Alternating Metal Layer Reflective Stack for LED Efficiency
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Solution Overview
Problem
Conventional light-emitting diodes (LEDs) face challenges with light absorption by conductive substrates reducing efficiency and poor heat dissipation due to epitaxial etching processes in lateral LEDs, and instability of high reflectivity metals at high temperatures affecting light reflectivity.
Innovation Solution
A light-emitting device design featuring a reflective stack with alternating first and second metal layers, where the first metal layer has high thermal stability and the second metal layer has high reflectivity, ensuring reflectivity above 95% and stability under high current conditions, and a current blocking layer to manage electron flow efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conductive substrate is used as the epitaxial substrate, then the LED structure is simplified and heat dissipation is improved, but the conductive substrate absorbs light and reduces light efficiency
Solution Approach 1:
The patent extracts the light-absorbing conductive substrate from the light path by using a lateral LED structure where the substrate is positioned perpendicular to the light emission direction. The light is emitted laterally from the edge of the substrate, extracting the substrate's harmful light absorption effect while retaining its structural support and heat dissipation functions.
Solution Approach 2:
The patent introduces a reflective layer as an intermediary between the conductive substrate and the active layer. This reflective layer mediates the interaction by reflecting light that would otherwise be absorbed by the substrate back into the active region, thereby reducing energy loss while maintaining the simplified conductive substrate structure.
2Illumination intensity
If a single metal layer with high reflectivity is used, then light reflectivity is maximized, but thermal stability deteriorates under high temperature conditions
Solution Approach 1:
The patent uses a composite reflective layer structure consisting of multiple metal layers with different properties. The first metal layer provides high reflectivity for light extraction, while the second metal layer provides thermal stability and oxidation resistance. This composite structure combines the advantages of different materials to simultaneously achieve high reflectivity and thermal stability.
Solution Approach 2:
The patent applies different material qualities to different layers of the reflective structure. The first metal layer is optimized for optical properties (high reflectivity), while the second metal layer is optimized for thermal and chemical stability. Each layer performs its specific function locally, and together they solve the contradiction between reflectivity and thermal stability.
3Adaptability or versatility
If a lateral LED structure with transparent substrate is used, then light emission in all directions is achieved, but heat dissipation performance deteriorates
Solution Approach 1:
The patent segments the light emission function from the heat dissipation function by using a lateral LED structure with a conductive substrate. The substrate is positioned to allow light emission from the lateral edges while maintaining direct thermal contact with the active layer for efficient heat conduction. This segmentation allows independent optimization of light emission geometry and heat dissipation pathways.
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 design enhances light reflectivity and thermal stability, maintaining high reflectivity even under high current conditions, thereby improving light-emitting efficiency and heat dissipation in LEDs.
Implementation Method 1
the first electrode has a reflectivity larger than 95% for reflecting the light
Implementation Method 2
the first metal layer has high thermal stability and the second metal layer has high reflectivity
Data Source
AI summary
A light-emitting device comprises a light-emitting stack comprising a first surface and a second surface opposite to the first surface; a first electrode formed on the second surface of the light-emitting stack; a current blocking layer formed on the first surface of the light-emitting stack and corresponding to a location of the first electrode; and a second electrode covering the current blocking layer and comprising a plurality of first metal layers and a plurality of second metal layers alternating with the plurality of first metal layers, wherein the plurality of first metal layers is discontinuous.