International researchers figure out how molecules can emit purer colours on mobile device displays

A team of international researchers has just resolved how molecules can emit purer colours (blue) for screen pixels using mechanical-quantum calculations. Achieving maximum efficiency, resolution and lower energy consumption in devices such as mobile phones, smart clocks or tablets is one of the scientific and technological challenges of the moment.

The study, published in the scientific journal Nature Communications, has been contributed to by Juan Carlos Sancho, researcher from the Department of Physical Chemistry and member of the University of Alicante Quantum Chemistry Group, along with colleagues from the universities of Mons (Belgium), Bologna (Italy) and Saint Andrews (United Kingdom).

According to the UA researcher, it did not seem possible to have a pure blue colour so far. Either the molecule emitted many blue photons with so little intensity that they were hardly seen, or the molecule offered few, yet bright, photons. In this sense, neither option was finally suitable for the efficiency of the mobile device, the resolution of the screen or its energy consumption.

In 2016, Japanese scientist Takuji Hatekayama verified by experience that there was a type of molecules that contradicted this behaviour, although the reasons for this phenomenon were not known. It has been only with this international work that has managed to prove how these antagonistic effects (many yet quite inconvenient photons vs. few yet very effective photons) can be redirected and explained from the molecular point of view, which clears the way to continue advancing in that direction. Juan Carlos Sancho stated that they have found the physical reasons for this behaviour by applying more sophisticated chemical-quantum methods than usual.

Currently, in order to achieve sufficient screen resolution, blue sub-pixels are needed, that are approximately 50% of the total size of each pixel, with red and green colours completing the range of primary or RGB colours. This produces that an important part of the energy coming from the battery is lost at that same time, since only a part of the electrons that go to that blue sub-pixel ends up converted into photons.

However, as the UA researcher stressed, increasing the efficiency of the process by improving the capacity of the active molecules that form part of that sub-pixel would have a double advantage: on the one hand, we could reduce the size of the blue sub-pixel and even improve the quality of the image by being able to increase the density of pixels per inch; and, on the other hand, energy consumption would be considerably reduced since a greater proportion of electrons would thus be converted into photons.

Reference

“Highly emissive excitons with reduced exchange energy in thermally activated delayed fluorescent molecules”.Anton Pershin, David Hall, Vincent Lemaur, Juan-Carlos Sancho-Garcia, Luca Muccioli, Eli Zysman-Colman, David Beljonne & Yoann Olivier. Nature Communications volume 10, Article number: 597 (2019)