Three it-conjugated donor/acceptor polyimines have been synthesized for electrochromic applications. Intramolecular hydrogen bonds between the carbamate hydrogen and the imine nitrogen on the side chains gave semi-locked planar monomer M1 and M2. Additional C-H center dot center dot center dot N hydrogen bonds between the nitrogen on the pyrazine and the hydrogen of the azomethane resulted in a fully locked planar monomer M3. These monomers copolymerized with bis(trimethylstannyl)-2,3-dihydrothieno[3,4-b][1,4]dioxine (EDOT-Sn). Different imine acceptors can significantly affect the structures of polymers and thus their optoelectronic properties. Among them, P2 demonstrated the best electrochromic performances at a wavelength of 830 nm, including an optical contrast of 28.06 %, an ultrafast response time of 0.15 s, and a high optical stability with a reversibility of 88.54 % after 200 cycles, while the coloring efficiency was the highest at a wavelength of 592 nm (328.43 cm(2) C-1). The results indicate that hydrogen-bonded it-conjugated polyimines can be promising materials for electrochromic applications.

Current weakly solvating electrolytes (WSEs) for lithium metal batteries primarily rely on molecular engineering of weakly coordinating solvents to tailor solvation structures of Li+ and interfacial chemistry. However, this approach is hampered by synthetic complexity, high cost, and limited precision in solvation regulation. To overcome these limitations, we develop a diluent-enabled strategy that leverages non-coordinating solvents to reconfigure the solvation structures of WSEs, yielding localized WSEs, which is operationally simple, highly reproducible, and intrinsically efficient. Specifically, ethoxy(pentafluoro)cyclotriphosphazene (PFPN) is integrated into a WSE consisting of tetrahydropyran (THP) and lithium bis(fluorosulfonyl)imide (LiFSI) to precisely modulate its solvation structure. Strong dipole-dipole interactions between PFPN and THP, coupled with PFPN's dilution effect, suppress THP's coordination to Li+, thereby enriching anions in the primary solvation shell of Li+ and promoting ion-aggregate-dominated solvation structures. These solvation structures enable the formation of robust, anion-derived solid electrolyte interphases and cathode electrolyte interphases rich in LiF. As a result, Li|| NCM811 cells retain 82.6 % of their initial capacity after 600 cycles at 4.3 V. Moreover, under demanding conditions of 4.5 V cut-off voltage and 21.5 mg cm- 2 cathode loading, the cells exhibit markedly enhanced cycling stability. This work establishes a broadly applicable paradigm for engineering high-performance electrolytes tailored to practical lithium metal batteries.

High-voltage Li metal batteries hold great promise for next-generation energy storage, but constructing robust and highly conductive electrode/electrolyte interfaces via electrolyte engineering to enhance the battery performance is still a challenge. Herein, we propose a non-coordinating solvent anchoring strategy to regulate fluorinated amide electrolyte to enhance the stability and ionic conductivity of the interfaces. Specifically, hexafluorobenzene is employed to anchor fluorinated amide solvent by the robust dipole-dipole interactions, which weaken the coordination between fluorinated amide and Li* , facilitate more anions coordinating with Li* , and form more ion aggregates. Consequently, stable and highly conductive electrode/electrolyte interfaces enriched with LiF and Li3N are constructed, drastically improving the interfacial stability and reducing interface impedance of Li metal anodes and LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes. Such a rationally designed electrolyte demonstrates excellent flame retardancy, high oxidation stability (5.1 V vs. Li* /Li), and enhanced low-temperature ionic conductivity. As a result, this electrolyte substantially enhances the high-voltage cycle stability (similar to 4.8 V), rate capability (similar to 50 C) and low-temperature cycle performance (-20 degrees C) of Li||NCM811 cells, which retain 80.0 % of the initial capacity over 600 cycles at 4.7 V. This research offers a promising strategy to design ideal electrolytes for highperformance Li metal batteries. (c) 2025 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

