Organic Electroluminescent Device Electron Blocking Layer Lifespan

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Solution Overview

Problem

The lifespan of green and blue sub-pixel light emitting layers in organic electroluminescent devices is shorter than that of red sub-pixel layers, leading to chromaticity shifts and reduced display quality, limiting their application in long-lasting devices.

Innovation Solution

Incorporating an electron blocking layer with specific HOMO and LUMO energy levels between the hole transport layer and the light emitting layer, made of materials like single aromatic amines with spirofluorene or spirocyclic units, to regulate carrier balance and extend the lifespan of the green and blue sub-pixel layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of moving object

If conventional organic electroluminescent device structure is used, then device simplicity and manufacturing ease are maintained, but the lifespan of green and blue sub-pixel layers deteriorates significantly

Engineering Contradiction:

Improvelifespan of green and blue sub-pixel light emitting layersVSAvoidstructure complexity of conductive layers

Core Design Contradiction:

Duration of action of moving objectVSDevice complexity

Solution Approach 1:

The device is segmented into distinct conductive layer groups (first conductive layer group with electron blocking layer and hole transport layer, second conductive layer group with electron transport layer and hole blocking layer) to specifically address the lifespan issue of green and blue sub-pixels without redesigning the entire device structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The electron blocking layer and hole blocking layer act as intermediary layers between the electrodes and light emitting layers, regulating carrier injection to protect the green and blue sub-pixel light emitting layers from excessive carrier accumulation, thereby extending their lifespan

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If conventional carrier injection structure is used, then device simplicity is maintained, but chromaticity stability deteriorates due to differential degradation of sub-pixels

Engineering Contradiction:

Improvechromaticity stability of white light emissionVSAvoidconductive layer configuration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Different conductive layer groups are designed with different properties: the first conductive layer group (with electron blocking layer) is optimized for the blue sub-pixel, while the second conductive layer group (with hole blocking layer) is optimized for the green sub-pixel, providing localized protection against differential degradation

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The energy level configurations of the conductive layers create a self-regulating system where carrier injection is automatically balanced based on the HOMO and LUMO energy levels, ensuring stable chromaticity without external control

Inventive Principle:

Principle #23Feedback

3Duration of action of moving object

If standard energy level configuration is used, then manufacturing simplicity is maintained, but carrier balance deteriorates leading to reduced lifespan

Engineering Contradiction:

Improvelifespan of organic electroluminescent deviceVSAvoidmaterial selection complexity

Core Design Contradiction:

Duration of action of moving objectVSEase of manufacture

Solution Approach 1:

The patent specifies precise energy level parameters (HOMO and LUMO levels) for each conductive layer to optimize carrier balance. The electron blocking layer has HOMO level between the hole transport layer and light emitting layer, and LUMO level shallower than both, creating optimal energy level alignment for extended device lifespan

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 solution significantly prolongs the lifespan of the organic electroluminescent device by improving carrier balance, with demonstrated lifespan extensions of up to 40% for blue and 35% for green sub-pixel layers, enhancing overall device performance.

Implementation Method 1

a first conductive layer group, a second conductive layer group, and a light emitting layer disposed between the first conductive layer group and the second conductive layer group and in ohmic contacts with the two groups

Methodology Applied

Scientific EffectOhmic contact: Conduction (electrical)

Data Source

PatentUS11349093B2Organic electroluminescent device and display apparatus

Publication Date: 2022.05.31 KUNSHAN GO VISIONOX OPTO ELECTRONICS CO LTD

AI summary

The present application provides an organic electroluminescent device and a display apparatus. The organic electroluminescent device includes a first conductive layer group, a second conductive layer group, and a light emitting layer disposed between the first conductive layer group and the second conductive layer group and in ohmic contact with the two groups. The first conductive layer group includes an electron blocking layer in ohmic contact with the light emitting layer, and a hole transport layer in ohmic contact with the electron blocking layer. The HOMO energy level of the electron blocking layer is between that of the hole transport layer and that of the light emitting layer, and the LUMO energy level of the electron blocking layer is shallower than that of the hole transport layer and that of the light emitting layer.