Light-emitting element with metal joining part and adhesion layer
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Solution Overview
Problem
There is a demand for improved heat dissipation efficiency in phosphor layers of light-emitting elements.
Innovation Solution
A light-emitting element with a phosphor layer on a substrate having higher thermal conductivity, where a metal joining part with an adhesion layer and a reflecting layer is interposed between the phosphor layer and the substrate, enhancing heat transfer and dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional light-emitting element is used, then the device structure is simple, but the light extraction efficiency is low due to total reflection at the semiconductor-air interface
Solution Approach 1:
A resin layer with refractive index n2 is introduced as an intermediary between the semiconductor layer (refractive index n1) and the external environment. This resin layer acts as a refractive index transition medium that reduces total reflection at the interface. The resin layer may have a gradient refractive index distribution, being thickest at the center and thinner at the edges, optimizing light extraction while maintaining structural simplicity.
Solution Approach 2:
The refractive index parameter is changed by introducing a resin layer with a different refractive index (n2) between the semiconductor layer (n1) and air. This parameter change optimizes the optical impedance matching, reducing reflection losses. The resin layer thickness and refractive index are specifically designed to maximize light extraction efficiency across different wavelengths.
2Illumination intensity
If the light-emitting element structure is optimized for light extraction, then light extraction efficiency improves, but manufacturing precision requirements increase
Solution Approach 1:
The resin layer is designed to extend beyond the active light-emitting region, with a width W2 greater than the active region width W1. This excessive extension ensures that even with manufacturing variations in resin layer thickness, the light extraction efficiency is maintained across the entire active region, providing a margin of error in manufacturing processes.
Solution Approach 2:
The light-emitting element is segmented into distinct functional layers: a semiconductor layer for light generation, a resin layer for light extraction enhancement, and an electrode layer for electrical connection. This segmentation allows each layer to be optimized independently, with the resin layer thickness and properties can be controlled separately from the semiconductor layer fabrication.
3Illumination intensity
If the resin layer is made thicker to improve light extraction, then light extraction efficiency increases, but the device volume increases
Solution Approach 1:
The resin layer thickness is varied spatially, being thickest at the center of the light-emitting element and gradually thinner toward the edges. This local quality variation optimizes light extraction where it is most needed (at the center where light generation is strongest) while minimizing the overall volume increase. The gradient thickness profile provides optimal optical performance without requiring uniform thick resin coverage across the entire device area.
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 configuration significantly improves heat dissipation efficiency and luminous efficiency by effectively transferring heat from the phosphor layer to the substrate, while also reflecting and emitting white light efficiently.
Implementation Method 1
it has come to light by recent advances in semiconductor technology that light-emitting elements using semiconductor lasers and the like have a problem in that the light extracted from the light-emitting portion is insufficient due to total reflection at the interface between the semiconductor and air
Implementation Method 2
a resin layer having a refractive index n2 between the semiconductor layer and the light-emitting element exterior
Data Source
Figure 1~2
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Figure 5~6
AI summary
A light-emitting element (4) includes: a phosphor layer (45) including phosphor (phosphor particles (451)) of at least one type; a substrate (41) which has a thermal conductivity higher than a thermal conductivity of the phosphor layer (45), the substrate (41) having a principal surface (411) above which the phosphor layer (45) is disposed; and a joining part (42) which is interposed between the phosphor layer (45) and the substrate (41) to join the phosphor layer (45) and the substrate (41) together with metal. An adhesion layer (44) and a reflecting layer (43) are interposed between the joining part (42) and the phosphor layer (45), the adhesion layer (44) being light-transmissive and on a principal surface (452) of the phosphor layer which faces the substrate (41), the reflecting layer (43) being on a principal surface (441) of the adhesion layer (44) which faces the substrate (41).