Multi-Emission-Layer OLED Transport Stack for Lifetime and Efficiency
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Solution Overview
Problem
Existing multi-emission-layer organic light-emitting diodes (OLEDs) face challenges in improving lifetime and efficiency, particularly in top emission OLEDs.
Innovation Solution
The OLED structure includes a first electron transport layer and a second electron transport layer, each comprising specific compounds of Formulas (I) and (II), with a first charge generation layer between the emission layers, and both electron transport layers being free of electrical dopants, to enhance electron transport and balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional electron transport materials are used in multi-emission-layer OLEDs, then the device structure can be simplified, but the lifetime and efficiency are insufficient
Solution Approach 1:
The electron transport layer is divided into multiple sub-layers (first electron transport layer, second electron transport layer, third electron transport layer) with different materials and functions. Each sub-layer is optimized for specific electron transport requirements, enabling improved lifetime and efficiency without requiring overall structural simplification
Solution Approach 2:
Different electron transport materials are selected for different positions within the electron transport layer. The first electron transport layer uses material with specific LUMO levels for electron injection from emission layer, while the second and third layers use materials optimized for electron transport toward the charge generation layer, creating locally optimized electron transport pathways
2Ease of manufacture
If conventional electron transport materials are used in multi-emission-layer OLEDs, then the material selection process is simplified, but the efficiency (CEff) is insufficient
Solution Approach 1:
The patent specifies precise parameter ranges for electron transport materials, including LUMO energy levels (first layer: -2.0 to -1.5 eV, second layer: -2.5 to -2.0 eV, third layer: -3.0 to -2.5 eV) and thickness parameters. These parameter optimizations enable high efficiency while maintaining systematic material selection criteria
Solution Approach 2:
The electron transport layer employs composite material structure with three different electron transport materials in sequential layers. This composite approach combines the advantages of each material to achieve superior overall efficiency compared to single-material systems
3Productivity
If balanced hole and electron injection is achieved, then excellent device efficiency is obtained, but the lifetime remains insufficient
Solution Approach 1:
The electron transport function is segmented into three layers with progressively different materials and energy levels. This segmentation allows independent optimization of electron injection (first layer), electron transport (second layer), and interface management with charge generation layer (third layer), achieving both efficiency and lifetime improvement
Solution Approach 2:
The multi-layer electron transport structure acts as an intermediary system between the emission layer and the charge generation layer. Each layer mediates specific aspects of electron transport, creating optimized pathways that reduce stress on individual materials and improve overall device lifetime
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 improves the lifetime and efficiency of the OLEDs by optimizing electron transport and reducing voltage, leading to enhanced performance.
Implementation Method 1
the first electron transport layer stack is arranged between the first emission layer and the second emission layer... the first electron transport layer stack comprises a first electron transport layer and a second electron transport layer
Implementation Method 2
The holes and electrons recombine in the EML to generate excitons. When the excitons drop from an excited state to a ground state, light is emitted
Data Source
AI summary
The present invention relates to an organic light emitting diode comprising an anode, a cathode, a first emission layer, a second emission layer, a first charge generation layer and a first electron transport layer stack; and to a display device or lighting device comprising the same.