Organic EL Element Charge Transport Layer with Blocking Regions
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Solution Overview
Problem
Conventional organic electroluminescent elements with a single host material struggle to achieve high luminance and long lifetime due to unbalanced hole and electron mobility, leading to inefficient charge trapping and recombination, and complex manufacturing processes.
Innovation Solution
A homojunction-type organic electroluminescent element with a positive and negative charge transport layer including a light-emitting region and at least one blocking region, where the electron blocking region has a lower LUMO and the hole blocking region has a higher HOMO than the light-emitting region, enhancing electron-hole recombination and reducing drive voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single host material is used in homojunction-type organic EL element, then manufacturing process is simplified, but charge trapping efficiency and recombination efficiency deteriorate due to unbalanced hole and electron mobility
Solution Approach 1:
The patent introduces blocking regions with different energy levels (HOMO/LUMO) at specific locations within the homojunction layer. These localized regions have distinct electrical properties (electron blocking or hole blocking) that address the unbalanced charge transport issue without requiring a complete change to the single-host-material structure, thus maintaining manufacturing simplicity while improving charge trapping efficiency
Solution Approach 2:
The patent modifies the energy level parameters (HOMO and LUMO levels) of the host material by introducing dopants or selecting specific materials with tailored energy levels. This changes the electrical characteristics of blocking regions to create potential barriers that enhance charge trapping efficiency while maintaining the overall homojunction structure
2Reliability
If heterojunction-type multilayer structure is used, then charge injection efficiency and luminous efficiency are improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent merges the functions of multiple separate layers (hole injection layer, electron injection layer, hole transport layer, electron transport layer) into a single homojunction-type layer with integrated blocking regions. This consolidation maintains the charge injection and transport functions while eliminating the need for complex multilayer structures, thus reducing device complexity and manufacturing cost
Solution Approach 2:
The homojunction-type layer with blocking regions serves multiple functions simultaneously: it acts as both the charge transport medium and the charge trapping mechanism. The single host material system performs the roles of multiple different materials in heterojunction structures, achieving multi-functionality with a simplified architecture
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 increases the probability of electron-hole recombination, resulting in higher internal quantum efficiency and luminous efficiency, while simplifying the manufacturing process and maintaining balanced hole and electron mobility.
Implementation Method 1
a positive and negative charge transport layer having a hole transporting capability and an electron transporting capability
Implementation Method 2
an organic electroluminescent element including a positive and negative charge transport layer having a hole transporting capability and an electron transporting capability
Data Source
AI summary
An organic EL element (1) according to the present invention is such that a positive and negative charge transport layer (30) is interposed between a cathode (20) and an anode (10). The positive and negative charge transport layer (30) is composed of a single host material and has a light-emitting region (33) which is doped with a light-emitting dopant. The positive and negative charge transport layer (30) further has at least one of the following blocking regions: an electron blocking region (32), provided closer to the anode (10) than the light-emitting region (33), having a lowest unoccupied molecular orbital lower than that of the lowest unoccupied molecular orbital of the light-emitting region (33); and a hole blocking region (34), provided closer to the cathode (20) than the light-emitting region (33), having a highest occupied molecular orbital higher than that of the highest occupied molecular orbital of the light-emitting region (33).