Phosphor Layer Arrangement for LED Color Stability
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Solution Overview
Problem
Conventional phosphor-converted LEDs (pcLEDs) face challenges in achieving stable white output due to blue light leakage, which varies with drive current and operating temperature, and suffer from increased Stokes' loss and cascading conversion loss when using violet or ultraviolet radiation sources.
Innovation Solution
The use of multiple layers of phosphor materials excited by radiation sources emitting in different wavelengths, including UV, violet, or near-ultraviolet radiation, with specific arrangements and ratios of LED sources to optimize wavelength conversion and reduce cascading loss, such as positioning blue phosphor materials near short-wavelength LEDs to minimize blue photon pumping of longer-wavelength phosphors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If blue phosphor materials are positioned near short-wavelength LEDs to minimize blue photon pumping, then conversion efficiency is improved, but device complexity increases due to specific spatial arrangements required
Solution Approach 1:
The patent applies local quality by positioning blue phosphor materials specifically near short-wavelength LEDs rather than uniformly distributing phosphors. This localized arrangement ensures that blue phosphor conversion occurs proximal to the excitation source, minimizing the distance blue photons must travel and reducing cascading conversion loss when blue photons pump green and red phosphors.
Solution Approach 2:
The patent segments the phosphor distribution into distinct zones: blue phosphor materials are positioned near short-wavelength LEDs, while green and red phosphor materials are positioned away from blue light sources. This segmentation prevents unnecessary blue photon pumping of longer-wavelength phosphors and optimizes the conversion efficiency for each phosphor type.
2Reliability
If UV or violet LEDs are used to excite phosphors, then blue light leakage is reduced, but Stokes' loss increases due to larger wavelength conversion gaps
Solution Approach 1:
The patent changes the excitation wavelength parameter by using UV or violet LEDs (shorter wavelengths) instead of blue LEDs. This parameter change eliminates blue light leakage issues and improves white output stability, though it introduces increased Stokes' loss due to the larger energy gap between excitation and emission wavelengths.
Solution Approach 2:
The patent applies local quality by positioning blue phosphor materials specifically near the UV/violet LED sources. This localized placement ensures efficient blue light generation despite the high Stokes' loss, as the blue photons are generated close to where they are needed, minimizing further energy loss in subsequent conversions.
3Reliability
If green and red phosphor materials are positioned away from blue LEDs, then blue light leakage is reduced, but blue phosphor conversion efficiency decreases due to increased distance from excitation source
Solution Approach 1:
The patent segments the phosphor arrangement into distinct functional zones: blue phosphor materials are positioned near short-wavelength LEDs for efficient excitation, while green and red phosphor materials are positioned away from blue light sources to prevent blue light leakage. This segmentation resolves the contradiction by optimizing each phosphor's position for its specific function.
Solution Approach 2:
The patent inverts the conventional approach by not positioning all phosphors uniformly near the LED source. Instead, it positions blue phosphor near UV/violet LEDs while positioning green and red phosphors away from blue light sources, achieving both efficient blue conversion and reduced blue light leakage through this inverted spatial arrangement.
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 enhances color rendering and conversion efficiency by localizing blue phosphor conversion near short-wavelength LEDs, reducing optical losses and maintaining the benefits of UV- or V-pumped LEDs while achieving higher efficacy in producing white light for general illumination.
Implementation Method 1
two or more layers of phosphor materials excited by radiation sources that emit radiations in two or more wavelengths
Implementation Method 2
LED radiation sources that emit ultra-violet (UV), violet (V), or near-ultraviolet (NUV) radiation are used to excite blue phosphor material
Data Source
AI summary
An optical device includes a light source with at least two radiation sources, and at least two layers of wavelength-modifying materials excited by the radiation sources that emit radiation in at least two predetermined wavelengths. Embodiments include a first plurality of n radiation sources configured to emit radiation at a first wavelength. The first plurality of radiation sources are in proximity to a second plurality of m of radiation sources configured to emit radiation at a second wavelength, the second wavelength being shorter than the first wavelength. The ratio between m and n is predetermined. The disclosed optical device also comprises at least two wavelength converting layers such that a first wavelength converting layer is configured to absorb a portion of radiation emitted by the second radiation sources, and a second wavelength converting layer configured to absorb a portion of radiation emitted by the second radiation sources.