Organic Light-Emitting Element with Electron Trapping Layers

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Solution Overview

Problem

Current current excitation light-emitting elements have short lifetimes and low light emission efficiency due to the lack of durability in hole blocking layers, leading to inefficient light emission and rapid degradation.

Innovation Solution

A light-emitting element structure is developed with multiple organic layers, including an electron transporting layer and a hole transporting layer, where the first layer contains an organic compound with electron transporting properties and the second layer contains an organic compound with hole transporting properties, with a third organic compound having electron trapping properties, ensuring improved carrier balance and recombination efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a hole blocking layer is provided to improve light emission efficiency, then light emission efficiency is improved, but the lifetime becomes very short due to lack of durability

Engineering Contradiction:

Improvelight emission efficiencyVSAvoidlifetime

Core Design Contradiction:

Use of energy by moving objectVSDuration of action of stationary object

Solution Approach 1:

The light-emitting layer is segmented into multiple layers with different functions: a first layer containing electron transporting compound and electron trapping compound, and a second layer containing hole transporting compound and electron trapping compound. This segmentation allows each layer to be optimized for its specific function while working together to achieve both high efficiency and long lifetime.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the light-emitting layer are given different local qualities: the first layer is optimized for electron transport and trapping, while the second layer is optimized for hole transport and electron trapping. This local differentiation enables simultaneous achievement of high light emission efficiency and durability without requiring a separate hole blocking layer.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If conventional materials are used in light-emitting layers, then manufacturing is simpler, but carrier balance is poor and light emission efficiency is low

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidlight emission efficiency

Core Design Contradiction:

Ease of manufactureVSUse of energy by moving object

Solution Approach 1:

The light-emitting layer uses composite materials combining multiple organic compounds with complementary properties: electron transporting compounds (e.g., Alq3, BAlq2), hole transporting compounds (e.g., NPB, TPD), and electron trapping compounds (e.g., BPAPQ). This composite approach achieves excellent carrier balance and high light emission efficiency while remaining compatible with conventional vacuum evaporation manufacturing processes.

Inventive Principle:

Principle #40Composite materials

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 proposed structure enhances light emission efficiency and extends the lifetime of the light-emitting element by maintaining good carrier balance and reducing exciton density, resulting in high luminance and power efficiency with improved color purity and reduced power consumption.

Implementation Method 1

the first organic compound is an organic compound with an electron transporting property

Methodology Applied

Scientific EffectElectron transport: Conduction (electrical)

Implementation Method 2

the second organic compound is an organic compound with a hole transporting property

Methodology Applied

Scientific EffectHole transport: Conduction (electrical)

Implementation Method 3

the third organic compound has an electron trapping property

Methodology Applied

Scientific EffectElectron trapping:

Implementation Method 4

Light-emitting elements utilizing electroluminescence are broadly classified according to whether they use an organic compound or an inorganic compound as a substance with a light-emitting property

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS7911135B2Light-emitting element, light emitting device, electronic appliance, and method of manufacturing the same

Publication Date: 2011.03.22 SEMICON ENERGY LAB CO LTD

AI summary

A light-emitting element is provided which has a light-emitting layer between a first electrode and a second electrode, where the light-emitting layer has a first layer and a second layer; the first layer contains a first organic compound and a third organic compound; the second layer contains a second organic compound and the third organic compound; the first layer is provided to be in contact with the second layer on the first electrode side; the first organic compound is an organic compound with an electron transporting property; the second organic compound is an organic compound with a hole transporting property; the third organic compound has an electron trapping property; and light emission from the third organic compound can be obtained when voltage is applied to the first electrode and the second electrode so that the potential of the first electrode is higher than that of the second electrode.