An inverted stack combines quantum dots, an ionic liquid and an insulating barrier to improve laboratory light emitters in red, green and blue. A peer-reviewed experiment also fabricated active-matrix display examples. Efficiency differed between colours, and the durability assessment combined accelerated measurements with lifetime estimates under specified brightness assumptions and protected conditions.
Science··Night
Ionic motion helps charges enter the emitting layer
Researchers reorganized the layers of quantum-dot light-emitting diodes (LEDs) in a peer-reviewed experiment published on 2 November. The dots share their emitting layer with an ionic liquid. Charged particles redistribute when an electric field is applied, helping electrical charges enter and move through that layer. The inverted stack also reduces damage occurring when the solvent depositing a new layer attacks the material already underneath.[1]
An insulating barrier limits electron leakage
An insulating film separates the emitting region from the layer carrying electrons, curbing excessive leakage. Peak external quantum efficiency reached 24.2 per cent for red, 20.3 per cent for green and 13.5 per cent for blue. This measures light particles escaping the device relative to electrical charge injected into it. Blue retained a different stability profile from the other colours.[1]
The team made three-colour active-matrix displays as well as individual emitters. Durability was assessed by the time needed for brightness to fall to 95 per cent of its starting value. Higher-brightness tests and an empirical relationship supplied estimates for other operating levels. Those estimates depend on that relationship; they are not all directly observed running times. Emission testing took place under nitrogen, restricting how far the laboratory results describe ordinary display use.[1]