As part of this research, three distinct chlorinated monomers (various chlorinated benzene derivatives served as the central core, while the EDOT group was utilized as the terminal unit) namely Y2Cl-EDOT, T2Cl-EDOT, and Cl-EDOT, have been synthesized successfully using the Stille coupling reaction. Subsequently, three chlorinated polymers-P(Y2Cl-EDOT), P(T2Cl-EDOT), and P(Cl-EDOT), were characterized by cyclic voltammetry and UV-vis spectrophotometer. These chlorinated monomers exhibit a low initial oxidation potential of approximately 0.75 V. This characteristic of relatively low polymerization potential helps to produce high-quality polymers. Moreover, the number of chlorine atoms exerts a significant influence on the quality of the resulting polymers. The UV-Vis spectrum of the di-chlorinated monomers shows a blue-shifted trend (the blue shift of T2Cl-EDOT is the most obvious); the emission spectra of them are very similar. All the chlorinated polymers show very different redox peak potentials, favorable electrochemical activity and stability. Compared to P(Y2Cl-EDOT), P(Cl-EDOT) exhibits similar absorption spectra, coloration efficiency, and open-circuit stability, but demonstrates a faster response time (0.44 s at 465 nm). In contrast, P(T2Cl-EDOT) shows the most distinct color change and achieves the highest coloration efficiency (314 cm(2) C-1 at 1100 nm). These findings collectively demonstrate that both the substitution position of chlorine atoms on the benzene unit and the number of substituted chlorine atoms significantly modulate the spectroelectrochemical and electrochromic properties of the resulting chlorinated hybrid polymers.

In this work, two asymmetric acceptor and donor electrochromic conjugated polymers (pEFBTT48E and pTFBTT48T) were prepared. pTFBTT48T exhibits superior planarity and HOMO/LUMO electron clouds delocalized throughout the backbone, which may allow charge carriers (polarons/bipolarons) to transport more rapidly along the chain, enhancing optical contrast, and shortens coloring/bleaching times. Meanwhile, the compact morphology facilitates pTFBTT48T achieved the highest optical contrast of 48% at 1100 nm, the fastest response time of 0.22 s at 898 nm, the highest coloration efficiency of 312 cm2 C-1 at 1100 nm, and superior stability with 90% degradation after 1000 cycles, whereas pEFBTT48E maintained only 49%. We have deeply investigated the relationship between their structures and electrochromic performance, contributing to the development of asymmetric electrochromic polymers.

In this study, two novel hybrid monomers (4BD-EDOT and 3BD-EDOT) containing a biphenyl group and a 3,4-ethylenedioxythiophene (EDOT) unit were synthesized and polymerized electrochemically in a CH2Cl2-Bu4NPF6 electrolyte solution. Characterizations of the resulting P4BD-EDOT and P3BD-EDOT were studied by CV, scanning electron microscopy (SEM), and spectroelectrochemistry in order to examine the effect of different substitution positions of biphenyl on the electrochromic performance of the resultant hybrid polymers. Both polymers have favorable redox activity (a distinct redox peak) and good redox stability (55–49% electroactivity was retained after 1000 cycles). The spectro-electrochemistry study found that both show a distinct color change from reddish brown to blue/purple for P4BD-EDOT with a lower band gap (1.54 eV) and from transparent color to light blue for P3BD-EDOT with a larger band gap (1.73 eV). These electrochromic polymer films also have fast switching speed (0.5–0.2 s), with the favorable optical contrast (22.6% at 1100 nm for P4BD-EDOT) and decent coloration efficiency (250.4 cm2 C−1 at 780 nm for P3BD-EDOT). All these results show that both monomers have important values related to the electrochromic field. This work also shows that the different substitution positions of the biphenyl unit affect the spectroelectrochemistry and electrochromic characteristics of the resultant hybrid polymers.

Four donor-acceptor-donor (D-A-D) type monomers EEEBD, TTTBD, TEEBD and ETTBD, were designed and synthesized by varying the different it-bridges and terminal active groups in monomeric backbone based on the benzo [1,2-c:4,5-c']dithiophene-4,8-dione acceptor unit. The corresponding polymers PEEEBD, PTTTBD, PTEEBD and PETTBD were synthesized by electrochemical polymerization. The structure-property relationships of these monomers and polymers, such as optical properties, electrochemical behavior, band gap, optical contrast and electrochromic performance were comparatively investigated. EEEBD exhibited the most red-shifted absorption peak at 521 nm and the lowest onset oxidation potential (Eonset) of 0.11 V among these monomers. Notably, in comparison with PEEEBD, polymers PTTTBD, PTEEBD and PETTBD achieved much higher optical contrast of 23.50 % at 1100 nm, 18.76 % at 660 nm and 32.48 % at 1100 nm, respectively, which is highly advantageous for electrochromic applications in the visible and near-infrared regions. PTTTBD exhibited excellent electrochromic performance and displayed a color transition from dark purple in the reduced state to black in the oxidation state, and achieved the best coloration efficiency (CE) value of 265.68 cm2 C-1 at 1100 nm among these polymers. These results indicated that varying the different it-bridges and terminal active groups in polymer backbone based on the benzo [1,2-c:4,5-c']dithiophene-4,8-dione acceptor could improve the electrochromic performance, opening up a new page to develop the high-performance electrochromic polymers.

