Conductive Polymer Composite with Fluorinated Dopant
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Solution Overview
Problem
Conductive polymer composites based on polythiophene with polystyrene sulfonic acid (PSS) as a dopant face issues with transparency, film-formability, and stability due to high hydrophilicity, leading to defects and shortening of organic electroluminescent (EL) device lifetime, and poor filterability and film flatness in spin coating processes.
Innovation Solution
A conductive polymer composite comprising a π-conjugated polymer and a dopant polymer with a repeating unit containing a superacidic sulfo group substituted with trifluoromethyl groups, which enhances interaction with the π-conjugated polymer, improving transparency, stability, and film-formability, and allowing for the formation of a conductive film with high conductivity and flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polythiophene with PSS as dopant is used to achieve high conductivity, then conductivity is improved, but transparency deteriorates due to absorption at 500 nm wavelength
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 adjust the absorption characteristics and shift the absorption peak away from the visible region, thereby improving transparency while maintaining conductivity
Solution Approach 2:
The patent creates a composite conductive polymer material by combining polythiophene with a specifically designed fluorinated dopant polymer, where the dopant polymer contains both sulfonic acid groups for conductivity and fluorinated groups for transparency, achieving a balance between conductivity and optical properties
2Ease of operation
If PSS is used as dopant to enhance water dispersibility, then dispersibility is improved, but film-formability deteriorates due to poor affinity with organic substrates
Solution Approach 1:
The dopant polymer is designed with local functional groups: sulfonic acid groups for water dispersibility and fluorinated hydrocarbon groups for organic substrate affinity, allowing the material to exhibit both hydrophilic and lipophilic characteristics simultaneously
Solution Approach 2:
The patent modifies the chemical composition parameters of the dopant by incorporating fluorinated alkyl groups with specific chain lengths and branching structures, which change the surface energy and wetting properties to improve film-formability on organic substrates
3Reliability
If high solid concentration or film thickness is used to achieve required conductivity, then conductivity is improved, but transmittance deteriorates
Solution Approach 1:
The patent changes the intrinsic optical parameters of the conductive polymer by using a dopant with fluorinated groups that reduce the absorption coefficient in the visible region, allowing lower solid concentrations to achieve the same conductivity with higher transmittance
4Reliability
If polythiophene with PSS is used for conductive film formation, then conductivity is improved, but manufacturing precision deteriorates due to particle agglomeration and rough film surface
Solution Approach 1:
The patent modifies the molecular weight and molecular weight distribution parameters of the dopant polymer, and adjusts the ratio of hydrophilic to hydrophobic groups, which changes the intermolecular interaction parameters to prevent particle agglomeration and achieve smooth film surfaces
Solution Approach 2:
The patent creates a composite structure where the fluorinated dopant polymer forms a uniform matrix with the polythiophene, preventing phase separation and particle agglomeration that lead to rough surfaces, while maintaining high conductivity
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 composite achieves excellent filterability, film-formability, and transparency, enabling the creation of conductive films with improved durability and conductivity suitable for use as transparent electrodes and hole injection layers.
Implementation Method 1
A polymer having a conjugated double bond (i.e. π-conjugated polymer) does not show a conductivity by itself; however, if an appropriate anionic molecule is doped therein, it can express a conductivity
Implementation Method 2
it has excellent filterability and film-formability by spin coating, and also can form a conductive film having high transparency and flatness when the film is formed from the composite
Data Source
AI summary
The present invention provides a conductive polymer composite including: (A) a π-conjugated polymer, and (B) a dopant polymer which contains a repeating unit “a” shown by the following general formula (1) and having a weight-average molecular weight in the range of 1,000 to 500,000. There can be provided a conductive polymer composite which has excellent filterability and film-formability by spin coating, and can form a conductive film having high transparency and excellent flatness.wherein R1 represents a hydrogen atom or a methyl group; R2 represents any of a single bond, an ester group, and a linear, branched, or cyclic hydrocarbon group having 1 to 12 carbon atoms, the hydrocarbon group optionally containing an ether group, an ester group, or both; “Z” represents any of a single bond, a phenylene group, a naphthylene group, an ether group, and an ester group; and “a” is a number satisfying 0<a≦1.0.