Electrochromic device containing highly transparent electrochromic polymers

Abstract

An electrochromic device includes: a first insulating substrate; a first conductive layer disposed on the first insulating substrate; an electrochromic layer disposed on the first conductive layer, wherein the electrochromic layer comprises an electrochromic polymer with a polymer backbone comprising one or more meta-conjugated linkages (MCLs) and one or more aromatic groups (Ars), where each of the MCLs is partially conjugated to one of the Ars at a meta position of the MCLs; an electrolytic layer disposed on the electrochromic layer; a second conductive layer disposed on the electrolytic layer; and a second insulating substrate disposed on the second conductive layer. The thickness of the electrochromic layer is from 10 nm to 1500 nm, resulting in a transmittance of 85% to 99.9% at a wavelength of 550 nm in the neutral state of the electrochromic layer.

Description

Electrochromic device containing highly transparent electrochromic polymers Cross-reference to related applications This application is an application for continuation in part of non-provisional application no. 18 / 093.287, filed on 4 January 2023, which is an application for continuation in part of non-provisional application no. 17 / 748.383, filed on 19 May 2022, which is an application for continuation in part of non-provisional application no. 17 / 668.300, filed on 9 February 2022. Technical field This disclosure relates to a novel type of electrochromic polymer comprising meta-conjugated linkers and aromatic moieties, which exhibit high transparency in the visible light region in the neutral state. The polymers become highly absorptive in the visible and near-infrared regions and thus become colored when their films are oxidized. A device incorporating such conjugated electrochromic polymer films with high optical contrast and high transmittance is also disclosed. Background Electrochromic devices allow for the adjustment of light transmittance and the control of solar heat gain. Compared to inorganic-based electrochromic devices manufactured through vacuum sputtering, polymer-based electrochromic windows can be produced by coating and roll-to-roll lamination. This offers production flexibility and low-cost manufacturing. Polymer-based electrochromic devices are typically composed of conjugated electrochromic polymers (ECPs), which have a fully conjugated polymer backbone made of sp2-hybridized carbons. Conventionally, ECPs usually have strong absorbance in the visible light region and are therefore colored in their neutral state. When oxidized, their absorption shifts into the near-infrared (near-IR) region, and they become transmissive in the visible light region.However, oxidized polymers still exhibit weak absorption in the visible light region, leading to residual colors. This problem becomes more pronounced with thick polymer films. As a result, it negatively impacts the optical contrast of the polymers. Furthermore, it limits the maximum optical transmittance achievable with a conjugated electrochromic polymer. In addition, conventional ECPs in the neutral state block visible light while allowing near-infrared light to pass through; in the transmissive state, they allow visible light to pass through while blocking near-infrared light. This combination is ineffective for thermal management and solar heat gain (SHG) control. SHG describes how solar radiation is converted into heat through a window product.HSIAO SHENG-HUEI ET AL: "Fluorescent and electrochromic polymers from 2,8-di(carbozal-9-yl)dibenzothiophene and its S,S-dioxide derivative", Tyes AND PIGMENTS, ELSEVIER APPLIED SCIENCE PUBLISHERS, vol. 134, June 29, 2016, pages 51-63, XP029708707, reports on the synthesis and characterization of two carbazole-terminally protected monomers and their derivative polymers PSCz and PSO2Cz. Dilute solutions of PSCz and PSO2Cz prepared by oxidative chemical coupling showed fluorescent and solvatochromic behavior. Summary This disclosure relates to a new type of electrochromic polymer and to devices that utilize the polymer. In one aspect, an electrochromic device is provided. The electrochromic device includes: a first insulating substrate; a first conductive layer disposed on the first insulating substrate; an electrochromic layer disposed on the first conductive layer, wherein the electrochromic layer comprises an electrochromic polymer having a polymer backbone comprising one or more metaconjugated linkers (MCLs) and one or more aromatic moieties (Ars), wherein each of the one or more MCLs is partially conjugated with one of the one or more Ars at a meta position of the one or more MCLs; an electrolyte layer disposed on the electrochromic layer; a second conductive layer disposed on the electrolyte layer; and a second insulating substrate disposed on the second conductive layer.The electrochromic layer thickness ranges from 10 nm to 1500 nm, resulting in a transmittance of 85%–99.9% at a wavelength of 550 nm in a neutral state of the electrochromic layer. For example, an electrochromic layer thickness of 106 nm at 1500 nm produces a transmittance of 85%, 87%, 90%, 92%, 95%, 96%, 97%, 98%, 99%, 99.9%, or any two of these values. Electrochromic device 100 has a transmittance of 60% or more at a wavelength of 550 nm in a bleached state of the device. For example, by adjusting the material and thickness of the electrochromic layer, the electrochromic device 100 can have in its bleached state a transmittance of 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92%, 95%, 96%, 97%, 98%, or 99%, or between any two of the above numbers. In some embodiments, the electrochromic layer has a transmittance of 40%–0.1% at a wavelength of 550 nm in an oxidized state. For example, the electrochromic layer in the oxidized state has a transmittance at a wavelength of 550 nm of 40%, 35%, 30%, 25%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1%, or any two of the above numbers. In some embodiments, the electrochromic coating has an optical contrast ratio of 60% or more. For example, the electrochromic coating may have an optical contrast ratio of 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or any two of the above numbers. In some embodiments, the electrochromic device further includes the ion storage layer 110, which is disposed between the electrolyte layer 108 and the second conductive layer, and the ion storage layer has a transmittance of 80% or more at a wavelength of 550 nm. In some embodiments, the ion storage layer may include (1) one or more oxides of metal elements in group 4-12, or (2) a mixture of the oxides, or (3) one of the oxides doped with a different metal oxide, or (4) a transition metal complex, or (5) one or more redox-active polymers, including nitroxyl radical polymers, redox-active galvinoxyl polymers, and conjugated polymers. In some embodiments, the ion storage layer includes ITO particles, wherein the ion storage layer has a transmittance of 90% or more at a wavelength of 550 nm. In some embodiments, the ITO particles may be nanoparticles with a size of 1–900 nm. In some embodiments, at least one of the first conductive layer and the second conductive layer includes ITO, aluminum zinc oxide (AZO), fluorine-doped tin oxide (FTO), silver nanowires, graphene, carbon nanotubes, transparent conductive electrodes based on metal mesh, silver nanoparticle ink, or an organic conductive polymer. In some embodiments, the electrochromic device has an optical contrast ratio of 60% or more. For example, the electrochromic device may have an optical contrast ratio of 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or any two of the above numbers. In some embodiments, the color of the electrochromic layer in an oxidized state is varied by varying / adjusting a conjugation length of one or more MCLs and one or more Ars. In some embodiments, the electrochromic layer includes a mixture of different electrochromic polymers without an intermediate color. The electrochromic layer includes an electrochromic polymer. The electrochromic polymer consists of a polymer backbone comprising one or more metaconjugated linkers (MCLs) and one or more aromatic moieties (Ars). Each of the one or more MCLs is partially conjugated to one of the one or more Ars at a meta position of the one or more MCLs. The thickness of the electrochromic polymer ranges from 10 nm to 1500 nm, resulting in a transmittance of 85%–99.9% at a wavelength of 550 nm in a neutral state of the electrochromic layer. For example, an electrochromic layer thickness of 10 nm to 1500 nm yields a transmittance of 85%, 87%, 90%, 92%, 95%, 96%, 97%, 98%, 99%, 99.9%, or any two of these values. In some embodiments, the electrochromic polymer described in this application consists of a polymer backbone 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 to one or more Ars at the meta positions of the one or more MCLs to form the polymer backbone of an electrochromic polymer. In some embodiments, the described electrochromic polymer is an anodic coloring electrochromic polymer (AC-ECP), which is colored upon oxidation. In some embodiments, the described electrochromic polymer has an energy band gap equal to or greater than 2.9 eV and less than 4.0 eV in the neutral state. In some embodiments, the absorption maxima (max, the wavelength at which the polymer has its strongest photon absorption) are below 410 nm in the neutral state. In some embodiments, the