Organic EL Element Host Material π-π Stacking Morphology Stability
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Solution Overview
Problem
Organic electroluminescent elements using phosphorescent materials face challenges in controlling exciton recombination location and morphology changes under voltage, leading to decreased efficiency and lifetime due to aggregation of host material molecules.
Innovation Solution
Incorporating a compound with condensed aromatic rings bonded by linking groups that form a π-π stacking structure, inhibiting the formation of excimers and exciplexes, thereby stabilizing the molecular arrangement and reducing morphology changes during voltage application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If phosphorescent materials are used in organic EL elements, then light emission efficiency is improved, but voltage increases and lifetime decreases during operation
Solution Approach 1:
The patent changes the molecular structure parameters of the host material by introducing condensed aromatic rings with specific linking groups. This structural modification alters the electronic properties and molecular packing behavior, enabling the system to maintain high light emission efficiency while reducing voltage increase and extending lifetime during operation.
Solution Approach 2:
The patent employs composite material design by combining phosphorescent dopant materials with specifically structured host materials featuring condensed aromatic rings. This composite approach leverages the advantages of both components: the phosphorescent material provides high efficiency light emission while the structured host material ensures stability and longevity.
2Length of stationary object
If organic materials are used in the organic functional layer, then the element can be made thin, but charge mobility is low making electrification difficult
Solution Approach 1:
The patent changes the molecular structure parameters of the organic material by incorporating condensed aromatic rings with linking groups. This structural modification enhances charge mobility through improved π-π stacking and electron delocalization, enabling thin film fabrication while maintaining sufficient electrification capability.
3Ease of manufacture
If amorphous films are used instead of single crystalline organic molecules, then thin film fabrication is enabled, but molecular arrangement order is lost reducing charge transfer efficiency
Solution Approach 1:
The patent changes the molecular structure parameters by introducing rigid condensed aromatic ring systems with specific linking groups. This structural modification promotes spontaneous formation of ordered π-π stacking arrangements even in amorphous films, thereby maintaining charge transfer efficiency while enabling thin film fabrication.
Solution Approach 2:
The patent incorporates molecular structures pre-designed with condensed aromatic rings and linking groups that are predisposed to form ordered π-π stacking arrangements. This preliminary structural design ensures that even in amorphous films, the molecules self-organize into efficient charge transfer pathways during film formation.
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 approach minimizes voltage increase, extends lifetime, and maintains light-emission efficiency by preventing morphology changes in the host compound, enhancing the performance of organic electroluminescent elements in lighting and display devices.
Implementation Method 1
When an organic molecule is in a single crystalline state, it will be produced energy bands formed by a π-π interaction between the molecules.
Implementation Method 2
electrons will be passed by space-charge limited current not by ohm current. This space-charge limited current has a property to be inversely proportional to the cube of the film thickness, and to be proportional to the square of the applied voltage.
Implementation Method 3
it was reported an organic EL element using a phosphorescent material from an excited triplet state
Implementation Method 4
The charge transfer in the organic material is largely affected by the crystalline condition of the organic material.
Data Source
AI summary
Provided is an organic electroluminescent element containing an anode, a cathode, and an organic functional layer containing one or a plurality of light-emitting layers, the organic functional layer being interposed between the anode and the cathode, wherein at least one of the light-emitting layers contains a compound having two condensed aromatic rings bonded to each other with a linking group; and the condensed aromatic rings form a π-π stacking structure in the molecule.