Organic EL Hole Transporting Layer for Uniform Charge Distribution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In organic electroluminescent elements with multiple luminescent materials, uniform charge distribution is challenging, leading to reduced light emission efficiency and durability, particularly in wet film formation methods where solubility differences cause aggregation and non-uniform mixing.
Innovation Solution
Incorporating a hole injecting and transporting layer between the anode and luminescent layer, with charge-transporting materials having specific partial structures, and using luminescent materials with multiple emission maxima, including phosphorescent organic metal complexes, to ensure uniform charge transport and emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple luminescent materials are used in a wet film formation method, then white light emission is achieved, but uniform charge distribution deteriorates due to solubility differences causing aggregation
Solution Approach 1:
A hole injecting and transporting layer is introduced as an intermediary between the anode and the luminescent layer. This layer mediates charge distribution by facilitating hole injection and transport to multiple luminescent materials with different solubilities, preventing aggregation and ensuring uniform charge distribution across the luminescent layer.
Solution Approach 2:
The charge-transporting material is designed as a composite structure with specific partial structures (formula 2-A or 2-B) that enable it to interact effectively with multiple luminescent materials. This composite material approach allows the single charge-transporting material to maintain uniform mixing and charge distribution despite the diversity of luminescent materials present.
2Illumination intensity
If vacuum vapor deposition is used to deposit multiple luminescent materials, then white light emission is achieved, but manufacturing complexity and difficulty of control increase
Solution Approach 1:
Multiple luminescent materials that would otherwise require separate vapor deposition processes are merged into a single luminescent layer formed by wet film formation. This combining approach eliminates the need for complex sequential vapor deposition of multiple materials, simplifying the manufacturing process while achieving the same white light emission effect.
Solution Approach 2:
The patent transitions from vacuum vapor deposition (pneumatic/vacuum-based process) to wet film formation (liquid-based process). This replacement of gas-phase deposition with liquid-phase coating simplifies the equipment and process control, as wet film formation does not require complex vacuum systems and can be performed under atmospheric conditions.
3Ease of manufacture
If polymer materials are used in wet film formation, then film formation is facilitated, but luminescent efficiency decreases due to purification difficulties
Solution Approach 1:
The patent changes the molecular weight parameter of the charge-transporting material from high (polymer) to low (small molecule). This parameter change enables sufficient purification of the charge-transporting material while maintaining ease of film formation through wet processing, thereby restoring luminescent efficiency that was previously compromised by polymer use.
4Manufacturing precision
If a single charge-transporting material is used with low-molecular luminescent materials, then purification is improved, but driving voltage increases due to high crystallinity
Solution Approach 1:
The charge-transporting material is designed with specific local structural features (partial structures of formula 2-A or 2-B) that create localized amorphous regions within the material structure. This local quality modification prevents excessive crystallization while maintaining overall material purity, thereby reducing driving voltage without sacrificing purification benefits.
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 enables high-efficiency light emission at low driving voltage with improved durability and reproducibility, addressing issues of aggregation and non-uniformity in wet film formation.
Implementation Method 1
a hole injecting and transporting layer provided between the anode and the luminescent layer and adjacent to the luminescent layer
Implementation Method 2
the luminescent material includes at least three kinds of materials and has an emission spectrum having at least two kinds of emission maximums
Implementation Method 3
Organic electroluminescent elements enable various light emissions depending on the combination of the constituent materials
Data Source
AI summary
An organic electroluminescent element comprising: an anode; a cathode; a luminescent layer provided between the anode and the cathode; and a hole injecting and transporting layer provided between the anode and the cathode and adjacent to the luminescent layer, wherein at least the luminescent layer is formed by a wet film forming method, and contains a charge transporting material and a luminescent material, in which the charge transporting material contains a hole transporting material and an electron transporting material each having a specific partial structure, and the luminescent material contains at least three kinds of materials and has an emission spectrum having at least two kinds of emission maximums.