pH-Adjusted Polythienothiophene Films for Corrosion-Free Conductivity
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Solution Overview
Problem
Aqueous electrically conductive polymer dispersions synthesized with water-soluble polymeric sulfonic acids have undesirable low pH levels, leading to decreased stress life and corrosion in electroluminescent devices, and provide conductivity in the range of 10−3 S/cm or lower, which is not suitable for electronic devices requiring higher conductivity.
Innovation Solution
The development of pH-adjusted aqueous dispersions comprising polythienothiophenes and colloid-forming fluorinated polymeric acids, which are synthesized by combining an oxidant and catalyst with a polymeric acid dispersion, adding a thienothiophene monomer, and adjusting the pH to achieve resistivity stability, resulting in films with improved conductivity and processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If water-soluble polymeric sulfonic acids are used to synthesize conductive polymer dispersions, then the dispersions can be easily processed in aqueous solution, but the resulting films have low pH levels causing corrosion and decreased device lifetime
Solution Approach 1:
The patent changes the chemical parameters of the polymeric acid by using fluorinated polymeric acids (such as perfluorinated polymeric sulfonic acids) instead of conventional water-soluble polymeric sulfonic acids. This parameter change raises the pH level of the dispersion and film, eliminating corrosion issues while maintaining processability. The fluorinated polymers provide high pH stability without sacrificing ease of manufacture.
Solution Approach 2:
The patent creates a composite system by combining conductive polymers (such as polythiophenes, poly(3,4-ethylenedioxythiophene)) with fluorinated polymeric acids. This composite material approach allows the dispersion to inherit the electrical conductivity of the conductive polymer while the fluorinated acid provides high pH stability and corrosion resistance, resolving the contradiction between processability and device lifetime.
2Ease of manufacture
If conventional polymeric acids are used to synthesize conductive polymer dispersions, then the synthesis process is simple, but the resulting films exhibit resistivity changes during annealing
Solution Approach 1:
The patent changes the chemical composition parameter by introducing fluorinated polymeric acids with specific molecular structures and functional groups. These parameter changes result in films that maintain resistivity stability during annealing processes, as the fluorinated acid forms stable complexes with the conductive polymer that resist structural changes under thermal treatment.
Solution Approach 2:
The patent employs a straightforward synthesis procedure using readily available fluorinated polymeric acids and standard conductive polymer monomers. The simplicity of the synthesis process (mixing monomer, oxidant, and fluorinated acid in aqueous solution) maintains ease of manufacture while the resulting stable films provide long-term resistivity consistency, effectively addressing both synthesis simplicity and composition stability.
3Reliability
If aqueous dispersions with low pH are used, then conductivity can be achieved, but corrosion occurs within the device
Solution Approach 1:
The patent fundamentally changes the pH parameter of the aqueous dispersion by using fluorinated polymeric acids instead of conventional sulfonic acids. This parameter change raises the pH to neutral or near-neutral levels, eliminating corrosion of device components (such as ITO anodes and metal contacts) while preserving the electrical conductivity needed for device operation.
Solution Approach 2:
The patent converts the typically harmful low-pH environment into a beneficial high-pH stable environment by selecting fluorinated polymeric acids. These acids provide the necessary electrical conductivity through their association with conductive polymers while simultaneously providing a high-pH environment that protects device components from corrosion, thus turning a harmful factor (acidity) into a beneficial property (alkaline stability).
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 pH-adjusted dispersions provide resistivity stability and enhanced conductivity, suitable for use in organic electronic devices such as OLEDs and photovoltaic devices, with improved device performance and lifetime, while reducing the impact of annealing on resistivity changes.
Implementation Method 1
combining an oxidant and catalyst with a polymeric acid dispersion, adding a thienothiophene monomer
Implementation Method 2
combining an oxidant and catalyst with a polymeric acid dispersion
Implementation Method 3
adjusting the pH to achieve resistivity stability
Data Source
AI summary
A resistivity stable aqueous dispersion and a method for making an aqueous dispersion. The dispersion including polythienothiophene and at least one colloid-forming polymeric acid having a pH of from about 3 to about 10. The method includes preparing an aqueous dispersion containing polythienothiophene and adjusting the pH of the dispersion to a sufficiently high pH to provide resistivity stability. Devices utilizing layers formed of pH adjusted polythienothiophene are also disclosed.