Waveguide Display Element for High Light Utilization Efficiency
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Solution Overview
Problem
Existing display elements and devices face limitations in achieving high macroscopic light utilization efficiency and color purity due to the antagonism between light emission and absorption in wavelength conversion layers, particularly when adjusting the optical density of quantum dots.
Innovation Solution
A display element comprising a light-emitting-layer array and a conversion-layer array, where the conversion-layer array includes first conversion layers with a waveguide-shaped optical structure, featuring a coupling portion, an extraction portion, and a reflection portion, which alternately reflect and guide primary light to enhance wavelength conversion and light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the optical density of quantum dots in the wavelength conversion layers is increased to increase light emission intensity, then the light emission intensity per unit depth increases, but the absorption per unit depth of primary light and secondary light also increases, causing the macroscopic light utilization efficiency to reach a plateau
Solution Approach 1:
The patent transitions from a conventional planar conversion layer to a three-dimensional waveguide structure. The conversion layer is formed with a specific refractive index to create total internal reflection at the waveguide boundaries, enabling light to propagate along the waveguide path. This dimensional transformation allows light to travel a longer effective path length through the conversion material without increasing the absorption density, thereby resolving the contradiction between emission intensity and light utilization efficiency.
Solution Approach 2:
The patent applies local quality by creating a spatially differentiated optical structure where the conversion layer has specific refractive index properties only in the waveguide region. The waveguide structure confines light propagation to specific paths with high reflection at boundaries, while other regions maintain different optical characteristics. This localized optimization enables enhanced light-matter interaction along the waveguide path without uniformly increasing absorption throughout the entire layer.
2Loss of energy
If the optical density of quantum dots is reduced to decrease absorption, then the color purity is reduced because primary light reaches the light emitting surface
Solution Approach 1:
By transforming the conversion layer into a three-dimensional waveguide structure, the patent extends the light propagation path from a simple vertical traversal to a prolonged path along the waveguide. This dimensional change ensures that even with reduced quantum dot density, the light interacts sufficiently with the conversion material to achieve high color purity, while simultaneously reducing unwanted absorption effects.
3Manufacturing precision
If an optical filter is placed on the light emission side to maintain color purity, then the macroscopic light utilization efficiency is limited by the optical filter
Solution Approach 1:
The patent extracts the wavelength selection function from a separate optical filter component and integrates it directly into the waveguide structure itself. The waveguide's refractive index properties and total internal reflection mechanism inherently provide wavelength-dependent light propagation characteristics, eliminating the need for additional filtering elements that would cause energy loss.
4Productivity
If the concentration of quantum dots is increased to increase wavelength conversion efficiency, then self-absorption and fluorescence resonance energy transfer (FRET) increase, reducing overall efficiency
Solution Approach 1:
The waveguide structure creates a three-dimensional light propagation path that separates the excitation light path from the emitted light extraction paths. This spatial separation in the waveguide dimension allows for optimized quantum dot concentration without the harmful interactions of self-absorption and FRET, as the guided mode confinement and extended path length provide sufficient conversion efficiency at lower concentrations.
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
The proposed solution increases both the macroscopic light utilization efficiency and color purity of the display elements by optimizing the optical path length and reducing the concentration of quantum dots, thereby minimizing self-absorption and fluorescence resonance energy transfer (FRET).
Implementation Method 1
a waveguide-shaped optical structure, featuring a coupling portion, an extraction portion, and a reflection portion, which alternately reflect and guide primary light
Implementation Method 2
a light-emitting layer including quantum dots. When the light-emitting layer uses primary light as excitation light, the light-emitting layer performs wavelength conversion
Implementation Method 3
The proposed solution increases both the macroscopic light utilization efficiency and color purity of the display elements by optimizing the optical path length and reducing the concentration of quantum dots, thereby minimizing self-absorption and fluorescence resonance energy transfer (FRET)
Data Source
AI summary
A display element includes a light-emitting-layer array and a conversion-layer array. The conversion-layer array includes a plurality of first conversion layers including a first coupling portion optically coupled to a portion of the plurality of light-emitting layers, a first extraction portion, and a first reflection portion. The first extraction portion and the first reflection portion face each other to alternately reflect the light of a first wavelength received through the first coupling portion and guide the light of the first wavelength in a direction away from the first coupling portion.