Electrochromic Device Segmented Chromoactive Layers
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Solution Overview
Problem
Electrochromic devices face limitations in switching speed and transmittance change due to limited diffusion of Li-ions and restricted optical extinction coefficient changes, necessitating a trade-off between switching speed and transmittance range.
Innovation Solution
An electrochromic device with a configuration of two chromoactive materials and an electrolyte that constrains volume expansion of reaction products perpendicular to the interface, allowing for a large change in optical transmittance across a broad spectrum while maintaining a thin structure, enabling faster switching and broader wavelength coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the layer thickness is increased to ensure sufficiently large change in transmittance, then the change in optical extinction is improved, but the switching speed deteriorates due to limited Li-ion diffusion through the whole layer thickness
Solution Approach 1:
The device is divided into two separate chromoactive layers (first and second chromoactive materials) positioned on opposite sides of the electrolyte. Each layer undergoes independent electrochemical reactions, with the first layer being reduced and the second layer being oxidized. This segmentation allows the total optical effect to be achieved through two thinner layers rather than one thick layer, thereby improving switching speed while maintaining sufficient transmittance change.
2Quantity of substance
If the chromoactive material changes oxidation state to modify optical properties, then the transmittance change is achieved, but the volume expansion of reaction products limits the extent of transmittance change and switching speed
Solution Approach 1:
The patent addresses volume expansion by transitioning from a single-layer configuration to a two-layer configuration with the electrolyte positioned between them. This dimensional reorganization allows the reaction products in each layer to be constrained by the adjacent electrolyte, preventing lateral expansion and confining volume changes to a more controlled space. This enables faster switching and greater transmittance change without the limitations of uncontrolled volume expansion in a single thick layer.
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 device achieves a high change in transmittance with a thin structure, allowing for rapid switching and substantial optical changes across the visible spectrum, from 80% to 1% - 20% transmittance, enhancing its performance compared to traditional devices.
Implementation Method 1
The working principle of the device is that the optical properties of layers of materials are modified through changes in the oxidation state of chemical elements in the layer. The oxidation state is driven by an ion insertion reaction, wherein ions move through the layers of material and electrons are transported through an external circuit.
Implementation Method 2
ions move through the layers of material and electrons are transported through an external circuit
Implementation Method 3
the electrolyte is configured to constrain the volume expansion of the reaction products in a direction perpendicular to an interface between the second portion and the electrolyte
Implementation Method 4
At least one of the layers is a chromoactive layer, which changes optical extinction, upon reduction or oxidation
Data Source
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AI summary
According to an aspect of the present inventive concept there is provided an electrochromic device (100, 200) comprising a first portion (101, 201) comprising a first chromoactive material (101a, 201a), a second portion (102, 202) comprising a second chromoactive material (102a, 202a), an electrolyte (103, 203); wherein the first portion (101, 201) and the second portion (102, 202) are arranged on opposite sides of the electrolyte (102, 203); wherein the first chromoactive material (101a, 201a) and the second chromoactive material (102a, 202a) are configured to change oxidation states in response to an applied current, wherein reaction products (104) are generated in the second chromoactive material (102a, 202a) during the change in oxidation state, wherein the electrolyte (103, 203) is configured to constrain the volume expansion of the reaction products (104) in a direction perpendicular to an interface between the second portion (102, 202) and the electrolyte (103, 203).