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.
There is a possibility of ligands interfering with conduction properties and trials for modification may cause quantum dot fusion resulting in damage of its useful characteristics. 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 placed between two ceramic electrodes.
Current must be conducted via the quantum dots to generate light, but they have to be placed at a distance from each another to make them function appropriately. In a previous design, the electric current passing through the quantum dots did not generate light due to the existence of a minimal resistance path 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 electric current flow.
QD-LEDs can be used in lasers, general light sources, computer screens and televisions.
Source: http://www.harvard.edu