Meta-Conjugated Electrochromic Polymers for High Optical Contrast
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Solution Overview
Problem
Conventional electrochromic polymers have strong absorbance in the visible light region in their neutral state, leading to coloration, and when oxidized, they shift absorption to the near-infrared region, resulting in weak visible light absorption and limited optical contrast and transmittance, which is ineffective for thermal management and solar-heat gain control.
Innovation Solution
The development of electrochromic polymers with a backbone comprising meta-conjugated linkers and aromatic moieties, which are partially conjugated at meta positions, allowing the polymers to be transparent in the neutral state and colored and near-infrared absorbing in the oxidized state, achieving high optical contrast and transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional electrochromic polymers are used with fully conjugated polymer backbone, then the polymer shows strong absorbance in visible light region in neutral state, but the optical contrast is limited and residue colors remain in oxidized state
Solution Approach 1:
The patent changes the conjugation pattern parameter from fully conjugated to meta-conjugated with interrupted pi-electron delocalization. This structural parameter change shifts the absorption spectrum, enabling high transparency in neutral state and complete visible light absorption in oxidized state, achieving superior optical contrast
Solution Approach 2:
The patent creates a composite polymer structure combining meta-conjugated linker units with aromatic moieties. This composite architecture at the molecular level enables simultaneous achievement of high neutral state transparency and complete colored state absorption, resolving the contradiction between optical contrast and transmittance
2Illumination intensity
If polymer films are made thicker to enhance absorption, then the optical contrast improves, but the residue colors become more severe and highest optical transmittance is limited
Solution Approach 1:
The patent changes the optical absorption parameter through meta-conjugation design, enabling thin films to achieve complete visible light absorption in oxidized state. This eliminates the need for thick films and resolves the contradiction between optical contrast enhancement and visible light transmittance loss
3Device complexity
If conventional ECPs block visible light in neutral state and allow near-IR light passing through, then the structure is simple, but thermal management and solar-heat gain control are ineffective
Solution Approach 1:
The patent changes the absorption spectrum parameter through meta-conjugation to enable near-IR light blocking in neutral state while maintaining visible light transmission. This spectral parameter change achieves effective thermal management and solar-heat gain control without increasing device complexity
Solution Approach 2:
The patent utilizes electrochromic color change mechanism modified by meta-conjugation to achieve wavelength-selective optical properties. The polymer transitions from transparent to colored state with specific absorption characteristics that block near-IR while transmitting visible light, enabling effective thermal control
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 new electrochromic polymers demonstrate high transparency in the visible light range in the neutral state and significant absorption in the visible and near-infrared ranges in the oxidized state, enhancing optical contrast and transmittance while maintaining low oxidation potential, thus improving thermal management and solar-heat gain control.
Implementation Method 1
The electrochromic polymer has an absorption onset (c, the wavelength at higher than which the polymer has no photon absorption) at 480 nm or less in the neutral state... The oxidized electrochromic polymer has an absorption coefficient larger than 104 cm−1 in the visible and/or near-IR region and thus colored in the oxidized state
Implementation Method 2
Each of the one or more MCLs is partially conjugated with the one or more Ars at meta positions of the one or more MCLs to form the polymer backbone of an electrochromic polymer... demonstrate high transparency in the visible light range in the neutral state
Implementation Method 3
When they are oxidized, their absorption is shifted toward near-infrared (near-IR) region and they become transmissive in the visible light region... the electrochromic polymer is colorless or yellow in the neutral state, while it is colored and visible and near-infrared absorbing in the oxidized state
Data Source
AI summary
An electrochromic polymer is comprised of a repeat unit comprising one or more meta-conjugated linkers (MCLs) and one or more aromatic moieties (Ars). Each of the one or more MCLs is partially conjugated with the one or more Ars at meta positions of the MCLs to form a polymer backbone of the electrochromic polymer. The electrochromic polymer undergoes an optical switching and a color change in an electrochromic device, which shows a high transparency and a high optical contrast.