LED Chip Dielectric Lamination for Broadband Reflectivity
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Solution Overview
Problem
Existing LED chips face challenges in achieving high luminous efficiency due to limitations in reflective characteristics of alternating lamination structures, particularly in wavelength conversion and angle of incidence, and difficulties in determining optimal layer thickness and sequence.
Innovation Solution
The LED chip employs an alternating lamination structure with specific dielectric pairs, including first, second, and third dielectric pairs, strategically positioned to enhance reflectivity and transmittance, and a metal reflector to improve luminous efficiency, along with a method to determine optical thickness and lamination sequence effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an alternating lamination structure is used to improve reflectivity, then high reflectivity is achieved in a narrow wavelength band, but reflectivity decreases in other wavelength bands
Solution Approach 1:
The alternating lamination structure is divided into multiple distinct layers with different refractive indices (high refractive index layers and low refractive index layers). Each layer is designed with specific thickness and optical properties to contribute to the overall broadband reflective performance, allowing the structure to effectively reflect across a wide wavelength range rather than a narrow band.
Solution Approach 2:
The patent employs a composite alternating lamination structure combining materials with different refractive indices (such as TiO2/SiO2, Ta2O5/SiO2, or Nb2O5/SiO2). This composite approach creates optical interference effects that enhance reflectivity across broad wavelength bands, solving the limitation of narrowband reflection in conventional single-material laminated structures.
2Adaptability or versatility
If the total number of layers is increased to widen the wavelength band with high reflectivity, then reflectivity bandwidth increases, but it becomes difficult to adjust the thickness of each layer and determine optimal thickness
Solution Approach 1:
The patent optimizes the optical thickness parameters of individual layers to achieve broadband reflection. By carefully selecting the thickness of each layer (typically quarter-wave or half-wave multiples) and the refractive index contrast between adjacent layers, the structure achieves high reflectivity across a wide wavelength range without requiring an excessive number of layers, thus maintaining manufacturability.
Solution Approach 2:
Instead of using a very large number of thin layers, the patent employs a moderate number of layers with optimized thicknesses. This partial action approach achieves sufficient broadband reflection performance with fewer layers, making thickness control and manufacturing more feasible while still widening the reflective wavelength band.
3Loss of energy
If an alternating lamination structure is used to improve reflectivity, then high reflectivity is achieved for vertically incident light, but reflectivity decreases for light with high angle of incidence
Solution Approach 1:
The alternating lamination structure is designed with graded refractive index transitions and optimized layer thicknesses that create omnidirectional reflective properties. The local optical properties of each interface are engineered to reflect light effectively across a wide range of incident angles, not just normal incidence, by creating multiple internal reflections and interference patterns that are angle-insensitive.
4Loss of energy
If a metal reflector is used to improve luminous efficiency, then reflectivity is improved, but the metal reflector deteriorates upon oxidation and has relatively low reflectivity
Solution Approach 1:
The patent replaces the metal reflector (which degrades over time due to oxidation) with a dielectric alternating lamination structure. Although dielectric materials are more complex in structure, they provide stable, non-degrading reflective performance over the long term, eliminating the reliability issues associated with metal oxidation while maintaining high reflectivity.
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 structure achieves high reflectance and transmittance across a wide wavelength range, improving luminous efficiency and reducing optical loss, especially in LED packages emitting mixed colors like white light.
Implementation Method 1
a bottom structure which includes a plurality of first dielectric pairs and a plurality of second dielectric pairs, each of the first and second dielectric pairs comprising a first material layer and a second material layer alternately stacked
Implementation Method 2
each of the first and second dielectric pairs comprising a first material layer and a second material layer alternately stacked
Implementation Method 3
a metal reflector such as Al may be disposed on a chip mounting plane opposite to the light emitting plane to reflect light traveling towards the chip mounting plane
Data Source
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AI summary
Exemplary embodiments of the present invention provide light emitting diode (LED) chips and a method of fabricating the same. An LED chip according to an exemplary embodiment includes a substrate; a light emitting structure arranged on the substrate, and an alternating lamination bottom structure arranged under the substrate. The alternating lamination bottom structure includes a plurality of dielectric pairs, each of the dielectric pairs including a first material layer having a first refractive index and a second material layer having a second refractive index, the first refractive index being greater than the second refractive index.