Solid State Light Emitting Device Refractive Index Gradient
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Solution Overview
Problem
Conventional solid state light emitting devices, such as LEDs, face challenges in energy efficiency and light extraction due to significant backscattering of light from luminescent materials, leading to system losses and reduced efficacy.
Innovation Solution
Incorporating a first element with an index of refraction gradient, such as a stepped or substantially continuous index of refraction gradient, to minimize light reflection at interfaces and enhance light extraction efficiency by gradually reducing the refractive index difference as light passes through various layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If light emitting diodes are used to replace incandescent and fluorescent lights, then energy efficiency and lifetime are improved, but light extraction efficiency is reduced due to backscattering from luminescent materials
Solution Approach 1:
The patent introduces an intermediary element with a gradient refractive index positioned between the luminescent material and the external environment. This gradient layer acts as a mediator that gradually transitions the refractive index from the high-index luminescent material to the low-index external medium, reducing abrupt refraction and backscattering losses at the interface.
Solution Approach 2:
The patent changes the refractive index parameter spatially by implementing a gradient structure where the refractive index varies continuously or in steps from the luminescent material interface toward the external environment. This parameter variation optimizes light extraction by minimizing total internal reflection and backscattering effects.
2Illumination intensity
If luminescent materials are used in solid state light emitters, then color rendering and light output are improved, but significant backscattering occurs reducing overall system efficacy
Solution Approach 1:
The gradient refractive index element serves as an intermediary optical component between the luminescent material and the external environment. It facilitates more efficient light extraction by reducing the abrupt refractive index mismatch that causes backscattering, thereby improving system efficacy while preserving the beneficial light output characteristics of the luminescent materials.
3Ease of operation
If conventional light fixtures are designed for periodic replacement, then maintenance flexibility is maintained, but operational downtime and replacement costs increase
Solution Approach 1:
The patent employs cost-effective solid state light emitting devices with extended operational lifetimes (50,000-70,000 hours) that replace traditional incandescent and fluorescent bulbs. While the devices are designed to be replaceable for maintenance flexibility, their extended lifetime significantly reduces the frequency of replacements needed, thereby minimizing operational downtime and associated costs.
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 improves light extraction efficiency by reducing internal reflections, allowing more light to be emitted from the device, thereby increasing energy efficiency and efficacy.
Implementation Method 1
the first element has at least a first region which has an index of refraction gradient... to minimize light reflection at interfaces and enhance light extraction efficiency by gradually reducing the refractive index difference as light passes through various layers
Data Source
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AI summary
There is provided a solid state light emitting device comprising at least one light emitting active layer structure (22) and at least one structure selected from among: (1) a first element (21) having at least a first region which has an index refraction gradient, (2) a first element (21), at least a portion of which has an in of refraction which is lower than an index of refraction of a side of the active la (22), (3) first and second elements (21,23), in which one side of the second element (23) is positioned on a side of the active layer (22) and the first eleme (21) is positioned on the other side of the second element (23), and in which at least a portion of the first element (21) has an index of refraction which is lowe than the index of refraction of at least a portion of the second element (23). Also provided are methods of making such devices.