New hybrid material transforms light

Researchers from the University of Texas at Austin have created a new class of materials that can absorb low energy light and transform it into higher energy light. The new material is composed of ultra-small silicon nanoparticles and organic molecules closely related to ones used in OLED TVs. This new composite moves electrons between its organic and inorganic components, with applications for more efficient solar panels, more accurate medical imaging and better night vision goggles. The material is described in the journal Nature Chemistry.

Sean Roberts, an associate professor of chemistry at UT Austin, said the new process gives researchers a new method to design materials. “It allows us to take two extremely different substances, silicon and organic molecules, and bond them strongly enough to create not just a mixture, but an entirely new hybrid material with properties that are completely distinct from each of the two components,” Roberts said.

Composites are made of two or more components that adopt unique properties when combined. For example, composites of carbon fibres and resins find use as lightweight materials for airplane wings, racing cars and many sporting products. In the paper co-authored by Roberts, the inorganic and organic components are combined to show unique interaction with light. Among those properties are the ability to turn long-wavelength photons — the type found in red light, which tends to travel well through tissue, fog and liquids — into short-wavelength blue or ultraviolet photons, which are the types that usually make sensors work or produce a range of chemical reactions. This means the material could prove useful in new technologies as diverse as bioimaging, light-based 3D printing and light sensors that can be used to help self-driving cards travel through fog.

“This concept may be able to create systems that can see in near infrared. That can be useful for autonomous vehicles, sensors and night vision systems,” Roberts said.

Taking low energy light and making it higher energy could also help to boost the efficiency of solar cells by allowing them to capture near-infrared light that would normally pass through them. When the technology is optimised, capturing low energy light could reduce the size of solar panels by 30%. Members of the research team have been working on light conversion of this type for several years. In a previous paper, they described successfully connecting anthracene, an organic molecule that can emit blue light, with silicon, a material used in solar panels and in many semiconductors. Seeking to amplify the interaction between these materials, the researchers developed a new method for forging electrically conductive bridges between anthracene and silicon nanocrystals.

The resulting strong chemical bond increases the speed with which the two molecules can exchange energy, almost doubling the efficiency in converting lower energy light to higher energy light, compared with the team’s previous research findings.

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