Multi-Layer Wavelength Conversion for Low-Scattering Planar Light Sources
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Solution Overview
Problem
Existing light-emitting devices face challenges in enhancing luminous efficiency and reliability, particularly when using wavelength conversion materials with light-emitting diodes (LEDs).
Innovation Solution
A light-emitting device configuration that includes a light-emitting element, a first wavelength conversion member, a second wavelength conversion member, and a first light-reflective member, where each member absorbs and emits light of different peak wavelengths, with the members forming a continuous light-emitting surface to enhance light extraction efficiency and reduce scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a wavelength conversion material is bonded with an LED, then the LED can convert light to different wavelengths, but the luminous efficiency is insufficient due to light scattering and poor light extraction
Solution Approach 1:
The wavelength conversion structure is divided into multiple independent members (first wavelength conversion member, second wavelength conversion member, third wavelength conversion member) with different refractive indices, arranged in sequence from the light-emitting element outward. This segmentation allows each member to independently optimize light extraction at its interface, converting previously scattered light into extractable light and improving overall luminous efficiency.
Solution Approach 2:
Each wavelength conversion member is assigned a specific refractive index that differs from its adjacent members, creating localized refractive index differences at each interface. This local quality variation enables targeted light extraction at each boundary, addressing the specific need for improved light extraction efficiency at different stages of wavelength conversion.
2Adaptability or versatility
If multiple wavelength conversion layers are stacked, then multiple wavelengths can be converted, but light scattering increases and reduces overall efficiency
Solution Approach 1:
Instead of using a single thick wavelength conversion layer, the patent divides it into multiple thin layers with different refractive indices. The light that would have scattered within a single thick layer is instead extracted at the interfaces between the segmented layers, reducing internal scattering losses while maintaining the ability to convert to multiple wavelengths.
Solution Approach 2:
The multiple wavelength conversion members are arranged in continuous sequence from the light-emitting element outward, creating a continuous path for light extraction. Each interface continuously extracts light that would otherwise scatter, ensuring that the useful action of light extraction occurs throughout the entire wavelength conversion structure rather than being concentrated in one location.
3Loss of energy
If wavelength conversion materials are placed close to the LED, then conversion efficiency improves, but electrode corrosion and ion migration increase
Solution Approach 1:
The first wavelength conversion member, with a refractive index between that of the light-emitting element and the second wavelength conversion member, acts as an intermediary layer. This intermediate structure allows the wavelength conversion function to be maintained while physically separating the conversion materials from direct contact with the LED electrode, thereby reducing corrosion and ion migration issues.
Solution Approach 2:
The patent transitions from a single-layer planar structure to a multi-layer three-dimensional structure with varying refractive indices. This dimensional change allows the system to maintain efficient wavelength conversion while introducing spatial separation between the conversion materials and the LED electrode, thereby addressing the reliability issue through structural design rather than material substitution.
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 configuration achieves high luminous efficiency and reliability by minimizing light scattering and promoting efficient conversion and extraction of light, while also reducing corrosion and ion migration at the electrodes.
Implementation Method 1
The first wavelength conversion member includes a wavelength conversion material that absorbs at least a portion of the first light and emits a second light. The second light has a second peak wavelength different from the first peak wavelength.
Implementation Method 2
The second wavelength conversion member includes a wavelength conversion material that absorbs at least a portion of the first light and emits a third light. The third light has a third peak wavelength different from the first peak wavelength and the second peak wavelength.
Implementation Method 3
The first light-reflective member is located on the second wavelength conversion member and is located at least on the light-emitting element.
Data Source
AI summary
A light-emitting device includes: a light-emitting element emitting a first light having a first peak wavelength; a first wavelength conversion member contacting a side surface of the light-emitting element and including a wavelength conversion material absorbing at least a portion of the first light and emitting a second light having a second peak wavelength different from the first peak wavelength; a second wavelength conversion member on the first wavelength conversion member, the second wavelength conversion member including a wavelength conversion material absorbing at least a portion of the first light and emitting a third light having a third peak wavelength different from the first and second peak wavelengths; and a first light-reflective member on the second wavelength conversion member and at least on the light-emitting element. A continuous light-emitting surface includes a side surface of the first wavelength conversion member and a side surface of the second wavelength conversion member.