LED Component Micro-Optical Multilayer Structure Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor-based light emitting diodes (LEDs) face low external quantum efficiency due to refractive index mismatch between the epitaxial layer and surrounding media, leading to scattered or reflected light, which reduces brightness, especially in white light generation where phosphor materials cause additional losses.
Innovation Solution
A micro-optical multilayer structure with alternating layers of decreasing refractive index is used to guide light out from the LED, reducing total internal reflection and light trapping, and a wavelength converting layer adjusts the spectral range, enhancing light output and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a high refractive index epitaxial layer is used to generate light, then light generation efficiency is improved, but light extraction efficiency deteriorates due to refractive index mismatch with surrounding media
Solution Approach 1:
A micro-optical multilayer structure with intermediate refractive indices is introduced between the high refractive index epitaxial layer and the low refractive index surrounding medium. The layers have refractive indices that gradually decrease from the epitaxial layer outward (n1 > n2 > n3 > ... > nsurrounding), serving as optical intermediaries that reduce the abrupt refractive index mismatch and enable more efficient light extraction while preserving the high light generation efficiency of the GaN epitaxial layer
2Adaptability or versatility
If phosphor material is used to convert blue light to white light, then white light generation is achieved, but additional light losses occur due to scattering at interfaces
Solution Approach 1:
The micro-optical multilayer structure serves as an intermediary optical path that guides light from the epitaxial layer through the phosphor material and out to the surrounding medium. By providing gradual refractive index transitions, the structure reduces scattering losses at interfaces between the phosphor material and other layers, enabling efficient white light generation while minimizing the additional light losses that would otherwise occur at these interfaces
3Ease of manufacture
If conventional LED structure with planar interface is used, then manufacturing is simple, but light is trapped due to total internal reflection at the interface
Solution Approach 1:
The interface between the epitaxial layer and surrounding medium is segmented into multiple thin layers with different refractive indices, transforming a single planar interface into a multilayer gradient structure. This segmentation maintains manufacturing feasibility through sequential deposition processes while eliminating total internal reflection by providing gradual refractive index transitions that allow light to escape at multiple angles
Solution Approach 2:
The solution transitions from a two-dimensional planar interface to a three-dimensional multilayer gradient structure. By adding the vertical dimension with multiple layers of varying thickness and refractive index, the structure provides multiple escape paths for light that would otherwise be trapped, converting a simple planar geometry into a sophisticated gradient optical path without significantly complicating the manufacturing process
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 solution improves light extraction efficiency, reduces the need for bulky encapsulation, and increases the brightness of LEDs, achieving higher light output and cost-effectiveness.
Implementation Method 1
a refractive index, n i , of the i:th layer is greater than a refractive index, n i+ 1 , of the i+1:th layer. The value of i is selected from the set of positive integers, thus i can be 1, 2, 3, 4, etc. Hence, the invention exploits local index matching techniques to reduce light trapping
Implementation Method 2
Only light travelling at angles within a relatively narrow escape cone associated with the interface can refract into the surrounding medium and escape the epitaxial layer. The use of sufficiently thick micro-optics layers reduces total internal reflection and boosts light outcoupling.
Implementation Method 3
a wavelength converting layer, wherein the wavelength converting layer is arranged to convert light of a first wavelength range into light of a second wavelength range
Data Source
Figure 1a~1d
Figure 2
Figure 3a~3b
AI summary
The present invention relates to a light emitting diode component (101), comprising a light emitting semiconductor structure (104) having a top surface, and a micro-optical multilayer structure (102) arranged to guide light out from said light emitting semiconductor structure (104), said micro-optical multilayer structure (102) comprising a plurality of layers, wherein an i+1:th layer is arranged on top an i:th layer in a sequence as seen from said semiconductor structure (104), wherein a refractive index, ni, of the i:th layer is greater than a refractive index, ni+1, of the i+1:th laye, and wherein a thickness of the i+1:th layer is greater than a thickness of the i:th layer. The present invention also relates to a light emitting diode comprising such a light emitting diode component.