Roughened Electrode Interface for Quantum Dot LED Light Extraction
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Solution Overview
Problem
Conventional quantum dot light-emitting diode (QD-LED) devices have limited light extraction efficiency due to high refractive indices of materials, leading to significant light being trapped or absorbed, with existing solutions either reducing electrical performance or increasing manufacturing complexity.
Innovation Solution
Incorporating a charge transporting layer with a roughened electrode interface using nanoparticles to disrupt surface plasmon modes and reduce total internal reflection, thereby increasing the outcoupling of light without compromising electrical performance or manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If planar layers are used in QD-LED device, then manufacturing is simple, but light extraction efficiency is limited to 20-25%
Solution Approach 1:
The patent applies surface curvature by roughening the electrode interface using nanoparticles, transforming the flat planar surface into a curved/rough surface. This curvature disrupts total internal reflection and enhances light outcoupling, resolving the contradiction between manufacturing simplicity and light extraction efficiency.
Solution Approach 2:
The patent changes the surface roughness parameter of the electrode interface by incorporating nanoparticles with specific size ranges (5-50 nm). This parameter change increases light extraction efficiency from 20-25% to potentially 30-40% while maintaining the same manufacturing process flow.
2Loss of energy
If surface roughening is applied to improve light extraction, then light outcoupling increases, but electrical performance may deteriorate
Solution Approach 1:
The patent applies local quality by creating roughness only at the electrode interface where light outcoupling is needed, while keeping the bulk electrode and other functional layers planar. This localized surface modification enhances light extraction without affecting the electrical transport properties of the device.
Solution Approach 2:
The patent uses composite materials by combining metal nanoparticles (Au, Ag, Al) with the electrode material or charge transporting layer. This composite structure provides both the optical benefit of surface roughness for light outcoupling and maintains electrical conductivity through the metallic nature of the nanoparticles.
3Device complexity
If conventional planar structure is used, then device structure is simple, but significant light is trapped or absorbed
Solution Approach 1:
The patent introduces surface curvature through nanoparticle incorporation, creating a rough interface that reduces light trapping via total internal reflection and minimizes absorption by disrupting surface plasmon modes. This maintains structural simplicity while reducing energy loss.
4Loss of energy
If existing light extraction solutions are implemented, then light extraction efficiency improves, but manufacturing complexity increases
Solution Approach 1:
The patent merges the light extraction enhancement function with the existing electrode or charge transporting layer by incorporating nanoparticles during the same deposition process. This combines multiple functions (electrical conduction, charge transport, and light extraction enhancement) into a single integrated layer, avoiding additional manufacturing steps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances light extraction efficiency by increasing the amount of light outcoupled from the QD-LED device, maintaining electrical performance and simplifying manufacturing processes, while improving angular distribution and viewing angle stability.
Implementation Method 1
trapped within the electrodes as surface plasmons
Implementation Method 2
trapped within the layer stack
Implementation Method 3
The increased surface roughness also scatters light to reduce the amount of light that undergoes total internal reflection within the QD-LED device
Data Source
AI summary
A light-emitting device includes an emissive layer that emits light by recombination of first charges and second charges, a first electrode from which the first charges are supplied, a second electrode located on an opposite side of the emissive layer relative to the first electrode from which the second charges are supplied, and a charge transporting layer that is located between the emissive layer and the first electrode that injects the first charges from the first electrode into the emissive layer. The charge transporting layer includes a nanoparticle layer that provides a roughened electrode interface between the first electrode and the charge transporting layer and the emissive layer includes a plurality of quantum dots in electrical contact with the first electrode and the second electrode.