Violet-UV Pump LED Phosphor Layout for Higher Light Output
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Solution Overview
Problem
Existing high-intensity, high-efficiency InGaN-based green LEDs are difficult to produce on a wide scale and have limitations in emission wavelength, leading to inefficiencies and high costs, while conventional white LED approaches face challenges in maintaining high internal quantum efficiency at high current densities and are constrained by narrow spectral excitation ranges of YAG-based phosphors.
Innovation Solution
The use of LEDs emitting radiation at violet and ultraviolet wavelengths with multiple phosphors, specifically a peak emission wavelength of 405 to 430 nm, to pump phosphor materials that convert radiation into a wider wavelength range, improving light-output efficiency and maintaining high internal quantum efficiency at high current densities, and employing blue phosphors with strong absorption beyond 405 nm to enhance light extraction and color stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If InGaN-based green LEDs are used to achieve high intensity and high efficiency, then light output efficiency is improved, but manufacturing difficulty and cost increase significantly
Solution Approach 1:
The patent uses violet/UV pump LEDs (405-430 nm) as an intermediary light source to excite multiple phosphors (yellow, red, green) that together produce the desired green output. This mediator approach avoids the need to directly manufacture difficult InGaN green LEDs, as the phosphors convert the pump light into the target wavelength range with easier-to-produce materials.
Solution Approach 2:
The invention employs a composite phosphor system combining multiple phosphor materials (yellow phosphor, red phosphor, green phosphor) that are each easier to manufacture than InGaN green LEDs. The composite system collectively achieves the desired spectral output while avoiding the manufacturing challenges of direct green LED production.
2Illumination intensity
If YAG-based phosphors are used in conventional white LEDs, then white light is produced, but the narrow spectral excitation range limits efficiency at high current densities
Solution Approach 1:
The patent segments the single YAG phosphor absorption function into multiple specialized phosphors (yellow, red, green), each with different excitation spectra. This segmentation allows the system to utilize a broader range of the pump LED spectrum, improving overall absorption efficiency and reducing spectral mismatch losses at high current densities.
Solution Approach 2:
Each phosphor in the mixture is optimized for specific local spectral requirements, with yellow phosphor absorbing in the violet region, red phosphor absorbing in the blue-violet region, and green phosphor absorbing in the blue region. This local optimization of absorption characteristics across different spectral regions enhances overall system efficiency.
3Loss of energy
If blue phosphors with strong absorption beyond 405 nm are employed, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple phosphor materials into a single composite phosphor layer that can be applied using conventional coating techniques. While the phosphor mixture itself is complex, the merging approach allows all phosphors to be deposited simultaneously in one step, avoiding the need for multiple separate deposition processes and simplifying the overall manufacturing workflow.
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 achieves high internal quantum efficiency exceeding 70% at 100 A/cm2 and 100°C, reduces light-extraction inefficiencies, and allows for a larger tunable color gamut and improved manufacturing throughput with stable color performance, while mitigating Stokes loss and absorption issues.
Implementation Method 1
LEDs emitting radiation at violet and/or ultraviolet wavelengths are used to pump phosphor materials that emit light of a different frequency
Implementation Method 2
blue phosphor material within a vicinity of the LED device with strong absorption at wavelengths longer than about 405 nm
Data Source
AI summary
An LED pump light with multiple phosphors is described. LEDs emitting radiation at violet and/or ultraviolet wavelengths are used to pump phosphor materials that emit other colors. The LEDs operating in different wavelength ranges are arranged to reduce light re-absorption and improve light output efficiency.