Organic light-emitting diodes (OLEDs) are a class of organic electronics found in smartphones and displays and can be more efficient than competing technologies.
Although OLED television screens have vivid picture quality, they also have drawbacks such as high cost, comparatively short lifespans, and blue light stability.
The screen pixels used in OLED displays are composed of red, green and blue subpixels that light up at different intensities to create different colours.
However, the subpixels that emit blue light are the least stable and can be susceptible to so called screen burn-in, which can discolour the screen.
In a paper published in Nature Materials, a team of researchers from Loughborough, Cambridge, and Northumbria Universities, plus Imperial College London, describe a new design that overcomes these issues and may lead to simpler, less expensive systems with purer and more stable blue light.
The findings may pave the way for TV and smartphone screens that consume less energy.
An OLED is built in layers, with sheets of an organic semiconductor between two electrodes. In the middle of the stack is the emissive layer, which lights up when electricity is passed through it.
According to Loughborough University, an ideal OLED turns most of the electric energy into light, but the energy can get diverted and degrade the structure of the OLED. This is especially a problem with blue light, and reduces the OLED efficiency and lifetime. The design of efficient OLEDs comes down to managing how the structure of an OLED can channel energy constructively.
To solve this problem, the research team designed a new light emitter molecule that blocks the destructive energy pathways by adding shields to the emitter, which controls how the molecules interact.
Loughborough University's Dr Felix Plasser used computational models to explain the remarkable properties of the central light-emitting molecule.
"We were particularly interested in understanding why light emission occurred within the specific energy range required for clear blue emission", Dr Plasser said in a statement.
"Our computational models underlined the idea that the molecule in its normal, stable state - called the 'ground state' - is already in a state that makes it ready or 'pre-relaxed' to transition to an excited state when energy is applied. This readiness in the ground state helps explain the molecule's unique properties."
This better understanding of how efficient a molecule in an OLED can be will inform how materials are designed and used in future, supporting the push towards higher device performance.
Cambridge University's Dr Daniel Congrave, who led the material design and synthetic work alongside Professor Hugo Bronstein, said: "Pixels that emit blue light are essential for a practical display but are also where the problems lie. We've designed a molecule that's allowed us to simplify the emissive layer of the blue pixel to only two components, while maintaining high efficiency, which could help to drive down cost.
"The molecule we describe in this paper is also one of the narrowest emitting blue molecules out there, which is very useful for screens because it allows for high colour purity."
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