ETH researchers have further developed QLED technology for screens. They made light sources that for the first time emit light in high intensity in only one direction. This makes the technology extremely energy efficient.
QLED screens have been available for purchase for a few years. They are known for their bright, intense colors, which are generated with the so-called quantum dot technology. QLED stands for quantum dot light emitting diode. Researchers at ETH Zurich have now developed a technology that increases the energy efficiency of the QLEDs. The scientists achieved this by minimizing the scattering losses of the light inside the diodes. This means that a larger proportion of the light generated is released to the outside.
Conventional QLEDs consist of a large number of spherical semiconductor nanocrystals, which are also called quantum dots. These nanocrystals are excited from behind with UV light on a screen. The crystals convert this into colored light in the visible area. Depending on the material composition of the nanocrystal, a different color is created.
However, these spherical nanocrystals scatter the light generated on the inside of the screen on all sides. Only around a fifth of the light generated emerges and is visible to the viewer. To increase the energy efficiency of the technology, scientists have been trying for years to develop nanocrystals that emit light only in one direction (forward, towards the viewer). The first such light sources already exist. They do not consist of spherical crystals, but of ultra-thin nanoplates. These emit light only in one direction – perpendicular to the platelet level.
If these nanoplates are arranged next to one another in a layer, they generate a relatively weak light that is not sufficient for screens. In order to increase the light intensity, scientists are pursuing the approach of laying several layers of such platelets on top of one another. However, the plates begin to interact with each other, and the light is not only emitted in one direction, but on all sides.
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