described electrochromic polymer is colorless in the neutral state, while it is colored and visible and absorbs in the near-infrared in the oxidized state. The oxidized electrochromic polymer has an absorption coefficient greater than 10⁴ cm⁻¹ in the visible and / or near-infrared region and is therefore colored in the oxidized state. Despite their high band gaps, the described electrochromic polymers still have a relatively low oxidation potential in the 0, 1-1, 5 V range inclusive with respect to the Ag / AgCl electrode in some embodiments. The MCL comprises at least one aromatic structure, or a fused aromatic structure, or combinations thereof. The aromatic structure comprises a benzene or heterocyclic structure. The fused aromatic structure comprises a fused benzene structure, a fused heterocyclic structure, or a fused benzene and heterocyclic structure. In some embodiments, for the electrochromic polymers described, the one or more MCLs and the one or more Ars are arranged in an alternative or random manner with a general formula of In the structures here, n is an integer greater than 0 and each of m1, m2, ..., mn is an integer equal to or greater than 0 with at least one of m1, m2, ..., mn being greater than 0. The one or more MCLs (or the one or more Ars) may be equal to or different from each other. The one or more MCLs and the corresponding meta-positions comprise one of the following formulas: where each of the wavy lines represents meta-positions to join adjacent to one or more Ars; X is S, Se, N, C or O; R1 - R12 is selected independently from, but not limited to, the following substituents: hydrogen, C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C2-C30 alkylcarbonyl, C1-C30 alkoxy, C3-C30 alkoxyalkyl, C2-C30 alkoxycarbonyl, C4-C30 alkoxycarbonylalkyl, C1-C30 alkylthio, C1-C30 aminylcarbonyl, C4-C30 aminylalkyl, C1-C30 alkylaminyl, C1-C30 alkylsulfonyl, C3-C30 alkylsulfonylalkyl, C6-C18 aryl, C3-C15 cycloalkyl, C3-C30 cycloalkylaminyl, C5-C30 cycloalkylalkylaminyl, C5-C30 cycloalkylalkylalkyl, C5-C30 cycloalkylalkyloxy, C1-C12 heterocyclyl, C1-C12 heterocyclyloxy, C1-C30 heterocyclylalkyloxy, C1-C30 heterocyclylaminyl, C5C30 heterocyclylalkylaminyl, C2-C12 heterocyclylcarbonyl, C3-C30 heterocyclylalkyl, C1-C13 heteroaryl or heteroarylalkyl C3-C30. The one or more Ars comprise one of a thiophene-based unit, one furan-based unit, one selenophene-based unit, or one pyrrole-based unit with a formula of any combination thereof, wherein each of R13, R14 and R15 is independently selected from, but not limited to, the following substituents: hydrogen, C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C2-C30 alkylcarbonyl, C1-C30 alkoxy, C3-C30 alkoxyalkyl, C2-C30 alkoxycarbonyl, C4-C30 alkoxycarbonylalkyl, C1-C30 alkylthio, C1-C30 aminylcarbonyl, C4-C30 aminylalkyl, C1-C30 alkylaminyl, C1-C30 alkylsulfonyl, C3-C30 alkylsulfonylalkyl, C6-C18 aryl, C3-C15 cycloalkyl, C3-C30 cycloalkylaminyl, C5-C30 cycloalkylalkylaminyl, cycloalkylalkyl C5-C30, C5-C30 cycloalkylalkyloxy, C1-C12 heterocyclyl, C1-C12 heterocyclyloxy, C1-C30 heterocyclylalkyloxy, C1-C30 heterocyclylalkyloxy, C1-C30 heterocyclylaminyl, C5-C30 heterocyclylalkylaminyl, C2-C12 heterocyclylcarbonyl, heterocyclylalkyl C3-C30, C1-C13 heterocyclylalkyl or C3-C30 heteroaryl. In some embodiments, the thiophene-based unit comprises a formula of combination of the same, where X is S, Se, N, C or O; Each of R15 - R18 is independently selected from, but not limited to, the following substituents: hydrogen, C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C2-C30 alkylcarbonyl, C1-C30 alkoxy, C3-C30 alkoxyalkyl, C2-C30 alkoxycarbonyl, C4-C30 alkoxycarbonylalkyl, C1-C30 alkylthio, C1-C30 aminylcarbonyl, C4-C30 aminylalkyl, C1-C30 alkylaminyl, C1-C30 alkylsulfonyl, C3-C30 alkylsulfonylalkyl, C6-C18 aryl, C3-C15 cycloalkyl, C3-C30 cycloalkylaminyl, C5-C30 cycloalkylalkylaminyl, C5-C30 cycloalkylalkyl C5-C30 cycloalkylalkyloxy, C1-C12 heterocyclyl, C1-C12 heterocyclyloxy, C1-C30 heterocyclylalkyloxy, C1-C30 heterocyclylamyl, C5-C30 heterocyclylalkylamyl, C2-C12 heterocyclylcarbonyl, C3-C30 heterocyclylalkyl, C1-C13 heteroaryl, or C3-C30 heteroarylalkyl. And it is any one or more of Ars, or aromatic structures, or fused aromatic structures, or a combination thereof. In some embodiments, X in the thiophene-based unit is O. In some embodiments, the described electrochromic polymers comprise a formula of where n, ym are integers greater than 0, ayb are integers equal to or greater than 0 with at least one of ayb being greater than 0. In some embodiments, the electrochromic layer has a transmittance of 40%-0.1% at a wavelength of 550 nm in an oxidized state of the electrochromic layer. In some embodiments, the electrochromic layer has an optical contrast of 60% or more. In some realizations, each of the one or more MCLs and the corresponding metapositions comprises one of the following formulas: where X is S, Se, N, C or O; Each of R1-R12 is independently selected from one of hydrogen, C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C2-C30 alkylcarbonyl, C1-C30 alkoxy, C3-C30 alkoxyalkyl, C2-C30 alkoxycarbonyl, C4-C30 alkoxycarbonylalkyl, C1-C30 alkylthio, C1-C30 aminylcarbonyl, C4-C30 aminylalkyl, C1-C30 alkylaminyl, C3-C30 C3-C30 alkylsulfonylalkyl, C6-C18 aryl, C3-C15 cycloalkyl, C3-C30 cycloalkylaminyl, C5-C30 cycloalkylalkylaminyl, C5-C30 cycloalkylalkyl, C5-C30 cycloalkylalkyloxy, heterocyclyl C1-C12, C1-C12 heterocyclyloxy, C1-C30 heterocyclylalkyloxy, C1-C30 heterocyclylamyl, C5-C30 heterocyclylalkylamyl, C2-C12 heterocyclylcarbonyl, C3-C30 heterocyclylalkyl, C1-C13 heteroaryl or C3-C30 heteroarylalkyl; and each of these the wavy lines represent one of the meta positions. In some embodiments, where each of the one or more Ars comprises one of a thiophene-based unit, one of a furan-based unit, one of a selenophene-based unit, or one of a pyrrole-based unit with one of the following formulas: wherein each of R13, R14 and R15 is independently selected from one of hydrogen, C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C2-C30 alkylcarbonyl, C1-C30 alkoxy, C3-C30 alkoxyalkyl, C2-C30 alkoxycarbonyl, C4-C30 alkoxycarbonylalkyl, C1-C30 alkylthio, C1-C30 aminylcarbonyl, C4-C30 aminylalkyl, C1-C30 alkylaminyl, C1-C30 alkylsulfonyl, C3-C30 alkylsulfonylalkyl, C6-C18 aryl, C3-C15 cycloalkyl, C3-C30 cycloalkylaminyl, C5-C30 cycloalkylalkylaminyl, C5-C30 cycloalkylalkyl, cycloalkylalkyloxy C5-C30, C1-C12 heterocyclyl, C1-C12 heterocyclyloxy, C1-C30 heterocyclylalkyloxy, C1-C30 heterocyclylaminyl, C5-C30 heterocyclylaminyl, C2-C12 heterocyclylalkylaminyl, C3-C30 heterocyclylcarbonyl, C1-C13 heterocyclylalkyl, or C3-C30 heteroaryl. In some embodiments, the thiophene-based unit comprises one of the following formulas: where X is S, Se, N, C or O; Each of R15 - R18 is independently selected from one of hydrogen, C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C2-C30 alkylcarbonyl, C1-C30 alkoxy, C3-C30 alkoxyalkyl, C2-C30 alkoxycarbonyl, C4-C30 alkoxycarbonylalkyl, C1-C30 alkylthio, C1-C30 aminylcarbonyl, C4-C30 aminylalkyl, C1-C30 alkylaminyl, C1-C30 alkylsulfonyl, C3-C30 alkylsulfonylalkyl, C6-C18 aryl, C3-C15 cycloalkyl, C3-C30 cycloalkylaminyl, C5-C30 cycloalkylalkylaminyl, C5-C30 cycloalkylalkyl, cycloalkylalkyloxy C5-C30, C1-C12 heterocyclyl, C1-C12 heterocyclyloxy, C1-C30 heterocyclylalkyloxy, C1-C30 heterocyclylamyl, C5-C30 heterocyclylalkylamyl, C2-C12 heterocyclylcarbonyl, C3-C30 heterocyclylalkyl, C1-C13 heteroaryl or C3-C30 heteroarylalkyl; And is any one or more of Ars, or aromatic structures, or fused aromatic structures, or a combination thereof. Brief description of the figures Certain features of various embodiments of the present technology are set forth in detail in the appended claims. A better understanding of the features and advantages of the technology will be obtained by referring to the following detailed description, which sets forth illustrative embodiments in which the principles of the invention are used, and the accompanying drawings. For the purpose of illustrating the invention, the drawings show aspects of one or more embodiments of the invention. However, it should be understood that the present invention is not limited to the precise arrangements and instrumentation shown in the drawings. Figures 1(A)–(B) are diagrams depicting the different color-changing mechanisms of the described ECP (Figure 1(A)) compared to the conventional ECP (Figure 1(B)). Figure 2 shows the CV data of an example solid-state device using an example ECP-1, according to one embodiment. Figure 3 is the switching kinetics of the solid-state device as an example using the ECP-1 example at 545 nm, according to one embodiment. Figure 4 shows the absorbance spectra of the example ECP-1 thin film at different voltages, according to one embodiment. Figure 5 shows the CV data of an example solid-state device using another example ECP-2, according to one embodiment. Figure 6 is the switching kinetics of the solid-state device as an example using the ECP-2 example at 550 nm, according to one embodiment. Figure 7 shows the absorbance spectra of the example ECP-2 thin film at different voltages, according to one embodiment. Figure 8(A) illustrates calculated neutral-state UV-Vis spectra of the described metaconjugated polymers with three representative MCLs, according to certain embodiments. Figure 8(B) illustrates calculated oxidized state UV-Vis spectra of the described metaconjugated polymers with three