Organic Electroluminescent Device Naphthacene Hole Trapping Layer

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Solution Overview

Problem

Organic electroluminescent devices suffer from color mixing and reduced light-emitting layer functionality due to doping with rubrene, which affects the longevity and color purity of the emitted light.

Innovation Solution

Incorporating a naphthacene compound layer of specific thickness and purity between the electron transport layer and the light-emitting layer, composed of a light-emitting guest material and an aromatic hydrocarbon compound, to trap holes and prevent deterioration, thereby extending the device's life and maintaining color purity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If rubrene is doped into the light-emitting layer to trap holes and extend device life, then the device longevity is improved, but color mixing occurs and light-emitting layer functionality deteriorates

Engineering Contradiction:

Improvedevice lifeVSAvoidcolor mixing

Core Design Contradiction:

Duration of action of stationary objectVSObject-generated harmful factors

Solution Approach 1:

The patent divides the light-emitting layer into two distinct functional layers: a light-emitting layer containing the light-emitting complex and a hole-trapping layer containing rubrene. This segmentation allows each layer to perform its specific function without interference, preventing color mixing while maintaining hole-trapping capability for extended device life.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent extracts the hole-trapping function from the light-emitting layer by creating a separate hole-trapping layer. This removes the harmful effect of rubrene's yellow light mixing with the blue light from the light-emitting complex, while preserving the beneficial hole-trapping effect that extends device longevity.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If rubrene is doped to protect the electron transport layer from hole injection, then reliability is improved, but the light-emitting layer emits light with reduced color purity

Engineering Contradiction:

Improvedevice reliabilityVSAvoidcolor purity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent introduces a hole-trapping layer as an intermediary between the light-emitting layer and the electron transport layer. This intermediate layer captures holes before they can reach the electron transport layer, protecting it from deterioration, while being positioned and designed to prevent its light emission from mixing with the light-emitting layer's output.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Duration of action of stationary object

If a thick rubrene-doped layer is used to enhance hole trapping, then device life is extended, but light emission efficiency and color purity deteriorate

Engineering Contradiction:

Improvedevice lifeVSAvoidlight emission efficiency

Core Design Contradiction:

Duration of action of stationary objectVSUse of energy by moving object

Solution Approach 1:

The patent optimizes the thickness of the hole-trapping layer to a specific range (5-50 nm) to achieve the right balance between hole-trapping capability and light emission efficiency. This parameter optimization ensures sufficient hole trapping for extended device life while minimizing the impact on light emission efficiency and color purity.

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

The naphthacene compound layer effectively traps holes, preventing them from entering the electron transport layer, which results in a longer-lasting organic electroluminescent device that emits light with high color purity and reproducibility without color mixing.

Implementation Method 1

the naphthacene compound layer effectively traps holes, preventing them from entering the electron transport layer

Methodology Applied

Scientific EffectCharge carrier trapping:

Implementation Method 2

the light-emitting layer causes recombination to occur between electrons injected from the cathode and holes injected from the anode and recombination emanates light

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS7935962B2Organic electroluminescent device and display unit

Publication Date: 2011.05.03 MAGNOLIA BLUE CORP

AI summary

Disclosed herein is an organic electroluminescent device including: an anode; a cathode; and an organic layer including a light-emitting layer, a naphthacene compound layer containing a naphthacene compound, and an electron transport layer; the light-emitting layer being composed of a light-emitting guest material and an aromatic hydrocarbon compound having the skeleton of anthracene, and the naphthacene compound layer containing no less than 80 wt % of naphthacene compound represented by the formula (1) below and having a thickness of 0.5 to 10 nm and being in contact with that side of the electron transport layer which faces the light-emitting layer.