Phosphor Converted LED With Staged Layer Structure

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Solution Overview

Problem

Phosphor-phosphor interaction in phosphor converted white LED devices leads to photon losses and absorption losses due to redirection of emitted light, which decreases efficiency and increases the need for high concentration of phosphor materials, particularly affecting the spectral power distribution (SPD) and color rendering indices (CRI).

Innovation Solution

The use of multiple phosphor layers on an LED device, where a second phosphor layer with a peak emission wavelength located between the peak emission wavelengths of the LED die and the first phosphor layer, reduces reabsorption of light emitted by the outermost phosphor layer, enhancing efficiency and improving the spectral power distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single phosphor layer is used to convert blue LED light, then the device structure is simple, but photon losses and absorption losses occur due to phosphor-phosphor interaction, decreasing efficiency and affecting spectral power distribution

Engineering Contradiction:

Improvephosphor layer structureVSAvoidphoton loss

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The single phosphor layer is segmented into multiple phosphor layers with different peak emission wavelengths. The first phosphor layer has a peak emission wavelength between the blue LED peak and the second phosphor layer peak, creating a staged conversion structure that reduces reabsorption losses by distributing phosphor materials across separate layers rather than mixing them in a single layer.

Inventive Principle:

Principle #1Segmentation

2Illumination intensity

If high concentration of phosphor materials is used to improve color rendering, then color quality improves, but absorption losses increase due to phosphor-phosphor interaction

Engineering Contradiction:

Improvecolor rendering indexVSAvoidabsorption loss

Core Design Contradiction:

Illumination intensityVSLoss of energy

Solution Approach 1:

Different phosphor materials with specific peak emission wavelengths are placed in different layers according to their optical properties. The first phosphor layer contains materials optimized for converting blue light to intermediate wavelengths, while the second layer contains materials for further wavelength conversion. This local optimization of phosphor placement reduces unwanted absorption interactions while maintaining high color rendering index.

Inventive Principle:

Principle #3Local quality

3Productivity

If multiple phosphor layers are used to reduce reabsorption losses, then light emission efficiency improves, but device complexity increases

Engineering Contradiction:

Improvelight emission efficiencyVSAvoidphosphor layer configuration

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The phosphor conversion process transitions from a two-dimensional mixed powder layer to a three-dimensional stacked layer structure. By arranging phosphor materials in vertical layers with specific wavelength relationships, the patent achieves more efficient light conversion while organizing the complexity in a structured, manufacturable way that balances performance improvement with device fabrication feasibility.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 increases the color rendering index (CRI) from 91.4 to 94.2 and reduces the local minimum in the spectral power distribution adjacent to the blue emission peak, improving the overall light emission efficiency and color quality.

Implementation Method 1

A light emitting diode (LED) device may include an LED die having a first surface on a substrate

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Implementation Method 2

A first phosphor layer may be formed on a second surface and sides of the LED die. The second phosphor layer may be formed on the first phosphor layer

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Implementation Method 3

A reflective coating formed on sides of the LED die, sides of the first phosphor layer, and sides of the second phosphor layer

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS11233180B2Phosphor converted LED with high color quality

Publication Date: 2022.01.25 LUMILEDS SINGAPORE PTE LTD

AI summary

A light emitting diode (LED) device may include an LED die having a first surface on a substrate. A first phosphor layer may be formed on a second surface and sides of the LED die. The second surface may be opposite the first surface. A second phosphor layer may be formed on the first phosphor layer. The second phosphor layer may have a peak emission wavelength (Lpk2) located between a peak emission wavelength of the LED die (LpkD) and a peak emission wavelength of the first phosphor layer (Lpk2).