Redox Element Charge Sequestration for Electrochromic Devices
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Solution Overview
Problem
Electrochromic devices face performance degradation due to faradaic losses, leading to changes in optical transmissivity and durability issues over time, especially affected by temperature, bias ranges, switching rates, and solar radiation, which compromise their ability to maintain electrochromic properties throughout their lifetime.
Innovation Solution
Incorporating a redox element that sequesters excess charge by oxidizing or reducing layers of the electrochromic device to mitigate faradaic losses, thereby maintaining the photopic transmittance ratio and optical performance by adjusting the oxidation state of electrodes and sequestering charge through a sequestration protocol.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If electrochromic devices are operated over time with repeated cycling, then the device can switch between transparent and colored states, but faradaic losses accumulate causing drift in optical transmissivity and degradation of electrochromic properties
Solution Approach 1:
The patent extracts and removes excess charge from the electrochromic device through a redox mediator layer. The mediator selectively removes excess charge carriers (electrons or holes) that accumulate due to faradaic losses, preventing charge buildup that would otherwise cause optical transmissivity drift and performance degradation over time
Solution Approach 2:
The patent introduces a redox mediator layer as an intermediary component between the electrochromic layers. This mediator acts as a charge buffer, accepting excess charge when faradaic losses occur and releasing it when needed, thereby maintaining charge balance and stabilizing optical properties throughout the device's operational lifetime
2Reliability
If the device is designed to maintain electrochromic properties throughout its lifetime, then durability and performance consistency are improved, but the device architecture becomes more complex requiring additional components
Solution Approach 1:
The redox mediator layer serves multiple functions simultaneously: it acts as a charge buffer to compensate for faradaic losses, provides ion transport pathways, and maintains electrochemical stability. This multi-functionality allows the device to maintain reliable electrochromic properties without adding excessive complexity, as a single component performs several critical roles
Solution Approach 2:
The patent optimizes the redox mediator's chemical composition and electrochemical parameters (such as redox potential, ion conductivity, and stability) to achieve the desired performance. By carefully selecting and tuning these parameters, the device maintains consistent electrochromic properties throughout its lifetime while keeping the architecture manageable through parameter optimization rather than structural complexity
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 solution effectively compensates for faradaic losses, maintaining the electrochromic properties and optical performance of the device over its lifetime, ensuring consistent transmissivity and durability across various environmental conditions.
Implementation Method 1
Incorporating a redox element that sequesters excess charge by oxidizing or reducing layers of the electrochromic device
Implementation Method 2
Electrochromic devices typically utilize a combination of two types of electrochromic materials, one of which becomes optically less transmissive (e.g., takes on color) in its electrochemically oxidized state while the other becomes optically less transmissive (e.g., takes on color) in its electrochemically reduced state
Data Source
AI summary
A method of controlling an electrochromic device is provided. The method includes measuring an open circuit voltage between a first electrode and a reference electrode in the electrochromic device in a fully bleached state. The method includes calculating a charge Q to return the first electrode to a baseline state and darkening the first electrode in the electrochromic device to a darkened state. The method includes transferring charge from the first electrode in the darkened state to a redox element.