Non-overlapping Phosphor Layers for LED Light Conversion Efficiency
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Solution Overview
Problem
The existing methods for producing white light using LEDs suffer from reduced light conversion efficiency due to the absorption of green light by red phosphor particles, leading to decreased color purity and increased stray light.
Innovation Solution
The implementation of a light emitting assembly where non-overlapping first and second phosphor layers are used on the LED chip, with the first phosphor layer made of red phosphor powder and the second of green phosphor powder, arranged such that they do not overlap, to reduce absorption and improve light conversion efficiency, and the use of physical vapor deposition (PVD) to enhance the density and efficiency of the phosphor layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If green phosphor powder is formed on the LED surface and red phosphor powder is formed on the green phosphor powder, then white light can be generated through sequential light conversion, but the green light is absorbed by red phosphor particles resulting in decreased light conversion efficiency
Solution Approach 1:
The phosphor layers are segmented into non-overlapping regions on the LED chip surface. The red phosphor layer and green phosphor layer are spatially separated so that green light converted from blue light does not pass through the red phosphor layer, eliminating the harmful absorption effect while maintaining white light generation capability.
Solution Approach 2:
The patent transitions from a vertical stacking arrangement (red phosphor on green phosphor) to a lateral spatial arrangement where red and green phosphor layers are positioned in non-overlapping regions on the same LED chip surface. This dimensional change allows green light to reach the green phosphor layer directly without passing through the red phosphor layer.
2Quantity of substance
If red phosphor powder is formed on green phosphor powder, then both red and green light can be produced, but color purity decreases due to cross-absorption and stray light increases
Solution Approach 1:
The phosphor layers are segmented into non-overlapping regions on the LED chip surface. The red phosphor layer and green phosphor layer are spatially separated so that green light converted from blue light does not pass through the red phosphor layer, eliminating the harmful absorption effect while maintaining white light generation capability.
Solution Approach 2:
Different regions of the LED chip surface are assigned different phosphor materials with specific optical properties. The red phosphor layer is positioned in regions where it will not interfere with green light conversion, while the green phosphor layer is positioned to receive blue light directly. This local differentiation maintains color purity.
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 configuration enhances the light conversion efficiency, reduces stray light, and improves color purity by minimizing cross-interference between red and green light, resulting in a high-purity RGB spectrum for improved display performance.
Implementation Method 1
a first phosphor layer and a second phosphor layer which do not overlap are included in one light emitting element. The first phosphor layer is made of red phosphor powder and the second phosphor layer is made of green phosphor powder
Implementation Method 2
the use of physical vapor deposition (PVD) to enhance the density and efficiency of the phosphor layers
Data Source
AI summary
A light emitting element, used behind a display, comprises LED chips emitting blue light and separated red and green phosphor layers on the LED chip, the layers receiving the emitted blue light and respectively converting the same into precise colors for the display. A portion of the light directly from the LED chip is also combined with the converted light and passed on as lighting for the display. Partial absorption of green light by the red phosphor and red light by the green phosphor, occurring when the red and green phosphor layers are overlapped, is avoided. Light conversion efficiency of the green and red phosphor layers is thereby improved. A light emitting assembly, a display device, and a method for making the light emitting assembly are also disclosed.