Brighter, thinner, and less power-hungry screens could emerge from a surprisingly simple solution.
Researchers from MIT and Samsung have coated quantum dot diodes with a protective resin. On certain blue prototypes, this operation multiplied their lifespan by more than 5,000 times, without disrupting their manufacturing process.
Quantum dots are tiny semiconductor crystals, measuring only a few nanometers. When they receive energy, they emit light whose color depends precisely on their size. This allows them to produce particularly pure reds, greens, and blues, with less light loss than several current technologies.
Some televisions already use these nanoparticles, but only as color filters in front of another light source. The QD-LEDs studied here work differently. The electric current directly excites the quantum dots, which themselves produce the light. This architecture could simplify screens while reducing their thickness and energy consumption.
However, one obstacle persisted: blue diodes aged far too quickly. Their stability remained 50 to 100 times lower than that of red and green versions. In a complete television, this weakness could have limited the operating life to just a few months, making any realistic commercialization impossible.
To understand this degradation, the researchers cut the diodes into extremely thin slices. Powerful microscopes then allowed them to observe each layer before and after intensive operation. In the blue components, several materials thinned, changed shape, and eventually mixed together. The quantum dots then lost their initial structure.
These transformations seem to be linked in particular to the release of hydrogen and oxygen during operation. These elements would promote the formation of moisture around the nanoparticles, accelerating their deterioration. The team therefore encapsulated the diodes in an acrylate-based resin, which is already compatible with simple and relatively inexpensive industrial processes.
The protection improved the lifespan of red diodes eightfold. For blue ones, the gain exceeded a factor of 5,000 in some experiments. The resin limits the release of gases and slows down the physical changes observed in the different layers. It does not, however, eliminate all the mechanisms responsible for aging.
The researchers now wish to add other protective layers to further increase stability and efficiency. This technology could equip televisions, smartphones, virtual reality headsets, or medical imaging devices. It could also be used to manufacture large light-emitting surfaces, sensors, or lasers using very precise colors.