Phosphor-Converted LED Spacer Structure for Thin-Layer Light Conversion
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Solution Overview
Problem
Existing phosphor-converted light-emitting diodes (pcLEDs) face challenges in efficiently converting diode output light into down-converted light, particularly in mini- or microLED arrays where the thickness of the wavelength-converting layer is limited due to device pitch constraints, leading to reduced absorption and emission efficiency.
Innovation Solution
The semiconductor light-emitting device incorporates a semiconductor diode structure, a reflector, a wavelength-converting layer, and an intermediate spacer. The wavelength-converting layer absorbs diode output light and emits down-converted light, while the intermediate spacer, comprising one or more dielectric layers, acts as an optical waveguide to enhance the absorption and emission efficiency by supporting laterally propagating optical modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the thickness of the wavelength-converting layer is increased to improve light absorption, then absorption efficiency is improved, but device pitch increases which is not suitable for mini- or microLED arrays
Solution Approach 1:
The patent transitions from vertical light propagation through a thick phosphor layer to lateral propagation within a waveguide structure. By confining light to propagate laterally along the phosphor layer rather than vertically through it, the system achieves enhanced absorption efficiency without increasing the vertical device pitch, making it suitable for mini- and microLED arrays.
Solution Approach 2:
The patent segments the optical path into distinct functional regions: an input coupling region where light enters the waveguide, a lateral propagation region where light travels along the phosphor layer enabling extended interaction length, and an output extraction region where converted light exits. This segmentation allows independent optimization of each region to achieve both compact pitch and high absorption efficiency.
2Loss of energy
If the thickness of the wavelength-converting layer is increased to improve emission efficiency, then emission efficiency is improved, but device complexity increases
Solution Approach 1:
The phosphor layer serves multiple functions simultaneously: it acts as the wavelength-converting medium, forms the core of the optical waveguide structure, and provides the lateral propagation path for light. This multi-functionality eliminates the need for separate emission enhancement structures, reducing overall device complexity while improving emission efficiency.
Solution Approach 2:
The patent merges the wavelength conversion function with the waveguide function by making the phosphor layer itself the waveguide core. This consolidation of functions into a single integrated structure simplifies the device architecture compared to having separate conversion and guiding components.
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 significantly enhances the absorption and emission efficiency of down-converted light, even with a thin wavelength-converting layer, thereby improving the overall performance of pcLEDs in mini- or microLED arrays.
Implementation Method 1
The wavelength-converting layer absorbs diode output light at the vacuum wavelength λ0 and in response emits down-converted light at a vacuum wavelength λ1 that is greater than λ0
Implementation Method 2
the intermediate spacer having an effective refractive index nS less than an effective refractive index nC of the wavelength-converting layer. The wavelength-converting layer thereby acts as an optical waveguide supporting one or more laterally propagating optical modes at the vacuum wavelengths λ0 and λ1
Implementation Method 3
The reflector is positioned against a back surface of the second semiconductor layer and internally reflects diode output light incident from within the diode structure
Data Source
AI summary
A light-emitting device includes: a semiconductor diode structure, a reflector, a wavelength-converting layer, and an intermediate spacer between the diode structure and the wavelength-converting layer. The diode structure emits diode output light at a vacuum wavelength λ0 to propagate within the diode structure. The reflector is on the back diode structure and internally reflects diode internally incident output light. The wavelength-converting layer is positioned with its back surface facing and spaced-apart from a front surface of the diode structure, and absorbs diode output light at λ0 and emits down-converted light at a vacuum wavelength λ1>λ0, which exits the wavelength-converting layer through its front surface. The intermediate spacer includes one or more transparent dielectric layers and has an effective refractive index less than that of the wavelength-converting layer, so that the wavelength-converting layer acts as an optical waveguide supporting one or more laterally propagating optical modes at λ0 and λ1.