Multi-Surface LED Structure for Higher Light Extraction
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Solution Overview
Problem
Conventional vertical LEDs face issues with heat dissipation and current-crowding effects at high current densities, leading to reduced external quantum efficiency and lumen density due to inadequate light extraction efficiency, particularly as they emit light through a single surface.
Innovation Solution
The proposed LED features an epitaxial layered structure with a reflective layered unit on its lower surface and a light-transmissive structure covering the upper and side surfaces, allowing emission light to exit at a light-exit angle of not smaller than 125°, thereby increasing the light-exit surfaces and reducing internal scattering through a light conversion layer of reduced phosphor density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional vertical LED emits light through a single upper surface, then the device structure is simple, but the light extraction efficiency is insufficient and lumen density is reduced
Solution Approach 1:
The patent transitions from single-surface light emission to multi-surface light emission by adding side surface emission capability. The light-transmissive structure is extended to cover side surfaces, and the reflective layered unit is configured to redirect light toward side exit surfaces, effectively adding a dimensional aspect to light extraction and significantly improving overall light extraction efficiency.
Solution Approach 2:
The light emission function is segmented across multiple surfaces (upper surface and side surfaces) rather than concentrated on a single surface. The light-transmissive structure is divided into portions covering different surfaces, allowing light to exit through multiple pathways, which increases total light extraction while distributing the optical function across separate regions.
2Use of energy by moving object
If phosphors are densely packed in the light conversion layer to convert blue light to white light, then the color conversion efficiency is improved, but internal scattering increases and reduces overall lumen density
Solution Approach 1:
The patent applies different phosphor densities in different regions of the light conversion layer. By positioning higher phosphor density in areas where color conversion is most needed and lower density in areas where light extraction is prioritized, the design achieves local optimization of both color conversion efficiency and light extraction efficiency, reducing unnecessary internal scattering while maintaining effective color conversion.
3Power
If the LED operates under high current density to meet market demands, then the luminous output is improved, but heat accumulation increases and damages the sapphire substrate
Solution Approach 1:
The patent adds side surface light emission as an additional dimension for light extraction, which improves luminous output without requiring proportional increases in current density. By utilizing both upper and side surfaces for light emission, the LED achieves higher total luminous flux at lower current densities, thereby reducing heat generation and improving thermal management.
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 light extraction efficiency and lumen density by allowing light to exit through multiple surfaces, reducing internal scattering, and maintaining high performance under high current densities.
Implementation Method 1
The reflective layered unit is disposed on the lower surface of the epitaxial layered structure
Implementation Method 2
Taking the conversion of blue light to white light as an example, when the blue light emitted from the active layer 122
Data Source
AI summary
A light-emitting diode includes an epitaxial layered structure, a reflective layered unit, and a light-transmissive structure. The epitaxial layered structure has opposite upper and lower surfaces and a side surface interconnecting the upper and lower surfaces. The reflective layered unit is disposed on the lower surface of the epitaxial layered structure. The light-transmissive structure covers the upper surface of the epitaxial layered structure and a portion of the side surface of the epitaxial layered structure, and is configured to allow light emitted from the epitaxial layered structure to exit therefrom at a light-exit angle of not smaller than 125°.