Conductive Polymer Composition for Low-Moisture OLED Coatings
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Solution Overview
Problem
Conductive polymer compositions used in organic electroluminescent devices face issues with moisture retention, surface roughness, and aggregation, leading to decreased device performance and shortened lifespan, particularly when using sulfonic acid-based dopants like PSS, which also result in poor film formability and increased acidity.
Innovation Solution
A conductive polymer composition comprising a π-conjugated polymer, a dopant polymer with a fluorinated acid unit, and a water-soluble organic solvent, along with a compound to control acidity, is developed to reduce moisture retention, improve film formability, and prevent light emission from unintended areas, using a specific molecular structure and solvent combination to achieve low surface tension and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PSS (polystyrenesulfonic acid) is used as a dopant to achieve high conductivity and good dispersibility, then the conductive polymer can be handled as a highly conductive liquid material with improved dispersibility in water, but the PSS retains moisture which significantly lowers device performance and shortens device lifetime
Solution Approach 1:
The patent changes the chemical structure of the dopant polymer by introducing fluorinated acid units (such as perfluoroalkyl ether sulfonic acid groups) instead of using conventional PSS. This parameter change in the dopant's molecular structure fundamentally alters its moisture interaction properties, reducing hygroscopy while maintaining doping efficiency and conductivity, thereby resolving the contradiction between device performance and moisture retention
Solution Approach 2:
The patent creates a composite conductive polymer material by combining π-conjugated polymers with fluorinated acid-containing dopant polymers. This composite approach integrates the high conductivity of π-conjugated polymers with the low moisture-retention properties of fluorinated dopants, achieving both high device performance and reduced moisture harm
2Reliability
If PSS is used as a dopant to achieve high conductivity, then the material can function as a transparent electrode or injection layer, but the composite disperses as particles in water and forms films with remaining moisture that degrades device performance
Solution Approach 1:
The patent modifies the dopant polymer's chemical composition by incorporating fluorinated acid units, which change the film's moisture absorption characteristics and compositional stability. This parameter change ensures the film maintains its intended composition without moisture degradation, extending device lifetime
3Object-affected harmful factors
If efforts are made to disperse the composite in organic solvent to avoid moisture retention, then moisture problems may be reduced, but the affinity to organic solvent is so low that it is difficult to obtain a uniform dispersion
Solution Approach 1:
The patent changes the solvent system from organic solvent to water by modifying the dopant's hydrophilicity through fluorinated acid units. This parameter change enables uniform dispersion in water without the moisture retention problems associated with conventional PSS, simultaneously achieving low moisture retention and high dispersion uniformity
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 a conductive film with high transparency, flatness, and appropriate conductivity, effectively preventing light emission from areas other than the intended electrode surface, while reducing residual moisture and enhancing the durability and luminance lifetime of organic electroluminescent devices.
Implementation Method 1
A polymer having a conjugated double bond (a π-conjugated polymer) does not exhibit electrical conductivity by itself, but becomes an electro-conductive polymer material by doping with an appropriate anion molecule which causes electron or hole to move
Implementation Method 2
along with a compound to control acidity, is developed to reduce moisture retention, improve film formability, and prevent light emission from unintended areas, using a specific molecular structure and solvent combination to achieve low surface tension and conductivity
Implementation Method 3
H 2 O (D) for dispersing the composite
Data Source
AI summary
An object is to obtain a composition capable of: forming a uniform film even by spray coating or even when the composition is applied in the form of ink for inkjet printing; and preventing light emission from a portion other than an ITO electrode surface when the film is mounted on an organic EL device and light is emitted from the device. A conductive polymer composition contains: a composite containing a n-conjugated polymer (A) and a polymer (B) shown by a general formula (1); H2O (D) for dispersing the composite; a water-soluble organic solvent (C); and a compound (E) shown by a general formula (2). The electric conductivity of a film with a thickness of 20 to 200 nm formed from the conductive polymer composition is less than 1.00E-05 S/cm.