representative MCLs, according to certain embodiments. Figure 9(A) illustrates the absorption electrochemical spectrometry from the neutral state in transition to the oxidized state of the CBZ mixture with a film thickness of 300 nm, according to certain embodiments. From the bottom line to the top line, the potential is respectively 0.6 V, 0.65 V, 0.7 V, 0.75 V, 0.8 V, 0.85 V, 0.9 V, 0.95 V, 1.0 V versus Ag / AgCl. Figure 9(B) illustrates Beer-Lambert plots of CBZ-Blend in the neutral state (dashed line) and the oxidized state (solid) at 550 nm. Figure 9(C) illustrates the transmittance of CBZ-Blend at 550 nm in neutral and oxidized states as a function of film thickness, according to certain realizations. Experimental results are shown as dots, and calculated results are shown as dashed and dashed lines. Figure 9(D) illustrates the transmittance of CBZ-Blend in both neutral and oxidized states of the EC layer at different thicknesses, according to some embodiments. Figure 9(E) illustrates the transmittance of CBZ-Blend in both neutral (bleached) and oxidized states of the EC layer below 10000 cycles, according to some realizations. Figure 10 represents a cross-sectional view of an electrochromic device, according to an example embodiment of the present disclosure. Detailed description of achievements The following description sets forth certain specific details to provide a comprehensive understanding of various embodiments of the invention. However, a person skilled in the art will understand that the invention can be implemented without these details. Furthermore, although various embodiments of the invention are disclosed herein, many adaptations and modifications within the scope of the invention are possible in accordance with the common knowledge of those skilled in the art. Such modifications include the substitution of known equivalents for any aspect of the invention to achieve substantially the same result in the same manner. Unless the context requires otherwise, throughout this specification and the claims, the word "comply" and variations thereof, such as "comprises" and "comprising," should be interpreted in an open and inclusive sense, i.e., as "including, but not limited to." The enumeration of numerical ranges of values ​​throughout this specification is intended as shorthand for referring individually to each independent value within the range that includes the values ​​defining the range, and each independent value is incorporated into this specification as individually listed herein. Furthermore, the singular forms "a," "an," and "the" include plural referents unless the context clearly indicates otherwise. References throughout this specification to "an embodiment" mean that a particular feature, structure, or characteristic described in relation to that embodiment is included in at least one embodiment of the present invention. Therefore, the occurrence of the phrase "in an embodiment" or "in an embodiment" at various points throughout this specification does not necessarily refer to the same embodiment, but only in some cases. Furthermore, the distinctive features, structures, or particular characteristics may be combined in any suitable manner in one or more embodiments. This disclosure relates to a novel type of electrochromic polymer. The electrochromic polymer described herein consists of a polymer backbone comprising one or more metaconjugated linkers (MCLs) and one or more aromatic moieties (Ars). Each of the one or more MCLs is partially conjugated to one or more Ars at the meta positions of the one or more MCLs to form the polymer backbone of an electrochromic polymer. In some embodiments, the electrochromic polymer described herein consists of a repeating unit comprising one or more MCLs and one or more Ars, wherein the metaconjugation is introduced along the polymer backbone by means of the MCLs. In some embodiments, the electrochromic polymer is an anodic coloring electrochromic polymer (AC-ECP), which is colored upon oxidation. As illustrated in Figure 1, conventional conjugated ECPs (Figure 1(B)) are fully conjugated and exhibit strong absorbance in the visible light region, thus displaying color in their neutral state. When oxidized (oxidized state), their absorption shifts into the near-infrared region, making them transmissive. However, oxidized polymers still exhibit weak absorption in the visible light region, resulting in residual coloration. On the other hand, as illustrated for an example of an ECP described in Figure 1(A), the ECP shows no substantial absorption beyond 450 nm in the neutral state and exhibits several absorption peaks in both the visible and near-infrared ranges in the oxidized state, demonstrating coloration in the visible light range and absorption in the near-infrared. The described electrochromic polymers allow for the synchronized transmission or blocking of visible and near-infrared light, which in one embodiment is highly useful in an electrochromic window for managing solar heat gain. These polymers are transparent in the neutral state and colored and IR-absorbing in the oxidized state, characteristics highly desirable for achieving high optical contrast, high transmittance, and synergistic solar heat gain. The described electrochromic polymers are transparent in the visible light region in the neutral state and colored in the oxidized state. For example, the described electrochromic polymers can have a transmittance of at least 60% in the visible light range (e.g., 450–750 nm) in the neutral state. In some embodiments, the described electrochromic polymers can have a transmittance of at least 65%, 70%, 75%, 80%, 85%, 90%, 92%, 95%, 98%, or higher in the 450–750 nm range in the neutral state. In some embodiments, the described electrochromic polymers are transparent in the visible light range in the neutral state. In the oxidized state, the described electrochromic polymers have absorption in the visible light range (e.g., approximately 360 to 750 nm) and the near-IR range (e.g., approximately 750 to 1600 nanometers), so they are colored and absorb in the near-infrared. The described electrochromic polymer has UV absorption and an energy band gap. An energy band gap is the energy difference between the valence band of electrons and the conduction band. It is the minimum change in energy required to excite an electron to a state in the conduction band where it can participate in conduction. The absorption start (c) is the wavelength at which the polymer does not absorb photons. The energy band gap can be calculated as 1240 / absorption start wavelength. In some embodiments, the electrochromic polymers described in this application have an absorption start equal to or less than 450 nm in the neutral state. In some embodiments, the described electrochromic polymer has an absorption start equal to or less than 440 nm, 430 nm, 420 nm, 410 nm, 405 nm, or 400 nm in the neutral state.In some embodiments, the absorption maxima (max, the wavelength at which the polymer has its strongest photon absorption) are below 420 nm in the neutral state. In some embodiments, the absorption maxima are below 410 nm, 405 nm, or 400 nm in the neutral state. In some embodiments, the described electrochromic polymer has an energy band gap equal to or greater than 2.8 eV and less than 4.0 eV in the neutral state. In some embodiments, the described electrochromic polymer has an energy band gap equal to or greater than 2.9, 3.0, or 3.1 eV and less than 4.0 eV in the neutral state.In some embodiments, the described electrochromic polymer is colorless (e.g., no absorbance at 400–750 nm, 410–750 nm, or 420–750 nm) or yellow (e.g., tail absorption at 400–500 nm, 410–500 nm, 420–500 nm, 400–480 nm, 410–480 nm, 420–480 nm, 400–450 nm, 410–450 nm, or 420–450 nm) in the neutral state and is colored, visible, and absorbs in the near-infrared (NIR) in the oxidized state. The oxidized electrochromic polymer has an absorption coefficient greater than 10⁴ cm⁻¹ in the visible and / or NIR region and is therefore colored in the oxidized state. Due to the substantial lack of absorbance in the visible light range in the neutral state and the high absorbance in the visible light range in the oxidized state, the described electrochromic polymers demonstrate high optical contrast and high optical transmittance compared to conventional ECPs. Despite their wide band gaps, the described electrochromic polymers exhibit a relatively low oxidation potential in the 0.1–1.5 V range inclusive with respect to the Ag / AgCl electrode in some embodiments. This relatively low oxidation potential may benefit the cyclic durability of the ECPs.Therefore, the described electrochromic polymers can be successfully incorporated into a device with good cycle stability / reliability and high optical contrast. The MCL comprises at least one aromatic structure, or a fused aromatic structure, or combinations thereof. The aromatic structure comprises a benzene or heterocyclic structure. The fused aromatic structure comprises a fused benzene structure, a fused heterocyclic structure, or a fused benzene and heterocyclic structure. In some embodiments, the MCL comprises at least one benzene, or naphthalene, or five-membered heterocycle, or five-membered heterocycle fused with benzene, or a combination of these structures. Side chains or aromatic side chains may also be introduced into the MCL to adjust its performance, for example, solubility, processability, or stability. In some