Non-Dimerizing Electrochromic Compounds for Color Stability
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Solution Overview
Problem
Viologen derivatives in electrochromic devices exhibit uncontrolled changes in colored radical states due to intermolecular interactions, such as dimerization, leading to instability and temperature-dependent color changes, which affects the performance and reliability of these devices.
Innovation Solution
Development of non-dimerizing electrochromic compounds represented by specific formulas, which include substituted or unsubstituted alkyl, siloxyalkyl, hydroxyalkyl, or aralkyl groups, and anions like halides or borates, that prevent dimerization and maintain consistent color over a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If viologen derivatives are used as electrochromic materials, then intense colored radical states are achieved, but uncontrolled dimerization occurs leading to temperature-dependent color changes and instability
Solution Approach 1:
The viologen molecule is divided into two separate pyridinium units that are connected through a flexible spacer chain. This segmentation prevents the planar stacking and intermolecular interactions that cause dimerization, while each pyridinium unit retains its electrochromic functionality. The spacer acts as a physical barrier that segments the molecule into non-interacting units.
Solution Approach 2:
The invention introduces a third dimension (the spacer chain extending out of the plane) to break the two-dimensional stacking arrangement that leads to dimerization. By adding this dimensional element, the molecule adopts a three-dimensional conformation that prevents the face-to-face stacking responsible for temperature-dependent color changes.
2Reliability
If viologen derivatives undergo dimerization, then colored radical states are formed, but the color changes become uncontrolled and temperature-dependent
Solution Approach 1:
The harmful dimerization property is extracted and removed from the system by modifying the molecular structure. The spacer chain extracts the planar stacking tendency, preventing dimer formation. This allows the viologen to maintain its electrochromic function without the harmful temperature-dependent color changes associated with dimerization.
3Ease of operation
If conventional viologens are used, then electrochromic switching is achieved, but solubility changes and intermolecular interactions cause uncontrolled color variations
Solution Approach 1:
Different parts of the viologen molecule are given different properties: the pyridinium rings provide electrochromic functionality, the spacer provides solubility and steric separation, and the substituent groups provide additional stability. This local differentiation of molecular regions allows each part to perform its specific function without interfering with others.
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 non-dimerizing electrochromic compounds ensure temperature-independent color stability, enhancing the reliability and performance of electrochromic devices by preventing dimerization and maintaining consistent visible light absorption spectra across varying temperatures.
Implementation Method 1
Devices which rely on an electrochromic switch mechanism, i.e. reversible color change in the presence of an applied electric field or current
Implementation Method 2
the device exhibits a λ max of greater than about 580 nm
Data Source
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AI summary
The invention relates to an electrochromic device and uses thereof, wherein the electrochromic device includes an electrochromic compound with reduced intermolecular interactions resulting in uncontrolled color changes represented by Formula (I).