel.edu/udaily/2016/jul/high-energy-light-072315.html
The UD research team aims to develop new nanostructures that act like a ratchet to combine the energy of two red photons of light into a single blue photon, which has higher energy. Such an advance could improve solar cell efficiency to chemotherapy treatments. Credit: Image courtesy of University of Delawar
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