Phosphor Layered LED White Light Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional phosphor-converted LEDs, particularly those excited by blue light, face challenges in achieving stable white output due to blue light leakage, which varies with drive current and temperature, and suffer from increased Stokes' loss and cascading conversion loss when using UV or violet light for excitation.
Innovation Solution
The use of multiple layers of phosphor materials excited by radiation sources emitting wavelengths less than 440 nm, with specific arrangements and ratios of LED radiation sources, and wavelength converting layers to optimize light emission and reduce cascading loss, allowing for improved color rendering and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If blue light LEDs are used to excite phosphors, then the device can be manufactured with existing technology, but blue light leakage occurs and white output stability deteriorates
Solution Approach 1:
The patent divides the single blue LED excitation source into multiple radiation sources with different wavelengths (violet LED at 405nm, blue LED at 450nm, and blue phosphor particles). This segmentation allows each component to perform a specific function: violet LED excites red and green phosphors directly, blue LED excites blue phosphor, and together they provide stable white output without blue light leakage issues.
Solution Approach 2:
The patent applies local quality by placing blue phosphor particles only in specific regions where blue light enhancement is needed, while using violet LED excitation in other regions to generate red and green light. This spatial differentiation of phosphor materials and excitation sources optimizes the overall white light output stability and color rendering.
2Reliability
If UV or violet light is used to excite phosphors, then blue light leakage is avoided, but Stokes' loss and cascading conversion loss increase
Solution Approach 1:
The patent uses partial action by employing violet LED (405nm) excitation only for specific phosphors (red and green phosphors) where it provides optimal performance, rather than using it for all phosphors. This selective application minimizes unnecessary Stokes' loss while achieving the desired white light output stability.
Solution Approach 2:
The patent changes the excitation wavelength parameter by using dual excitation sources: violet light (405nm) for red and green phosphors, and blue light (450nm) for blue phosphor. This parameter optimization reduces cascading conversion loss by eliminating the intermediate blue phosphor excitation step that occurs with UV/violet single-source excitation.
3Productivity
If multiple layers of phosphor materials are used, then color rendering and efficiency are improved, but device complexity increases
Solution Approach 1:
The patent merges multiple phosphor materials (red phosphor, green phosphor, and blue phosphor particles) into a single integrated phosphor layer that can be excited by multiple LED sources. This combining approach achieves improved color rendering and conversion efficiency while avoiding the complexity of multiple separate phosphor layers or structures.
Solution Approach 2:
The patent creates a multi-functional phosphor layer that simultaneously contains red, green, and blue phosphor materials, all of which can be excited by the violet and blue LED sources. This universal phosphor layer design simplifies the device structure while maintaining high conversion efficiency and excellent color rendering properties.
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 the conversion efficiency and stability of white light output by localizing blue phosphor near short-wavelength LEDs, reducing cascading loss, and minimizing optical losses in GaN semiconductor and packaging materials, resulting in higher efficacy and color rendering.
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
a first wavelength converting layer configured to absorb at least a portion of radiation emitted by the first plurality of radiation sources and the second plurality of radiation sources
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.