LED Light-Extraction Structures for Lambertian Flip-Chip Emission
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Solution Overview
Problem
Solid-state lighting devices, such as LEDs, face limitations in light extraction efficiency due to internal reflection, which reduces the amount of photons that exit the device, leading to suboptimal emission profiles and illumination characteristics compared to conventional lighting sources.
Innovation Solution
The implementation of light-extraction features with specific dimensions and patterns on the substrate surfaces of LEDs, including repeating patterns and additional features on side surfaces, combined with reduced substrate thicknesses, to enhance light emission profiles, particularly achieving Lambertian emission profiles for flip-chip structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If light extraction features are added to enhance light extraction, then light emission efficiency is improved, but device complexity increases
Solution Approach 1:
The patent applies porous or textured light extraction features on the substrate surface, creating a non-planar interface that increases light scattering and extraction efficiency. The porous structure provides multiple refraction opportunities for photons, reducing internal reflection while maintaining a relatively simple overall device architecture.
Solution Approach 2:
The light extraction features incorporate curved or rounded geometries rather than sharp edges, creating smooth transitions that enhance light scattering. The curved surfaces provide varying refraction angles for incident photons, improving light extraction without requiring complex multi-layer structures.
2Illumination intensity
If substrate thickness is reduced to improve light extraction, then light emission intensity is improved, but mechanical strength deteriorates
Solution Approach 1:
The patent applies local quality by creating specific regions with different thicknesses or structural properties. The substrate maintains its overall structural integrity while localized areas have optimized thickness for light extraction. The light extraction features are concentrated in specific zones where they provide maximum optical benefit without compromising overall mechanical strength.
Solution Approach 2:
The patent employs composite structures combining the substrate material with additional light extraction features made of different materials. This composite approach allows the thin substrate to maintain mechanical strength through the supporting features while the optical interface is optimized for enhanced light extraction and emission intensity.
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 approach significantly increases the intensity of light emission at desired angles while reducing lateral waveguiding, resulting in improved illumination characteristics and directional lighting applications with enhanced efficiency and reduced complexity in fabrication.
Implementation Method 1
it has been found useful to pattern, roughen, or otherwise texture the interface between an LED surface and the surrounding environment to provide a varying surface that increases the probability of refraction over internal reflection and thus enhances light extraction
Implementation Method 2
Light extraction and external quantum efficiency of an LED can be limited by a number of factors, including internal reflection
Data Source
AI summary
Solid-state lighting devices including light-emitting diodes (LEDs) and more particularly light-extraction features for LED chips and related methods are disclosed. Light-extraction features include structures formed in or on light-emitting surfaces of substrates. Light-extraction features may include repeating patterns of features with dimensions that, along with reduced substrate thicknesses, provide targeted emission profiles for flip-chip structures, such as Lambertian emission profiles. Dimensions include certain height to width ratios for various substrate thicknesses. Additional light-extraction features with smaller dimensions may be formed along portions or side surfaces of larger light-extraction features.