embodiments, the one or more MCLs and the one or more Ars are arranged in an alternative or random manner with a general formula of In the structure here, n is an integer greater than 0 and each of m1, m2, ..., mn is an integer equal to or greater than 0 with at least one of m1, m2, ..., mn being greater than 0. The one or more Ars are aromatic residues, which may include one or more aromatic structures. Each of the one or more MCLs (or ARSs) may be the same or different from each other. Metaconjugation is introduced into the polymer backbone through the use of one or more MCLs. Each of the one or more MCLs is partially conjugated into the polymer backbone by connecting to one or more Ars through their meta-positions. For example, meta-positions are two positions on the aromatic structure or a fused aromatic structure of the MCLs. When meta-positions are connected, the pi electrons of an aromatic structure or a fused aromatic structure cannot be fully delocalized to another adjacently connected unit via p orbitals. In some embodiments, an aromatic structure of MCLs comprises a benzene ring or a five-membered heterocycle, and the aromatic structure of the MCLs is substituted at the meta positions, which are positions 1 and 3 in the aromatic structure. In some embodiments, a fused aromatic structure of MCLs comprises naphthalene, and the fused aromatic structure is substituted at the meta positions, which are positions 1 and 3, or 1 and 4, or 1 and 6 in naphthalene. In some embodiments, a fused aromatic structure of MCLs comprises benzene fused to a five-membered heterocycle, and the fused aromatic structure is substituted at the meta positions, which are positions 1 and 3, or 1 and 5 in the heterocycle fused to benzene. Example structures of one or more MCLs and their corresponding meta-positions include one of the following: where X is S, Se, N, C or O; R1-R12 is selected independently from, but not limited to, the following substituents: hydrogen, C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C2-C30 alkylcarbonyl, C1-C30 alkoxy, C3-C30 alkoxyalkyl, C2-C30 alkoxycarbonyl, C4-C30 alkoxycarbonylalkyl, C1-C30 alkylthio, C1-C30 aminylcarbonyl, C4-C30 aminylalkyl, C1-C30 alkylaminyl, C1-C30 alkylsulfonyl, C3-C30 alkylsulfonylalkyl, C6-C18 aryl, C3-C15 cycloalkyl, C3-C30 cycloalkylaminyl, C5-C30 cycloalkylalkylaminyl, C5-C30 cycloalkylalkyl, cycloalkylalkyloxy C5-C30, C1-C12 heterocyclyl, C1-C12 heterocyclyloxy, C1-C30 heterocyclylalkyloxy, C1-C30 heterocyclilaminyl, C5-C30 heterocyclylalkylaminyl, C2-C12 heterocyclylcarbonyl, C3-C30 heterocyclylalkyl, C1-C13 heteroaryl or C3-C30 heterocyclylalkyl heteroarylalkyl; and the wavy lines represent the meta-positions. The one or more Ars include any of a thiophene-based unit, a furan-based unit, a selenophene-based unit, or a pyrrole-based unit with a formula of any combination thereof. In the structures above, each of R13, R14, and R15 is independently selected from, but not limited to, the following substituents: hydrogen, C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C2-C30 alkylcarbonyl, C1-C30 alkoxy, C3-C30 alkoxyalkyl, C2-C30 alkoxycarbonyl, C4-C30 alkoxycarbonylalkyl, C1-C30 alkylthio, C1-C30 aminylcarbonyl, C4-C30 aminylalkyl, C1-C30 -alkylaminyl, C1-C30 -alkylsulfonyl, C3-C30 -alkylsulfonylalkyl, C6-C18 -aryl, C3-C15 -cycloalkyl, C3-C30 -cycloalkylaminyl, -cycloalkylalkylaminyl C5-C30, -C5-C30 cycloalkylalkyl, -C5-C30 cycloalkylalkyloxy, -C1-C12 heterocyclyl, -C1-C12 heterocyclyloxy, -C1-C30 heterocyclylalkyloxy, -C1-C30 heterocyclylaminyl, -C5-C30 heterocyclylalkylaminyl, -heterocyclylcarbonyl C2-C12, -C3-C30 -heterocyclylalkyl, -C1-C13 -heteroaryl or -C3-C30 -heteroarylalkyl. An example thiophene-based unit may include, but is not limited to, the formula of combination of the same. In the above structures, X is S, Se, N, C or O; Each of R15 - R18 is independently selected from, but not limited to, the following substituents: hydrogen, C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C2-C30 alkylcarbonyl, C1-C30 alkoxy, C3-C30 alkoxyalkyl, C2-C30 alkoxycarbonyl, C4-C30 alkoxycarbonylalkyl, C1-C30 alkylthio, C1-C30 aminylcarbonyl, C4-C30 aminylalkyl, C1-C30 alkylaminyl, C1-C30 alkylsulfonyl, C3-C30 alkylsulfonylalkyl, C6-C18 aryl, C3-C15 cycloalkyl, C3-C30 cycloalkylaminyl, C5-C30 cycloalkylalkylaminyl, C5-C30 cycloalkylalkyl C5-C30 cycloalkylalkyloxy, C1-C12 heterocyclyl, C1-C12 heterocyclyloxy, C1-C30 heterocyclylalkyloxy, C1-C30 heterocyclylaminyl, C5-C30 heterocyclylalkylaminyl, C2-C12 heterocyclylcarbonyl, C3-C30 heterocyclylalkyl, C1-C13 heteroaryl, or heteroarylalkyl C3-C30.And it is any one or more of Ars, or aromatic structures, or fused aromatic structures, or a combination of them. In some embodiments, the X in the thiophene-based unit is O. Introducing metaconjugation into the main structure of the electrochromic polymer disrupts the electronic conjugation along the polymer backbone, leading to a high band gap (>2.0 eV). Therefore, the described electrochromic polymer appears highly transmissive (or even transparent) in the neutral state. Oxidation of the ECP results in a lower band gap (<1.5 eV), and the polymer's absorbance shifts red from the UV region to the visible and near-IR region. Consequently, the polymer becomes highly colored. The one or more Ars include one or more aromatic or fused aromatic structures. By controlling the types and amounts of Ars, the redox potentials of the described electrochromic polymer can be easily tuned while maintaining its high transparency within the visible light range in the neutral state. For example, more electron-rich units (e.g., dioxythiophenes) can be introduced into the main structure to make the polymer more favorable to oxidation, thereby lowering its initiation potential and improving its electrochemical and electrochromic cycle stability. The redox potentials of the described electrochromic polymer can also be tuned by varying substituents in MCL (e.g., by introducing alkoxy side chains). The electrochromic polymers described can be dissolved in a solvent, such as toluene or p-xylene, which can be used for solution-processable film casting. By controlling the concentration of the polymer solution, a thin polymer film with a controllable thickness can be obtained. Furthermore, their excellent solubility makes the disclosed electrochromic polymers compatible with various casting methods, such as spin coating, spray coating, and drip casting. The user-friendly manufacturing process makes their widespread applications feasible. The following are examples. Achievements Example 1 ECP-1 In some embodiments, the described ECP-1 has a formula of ECP-1 is synthesized by preparing a reaction unit containing carbazole and then polymerizing it with a dimer unit. The detailed method includes the following steps: Step 1: Preparation of a reaction unit containing carbazole (compound 2). 3,6-Dibromocarbazole is dissolved in DMF. Subsequently, 1.2 eq of NaH are added, and the mixture is stirred for 2 hours. Then, 1.2 eq of compound 1 are added to the reaction, and the mixture is stirred overnight. After that, water is added to the reaction to precipitate the solid. The suspension is filtered to obtain the desired product compound 2 as a white solid. Step 2: Polymerization: Carbazole-containing reaction unit polymerizes with a dimer unit. Compound 2 (1 eq), compound 3 (1 eq), K₂CO₃ (2.6 eq), PivOH (0.3 eq), and Pd(OAc)₂ (0.02 eq) are added to a Schenk tube. The tube is then emptied (3–5 min) and refilled with nitrogen. This procedure is repeated three times. Subsequently, nitrogen-degassed dimethylacetamide (DMAc) solvent is added, and the mixture is heated to 120 °C for 14 hours. The mixture is then poured into methanol to precipitate the crude polymer solid. The solid is filtered and redissolved in chloroform, then washed with water three times. The chloroform solution is added to a large volume of methanol, precipitating the polymer. The suspension is filtered to obtain the desired polymer product, ECP-1. The resulting ECP-1 has an oxidation potential of approximately 0.75 V (vs. Ag / AgCl) and an energy band gap greater than 3.0 eV. ECP-1 is fabricated in a solid-state electrochromic dendritic cell (ECD) using ECP-1 as the electrochromic layer, 0.2 M LiTFSI in PEGDA as the electrolyte, and VOx as the ion storage layer. The solid-state ECD can be stably switched between -0.5 V and 1.5 V (Figure 2). The neutral-state and oxidized absorbance spectra of ECP-1 are shown in Figure 4, with c at 405 nm and max at 320 nm. The solid-state ECD exhibits high transparency with transmittance as high as 93% in the neutral state (Figure 3), and changes to a bright blue color when the ECP-1 is oxidized, with an absorption peak at approximately 614 nm and another edge absorption band in the near-IR region, around 900–1100 nm (Figure 4). The optical contrast of the solid-state ECD is approximately 75% (Figure 3). Example 2 ECP-2 In some implementations, the described ECP-2 has a formula of ECP-2 is synthesized by first preparing a substituted benzene reaction unit and then polymerizing it with an acyclic dioxythiophene (AcDOT) unit. The detailed method includes the following steps: Step 2-1: Preparation of a reaction unit containing benzene (compound 4) by two steps. Compound 5 and p-toluenesulfonic acid are dissolved in acetonitrile. N-bromosuccinimide is then added, and the mixture is stirred overnight. The suspension is filtered to obtain the desired product. Product 6 is a white