Conductive Material with Fluorinated Dopant for Flexible Electrodes
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Solution Overview
Problem
Conductive polymer films based on polythiophene with polystyrene sulfonic acid (PSS) as a dopant exhibit high hydrophilicity, leading to moisture absorption, film defects, and reduced conductivity, making them unsuitable for organic electroluminescent (EL) devices and flexible transparent electrodes.
Innovation Solution
A conductive material comprising a π-conjugated polymer, a dopant polymer with fluorinated sulfo groups, and gold or silver nanowires, which enhances film-formability, conductivity, and transparency, while maintaining flexibility and flatness, by forming a composite that improves stability and ionically bonds with the polymer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polythiophene with PSS as dopant is used to form conductive film, then conductivity is improved, but hydrophilicity increases causing moisture absorption and film defects
Solution Approach 1:
The patent changes the chemical structure parameters of the dopant polymer by introducing fluorinated groups and controlling the ratio of sulfonic acid groups to carboxylic acid groups (0.2-2.0 mol/mol). This parameter optimization reduces the hydrophilicity of the dopant while maintaining adequate doping efficiency, thereby preventing moisture absorption and film defects while preserving conductivity.
Solution Approach 2:
The patent creates a composite conductive material system comprising polythiophene (or its derivatives) combined with a specifically designed dopant polymer containing both sulfonic acid groups and carboxylic acid groups. This composite structure allows the carboxylic acid groups to reduce overall hydrophilicity while the sulfonic acid groups maintain doping effectiveness, resolving the contradiction between conductivity and moisture resistance.
2Ease of operation
If PSS is used as dopant, then water dispersibility is enhanced, but affinity to organic solvent and organic substrate decreases
Solution Approach 1:
The patent introduces local hydrophobic character into the dopant polymer structure by incorporating fluorinated alkyl groups and balancing hydrophilic (sulfonic acid) and amphiphilic (carboxylic acid) groups. This local quality modification enables the dopant to maintain water dispersibility through sulfonic acid groups while the fluorinated and carboxylic acid components provide organic solvent compatibility and substrate affinity.
Solution Approach 2:
The patent optimizes the chemical composition parameters of the dopant polymer, specifically controlling the ratio of sulfonic acid groups to carboxylic acid groups and incorporating fluorinated groups. These parameter changes create a dopant with dual-character solubility, allowing adequate water dispersibility for conductive polymer formation while simultaneously providing affinity to organic solvents and substrates for effective film formation.
3Reliability
If solid concentration or film thickness is increased to achieve required conductivity, then conductivity is improved, but transmittance decreases
Solution Approach 1:
The patent changes the chemical parameters of the dopant polymer to improve doping efficiency. The optimized dopant structure with fluorinated groups and controlled sulfonic acid to carboxylic acid group ratio achieves higher conductivity per unit concentration, allowing the formation of conductive films at lower solid concentrations that maintain high transmittance.
Solution Approach 2:
The patent develops a composite conductive system where the specially designed dopant polymer enhances the intrinsic conductivity of polythiophene. This composite material achieves higher conductivity at lower concentrations, reducing the need for thick films and thereby maintaining high optical transmittance while meeting conductivity requirements.
4Ease of manufacture
If polythiophene with PSS is used for organic EL, then conductive film can be formed, but water remains causing chemical changes and reduced lifetime
Solution Approach 1:
The patent modifies the hydrophilicity parameters of the dopant polymer by introducing fluorinated groups and optimizing the ratio of hydrophilic sulfonic acid groups to amphiphilic carboxylic acid groups. This parameter optimization reduces water retention in the conductive film while maintaining adequate doping efficiency, thereby preventing chemical degradation of the organic EL and extending device lifetime.
Solution Approach 2:
The patent converts the typically harmful excessive hydrophilicity of PSS dopants into a beneficial property by carefully controlling the balance between sulfonic acid groups (which provide doping) and carboxylic acid groups with fluorinated chains (which reduce excessive water absorption). This controlled amphiphilic character allows adequate water dispersibility for film formation while preventing harmful water retention that causes chemical degradation.
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 conductive material achieves high transparency, conductivity, and flexibility, preventing moisture absorption and film defects, enabling uniform light emission and durability in organic EL devices and flexible electrodes.
Implementation Method 1
a dopant polymer which contains one or more repeating units selected from a1 to a4 and a repeating unit b, and has a weight-average molecular weight in the range of 1,000 to 500,000
Implementation Method 2
gold or silver nanowire having a minor axis diameter of 2 to 200 nm and an aspect ratio of 10 to 50,000
Implementation Method 3
a dopant polymer which contains one or more repeating units selected from a1 to a4 represented by the following general formula (1)
Data Source
AI summary
The present invention provides a conductive material including: (A) a π-conjugated polymer, and (B) a dopant polymer which contains one or more repeating units selected from "a1" to "a4" respectively represented by the following general formula (1) and has a weight-average molecular weight in the range of 1,000 to 500,000, (C) gold or silver nanowire having a minor axis diameter of 2 to 200 nm and an aspect ratio of 10 to 50,000. There can be provided a conductive material that has excellent film-formability and also can form a conductive film having high transparency and conductivity, superior flexibility and flatness when the film is formed from the material.