Distributed Bragg Reflector Structure for Blue Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional light-emitting devices with distributed Bragg reflection (DBR) structures exhibit low reflectivity, especially for blue light and at various incident angles, which hampers their light extraction efficiency.
Innovation Solution
The proposed light-emitting device incorporates a DBR structure with a first film stack and a second film stack, each comprising dielectric-layer pairs with specific optical thickness ratios and refractive index differences, along with a conversion layer, to enhance reflectivity across a broader wavelength range and incident angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional DBR structure with uniform dielectric-layer pairs is used, then the structure is simple to manufacture, but the reflectivity is low especially for blue light and at various incident angles
Solution Approach 1:
The DBR structure is divided into multiple film stacks (first film stack, second film stack, third film stack) with different dielectric-layer pair configurations. Each film stack has different optical thickness ratios, creating segmented functional zones that collectively achieve high reflectivity across different wavelengths and incident angles without requiring a single complex uniform structure
Solution Approach 2:
Different film stacks are designed with locally optimized dielectric-layer pair optical thickness ratios. The first film stack has ratios optimized for certain wavelengths, the second for others, and the third for additional ranges. This local quality variation within the overall DBR structure enables high reflectivity across the entire blue light spectrum and various incident angles
2Reliability
If the optical thickness ratio of dielectric layers is optimized for normal incidence, then reflectivity at normal incidence is high, but reflectivity at larger incident angles deteriorates
Solution Approach 1:
The multi-stack DBR structure is designed to perform multiple functions simultaneously: the first film stack provides high reflectivity at normal incidence, while the second and third film stacks extend this high reflectivity performance to larger incident angles and broader wavelength ranges. This multi-functionality allows a single DBR structure to maintain high reflectivity across diverse operating conditions
3Ease of manufacture
If a single film stack with fixed optical thickness ratios is used, then the manufacturing process is simple, but the wavelength range with high reflectivity is limited
Solution Approach 1:
The DBR structure segments the wavelength coverage function across multiple film stacks. Each stack is relatively simple to manufacture with fixed optical thickness ratios, but collectively they cover a broad wavelength range from 380nm to 780nm. This segmentation allows each stack to be manufactured independently with standard processes while achieving comprehensive wavelength coverage when combined
Solution Approach 2:
The patent uses composite dielectric materials (silicon dioxide and titanium dioxide) arranged in multiple film stacks with different optical thickness ratios. This composite structure combines the advantages of different material combinations to achieve broad wavelength coverage and high reflectivity across the visible spectrum, particularly for blue light extraction
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 improved DBR structure significantly increases reflectivity, particularly for blue light, and enhances light extraction efficiency by achieving reflectivity greater than 90% across a wider wavelength range and at larger incident angles.
Implementation Method 1
a distributed Bragg reflection structure formed on one side light-emitting stack. The distributed Bragg reflection structure includes a first film stack, a second film stack and a conversion layer between the first and the second film stacks
Implementation Method 2
The light from the active layer 146 can be reflected by the DBR structure 120... The reflectivity of the DBR structure 120 to the blue light band such as 400 nm to 450 nm is low along with the average reflectivity lower than 50%
Implementation Method 3
a conversion layer between the first and the second film stacks
Data Source
AI summary
A light-emitting device includes a light-emitting stack and a distributed Bragg reflection structure formed on one side light-emitting stack. The distributed Bragg reflection structure includes a first film stack, a second film stack and a conversion layer between the first and the second film stacks; wherein the first film stack includes a plurality of first dielectric-layer pairs consecutively arranged, the second film stack includes a plurality of second dielectric-layer pairs consecutively arranged, each of the first dielectric-layer pairs and each of the second dielectric-layer pairs respectively includes a first dielectric layer having an optical thickness and a second dielectric layer having an optical thickness; wherein the second dielectric layer has a refractive index higher than that of the first dielectric layer; wherein in each of the first dielectric-layer pairs of the first film stack, the optical thickness of the first dielectric layer to the optical thickness of the second dielectric layer has a first ratio, and in each of the second dielectric-layer pairs of the second film stack, the optical thickness of the first dielectric layer to the optical thickness of the second dielectric layer has a second ratio; wherein the first ratio is greater than the second ratio; wherein the conversion layer has an optical thickness ranging between that of the first dielectric layer of one of the first dielectric-layer pairs of the first film stack and that of the first dielectric layer of one of the second dielectric-layer pairs of the second film stack.