Scientists Create Architecture for Quantum-Dot Light-Emitting Devices

Scientists at the Harvard School of Engineering and Applied Sciences (SEAS) have developed a novel single-layer design for building quantum-dot light-emitting devices (QD-LEDs) by stacking quantum dots within an insulating structure having the shape of an egg crate.

The researchers’ technique has overcome the functional difficulties of ligands, which are organic molecules used in the formation of quantum dots, and has made them to be used in the construction of more adaptable QD-LED structures. The innovative design can resist the application of chemical treatments to enhance the performance of the device for various applications.

The ligands try to modify them during their reaction with the current conduction, resulting in the fusion of quantum dots, eventually annihilating their functional properties. Organic molecules are also subjected to degradation under ultraviolet ray exposure over a period of time. The new QD-LED design looks like a sandwich, where a single-active quantum dot layer is placed in insulation and nestled between two electrodes made of ceramics.

Current must be conducted via the quantum dots to generate light, but they have to be placed at a distance from each other to make them work. In the previous design, the electric current passed through the quantum dots did not generate light due to the existence of a path of minimal resistance between the quantum dots.

The researchers replaced the conventional evaporation process utilized to apply insulating material to the equipment with atomic layer deposition (ALD) technique that uses jets of water. The ALD technique gets the full benefits of the water-resistant ligands over the quantum dots. Hence, when the aluminum oxide insulation is used to cover the surface, it carefully fills the voids between the dots, resulting in the formation of a flat surface over the top. The new design enables highly efficient control on the electrical current flow.

QD-LEDs can be used in lasers, general light sources, computer screens and televisions.

Source: http://www.harvard.edu

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