solid. Compound 6 is dissolved in DMF in N2. K2CO3 is added to the solution, and the reaction mixture is stirred for 15 minutes, after which 2-ethylhexyl bromide is added. The reaction mixture is stirred at 100 °C overnight. The reaction is stopped and cooled to room temperature. The solvent is removed under vacuum, and the residue is dissolved in diethyl ether. The organic phase is washed with water, and the aqueous phases are extracted with ethyl acetate. The combined organic phases are dried, and the volatiles are removed under vacuum. The crude product is passed through a small silica column, and the solvent is dried under vacuum to obtain compound 4 as a yellow oil. Step 2-2: Polymerization: The polymerization method is similar to that of step 1-2 with the reaction units of the substituted benzene reaction unit (compound 4) and AcDOT (compound 8) with a structure of Compound 8 The resulting ECP-2 has an oxidation potential of approximately 0.95 V (vs. Ag / AgCl) and a band gap greater than 3.1 eV. The ECP-2 is fabricated in a solid-state electrochromic device (ECD) using ECP-2 as the electrochromic layer, LiPF6 IM on PEGMEA as the electrolyte, and VOx as the ion storage layer. The solid-state ECD can be stably switched between -0.6 V and 1.7 V (Figure 5). The neutral and oxidized absorbance spectra of ECP-2 are shown in Figure 7, with c at 410 nm and max at 350 nm. The solid-state ECD exhibits high transparency, with a transmittance as high as 94% in the neutral state at 550 nm (Figure 6). It changes to a bright red color when ECP-2 is oxidized, with an absorption peak at around 546 nm and another, broader absorption band at a wavelength of around 800–1100 nm (Figure 7). The optical contrast of the solid-state ECD is 87% (Figure 6). Example 3 ECP-3 In some implementations, the described ECP-3 has a formula of ECP-3 is synthesized by preparing a reaction unit containing benzene and polymerizing it with a ProDot unit. The detailed method includes the following steps: Stage 3-1: same as Stage 2-1 Step 3-2: Polymerization: The polymerization method is similar to that of step 1-2 with the different reaction units of the reaction unit containing benzene (compound 4) and 3,4-ethylenedioxythiophene (EDOT, compound 9) with a structure of Compound 9 Example 4 ECP-4 In some implementations, the described ECP-4 has a formula of ECP-4 is synthesized by preparing a reaction unit containing naphthalene and then polymerizing it with an AcDOT unit. The detailed method includes the following steps: Step 4-1: Preparation of the reaction unit containing naphthalene (compound 10) by two steps. A solution of bromine in dichloromethane was added dropwise to a solution of compound 11 in dichloromethane for 15 minutes at -78 °C. The reaction mixture was stirred for 2 hours at -78 °C and then gradually warmed to room temperature and held at room temperature for an additional 2 hours. Excess bromine was inactivated by saturated aqueous sodium sulfite solution, and the mixture was stirred for 2 hours at room temperature. After extraction with dichloromethane, the combined organic phase was washed with brine, dried over sodium sulfate, and concentrated under vacuum. Compound 12 is dissolved in DMF under N2, K2CO3 is added to the solution, and the reaction mixture is stirred for 15 minutes, after which 2-ethylhexyl bromide is added. The reaction mixture is stirred at 100 °C overnight. The reaction is stopped and cooled to room temperature. The solvent is removed under vacuum, and the residue is dissolved in diethyl ether. The organic phase is washed with water, and the aqueous phases are extracted with ethyl acetate. The combined organic phases are dried under vacuum. Step 4-2: Polymerization: The polymerization method is similar to that of step 1-2 with the different reaction units of the reaction unit containing naphthalene (compound 10) and AcDOT (compound 8). Example 5 ECP-5 In some implementations, the described ECP-5 has a formula of ECP-5 is synthesized by a polymerization method similar to that of step 1-2 with the different reaction units of 1,5-dibromo-2,4-bis(hexyloxy)benzene and 3,4-dimethylthiophene. In some implementations, the described ECP has a formula of where nym are integers greater than 0, ayb are integers equal to or greater than 0 with at least one of ayb being greater than 0. In another aspect, the polymers described can have fluorescent emission and can be applied to fluorescent products. In conventional conjugated electrochromic polymers, the formation of polarons and bipolarons following electrochemical doping lowers the optical transition energy, resulting in a redshift of absorption from the visible to the near-infrared region, manifesting as a color change to transmissive. Consequently, the doped state exhibits residual absorption across the entire visible region. As film thickness increases, this residual absorption becomes more pronounced, and the residue color becomes visible. Therefore, conjugated electrochromic polymers exhibit relatively low optical contrast and contrast ratio, a significant factor limiting the further adoption of polymer-based ECDs in applications. In contrast to conventional conjugated ECPs that undergo a color-to-transmissive switch, the novel ECPs described here switch from transparent to colored. The described polymers exhibit higher energy band gaps, such that they absorb light in the UV region without absorbing it in the visible region in their neutral state, resulting in a transparent state, and in some embodiments, nearly 100% transparency. For example, polymers containing a triarylamine chromophore group achieve electrochromic switching from transparent to colored. Some conventional small molecules based on ethylenedioxythiophene derivatives can also switch from a transparent to a colored state. However, such designs also present specific challenges. First, these polymers generally exhibit poor switching stability.This is due to the fact that the charges formed in the doped state cannot be delocalized along the polymer chain, resulting in limited stability and durability. Secondly, electrochromic devices based on small organic molecules are usually in solution phase, so the color change depends on the diffusion of the molecules at the electrode, leading to slow switching speeds, intermediate colors, and hindering applications in flexible devices. The electrochromic polymers described exhibit nearly 100% transmittance (e.g., 85%–99.9%) in the neutral state, while showing high absorption in the oxidized state, leading to the highest optical contrast and contrast ratio recorded. The main polymer structure includes or consists of metaconjugated linkers (MCLs) and aromatic moieties (Ars), as previously described. The MCL connects the aromatic moieties at the meta position, disrupting charge delocalization. Therefore, the band gap of the described polymer increases through metaconjugation, allowing the absorption of the neutral polymer to be focused in the UV region to achieve a nearly 100% transparent state. Furthermore, the MCL and aromatic moieties provide the conjugation necessary to achieve a low oxidation potential for switching from transparent to colored and high switching stability. The color of the polymers can be easily controlled by adjusting the conjugation length of the MCL and aromatic moieties. In some embodiments, the described polymers can be prepared from MCLs such as carbazole, biphenyl, and binaphthalene, and thiophenes as aromatic moieties. The described polymers based on this inventive concept exhibit a wide range of color tuning capabilities and good electrochromic properties, including an optical contrast of over 95% and switching stability of over 10,000 cycles. Examples In the described polymer, each meta-conjugated polymer contains aromatic comonomers that are linked or MCL at the meta position. A series of polymers containing carbazole (CBZ), biphenyl (BP), and binaphthalene (BNP) as MCLs were designed, and the number of thiophenes (T1, T2, and T3) was varied to change the length of the aromatic moieties. The structures of these designs are shown below. To guide the experiment and probe the design paradigm from a molecular orbital perspective, density functional theory (DFT) calculations were performed on these meta-conjugated polymers, and theoretical spectra were generated for the neutral and radical cationic states. The absorption spectra of CBZ-T1, BP-T1, and BNP-T1 in their neutral states show almost 100% transparency in the visible region, with notable absorption occurring only in the UV region (Figure 8(A)). While CBZ-T1 and BNP-T1 exhibit a slightly redshifted absorption onset compared to BP-T1, all three polymers maintain absorption wavelengths below 400 nm. In the radical (oxidized) cationic states, absorption in the UV region decreases, leading to increased absorption within the visible region (Figure 8(B)).This electrochromism, from transparent to colored, can be further explained by the polymer's geometric change from neutral to radical cationic states. The polymers have a non-planar structure in their neutral state with twist angles of around 50 to 60 degrees between the MCL and the adjacent thiophene. This non-planar structure and significant torsional hindrance prevent charge delocalization, increasing the band gap of the neutral polymer, so the polymer absorbs only in the UV region. In the radical cationic state, however, the polymer becomes planarized with decreasing twist angles of 25 to 40 