Thin Wavelength-Conversion Layer With Sidewall Light Redirection
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Solution Overview
Problem
Conventional wavelength-converted light-emitting devices suffer from significant lateral light loss due to refractive index mismatch and thick phosphor layers, leading to increased size, weight, and cost, as well as reduced luminance and efficiency.
Innovation Solution
A light-emitting device design featuring a thin wavelength-converting layer with luminescent particles embedded in an index-matched inorganic medium, combined with an optical sidewall structure that redirects lateral light towards the phosphor layer, reducing the need for extensive optical sidewall coating and minimizing lateral emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a thick phosphor layer is used to absorb all LED light, then wavelength conversion efficiency is improved, but device size and weight increase
Solution Approach 1:
The patent changes the refractive index parameter of the phosphor layer by using an index-matched transparent medium, which improves light absorption efficiency without requiring a thick phosphor layer. This allows thin phosphor layers to achieve complete light absorption, reducing device weight while maintaining energy conversion efficiency.
Solution Approach 2:
The patent uses a composite structure combining phosphor particles with a transparent index-matched medium. This composite material approach enables efficient light absorption in a thin layer, achieving both high wavelength conversion efficiency and reduced device weight.
2Loss of energy
If a thick phosphor layer is used to absorb all LED light, then wavelength conversion efficiency is improved, but device complexity increases
Solution Approach 1:
By changing the refractive index parameter of the phosphor layer medium to match the substrate, the patent eliminates the need for complex optical sidewall coatings and structures. The index-matched medium naturally guides light through the phosphor layer, simplifying the overall optical structure while maintaining high absorption efficiency.
3Device complexity
If lateral light propagation is allowed, then device simplicity is maintained, but light loss increases
Solution Approach 1:
The patent changes the refractive index parameter of the phosphor layer to match the substrate, which transforms the optical behavior at the interfaces. This parameter change causes laterally propagating light to be refracted into the phosphor layer rather than escaping, reducing light loss without adding complex optical structures.
4Length of stationary object
If a thin phosphor layer is used, then device size is reduced, but light absorption efficiency decreases
Solution Approach 1:
The patent changes the refractive index parameter of the phosphor layer medium to match the substrate, which dramatically improves light absorption efficiency. This parameter change allows thin phosphor layers to absorb all incident light by preventing lateral escape, achieving both reduced device size and high absorption efficiency simultaneously.
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
This design enhances total flux and luminance by redirecting lateral light, resulting in a more compact and efficient light-emitting device with improved light outcoupling and emission angular distribution.
Implementation Method 1
The wavelength converting layer comprises a multitude of luminescent particles characterized by a D50 less than about 20. microns embedded in a substantially transparent inorganic medium substantially index-matched with the substrate. At least some of the luminescent particles are embedded entirely within the inorganic medium. The luminescent particles absorb incident first output light exiting the substrate and emit second output light in a second output wavelength range different from the first.
Implementation Method 2
The optical sidewall structure is interposed between at least a portion of the substrate sidewalls and the optical sidewall coating, and redirects at least a portion of output light exiting the substrate through the sidewalls to propagate toward or within the wavelength-converting layer.
Implementation Method 3
The optical sidewall structure is interposed between at least a portion of the substrate sidewalls and the optical sidewall coating, and redirects at least a portion of output light exiting the substrate through the sidewalls to propagate toward or within the wavelength-converting layer.
Implementation Method 4
The wavelength converting layer comprises a multitude of luminescent particles characterized by a D50 less than about 20. microns embedded in a substantially transparent inorganic medium substantially index-matched with the substrate.
Data Source
AI summary
A light-emitting device includes a substrate, a semiconductor diode structure, a wavelength-converting layer less than 50. microns thick with luminescent particles in an index-matched inorganic binder, optical sidewall coating, and an optical sidewall structure. The optical sidewall structure is interposed between substrate sidewalls and optical sidewall coating, and redirects side-propagating output light toward or within the wavelength-converting layer. The optical sidewall structure can be part of the wavelength-converting layer or part of an adhering layer between the substrate and the wavelength-converting layer.