Patterned Phosphor Layer for LED Light Extraction
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Solution Overview
Problem
Conventional white light emitting device packages face issues with phosphor concentration variability, heat transfer degrading wavelength conversion efficiency, and color temperature deviations due to phosphor placement and viewing angle, leading to optical losses and reduced light extraction efficiency.
Innovation Solution
A light emitting device with a patterned phosphor layer exposed on the light emitting surface, allowing partial exposure of the light emitting structure and electrode pattern, increasing light extraction efficiency and controlling optical characteristics like color temperature through varying phosphor layer shapes and positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If phosphor is mixed with encapsulating material to fill the reflective cup, then white light can be formed, but the reflective cup structure is required and heat transfer degrades wavelength conversion efficiency
Solution Approach 1:
The phosphor layer is divided into multiple patterns (e.g., annular patterns, radial patterns) with different phosphor materials in different regions. This segmentation allows different areas to convert wavelengths differently, optimizing overall conversion efficiency while maintaining white light formation.
Solution Approach 2:
Different regions of the phosphor layer have different phosphor compositions and concentrations tailored to local requirements. For example, inner annular regions may have phosphors optimized for blue light conversion while outer regions handle green light conversion, maximizing wavelength conversion efficiency in each local area.
2Illumination intensity
If phosphor is mixed with encapsulating material, then white light can be formed, but phosphor concentration varies according to process time
Solution Approach 1:
Phosphor particles are pre-sorted by size and type before application, and the encapsulating material is pre-prepared with controlled viscosity. This preliminary preparation ensures uniform phosphor distribution during the encapsulation process, eliminating concentration variations caused by settling.
Solution Approach 2:
A dispersant or viscosity-modifying agent is introduced as an intermediary substance between phosphor particles and encapsulating material. This intermediary prevents phosphor settling and ensures uniform distribution throughout the encapsulating material during the filling process.
3Ease of manufacture
If yellow phosphor is applied on the outermost part of blue LED, then light is emitted in all directions, but light re-incident to light emitting device is absorbed causing optical loss
Solution Approach 1:
The harmful function of the yellow phosphor layer (absorbing re-incident blue light) is extracted and eliminated. The patent removes the yellow phosphor from the outermost position or replaces it with transparent encapsulating material, allowing blue light to escape without absorption while maintaining ease of manufacture.
Solution Approach 2:
Instead of placing yellow phosphor on the outermost surface to emit light in all directions, the patent inverts the approach by placing it in intermediate layers or using transparent materials on the surface. This inversion allows light to be emitted in all directions without the harmful absorption effect, as the transparent surface layer does not absorb re-incident light.
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 patterned phosphor layer enhances light extraction efficiency and maintains consistent color temperature across viewing angles, improving the overall performance of white light emission by minimizing heat transfer to the phosphor layer and optimizing phosphor distribution.
Implementation Method 1
light having a first wavelength, which is emitted from the light emitting device may be mixed with light having a larger wavelength than the first wavelength, which collides with the phosphor, so as to form white light
Data Source
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AI summary
Provided are a light emitting device, a light emitting device package, and a lighting system. The light emitting device includes a substrate, a light emitting structure on the substrate, the light emitting structure comprising a first conductive type semiconductor layer, a second conductive type semiconductor layer on the first conductive type semiconductor layer, and an active layer between the first and second conductive type semiconductor layers; a first electrode on the light emitting structure; and a patterned phosphor layer on the light emitting structure, wherein the patterned phosphor layer converts light generated from the light emitting structure into light having a wavelength longer than that of the light generated from the light emitting structure, and wherein the pattern of the phosphor layer exposes the first electrode.