Researchers Design Metal-Free Molecules Capable of Glowing Persistently at Room Temperature


A new generation of electronics has been inspired by LEDs, however more research is still required to make luminescent materials that have prolonged lifespan and consume less energy. Although a few inorganic metals appear promising, they are rare, expensive to process, and likely to be toxic.

A team of researchers in China offers an alternative - a family of metal-free phosphorescent molecules possessing an efficient and constant glow in different colors at room temperature. In comparison to fluorescent organic LEDs, these molecules are nearly three times more efficient. The research details can be found in October 13 issue of Chem.

Typically phosphorescence from organic compounds have been studied in the absence of oxygen and at very low temperatures. This restricts their capacity for practical applications. Working with room-temperature phosphorescence (RTP) has been a lot more challenging as oxygen and physical vibrations obstruct the ability of organic phosphorescent molecules to discharge light.

Organic RTP systems are desirable, thanks to their wider availability and better tailorability, but are challenging to develop. In this paper, we report pure organic RTP molecules with high efficiencies and long lifetimes that will help promote basic study and practical applications of RTP processes.

Ben Zhong Tang, Chemist at the Hong Kong University of Science & Technology, and the South China University of Technology

Tang, Weijun Zhao, and Zikai He, graduate students at the Hong Kong University of Science & Technology, and colleagues found a solution to the challenge by modeling the way organic RTP systems perform. Based on this data, they planned and synthesized five carbonyl-containing aromatic molecules that remain excited and discharge light for up to 230 milliseconds.

It is also possible to tune the molecules to glow blue to orange-red. Other research teams working at the problem had focused primarily on blocking the non-radiative decays of phosphors.

The team hopes that these engineered phosphors can be repeatedly modified to match the requirements for light-sensitive switches and sensors.

Based on our model or structural design principle, we will try to develop RTP systems with lifetime up to seconds and efficiency up to unity (100%). In particular, we will work on the developments of RTP molecules and polymers with potential of finding high-tech applications in bioimaging, optical recording, anti-counterfeiting, and afterglow organic LEDs.

Ben Zhong Tang, Chemist at the Hong Kong University of Science & Technology, and the South China University of Technology


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