Quantum Dot Sub-Pixel Structure Using Low-Index Light Confinement
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Solution Overview
Problem
The existing display elements using quantum dots for color conversion face challenges in miniaturization due to increased aspect ratio of wavelength conversion layers, leading to difficulty in pattern formation and reduced luminance efficiency and color purity, especially when excitation light is incident at high angles, causing leakage and decreased reflectance in dielectric multilayer films.
Innovation Solution
Incorporating a low refractive index layer between the wavelength conversion portion and the optical member, and a reflective layer between the light source and the wavelength conversion portion, to reduce leakage of excitation and wavelength-converted light by total reflection, enhancing luminance efficiency and color purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the aspect ratio of the wavelength conversion layer is increased to improve color purity, then color purity is improved, but pattern formation becomes difficult and miniaturization becomes difficult
Solution Approach 1:
The patent introduces a new dimensional approach by adding a reflective layer beneath the wavelength conversion layer and using oblique incidence excitation light. This transforms the problem from a two-dimensional planar structure to a three-dimensional optical path control system, allowing improved color purity without compromising pattern formation capability.
Solution Approach 2:
The patent applies different properties to different regions: the wavelength conversion layer uses high quantum dot concentration for color purity, while the reflective layer uses specific refractive index properties for light control. This local differentiation allows each layer to optimize its function without interfering with manufacturing.
2Loss of energy
If the thickness of the wavelength conversion layer is increased to improve light absorption, then conversion efficiency is improved, but the aspect ratio increases making miniaturization difficult
Solution Approach 1:
The reflective layer acts as an intermediary between the wavelength conversion layer and the substrate. It reflects unabsorbed excitation light back into the wavelength conversion layer, providing additional absorption opportunities without increasing the physical thickness of the conversion layer, thus maintaining miniaturization capability.
Solution Approach 2:
The reflective layer enables continuous absorption of excitation light by bouncing it back through the wavelength conversion layer. This extends the useful action of light absorption without requiring additional thickness, allowing thin-layer designs to achieve high conversion efficiency.
3Loss of energy
If a dielectric multilayer film is used as the excitation light reflective layer to improve reflectance, then conversion efficiency is improved, but blue light penetrates through at high angles reducing color purity
Solution Approach 1:
The patent changes the optical parameters by using oblique incidence excitation light instead of normal incidence. This parameter change alters the interaction between light and the dielectric multilayer film, improving reflectance at the operating angles while maintaining the wavelength selectivity that prevents blue light penetration.
Solution Approach 2:
The system combines the dielectric multilayer film with the wavelength conversion layer containing quantum dots to form a composite structure. This composite approach allows the dielectric layers to provide broadband reflection while the quantum dots provide wavelength-selective conversion, together achieving high efficiency without blue light leakage.
4Loss of energy
If the concentration of quantum dots is increased to improve absorption coefficient, then light absorption is improved, but tradeoffs occur making it difficult to completely suppress blue light leakage
Solution Approach 1:
The reflective layer serves as an intermediary that redirects unabsorbed excitation light back through the quantum dot layer. This gives the quantum dots multiple opportunities to absorb photons at their optimal concentration, improving overall absorption efficiency without requiring excessively high quantum dot concentrations that would cause blue light leakage.
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 solution effectively reduces leakage of light, improving luminance and wavelength conversion efficiency by ensuring total reflection of light at high angles, thereby enhancing the performance of display elements with quantum dots.
Implementation Method 1
a low refractive index layer provided in a region between the wavelength conversion portion and the optical member... to reduce leakage of excitation light
Implementation Method 2
a wavelength conversion layer made up of quantum dots that produce light in red and a wavelength conversion layer made up of quantum dots that produce light in green
Implementation Method 3
an excitation light reflective layer made up of a dielectric multilayer film... When blue light that is excitation light is reflected by the reflective layer
Data Source
AI summary
A display element includes a sub-pixel region including a wavelength conversion layer that converts a wavelength of excitation light, and further includes a low refractive index layer provided in a region between a wavelength conversion portion and an optical member.