Coated Phosphor Particles for Lower Reflection Loss in LEDs

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Solution Overview

Problem

Existing light emitting diodes (LEDs) face inefficiencies in light transmission due to reflection losses at the interface between luminescent particles and encapsulants, leading to reduced light conversion and performance.

Innovation Solution

The use of coated phosphor particles with an optical coating having a refractive index between that of the luminescent particle and the encapsulant minimizes reflection, enhancing light transmission and conversion efficiency by acting as an intermediate index material.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If luminescent particles are incorporated into the encapsulant, then light conversion function is achieved, but light loss due to reflection at the interface occurs

Engineering Contradiction:

Improvelight conversion efficiencyVSAvoidlight loss due to reflection

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

An optical coating layer with intermediate refractive index is introduced between the luminescent particle and the encapsulant. This intermediary layer reduces the refractive index mismatch at the interface, thereby minimizing reflection losses and improving light transmission while maintaining the light conversion function.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The refractive index parameter of the interface is modified by applying an optical coating with a specific refractive index value that lies between that of the luminescent particle and the encapsulant. This parameter change optimizes the optical impedance matching and reduces reflection at the interface.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If uncoated luminescent particles are used, then device complexity is low, but reflection loss is high

Engineering Contradiction:

Improvestructure simplicityVSAvoidreflection loss

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

A simple optical coating layer is applied to the luminescent particle surface. This additional layer, while increasing complexity slightly, provides a straightforward solution to reduce reflection losses through refractive index matching without requiring complex multi-layer structures.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Illumination intensity

If optical coating is applied to luminescent particles, then light transmission is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvelight transmissionVSAvoidmanufacturing process simplicity

Core Design Contradiction:

Illumination intensityVSEase of manufacture

Solution Approach 1:

The optical coating is applied as a thin film layer on the luminescent particle surface using conventional coating techniques. This approach achieves improved light transmission while maintaining relatively simple manufacturing processes that can be integrated into existing LED production lines.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The manufacturing process is modified to include an additional coating step that changes the surface properties of the luminescent particles. This parameter change (adding the optical coating) is achieved through established thin-film deposition or sol-gel methods that are compatible with mass production.

Inventive Principle:

Principle #35Parameter changes

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 significantly reduces average reflection, increasing the brightness and efficiency of light emission while allowing for reduced luminescent particle usage, thereby improving the performance of light emitting devices.

Implementation Method 1

there is some light lost to reflection as a photon passing through the encapsulant encounters the luminescent particle

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

light lost to reflection as a photon passing through the encapsulant encounters the luminescent particle

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 3

forming an optical coating on a luminescent particle via a sol-gel reaction

Methodology Applied

Scientific EffectSol-gel reaction: Sol

Implementation Method 4

A phosphor may absorb a portion of the light emitted from an LED at a given wavelength and re-emit the light at different wavelength via the principle of photoluminescence

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Data Source

PatentUS20230402573A1Coated phosphor particle, light emitting device including a coated phosphor particle, and method of making a coated phosphor particle

Publication Date: 2023.12.14 CREELED INC

AI summary

A light emitting device comprises a light emitting diode (LED) chip having a dominant wavelength in a range from about 390 nm to about 560 nm, an encapsulant in optical communication with the LED chip, and coated phosphor particles dispersed in the encapsulant. Each of the coated phosphor particles comprises (a) a luminescent particle having a first refractive index at the dominant wavelength, and (b) an optical coating on the luminescent particle, where the optical coating has a second refractive index at the dominant wavelength. The second refractive index is between the first refractive index and a refractive index of the encapsulant at the dominant wavelength.