Free Radical OLEDs Will Advance The Next Generation Of Display Technology

- Nov 23, 2018-

It is reported that scientists have discovered that semiconductor molecules with unpaired electrons (called "free radicals") can be used to make very efficient organic light-emitting diodes (OLEDs), using their quantum mechanical "rotation" characteristics to overcome traditional non-free radical materials. Efficiency limits.


Free radicals are often known for their extremely high chemical reactions and their adverse effects, including human health and the ozone layer. Now, through the discovery of scientists, free radical OLEDs will become the foundation of next-generation display and lighting technologies.


The team from Cambridge University and Jilin University described the "upward" and "downward" rotational characteristics of the free radical, which is called the "double" electronic state. When these radical OLEDs are energized, a high-luminance double-excited state is generated, and a deep red light with an efficiency of nearly 100% can be emitted.


For traditional compounds (ie, non-free radicals without unpaired electrons), quantum force spins require charge injection to form 25% bright "single-state" and 75% dark "triplet" in the operation of the OLED. Free radicals provide a good solution to the most basic rotation problems that have plagued researchers since the advent of OLEDs in the 1980s.


Dr. Emile Evans, chief co-author of the team of Professor Richard Friend of the Cavendish Laboratory, said: "On the surface, free radicals in OLEDs should not have any practical effect, which makes our findings very surprising. The free radicals themselves are abnormally luminescent and operate in OLEDs with unusual physical properties." When separated in a host matrix and excited by a laser, the radicals atypically have a single efficiency close to luminescence. This highly luminescent behavior is translated into high-brightness LEDs, but there is another transformation: in devices where currents inject electrons into the unpaired electron energy levels in the free radicals and pull the electrons out of the lower energy levels. Together with another part of the molecule, a bright double excited state is formed.


In the future, this high-efficiency blue and green photo-radical diodes may further drive material innovation. At present, researchers are exploring the possibility of free radicals outside of lighting applications, hoping that free radicals can be inspired by other branches of organic electronics research.