degrees, allowing charges to delocalize along the polymer chain, and the absorption shifts towards the red end of the visible spectrum.In contrast to BP-T1, the absorption of radical cations from CBZ-T1 and BNP-T1 is more red-shifted due to the extended conjugation of the BNP unit. The length of the aromatic moieties impacts the polymer's optical properties. In their neutral states, CBZ-T1, CBZ-T2, and CBZ-T3 exhibit nearly identical absorption spectra, suggesting that the number of thiophene units does not affect the polymer's band gap in these states. Calculations show that the torsion angles between the MCL and thiophene remain nearly equivalent across the polymers as the number of thiophene units increases, resulting in corresponding absorption in the UV region to achieve transparency. However, in the radical cationic state, increasing the number of thiophene units leads to a redshift in the spectra. Consequently, the radical cationic polymers display distinct colors—specifically orange, purple, and blue—corresponding to CBZ-T1, CBZ-T2, and CBZ-T3, respectively.This color variation can be attributed to the significant change in the twist angle between the thiophenes. When transitioning from polymers with one thiophene (CBZ-T1) to two thiophenes (CBZ-T2), a change in the twist angle (~5 degrees) has been observed. A similar trend has been observed when transitioning from 2T to 3T, with twist angles of ~15 degrees, respectively. The MCL could hinder the delocalization of charge from the neutral polymer, resulting in almost 100% transparency. The color of the polymer in the radical cationic state could be adjusted by modifying / varying the polymer's conjugation length. Example of electrochromic polymer synthesis Carbazole, biphenyl, and binaphthalene MCL monomers are synthesized with different extended conjugations. Different side chains are added to the MCL to adjust the solubility and polarity of the polymers. The oligomer 3,4-dimethylthiophene T1, T2, and T3 is then prepared. After obtaining the monomers, direct arylation polymerization (DArP) is applied to prepare the nine transparent, metaconjugated electrochromic polymers. Each metaconjugated polymer solution is spin-coated onto an ITO glass as a working electrode and placed in a cuvette for electrochemical and optical measurements. The location of the absorption peaks in the oxidized state indicates a red shift following the incorporation of longer aromatic moieties. The techniques described allow for the rational shift of the absorption peak, enabling access to a wide range of colors across the visible spectrum.In some embodiments, oxidized polymers with different aromatic residue lengths exhibit distinct colors, specifically orange, purple, and blue, corresponding to T1, T2, and T3 for BP and CBZ polymers, respectively. The CIELAB color coordinates of all polymers in their neutral and oxidized states are obtained. The neutral-state polymers have L*a*b* values ​​close to (100, 0, 0), which is completely transparent. In the oxidized state, these polymers cover a wide range in the color space, providing potential for color mixing. By varying the conjugation length of one or more MCLs and one or more Ars, the described electrochromic polymer can be controlled to design for a broad color gamut. Furthermore, by mixing different described electrochromic polymers with different colors in varying proportions, another new batch of colors can be produced, greatly enriching the color library.Furthermore, unlike conventional electrochromic polymer blends, due to the close oxidation potentials of the described electrochromic polymers, the described electrochromic polymer blends do not suffer from the intermediate color issues commonly observed in conventional electrochromic polymer blends. In some embodiments, due to their high transmittance, the described electrochromic polymers or blends exhibit high optical contrast and good stability with a large color library and no intermediate colors. This disclosed electrochromic polymer / device can be used in a variety of applications, including smart windows and glasses, biosensors, electronic papers, displays, Augmented Reality (AR), Virtual Reality (VR), Mixed Reality (MR), patterned electrochromic displays, curtain walls, and sunroofs. The electrochemical properties of the polymers are evaluated using cyclic voltammetry and differential pulse voltammetry (DPV). The polymers exhibit nearly reversible oxidations. Upon examination of the polymers using DPV, CBZ-T1, CBZ-T2, and CBZ-T3 exhibit a peak indicating the formation of radical cations. However, polymers containing BP and BNP units show two peaks, with the second peak corresponding to the formation of dication. This oxidation makes the electrochemistry irreversible and leads to the formation of a new absorption peak in the visible range. It is worth noting that all polymers exhibit a relatively low oxidation initiation potential (CBZ polymers approximately 0.6-0.8 V vs. Ag / AgCl; BP polymers approximately 0.8-1.0 V vs. Ag / AgCl; BNP polymers approximately 0.8-1.0 V vs. Ag / AgCl), which is attributed to the conjugation of aromatic residues.The low oxidation initiation potential is beneficial for the electrochemical stability of the polymers, as it can prevent undesirable side reactions, such as oxidation with water. In general, CBZ polymers have a lower oxidation initiation potential and better reversibility at a higher potential, although these metaconjugated polymers are quite similar in their characteristics. The lowest energy absorption peak results from the electronic transition from the single-occupied molecular orbital with a downward electronic spin (Sβ) to the lowest unoccupied molecular orbital (Lβ). Therefore, the described meta-conjugated polymer is capable of synchronous modulation of both visible and near-infrared light. The described techniques allow for tuning the color of metaconjugated electrochromic polymers and their low oxidation potentials. These techniques can also be used to produce black electrochromism by mixing chromophores of vibrant colors whose collective absorption completely covers the visible spectrum. The inventors found that mixing the disclosed polymers can produce the desired colors. In some embodiments, the metaconjugated polymers CBZ-T1 (orange) and CBZ-T3 (blue) are used in blends to obtain transparent-to-black electrochromics. When making blends, the absorption coefficients of the polymers in their oxidized states are used to determine the appropriate polymer ratios to be blended to obtain the black color.Beer-Lamber charts of polymer films show the almost identical absorption coefficient of CBZ-T1 and CBZ-T3 in oxidized states, so the mass ratio of the CBZ mixture is determined to be 1:1. Other mass ratios of mixtures or blends of different polymers described can be used to prepare other desirable colors. The electrochemical absorption spectrometry of the CBZ blend with a film thickness of 300 nm is shown in Figure 9(A). The neutral film exhibits an absorption onset at 400 nm, indicating almost 100% transparency in the visible region. Oxidation of the CBZ blend to the radical cationic state results in two broad absorptions in the visible and near-infrared regions, with maxima at 550 and 950 nm, demonstrating synchronized light and heat modulation. Several CBZ blend films with different thicknesses were prepared, and the absorption coefficient was derived from the Beer-Lambert plot, as shown in Figure 9(B). The neutral (bleached) state absorption coefficient for CBZ-Blend is approximately 5 × 102 cm-1, which is 2 orders of magnitude lower than the oxidized (colored) state value, 3.7 × 104 cm-1.The transmittance of the neutral and oxidized states is plotted graphically as a function of film thickness using the respective absorption coefficient values, as shown in Figure 9(C). When the film is thin, the transmittance of both the neutral and oxidized states can be nearly 100%. Since the absorption coefficient of the neutral state is close to zero, the transmittance remains almost 100% and undergoes minimal decay as the film becomes thicker. In some embodiments, the optical contrast between the neutral and oxidized states can reach nearly 100%, for example, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or higher, or between any of these values. Figure 9(D) illustrates the transmittance of CBZ-Blend in both the neutral and oxidized states of the electrochromic layer at different thicknesses according to several embodiments.Optical contrast is equal to the difference in transmittance between the neutral and oxidized states. For different film thicknesses (270–700 nm) measured in the neutral state, the optical contrasts shown in Figure 9(D) are 78%, 87.7%, 92.1%, 93.3%, and 92%, respectively. The contrast ratio is calculated by dividing the transmittance in the neutral state by the transmittance in the oxidized state. For different film thicknesses (270–700 nm) measured in the neutral state, the contrast ratios shown in Figure 9(D) are 4.9%, 9.8%, 19.4%, 47.65%, and 93%, respectively. As shown in Figure 9(D), the optical contrast of the described electrochromic film increases with film thickness. As the thickness of the described EC film increases, the response time also increases.When the film thickness exceeds 1500 nm, the reported EC device can exhibit high optical contrast, for example, approximately 96% with 96% transmittance in the neutral state and approximately 0.06% in the oxidized