Light-Emitting Device With Low Refractive Index Layer
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Solution Overview
Problem
Conventional light-emitting diode (LED) devices face reduced luminous efficiency due to light absorption by the LED chip and carrier materials, as well as phosphor deterioration from high temperatures, especially in remote phosphor structures with significant refractive index differences, leading to internal reflection and scattering issues.
Innovation Solution
A light-emitting device design incorporating a carrier, a light-emitting element, a first and second light guide layer with gradient refractive indices, and a low refractive index layer to minimize total internal reflection and enhance light extraction, along with a wavelength conversion layer to produce white light by exciting phosphor powders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If phosphor is coated directly on the LED chip (conformal coating), then the coating thickness is uniform, but light from the phosphor is absorbed by the LED chip and carrier, reducing overall luminous efficiency
Solution Approach 1:
The phosphor layer is extracted from direct contact with the LED chip by introducing a transparent adhesive layer and remote phosphor structure. The phosphor is positioned away from the chip, allowing light to escape before being absorbed by the chip or carrier, thus resolving the contradiction between uniform coating and light absorption losses.
Solution Approach 2:
A transparent adhesive layer is introduced as an intermediary between the LED chip and phosphor layer. This mediator allows light to pass through while providing mechanical adhesion, preventing direct absorption of phosphor light by the chip and carrier materials.
2Device complexity
If phosphor is coated directly on the LED chip, then the structure is simple, but the phosphor layer deteriorates due to high temperature operation of the LED chip
Solution Approach 1:
The phosphor layer is extracted from the high-temperature environment near the LED chip by using a remote phosphor configuration. The phosphor is positioned in a location with lower temperature exposure, preventing thermal deterioration while maintaining structural simplicity through the use of a transparent adhesive layer for bonding.
3Reliability
If package resin is used to package the LED chip, then the chip is protected, but the refractive index difference between LED chip and package resin causes total internal reflection of light
Solution Approach 1:
The refractive index of the package resin is optimized to reduce the difference with the LED chip material. By selecting package resin with a refractive index closer to that of the LED chip, total internal reflection is minimized while maintaining the protective function of the package.
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 design significantly improves light extraction efficiency by reducing total internal reflection and scattering, maintaining luminous efficiency even under high temperature conditions, and effectively converts blue light to white light through the phosphor layer.
Implementation Method 1
the low refractive index layer has a refractive index smaller than one of the refractive indices of first light guide layer and the second light guide layer to reflect the light from the second light guide layer
Implementation Method 2
a wavelength conversion layer covering the second light guide layer; effectively converts blue light to white light through the phosphor layer
Data Source
AI summary
Disclosed is a light-emitting device comprising: a carrier; a light-emitting element disposed on the carrier; a first light guide layer covering the light-emitting element; a second light guide layer covering the first light guide layer; a low refractive index layer between the first light guide layer and the second light guide layer to reflect the light from the second light guide layer; and a wavelength conversion layer covering the second light guide layer; wherein the low refractive index layer has a refractive index smaller than one of the refractive indices of first light guide layer and the second light guide layer.