A New, More Efficient "Deep-Blue" OLED Could Boost Brightness and Lifespan in Future Displays

Researchers from the Karlsruhe Institute of Technology (KIT) and Shanghai University are blue, but for very good reason: they've come up with a better blue organic light-emitting diode (OLED), which uses "exciplex" to set a record in external quantum efficiency.

"The exciplex strategy allows [us] to achieve deep-blue electroluminescence," explains co-corresponding author Stefan Bräse of the team's work, "because the energy levels of the electron-donating carbazole fragments and electron-accepting triazine fragments can be adjusted independently of each other." The upshot: better, more stable, and higher-efficiency blue OLEDs alongside existing red and green counterparts.

The "exciplex strategy" revolves around a new molecule type with carbazole and triazine fragments linked by a silicon atom. As the molecules assemble into nanoparticles, the creation of an electronically-excited molecule complex or "exciplex" results the the emission of light — but in a different manner to single-molecule excitation, as with traditional approaches towards making blue OLEDs.

The team's prototype OLEDs offer, testing has shown, a 20.35 per cent external quantum efficiency — the ratio between the power you put into it and the radiation you receive out. That translates to a 5,000 candela per square meter (cd/m²) luminance — meaning the light is brighter and requires less energy to create than existing approaches. Better still, they're not complex to make: "Easy synthesis of the molecule and production of the components pave the way for a new generation of efficient and long-lived deep-blue OLEDs," Bräse claims.

The team's work has been published in the journal Science Advances under open-access terms, though there is no word yet on a timescale for commercialization in mass-produced OLED displays — such as those used in smartphones, TVs, and signage.