Light-Scattering Layer with Conductive Particles for LED Light Extraction

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Solution Overview

Problem

LED devices suffer from inefficiencies in light output due to trapped photons caused by total internal reflection within the device's layers, leading to significant light loss, and existing solutions like light-scattering layers do not adequately address conductivity issues or light distribution within the light-emitting areas.

Innovation Solution

A light-emitting device structure featuring a substrate with a first and second electrode, where at least one electrode is transparent, and a light-scattering layer comprising electrically-conductive, light-scattering particles in physical and electrical contact with the electrodes, which enhances light extraction and conductivity by scattering trapped light and improving current distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a light-scattering layer is added to improve light extraction, then light output efficiency is improved, but device complexity increases

Engineering Contradiction:

Improvelight output efficiencyVSAvoiddevice complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent combines the light-scattering function and electrical conductivity function into a single layer by incorporating electrically conductive particles (such as metal particles or conductive oxide particles) within the light-scattering layer. This merging eliminates the need for separate conductive electrode layers, thereby improving light extraction efficiency while avoiding increased device complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The light-scattering layer is designed to perform multiple functions simultaneously: (1) scattering trapped light to improve light extraction, (2) providing electrical conductivity through embedded conductive particles, and (3) maintaining structural integrity of the device. This multi-functionality resolves the contradiction by achieving improved light output without proportionally increasing device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Productivity

If conventional light-scattering layers are used to extract trapped light, then light output is improved, but electrical conductivity is insufficient

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoidelectrical conductivity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The light-scattering layer is constructed as a composite material containing both light-scattering particles (such as TiO2, SiO2, or ZrO2) and electrically conductive particles (such as aluminum, silver, or conductive oxide particles). This composite structure enables the layer to simultaneously achieve high light scattering efficiency and adequate electrical conductivity, resolving the contradiction between these two properties.

Inventive Principle:

Principle #40Composite materials

3Adaptability or versatility

If color filters are used to create full-color display, then color display capability is achieved, but light loss increases

Engineering Contradiction:

Improvecolor display capabilityVSAvoidlight loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

Instead of using color filters that absorb two-thirds of emitted light, the patent employs a light-scattering layer that redirects trapped light back into the light-emitting layer, causing it to re-emit light in useful directions. This converts the harmful effect of total internal reflection into a beneficial light extraction mechanism, achieving color display capability with minimal light loss.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 uniformity and efficiency of light output, enhances the sharpness of pixelated displays, and effectively extracts trapped light, improving the overall performance of LED devices.

Implementation Method 1

a light-scattering layer comprising electrically-conductive, light-scattering particles is located in physical and electrical contact with the first or second electrode

Methodology Applied

Scientific EffectLight scattering: Scattering

Implementation Method 2

At least one of the first and second electrodes is transparent

Methodology Applied

Scientific EffectTransparency to light:

Implementation Method 3

Holes and electrons recombine and emit light in the EL layer

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS7982396B2Light-emitting device with light-scattering particles and method of making the same

Publication Date: 2011.07.19 GLOBAL OLED TECHNOLOGY LLC

AI summary

A light-emitting device, including a substrate and a first electrode formed over the substrate. A light-emitting layer is formed over the first electrode. A second electrode is formed over the light-emitting layer. At least one of the first and second electrodes is transparent. A light-scattering layer comprising electrically-conductive, light-scattering particles is located in physical and electrical contact with the first or second electrode. The light-scattering layer is formed on a side of the first or second electrode, and opposite the light-emitting layer.