LED Filter Stack for Narrower FWHM and Better Color Purity
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Solution Overview
Problem
Existing light-emitting diode (LED) devices in display devices face challenges in maintaining photoelectric characteristics and improving display quality due to issues with light distribution and color purity.
Innovation Solution
A light-emitting device incorporating a semiconductor stack and a filter with alternately stacked layers of different refractive indices, which selectively transmits light to produce a second light with a narrower full width at half maximum (FWHM) and improved color purity, enhancing the beam angle and intensity distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional LED structure is used, then the device is simple and easy to manufacture, but the color purity and FWHM of emitted light are insufficient
Solution Approach 1:
The patent embeds a filter structure directly within the LED device, nesting the wavelength selection function inside the light-emitting component. The filter is integrated into the LED stack, allowing wavelength purification without external optical components, thus improving color purity while maintaining compactness
Solution Approach 2:
The patent employs a composite structure combining semiconductor light-emitting materials with filter materials having specific optical properties. The filter layer is composed of materials selected to absorb or block unwanted wavelengths while transmitting the desired emission wavelength, creating a composite system that achieves narrow FWHM
2Illumination intensity
If light is emitted in all directions, then the light distribution is uniform, but the intensity in specific directions is reduced
Solution Approach 1:
The patent applies directional control by making the filter structure selectively transmit light in specific angular ranges. The filter is designed with optical properties that allow high transmission in target directions (e.g., normal direction) while suppressing light in other directions, creating localized intensity enhancement without requiring complex external optics
3Manufacturing precision
If the FWHM of emitted light is wide, then the light intensity is high, but the color purity is reduced
Solution Approach 1:
The patent extracts or removes unwanted wavelength components from the broad-spectrum LED emission through the integrated filter. The filter selectively blocks wavelengths outside the desired narrow band, extracting only the pure color component while discarding the rest, thus achieving narrow FWHM with maintained intensity in the transmitted band
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
The solution achieves improved color purity and display quality by narrowing the FWHM of emitted light, increasing the intensity in specific directions, and reducing light loss, thereby enhancing the overall performance of LED-based display devices.
Implementation Method 1
the filter includes a plurality of pairs of layers with different refractive indexes alternately stacked
Implementation Method 2
the filter includes a plurality of pairs of layers with different refractive indexes alternately stacked
Data Source
AI summary
A light-emitting device, including: a semiconductor stack generating a first light; and a filter formed on the semiconductor stack, including a first surface facing the semiconductor stack and a second surface opposite to the first surface; and a transparent conductive layer formed on the semiconductor stack; wherein: the filter includes a plurality of first dielectric layers with a first refractive index and a plurality of second dielectric layers with a second refractive index alternately stacked, a portion of the first light is transmitted by the filter and extracted from the second surface, the light-emitting device has a beam angle in a range of 50 degrees to 110 degrees, and the filter comprises a light transmittance of more than 90% with respect to light incident at an incident angle in a range less than 10 degrees.