Electrochromic Element Vertical Color Separation Suppression
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Solution Overview
Problem
Existing electrochromic (EC) elements face the challenge of vertical color separation when driven for long periods, which is not adequately addressed by increasing the viscosity of the EC layer.
Innovation Solution
The EC element is designed with a specific configuration where the electrochromic layer contains a solvent, an anodic electrochromic compound, and a cathodic electrochromic compound, satisfying certain solvation free energy inequalities to maintain affinity for the solvent and inhibit aggregate formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the viscosity of the solution containing EC compound is increased, then migration of materials in the solution is inhibited to suppress vertical color separation, but response speed of the EC element is reduced
Solution Approach 1:
The patent changes the chemical composition parameters of the EC layer by incorporating specific compounds (ionic liquids, crown ethers, phase transfer catalysts) that modify the solvation properties and intermolecular interactions. This allows achieving adequate suppression of vertical color separation while maintaining acceptable response speed through chemical parameter optimization rather than simple viscosity increase
Solution Approach 2:
The patent creates a composite EC layer system combining multiple components: EC compounds, ionic liquids, crown ethers, and phase transfer catalysts. This composite approach enables the system to achieve both suppressed material migration (through the structured ionic liquid-crown ether complex) and maintained response speed (through the fluid nature of ionic liquids), resolving the contradiction between reliability and speed
2Reliability
If only the viscosity of the EC layer is increased, then migration of EC compounds is suppressed, but the suppression becomes insufficient when driven at high coloring concentration
Solution Approach 1:
The patent modifies the chemical parameters of the EC layer by introducing ionic liquids, crown ethers, and phase transfer catalysts that create strong solvation effects and stable complexes. This chemical parameter change enables the system to maintain effective suppression of vertical color separation even at high EC compound concentrations, where simple viscosity increase would be insufficient
Solution Approach 2:
The patent introduces ionic liquids and crown ethers as intermediary substances that mediate between the EC compounds and the solvent environment. These intermediaries form stable complexes with EC compounds through host-guest interactions, preventing aggregation and migration even at high concentrations, thereby enhancing both reliability and adaptability to high coloring conditions
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 configuration effectively suppresses vertical color separation in EC elements, maintaining the responsiveness of the EC element while preventing excessive viscosity that could slow down the response speed.
Implementation Method 1
Compounds whose optical properties (e.g., absorption wavelength and absorbance) change through electrochemical redox reactions are referred to as electrochromic
Implementation Method 2
it has been found that vertical color separation can be suppressed by using a specific combination of an anodic EC compound and a cathodic EC compound... the difference between a solvation free energy of an oxidized form of an anodic EC compound in water and a solvation free energy of the oxidized form in octanol is 35×4.184 kJ/mol (35 kcal/mol) or more
Data Source
Figure 1~2
Figure 3A~3B
Figure 4~5
AI summary
As an example of an EC element in which vertical color separation is suppressed, the present disclosure provides an EC element including a pair of electrodes, a solvent, an anodic EC compound, and a cathodic EC compound. In the EC element, the difference between a solvation free energy of an oxidized form of the anodic EC compound in water and a solvation free energy of the oxidized form in octanol is 35 kcal/mol or more, and the difference between a solvation free energy of a reduced form of the cathodic EC compound in propylene carbonate and a solvation free energy of the reduced form in octanol is -35 kcal/mol or less.