Organic Light Emitting Element Hole Injection Layer Design
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Solution Overview
Problem
Organic light emitting elements face challenges with low efficiency, short lifespan, and high driving voltage due to inefficient charge injection and transfer characteristics, primarily attributed to the low miscibility of organic electron acceptor compounds with hole transporting compounds.
Innovation Solution
Incorporating specific organic electron acceptor compounds with strong electron withdrawing groups into the hole injection layer to enhance hole generation, injection, and transfer, and using a tandem structure with charge generation layers to improve charge management, along with specific compounds represented by chemical formulas 1 and 2 in the organic material layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If organic electron acceptor compounds with strong electron withdrawing groups are used in the hole injection layer, then hole generation, injection and transfer efficiency is improved, but miscibility with hole transporting compounds deteriorates leading to high driving voltage and low luminous efficiency
Solution Approach 1:
The patent introduces a hole transporting compound as an intermediary layer between the electron acceptor compound and the hole injection layer. This intermediary facilitates efficient hole transfer from the electron acceptor compound to the hole injection layer while maintaining good miscibility and stable charge transfer characteristics, thereby resolving the contradiction between efficiency and stability.
Solution Approach 2:
The patent employs a composite material structure combining the electron acceptor compound with the hole transporting compound in a specific layered configuration. This composite approach allows the electron acceptor compound to provide high hole generation efficiency while the hole transporting compound ensures good miscibility and stable charge transfer, thus resolving the contradiction.
2Productivity
If the efficiency of the organic light emitting element is increased, then the driving voltage is decreased, but the crystallization of organic material by Joule heating increases leading to reduced lifespan
Solution Approach 1:
The patent extracts the charge generation function from the hole injection layer and places it in a separate electron acceptor compound layer. This separation allows the hole injection layer to focus on efficient hole injection without the crystallization issues caused by Joule heating, thereby extending the lifespan while maintaining high emission efficiency.
Solution Approach 2:
The patent segments the organic material layer into distinct functional layers: an electron acceptor compound layer for charge generation and a hole injection layer for hole injection. This segmentation allows each layer to perform its function optimally without the adverse effects of Joule heating-induced crystallization, thus improving both efficiency and lifespan.
3Duration of action of stationary object
If the driving voltage is reduced, then the crystallization of organic material is reduced, but the emission efficiency decreases
Solution Approach 1:
The hole transporting compound acts as an intermediary that enables efficient hole transfer at lower driving voltages. This intermediary facilitates charge transfer without requiring high driving voltages that would cause crystallization, while maintaining high emission efficiency through optimized charge injection and transport characteristics.
Solution Approach 2:
The patent changes the energy level parameters of the materials by selecting specific electron acceptor compounds with appropriate LUMO levels and hole transporting compounds with matching HOMO levels. This parameter optimization enables efficient charge transfer at reduced driving voltages, thereby extending lifespan while maintaining emission efficiency.
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 results in organic light emitting elements with improved emission efficiency, extended lifespan, and reduced driving voltage by optimizing hole and electron injection characteristics.
Implementation Method 1
it may withdraw electrons from a high occupied molecular orbital (HOMO) energy level of the adjacent hole transport layer to a low occupied molecular orbital (LUMO) energy level of the organic electron acceptor compound to generate holes and inject the holes into the hole transport layer
Implementation Method 2
In general, organic light emission refers to a phenomenon in which electric energy is converted into light energy by an organic material
Data Source
AI summary
An organic light emitting element and a display device, specifically, an organic light emitting element including a first compound represented by chemical formula 1 and a second compound represented by chemical formula 2 provides excellent efficiency, long lifespan or low driving voltage and a display device including the organic light emitting element.