state of the EC layer. However, the device may have a slow response time, for example, approximately 1 minute. As the film thickness increases, the transmittance of the EC layer in the neutral state may decrease to a lesser degree. However, the transmittance of the EC layer in the oxidized state may decrease significantly. Therefore, with increasing film thickness, the optical contrast (transmittance difference between the neutral and oxidized states) of the EC layer increases considerably. However, limited by the increased response time with increasing thickness, in some embodiments, the film thickness of the described EC layer is limited to 1500 nm or less.In some embodiments, the thickness of the described EC layer film is limited to 1200 nm, 1000 nm, 900 nm, 800 nm, 700 nm, 600 nm, 500 nm, 400 nm, 300 nm, 200 nm or 100 nm, to obtain a response time of less than 1 minute. The described metaconjugated electrochromic polymer layers exhibit ultra-high optical contrast and fast switching speed. They also exhibit high stability, including photostability and electrochromic switching stability. Photostability is examined by exposing the encapsulated polymer films to a solar simulator matching a standard air mass illuminant of 1.5. Their absorption spectra are measured, and the maximum absorption is plotted against irradiation time. The results indicate that the described polymers are stable even when used with other materials, such as ITO, electrolyte, and ion storage layer (e.g., ITO nanoparticles). To reveal the cyclic stability of the polymer thin film, 10,000 CV switching cycles are applied in a 3-electrode configuration, where the voltage is applied from -0.2 V to 1.0 V at 80 mV / s.The transmittance of the neutral and colored states was recorded every 1000 cycles. The optical contrast of the polymer decreased by 10%, suggesting that metaconjugated polymers are suitable for long-term performance. As shown in Figure 10, an electrochromic device 100 according to some example embodiments may have a first insulating substrate 102, a first conductive layer 104 disposed on the first insulating substrate 102, an electrochromic layer 106 disposed on the first conductive layer 104, an electrolyte layer 108 disposed on the electrochromic layer 106, a second conductive layer 112 disposed on the electrolyte layer 108, a second insulating substrate 114 disposed on the second conductive layer 112, and circuitry 116 for operating the electrochromic device 100. In some embodiments, the electrochromic device 100 may further include an ion storage layer 110 disposed between the second conductive layer 112 and the electrolyte layer 108. The electrochromic layer 106 may include an electrochromic polymer as described above.For example, the electrochromic polymer includes or consists of a polymer backbone comprising one or more metaconjugated linkers (MCLs) and one or more aromatic moieties (Ars), wherein each of the one or more MCLs is partially conjugated to one of the one or more Ars in a metaposition of the one or more MCLs. In some embodiments, an electrochromic layer thickness of 10⁶ is from 10 nm to 1500 nm, resulting in a transmittance of 85%–99.9% at a wavelength of 550 nm in a neutral state of the electrochromic layer. For example, an electrochromic layer thickness of 10⁶ from 10 nm to 1500 nm produces a transmittance of 85%, 87%, 90%, 92%, 95%, 96%, 97%, 98%, 99%, 99.9%, or any two of these values. The electrochromic device 100 has a transmittance of 60% or more at a wavelength of 550 nm in a bleached state of the device.For example, by adjusting the material and thickness of the electrochromic layer 106, the electrochromic device 100 can have in its bleached state a transmittance of 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92%, 95%, 96%, 97%, 98%, or 99%, or any two of the above numbers. In some embodiments, the electrochromic layer has a transmittance of 40%–0.1% at a wavelength of 550 nm in an oxidized state. For example, the electrochromic layer in the oxidized state has a transmittance at a wavelength of 550 nm of 40%, 35%, 30%, 25%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1%, or any two of the above numbers. In some embodiments, the electrochromic layer 106 has an optical contrast ratio of 60% or more. For example, the electrochromic layer 106 may have an optical contrast ratio of 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or any two of the above numbers. In some embodiments, when the electrochromic device 100 includes the ion storage layer 110, the ion storage layer 110 has a transmittance of 80% or more at a wavelength of 550 nm. In some embodiments, the ion storage layer 110 may include (1) one or more oxides of metal elements in group 4-12, or (2) a mixture of the oxides, or (3) one of the oxides doped with a different metal oxide, or (4) a transition metal complex, or (5) one or more redox-active polymers, including nitroxyl radical polymers, redox-active galvinoxyl polymers, and conjugated polymers. In some embodiments, the ion storage layer 110 includes ITO particles, wherein the ion storage layer has a transmittance of 90% or more at a wavelength of 550 nm. In some embodiments, the ITO particles may be nanoparticles having a size of 1–900 nm. In some embodiments, at least one of the first conductive layer 104 and the second conductive layer 112 includes ITO, aluminum zinc oxide (AZO), fluorine-doped tin oxide (FTO), silver nanowires, graphene, carbon nanotubes, transparent conductive electrodes based on metal mesh, silver nanoparticle ink, or an organic conductive polymer. In some embodiments, the electrochromic device 100 has an optical contrast ratio of 60% or more. For example, the electrochromic device 100 may have an optical contrast ratio of 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or any two of the above numbers. In some embodiments, a color of the electrochromic layer 106 in an oxidized state is varied by varying a conjugation length of one or more MCLs and one or more Ars. In some embodiments, the electrochromic layer 106 includes a mixture of different electrochromic polymers without an intermediate color. The structures of the polymer(s) in the electrochromic layer 106 are explained above and will not be repeated for brevity. This disclosure also provides an electrochromic device that can switch between transparent and black. Electrochromic materials that can reversibly switch between black and transmissive states are of great importance for various commercial and military applications. For example, the inventors discovered that CBZ-T1 and CBZ-T3 have a similar absorption coefficient; therefore, they mixed CBZ-T1 (switching transparent to orange) and CBZ-T3 (switching transparent to blue) at a 1:1 mass ratio to obtain a transparent-to-black electrochromic device. The configuration of the transparent-to-black electrochromic device is similar to the electrochromic device 100 described earlier. The device is assembled in a two-electrode configuration using a mixture of CBZ-T1 and CBZ-T3 as the electrochromic layer and ITO nanoparticles as the ion storage layer (at 1.5 m).In the spectroelectrochemical study, the device potential is increased from -0.6 to 2.4 V. As the potential increases, the transmittance in the visible region decreases due to the oxidation of the CBZ-T1 and CBZ-T3 mixture, and the device changes from a transparent to a black state. The potential is increased until no further changes in transmittance are observed, and the optical contrast is 88% (1–89%). The transmittance spectra are referenced to air, meaning that the transmittance loss includes the glass, ITO, electrolyte layer, and ion storage layer. The CIE color coordinates L*a*b* are investigated at different voltages. As the potential increases, the lightness (L*) in the CIE color coordinates L*a*b* decreases from 95 to 36, while * and b* remain close to 0, indicating a color change from transparent to black with no intermediate color.To reveal the cyclic stability of the device, 10,000 CV switching cycles were applied, and the transmittance spectra were measured. The transmittance at 550 nm of the transparent and colored states of the device indicates that the optical contrast decreased slightly from its original value of 85% to 78% (shown in Figure 9(E)), representing the best cyclic stability of the black electrochromic device with such high optical contrast. In summary, this disclosure provides metaconjugated polymers that enable electrochromic switching from transparent to colored with a wide color gamut, ultra-high optical contrast, low oxidation potential, and excellent switching stability.A transparent-to-black electrochromic device based on a polymer blend has been successfully obtained with an optical contrast ratio exceeding 91% and a contrast ratio of 91%, representing the best electrochromic black performance. This approach to accessing transparent electrochromic polymers opens promising avenues for future electrochromic innovations. The described electrochromic device can be used in various applications, such as smart windows and glasses, biosensors, electronic paper, displays, Augmented Reality (AR), Virtual Reality (VR), Mixed Reality (MR), printed electrochromic displays, curtain walls, and sunroofs. It should be noted that, in EC devices, the bleached state of the device corresponds to the oxidized state of the EC layer. However, for the described EC device, the bleached state corresponds to the neutral state of the EC layer.

