Improved TV, smartphone displays in the offing

Representational image

Boston: Scientists have designed more than 1,000 new blue-light emitting molecules for organic light-emitting diodes (OLEDs) that could dramatically improve displays for televisions, smartphones and tablets.

OLED screens use organic molecules that emit light when an electric current is applied. Unlike ubiquitous liquid crystal displays (LCDs), OLED screens do not require a backlight, meaning the display can be as thin and flexible as a sheet of plastic.

Individual pixels can be switched on or entirely off, dramatically improving the screen's colour contrast and energy consumption.

OLEDs are already replacing LCDs in high-end consumer devices but a lack of stable and efficient blue materials has made them less competitive in large displays such as televisions.

Researchers from Harvard University and Massachusetts Institute of Technology (MIT) in the US developed a large-scale, computer-driven screening process, called the Molecular Space Shuttle, that incorporates theoretical and experimental chemistry, machine learning and cheminformatics to quickly identify new OLED molecules that perform as well as, or better than, industry standards.

"People once believed that this family of organic light-emitting molecules was restricted to a small region of molecular space," said Alan Aspuru-Guzik from Harvard.

"But by developing a sophisticated molecular builder, using state-of-the art machine learning, and drawing on the expertise of experimentalists, we discovered a large set of high-performing blue OLED materials," said Aspuru-Guzik.

The biggest challenge in manufacturing affordable OLEDs is emission of the colour blue.

Like LCDs, OLEDs rely on green, red and blue subpixels to produce every colour on screen. But it has been difficult to find organic molecules that efficiently emit blue light.

To improve efficiency, OLED producers have created organometallic molecules with expensive transition metals like iridium to enhance the molecule through phosphorescence. This solution is expensive and it has yet to achieve a stable blue colour.

Researchers sought to replace these organometallic systems with entirely organic molecules.

They began by building libraries of more than 1.6 million candidate molecules. Then, to narrow the field, researchers developed new machine learning algorithms to predict which molecules were likely to have good outcomes, and prioritise those to be virtually tested.

This effectively reduced the computational cost of the search by at least a factor of ten.

"This research is an intermediate stop in a trajectory towards more and more advanced organic molecules that could be used in flow batteries, solar cells, organic lasers and more," said Aspuru-Guzik.

The findings were published in the journal Nature Materials.