Remote Phosphor Organic Colorant LED Stability
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Solution Overview
Problem
Existing lighting technologies, such as incandescent lamps and compact fluorescent tubes, face challenges in energy efficiency and color reproduction, while phosphor-on-chip LEDs suffer from thermal and radiative stress, making them unsuitable for organic fluorescent dyes.
Innovation Solution
The use of organic fluorescent colorants embedded in a polymeric matrix of polystyrene or polycarbonate in a remote phosphor arrangement with LEDs, allowing for improved stability and energy efficiency, and enabling the production of white light with high fluorescence quantum yield and pleasant color reproduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If organic fluorescent dyes are used directly on LED chip (phosphor on chip), then good color reproduction is achieved, but thermal and radiative stress reduces stability and lifetime
Solution Approach 1:
The invention separates the organic fluorescent dye from the LED chip by introducing a remote phosphor layer positioned at a distance from the chip. This segmentation allows the dye to be protected from direct thermal and radiative stress while still receiving sufficient excitation light for effective color conversion.
Solution Approach 2:
A remote phosphor layer acts as an intermediary between the LED chip and the organic fluorescent dye. This intermediate structure transmits the blue light from the chip to the dye while protecting the dye from direct exposure to high temperatures and intense radiation, thereby improving stability and lifetime.
2Reliability
If inorganic phosphors are used in phosphor on chip LEDs, then thermal stability is improved, but color reproduction and fluorescence quantum yield are reduced
Solution Approach 1:
The invention changes the physical parameters of the system by positioning the phosphor layer at an optimized distance from the LED chip. This parameter adjustment allows organic fluorescent dyes to operate in a thermal and radiative environment that maintains both their high fluorescence quantum yield and improved color reproduction properties.
3Reliability
If remote phosphor arrangement is used, then thermal and radiative stress on organic dyes is reduced, but device complexity increases
Solution Approach 1:
The remote phosphor layer is implemented as a thin film or sheet positioned at a distance from the LED chip. This thin-film approach maintains structural simplicity while effectively reducing thermal and radiative stress on the organic fluorescent dyes, avoiding significant increases in device complexity.
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 solution results in illumination devices with a long lifetime, high energy efficiency, and improved color reproduction, reducing material costs and environmental impact by eliminating the need for rare earths.
Implementation Method 1
a radiation conversion phosphor... absorb a certain proportion of the blue light and emit longer-wave light with a broad emission band
Implementation Method 2
organic fluorescent dyes give a much higher yield due to their substantially higher mass-specific absorption
Data Source
Figure 1~2
Figure 3~4
AI summary
Illumination device comprising at least one LED and at least one colour converter comprising at least one organic fluorescent colorant in a matrix consisting essentially of polystyrene or polycarbonate, wherein LED and colour converter are present in a remote phosphor arrangement.