http://www.digitaljournal.com/tech-and-science/technology/improving-leds-with-quantum-dots/article/512286

Improving LEDs with quantum dots

Posted Jan 16, 2018 by Tim Sandle
Getting lights to last for longer and remain bright is an important backdrop to furthering the development of many modern technologies. A type of quantum dot could well hold the answer to driving such improvements.
The pre-flight Saffire-I lit by green LEDs as it was during flight.
The pre-flight Saffire-I lit by green LEDs as it was during flight.
NASA
Researchers have been studying quantum dots in order to find a low-energy means of reproducing light in every color visible to the human eye and at a very bright luminescence. Given the success of the research, the quantum dots should provide the basis for a new generation of light-emitting diodes.
The research comes from an international research team led by ETH Zurich and IBM Research Zurich. At the basis of the technology is a class of nanocrystals that have the ability to shine a range of very bright colors. The nanocrystals are formed from caesium lead halide compounds.
One reason for the crustal properties is due to the molecular arrangement; here the crystals are arranged in a perovskite lattice structure. This enables the researchers to alter the emission wavelength by tuning both size and composition of nanoparticles.
Part of the special properties of the quantum dots comes down to the nanocrystals emitting light very quickly. The caesium lead halide quantum dots are capable of emitting light at room temperature after just one nanosecond.
Lead researcher Professor Maksym Kovalenko managed to create the nanocrystals from semiconductor material. Speaking with his university's website, the scientist states: “These tiny crystals have proved to be extremely bright and fast emitting light sources, brighter and faster than any other type of quantum dot studied so far.”
He goes onto explain how, by varying the composition of the chemical elements and the size of the nanoparticles, the researchers succeeded in producing a range of nanocrystals that can light up each of the colors across the visible spectrum.
The quantum dots can be controlled through the application of photons, used to excite semiconductor nanocrystals in an array. This forces an electron leaves its original place in the crystal lattice, leaving behind a hole. Illumination can also be controlled, since under given conditions, an electron hole pair is unable to revert to its energy ground state and therefore the light emission is suppressed and occurs delayed.
The research has been reported to the journal Nature. The research paper is titled “Bright triplet excitons in caesium lead halide perovskites.”
The primary application of the quantum dots will be with a next generation of light-emitting diodes for larger displays.