Hybrid Phosphor-Converted Red LEDs for Color Purity and Reliability
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Solution Overview
Problem
Current Phosphor-Converted Red LEDs (PC Red LEDs) face challenges in generating narrowband red light due to the high cost and low absorption efficiency of narrowband red fluoride phosphors, which also suffer from moisture sensitivity and 'blue pass through' issues, affecting color purity and device reliability.
Innovation Solution
Incorporating a combination of narrowband red fluoride phosphors and broadband red phosphors in a single or double-layer photoluminescence structure, with the broadband phosphor enhancing absorption efficiency and reducing the amount of narrowband phosphor needed, while also providing environmental protection to improve device reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If narrowband red fluoride phosphors are used to generate narrowband red light, then color purity is improved, but cost increases and absorption efficiency decreases
Solution Approach 1:
The patent combines narrowband red fluoride phosphors with broadband red phosphors in a hybrid phosphor system. The narrowband phosphor (e.g., K2SiF6:Mn4+) provides narrowband red emission for high color purity, while the broadband phosphor (e.g., CaAlSiN3:Eu2+) provides broad absorption of blue light to compensate for the low absorption efficiency of the narrowband phosphor. This merging of different phosphor types resolves the contradiction by achieving both high color purity and high absorption efficiency simultaneously.
2Manufacturing precision
If narrowband red fluoride phosphors are used, then color purity is improved, but device reliability deteriorates due to moisture sensitivity
Solution Approach 1:
The broadband red phosphor acts as an intermediary protective layer that absorbs blue light before it can reach and potentially degrade the moisture-sensitive narrowband red fluoride phosphor. Additionally, the hybrid phosphor system allows for optimized encapsulation strategies where the broadband phosphor's higher moisture resistance provides a buffer, reducing the overall moisture sensitivity of the device while maintaining the color purity benefits of the narrowband phosphor.
3Manufacturing precision
If narrowband red fluoride phosphors are used, then color purity is improved, but 'blue pass through' issues worsen
Solution Approach 1:
The patent merges narrowband red fluoride phosphors with broadband red phosphors in a hybrid system. The narrowband phosphor emits narrowband red light for high color purity, while the broadband phosphor absorbs the blue excitation light that would otherwise pass through unconverted. This combination resolves the contradiction by eliminating blue pass through while maintaining narrowband red emission quality.
4Manufacturing precision
If only narrowband red fluoride phosphors are used, then narrowband red light is achieved, but absorption efficiency decreases
Solution Approach 1:
The patent combines narrowband red fluoride phosphors with broadband red phosphors in a hybrid phosphor configuration. The narrowband phosphor provides the desired narrowband red emission, while the broadband phosphor compensates for low absorption efficiency by strongly absorbing blue excitation light across a broader spectral range. This merging allows the system to achieve both narrowband emission and high absorption efficiency simultaneously.
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 reduces the usage of expensive narrowband phosphors, minimizes 'blue pass through', and enhances color purity and luminous efficacy, achieving red light with high brightness and improved reliability.
Implementation Method 1
a blue LED chip and a photoluminescence material that converts substantially all of the excitation light generated by the LED chip to light of a selected color
Data Source
AI summary
A light emitting device comprising: a first LED for generating a first light with a dominant wavelength from 620 nm to 640 nm and a FWHM of less than 55 nm; a second LED for generating a second light with a dominant wavelength from 500 nm to 565 nm; and a third LED for generating a third light with a light with a dominant wavelength from 430 nm to 480 nm; wherein the first LED comprises a phosphor-converted LED comprising an LED for generating light with a dominant wavelength from 400 nm to 480 nm, and a narrowband red phosphor.