Graded Ceramic Body for LED Internal Quantum Efficiency
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Solution Overview
Problem
Current solid state light emitting devices, such as LEDs and OLEDs, face challenges in increasing internal quantum efficiency (IQE) without compromising luminance efficiency, which is crucial for applications like automobile headlights and general lighting where higher luminance intensity is required.
Innovation Solution
A ceramic body with a first region having a higher dopant concentration for luminescence and a second region with a lower dopant concentration, where the first region has a larger average grain size than the second region, is formed by sintering an assembly with a doped layer between non-doped layers, enhancing IQE to at least 0.80 when exposed to radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dopant concentration is increased to improve internal quantum efficiency, then IQE increases, but luminance efficiency diminishes
Solution Approach 1:
The patent applies local quality by creating distinct regions within the ceramic body with different dopant concentrations. The first region contains a first concentration of dopant optimized for high IQE, while the second region contains a second concentration of dopant optimized for luminance efficiency. This spatial differentiation allows each region to perform its specific function optimally without compromising the other, resolving the contradiction between IQE and luminance efficiency.
Solution Approach 2:
The ceramic body is segmented into multiple regions with different dopant concentrations and grain sizes. This segmentation allows the patent to optimize different portions of the material for different functions: one region for maximizing photon creation efficiency (high IQE) and another region for maximizing light output (luminance efficiency), thereby resolving the trade-off between these two parameters.
2Ease of manufacture
If uniform dopant concentration is used throughout the ceramic body, then manufacturing is simplified, but IQE cannot reach at least 0.80
Solution Approach 1:
Rather than using a uniform dopant concentration, the patent implements local quality by varying the dopant concentration in different regions. The first region has a first concentration effective to produce luminescence, while the second region has a second concentration that is less than the first concentration. This non-uniform distribution is necessary to achieve the high IQE of at least 0.80, demonstrating that the performance requirement takes precedence over manufacturing simplicity.
3Reliability
If grain size is increased to improve luminescence, then IQE increases, but mechanical strength decreases
Solution Approach 1:
The patent resolves the contradiction between grain size and mechanical strength by applying local quality: the first region has a first average grain size optimized for high IQE, while the second region has a second average grain size that provides mechanical support. This allows the ceramic body to achieve both high luminescence efficiency and adequate mechanical strength through spatial differentiation of grain sizes.
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 ceramic body achieves superior internal quantum efficiency, specifically exhibiting an IQE of at least 0.80 when exposed to radiation, thereby improving energy efficiency and luminance intensity in lighting applications.
Implementation Method 1
a first region comprising a host material and a first concentration of a dopant, wherein the first concentration is effective to produce luminescence
Implementation Method 2
the ceramic body exhibits an internal quantum efficiency (IQE) of at least 0.80 when exposed to radiation having a wavelength of 455 nm
Data Source
Figure 1A~1B
Figure 2A~3B
Figure 4
AI summary
Some embodiments disclosed herein include a ceramic body including a first region and a second region. The first region may include a host material and first concentration of a dopant that is effective to produce luminescence. The second region may include the host material and second concentration of the dopant. In some embodiments, the first region has an average grain size that is larger than an average grain of the second region. The ceramic body may, in some embodiments, exhibit superior internal quantum efficiency (IQE). Some embodiments disclosed herein include methods for the making and using the ceramic bodies disclosed herein. Also, some embodiments disclosed herein lighting apparatuses including the ceramic bodies disclosed herein.