Durham team makes blue OLED breakthrough

The findings by scientists at Durham University could help enable the next generation of energy-saving display technologies. Their results have been published in Nature Photonics.

OLED displays found in most smartphones and TVs rely on light emission from specialised organic molecules, but obtaining stable, efficient blue emission suitable for displays remains challenging.

Now, Durham University said its researchers have unlocked a new design strategy using ‘hyperfluorescent’ OLEDs, where energy is transferred from a ‘sensitiser’ molecule to a separate ‘emitter’ molecule.

The team found that sensitiser molecules, previously dismissed as poor emitters, perform remarkably well in hyperfluorescent OLEDs.

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In a statement, Durham University’s Kleitos Stavrou, lead author of the study, said: "We discovered a 'blind spot' where materials overlooked by conventional thinking can become highly effective when used as sensitisers in hyperfluorescence OLEDs.”

According to the University, the molecule ACRSA – a spiro compound that exhibits efficient thermally activated delayed fluorescence - was found to triple the OLED efficiency when used as a sensitiser in hyperfluorescence OLEDs.

The researchers attribute this to ACRSA's rigid molecular structure and long-lived excited states.

By using a greenish sensitiser, such as ACRSA, deep blue light emission can be achieved by transferring ACRSA’s energy to a blue terminal emitter.

“This approach reduces exciton energy compared to direct blue emission in devices, allowing more stable, longer-lasting blue OLEDs,” said senior author of the study, Professor Andrew Monkman of Durham University’s Physics Department.

Overall, the strategy is said to provide a new molecular design paradigm for stable and highly efficient displays.

“Our findings reveal an unexplored territory for hyperfluorescent OLEDs that could greatly expand material choices for the next generation of displays, that will also use up to 30 per cent less electricity” said Professor Monkman.

The researchers will further develop hyperfluorescent OLEDs with industrial partners and aim for commercial applications.