Claims

1. An electrochromic device comprising: a first insulating substrate; a first conductive layer disposed on the first insulating substrate; an electrochromic layer disposed on the first conductive layer, wherein the electrochromic layer comprises an electrochromic polymer having a polymer backbone comprising one or more meta-conjugated linkers (MCLs) and one or more aromatic moieties (Ars), wherein each of the one or more MCLs is partially conjugated with one of the one or more Ars at a meta position of the one or more MCLs; an electrolyte layer disposed on the electrochromic layer; a second conductive layer disposed on the electrolyte layer; and a second insulating substrate disposed on the second conductive layer, wherein the thickness of the electrochromic layer is from 10 nm to 1500 nm, resulting in a transmittance of 85%-99%.9% at a wavelength of 550 nm in a neutral state of the electrochromic layer; wherein the electrochromic device has a transmittance of 60% or more at a wavelength of 550 nm in a bleached state of the device; wherein each of the one or more MCLs and the corresponding metapositions comprises one of the following formulas: wherein X is S, Se, N, C or O; Each of R1-R12 is independently selected from one of hydrogen, C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C2-C30 alkylcarbonyl, C1-C30 alkoxy, C3-C30 alkoxyalkyl, C2-C30 alkoxycarbonyl, C4-C30 alkoxycarbonylalkyl, C1-C30 alkylthio, C1-C30 aminylcarbonyl, C4-C30 aminylalkyl, C1-C30 alkylaminyl, C1-C30 C1-C30 alkylsulfonylalkyl, C3-C30 alkylsulfonylalkyl, C6-C18 aryl, C3-C15 cycloalkyl, C3-C30 cycloalkylaminyl, C5-C30 cycloalkylalkylaminyl, C5-C30 cycloalkylalkylalkyl, C5-C30 cycloalkylalkyloxy, heterocyclyl C1-C12, C1-C12 heterocyclyloxy, C1-C30 heterocyclylalkyloxy,C1-C30 heterocyclylamyl, C5-C30 heterocyclylalkylamyl, C2-C12 heterocyclylcarbonyl, C3-C30 heterocyclylalkyl, C1-C13 heteroaryl or C3-C30 heteroarylalkyl; and each of these the wavy lines represent one of the meta positions. and wherein each of the one or more Ars comprises one of a thiophene-based unit, one furan-based unit, one selenophene-based unit, or one pyrrole-based unit with one of the following formulas: wherein each of R13, R14, and R15 is independently selected from one of hydrogen, C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C2-C30 alkylcarbonyl, C1-C30 alkoxy, C3-C30 alkoxyalkyl, C2-C30 alkoxycarbonyl, C4-C30 alkoxycarbonylalkyl, C1-C30 alkylthio, C1-C30 amylcarbonyl, C4-C30 amylalkyl, C1-C30 alkylamyl, C1-C30 alkylsulfonyl, C3-C30 alkylsulfonylalkyl, aryl C6-C18, C3 C15 cycloalkylaminyl, C3-C30 cycloalkylaminyl, C5-C30 cycloalkylaminyl, C5-C30 cycloalkylaminyl,1. C5-C30 cycloalkylalkyloxy, C1-C12 heterocyclyl, C1-C12 heterocyclyloxy, C1-C30 heterocyclylalkyloxy, C1-C30 heterocyclilaminyl, C5-C30 heterocyclilaminyl, C2-C12 heterocyclylalkylaminyl, C3-C30 heterocyclylcarbonyl, C1-C13 heterocyclylalkyl, or C3-C30 heteroaryl.

2. Electrochromic device according to claim 1, wherein the electrochromic layer has a transmittance of 40%-0.1% at a wavelength of 550 nm in an oxidized state of the electrochromic layer.

3. An electrochromic device according to claim 1, further comprising an ion storage layer, wherein the ion storage layer is disposed between the electrolyte layer and the second conductive layer and has a transmittance of 80% or more at a wavelength of 550 nm.

4. The electrochromic device according to claim 3, wherein the ion storage layer comprises one or more oxides of metal elements in group 4-12,or a mixture of the oxides, or one of the oxides doped with a different metal oxide, or a transition metal complex, or one or more redox-active polymers including nitroxyl radical polymers, redox-active galvinoxyl polymers, and conjugated polymers.

5. Electrochromic device according to claim 3, wherein the ion storage layer comprises indium tin oxide (ITO) particles, wherein the ion storage layer has a transmittance of 90% or more at a wavelength of 550 nm.

6. Electrochromic device according to claim 1, wherein at least one of the first conductive layer and the second conductive layer comprises ITO, aluminum zinc oxide (AZO), fluorine-doped tin oxide (FTO), silver nanowires, graphene, carbon nanotubes, transparent conductive electrodes based on a metal mesh,or silver nanoparticle ink or an organic conductive polymer.

7. Electrochromic device according to claim 1, wherein the electrochromic layer has an optical contrast of 60% or more.

8. Electrochromic device according to claim 1, wherein the electrochromic device has an optical contrast of 60% or more.

9. The electrochromic device of claim 1, wherein a color of the electrochromic layer in an oxidized state is varied by varying a conjugation length of one or more MCLs and one or more Ars.

10. Electrochromic device according to claim 1, wherein the electrochromic layer comprises a mixture of the electrochromic polymers without an intermediate color.

11. Electrochromic device according to any one of the preceding claims, wherein the thiophene-based unit comprises one of the following formulas: or wherein X is S, Se, N,C or O; each of R15-R18 is independently selected from one of hydrogen, C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C2-C30 alkylcarbonyl, C1-C30 alkoxy, C3-C30 alkoxyalkyl, C2-C30 alkoxycarbonyl, C4-C30 alkoxycarbonylalkyl, C1-C30 alkylthio, C1-C30 aminylcarbonyl, C4-C30 aminylalkyl, C1-C30 alkylaminyl, C1-C30 alkylsulfonyl, C3-C30 alkylsulfonylalkyl, C6-C18 aryl, C3-C15 cycloalkyl, C3-C30 cycloalkylaminyl, C5-C30 cycloalkylaminyl, C5-C30 cycloalkylalkyl, cycloalkylalkyloxy C5-C30, C1-C12 heterocyclyl, C1-C12 heterocyclyloxy, C1-C30 heterocyclylalkyloxy, C1-C30 heterocyclylamyl, C5-C30 heterocyclylalkylamyl, C2-C12 heterocyclylcarbonyl, C3-C30 heterocyclylalkyl, C1-C13 heteroaryl, or C3-C30 heteroarylalkyl; and is any one or more of aromatic structures, or fused aromatic structures, or a combination thereof.

12. Electrochromic device according to claim 1,wherein the electrochromic polymer comprises a formula of , which 0.,