QLED Reflective Electrode Phase Shift for Color Uniformity
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Solution Overview
Problem
The complexity and cost of fabricating quantum dot light emitting diodes (QLEDs) are increased due to the need for different sub-pixel structures and optical cavity designs for various colors, leading to inefficiencies and off-axis color shifts.
Innovation Solution
A light-emitting layer structure with a reflective electrode that introduces a specific phase shift based on the wavelength of emitted light, using similar layer thicknesses for charge transport and emissive layers across sub-pixels, and varying the configuration of conducting layers to optimize constructive interference for each color.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If different sub-pixel structures and optical cavity designs are used for various colors, then off-axis color shift is minimized and emission similarity is improved, but device complexity and fabrication cost increase
Solution Approach 1:
The patent applies local quality by making the optical cavity properties wavelength-specific. Each sub-pixel has a reflective electrode with tailored optical characteristics (reflectivity, phase shift) matched to its specific emission wavelength. This allows each location to be optimized for its color while maintaining overall device simplicity, resolving the contradiction between emission similarity and device complexity.
2Manufacturing precision
If different sub-pixel structures are used for various colors, then angular emission similarity is improved, but fabrication cost increases
Solution Approach 1:
The patent employs universality by using a common optical cavity structure and identical charge transport layer thicknesses across all sub-pixels. The wavelength-specific optimization is achieved through the reflective electrode properties rather than different cavity structures, allowing a universal fabrication process to produce color-optimized devices, thus reducing fabrication cost while maintaining angular emission similarity.
3Loss of energy
If additional processing steps such as roughening or patterning are added to improve performance, then light extraction efficiency is enhanced, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing the optical properties (reflectivity, phase shift) of the reflective electrode rather than modifying the physical structure of the cavity. This allows enhancement of light extraction efficiency through material composition and optical parameter tuning rather than adding complex structural features like roughening or patterning, thus improving efficiency without increasing device complexity.
4Loss of energy
If additional layers such as striped reflective index layers or prism layers are added, then light extraction efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the functions of light extraction enhancement and wavelength-specific optimization into a single reflective electrode component. Rather than adding separate striped layers or prism layers, the reflective electrode is designed with integrated optical properties that simultaneously achieve both light extraction efficiency and color-specific cavity resonance, simplifying manufacturing while maintaining performance.
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
This approach reduces manufacturing complexity and enhances light extraction efficiency by allowing for common layer thicknesses across sub-pixels while maximizing constructive interference and minimizing off-axis color shifts.
Implementation Method 1
A first reflective electrode configured to introduce a first phase shift, depending on a first wavelength, on reflection of light emitted by the first emissive material
Implementation Method 2
Embodiments of the present application provide an enhanced arrangement for an emissive display pixel using a reflective electrode that causes a specific phase shift with a quantum dot (QD) or organic electroluminescent material in an LED arrangement
Data Source
AI summary
A light-emitting layer structure that maximizes constructive interference for light emission by varying a phase shift introduced by reflective electrodes. The light-emitting layer structure includes a first and second optical cavity including a first and second reflective electrode; a first and second partially transparent electrode; and a first and second emissive layer (EML) disposed between the first and second reflective electrodes and the first and second partially transparent electrodes, wherein the first EML emits light having a first wavelength; wherein the first reflective electrode introduces a first phase shift, depending on the first wavelength, on reflection of light emitted by the first EML; and wherein the second EML emits light having a second wavelength and the second reflective electrode introduces a second phase shift, depending on the second wavelength, on reflection of light emitted by the second EML, and the first phase shift is different from the second phase shift.