Washington
Improved quantum-dot LED design
Harvard School of Engineering and Applied Sciences (SEAS) researchers have demonstrated a robust new architecture for quantum-dot light-emitting devices (QD-LEDs) by nestling quantum dots in an insulating egg-crate structure.
Quantum dots are crystals, each only 6 nanometers in diameter, that glow with bright, rich colors when stimulated by an electric current. QD-LEDs are expected to find applications in television and computer screens, general light sources, and lasers.
Previous work in the field had been complicated by organic molecules called ligands that dangle from the surface of the quantum dots. The ligands play an essential role in quantum dot formation, but they can interfere with current conduction, and attempts to modify them can cause the quantum dots to fuse together, destroying the properties that make them useful. Organic molecules can also degrade over time when exposed to UV rays.
Thanks to an inventive change in technique devised by the Harvard team, the once-troublesome ligands can now be used to build a more versatile QD-LED structure. The new single-layer design can withstand the use of chemical treatments to optimize the device’s performance for diverse applications. The new QD-LED resembles a sandwich, with a single active layer of quantum dots nestled in insulation and trapped between two ceramic electrodes.
To create light, current must be funneled through the quantum dots, but the dots also have to be kept apart from one another in order to function. The researchers used atomic layer deposition (ALD) — a technique that involves jets of water. ALD takes advantage of the water-resistant ligands on the quantum dots, so when aluminum oxide insulation is applied to the surface, it selectively fills the gaps between the dots, producing a flat surface on the top. The new structure allows more effective control over the flow of electrical current, and essentially creates a structure that acts as an “egg crate” for quantum dots.
Read more: http://goo.gl/q39Em
Harvard School of Engineering and Applied Sciences (SEAS) researchers have demonstrated a robust new architecture for quantum-dot light-emitting devices (QD-LEDs) by nestling quantum dots in an insulating egg-crate structure.
Quantum dots are crystals, each only 6 nanometers in diameter, that glow with bright, rich colors when stimulated by an electric current. QD-LEDs are expected to find applications in television and computer screens, general light sources, and lasers.
Previous work in the field had been complicated by organic molecules called ligands that dangle from the surface of the quantum dots. The ligands play an essential role in quantum dot formation, but they can interfere with current conduction, and attempts to modify them can cause the quantum dots to fuse together, destroying the properties that make them useful. Organic molecules can also degrade over time when exposed to UV rays.
Thanks to an inventive change in technique devised by the Harvard team, the once-troublesome ligands can now be used to build a more versatile QD-LED structure. The new single-layer design can withstand the use of chemical treatments to optimize the device’s performance for diverse applications. The new QD-LED resembles a sandwich, with a single active layer of quantum dots nestled in insulation and trapped between two ceramic electrodes.
To create light, current must be funneled through the quantum dots, but the dots also have to be kept apart from one another in order to function. The researchers used atomic layer deposition (ALD) — a technique that involves jets of water. ALD takes advantage of the water-resistant ligands on the quantum dots, so when aluminum oxide insulation is applied to the surface, it selectively fills the gaps between the dots, producing a flat surface on the top. The new structure allows more effective control over the flow of electrical current, and essentially creates a structure that acts as an “egg crate” for quantum dots.
Read more: http://goo.gl/q39Em
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