Electrochromic Devices Using Low Band Gap Polymers
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Solution Overview
Problem
Existing electrochromic devices face limitations in switching speed, power consumption, and color distortion, with a need for faster switching capabilities, long-term repeatability, and reduced power consumption while maintaining pure color transitions.
Innovation Solution
The design incorporates a dual polymer electrochromic device with a very low band-gap polymer as an ion-storage layer and a low band-gap polymer for electrochromic functionality, eliminating color distortion and optimizing energy matching for faster switching speeds and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional high band gap polymers are used in electrochromic devices, then the device structure is simpler, but color distortion occurs and switching speed is limited
Solution Approach 1:
The device is divided into two functional layers: a very low band gap polymer layer (Eg ≤ 1.5 eV) serving as ion-storage counter electrode and a low band gap polymer layer (Eg < 2.5 eV) providing electrochromic functionality. This segmentation allows each layer to be optimized for its specific function, achieving faster switching speeds while eliminating color distortion through proper energy level matching between layers
Solution Approach 2:
The patent combines two different conjugated polymer materials with complementary properties - one with very low band gap for ion storage and counter electrode function, and another with low band gap for electrochromic activity. This composite structure enables both fast switching and color purity while distributing functional requirements across different materials
2Speed
If thin film electrochromics are used, then switching speed improves due to reduced diffusion distance, but color distortion and power consumption issues persist
Solution Approach 1:
The patent changes the critical parameter of band gap energy by selecting very low band gap polymers (Eg ≤ 1.5 eV) for the counter electrode and low band gap polymers (Eg < 2.5 eV) for the electrochromic layer. This parameter optimization ensures that the HOMO-LUMO energy level matching prevents color distortion while maintaining fast switching speeds characteristic of thin film devices
Solution Approach 2:
The very low band gap polymer layer acts as an optical copy or neutral counterpart that does not introduce its own coloration in the visible region. By using a material with Lmax > 750 nm, it replicates the ion storage function without adding color distortion, allowing the low band gap electrochromic layer to display pure color transitions
3Reliability
If conventional electrochromic materials are used, then device operation is simpler, but long-term repeatability and memory retention are insufficient
Solution Approach 1:
By separating the ion storage function (very low band gap polymer) from the electrochromic function (low band gap polymer), each layer can be independently optimized for its specific role. The very low band gap polymer provides stable ion storage and electrical contact, while the low band gap polymer delivers repeatable electrochromic cycling, together achieving long-term operational reliability
Solution Approach 2:
The very low band gap polymer serves as an intermediary layer that facilitates efficient ion transfer and electrical contact between the electrode and the electrochromic layer. This intermediary structure improves charge transfer kinetics and stabilizes the electrochemical interface, enhancing long-term repeatability without requiring complex device architecture
4Use of energy by moving object
If standard band gap polymers are used, then manufacturing is simpler, but power consumption increases and switching speed decreases
Solution Approach 1:
The patent optimizes the energy parameters by selecting very low band gap polymers (Eg ≤ 1.5 eV) and low band gap polymers (Eg < 2.5 eV) with properly matched HOMO-LUMO energy levels. This energy level alignment reduces the voltage required for ion insertion/extraction, lowering power consumption while the thin film structure and efficient ion storage capability maintain fast switching speeds
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 dual polymer configuration achieves faster switching speeds, long-term memory retention of optical states, and negligible color distortion, suitable for applications in displays and transmission devices with reduced power consumption.
Implementation Method 1
Electrochromic devices take advantage of materials that are able to change their optical properties in a reversible and repeatable way under the application of an electrical current or potential
Implementation Method 2
thin films of organic or inorganic materials, which exhibit reversible electrochromism by undergoing electrochemical reactions
Implementation Method 3
an electrolyte layer disposed between and in contact with the first layer and the second layer
Data Source
AI summary
Disclosed herein are electrochromic devices using a very low band-gap conjugated polymer having a band gap (Eg) of less than or equal to about 1.5 eV, and having little or no electrochromism in the visible region of the electromagnetic spectrum.