Conjugated fused-ring extended benzothiadiazole derivatives are good electron-withdrawing moieties for constructing donor-acceptor (D-A) type conjugated polymers, but has not been well investigated in electrochromic performance. Herein, two D-D'-A-D'-D monomers, ETBT and ETBQx with the larger conjugated pi plane based on dithieno[3 ',2 ':3,4;2 '',3 '':5,6]benzo[1,2-c][1,2,5]thiadiazole and 7a,11a-dihydrodith-ieno[3 ',2 ':3,4;2 '',3 '':5,6]benzo[1,2-g]quinoxaline by the conjugated fused-ring extension of benzothiadiazole, were designed and synthesized. The D-D'-A-D'-D type polymers PETBT and PETBQx were successfully synthesized via electrochemical polymerization. ETBT exhibited a lower onset oxidation potential (Eonset) of 0.55 V, while ETBQx showed a noticeable red-shifted absorption by approximately 40 nm, along with a higher molar absorption coefficient compared to EBT. In terms of electrochromic properties, PETBQx displayed a color transition from green in its neutral state to a saturated blue in its oxidized state. It also demonstrated a superior coloration efficiency (CE) of 327.1 cm2 C-1 and a higher optical contrast of 37.5 % at 1100 nm, surpassing the performance of PEBT. These enhancements are attributed to the extended conjugated fused-ring system in PETBQx, which can significantly improve the electrochromic properties of conjugated polymers.

In this work, we designed and synthesized a series of donor (D)-it-acceptor (A)-it-donor (D) type monomers, namely ETBD, EEBD, TTBD and TEBD, by varying the different it-bridges and terminal active groups in monomeric backbone based on the benzo [1,2-c:4,5-c']dithiophene-4,8-dione acceptor. And then their corresponding polymers PTEBD, PETBD, PEEBD and PTTBD were synthesized by electrochemical polymerization. EEBD exhibited the most red-shifted absorption peak at 487 nm and the lowest Eonset of 0.44 V among these monomers. Notably, in comparison with PTEBD, polymers PETBD, PEEBD and PTTBD achieved much higher optical contrast of 50.93 % at 830 nm, 39.94 % at 660 nm and 45.65 % at 1100 nm, respectively. In addition, PTTBD possessed the best electrochromic performance and displayed a color transition from dark purple in the neutral state to grey in the oxidation state with the best coloration efficiency (CE) value of 570.84 cm2 C-1 at 1100 nm among these polymers. These results demonstrated that the strategy of varying the different it-bridges and terminal active groups in polymer backbone based on the benzo [1,2-c:4,5-c']dithiophene-4,8-dione acceptor could improve the electrochromic performance, offering a promising approach to the design of highperformance electrochromic polymers.

The combination of 3,4-ethylenedioxyphene (EDOT) unit with other units can make the resultant hybrid conjugated monomer/polymer have some excellent optoelectronic properties. Herein, in this work, a series of novel thiophene-EDOT hybrid monomers (EDOT-T, EDOT-2T, and EDOT-3T) with simple oligothiophene units as the core and EDOT unit as the end groups were designed and synthesized by Stille coupling reaction, and the corresponding hybrid electrochromic polymer films (P(EDOT-T), P(EDOT-2T), and P(EDOT-3T)) were successfully obtained by potential cycling. Subsequently, the electrochemical properties and electrochromic properties of these three hybrid polymers were systematically studied in ACN-Bu4NPF6 system. The photophysical study shows that the increase of conjugated length of monomer will lead to the stepwise red-shifted absorption and fluorescence spectra, decreased quantum yield, and increased Stokes shift. Due to the stronger electron donating ability of the EDOT unit, all the hybrid monomers show a lower initial oxidation potential (<= 0.6 V), which is beneficial to the preparation of high-quality electrochromic polymer films with fewer defects. The results show that as-formed polymers have good redox activity and excellent redox stability. Due to the increase of conjugation length, the obtained P(EDOT-3T) film has good electrochromic properties: the highest optical contrast is 44.3 %, the coloration efficiency is above 120 C- 1 cm2, and the fastest response time is 0.58 s, indicating that P (EDOT-3T) is a very promising electrochromic material. This work also successfully proved that changing the different initial monomers was an effective tool to construct electroactive polymers with very significant different physicochemical and electrochromic properties.

In this work, a series of donor (D)-acceptor (A)-donor (D) type monomers, including TBD, TTBD and TTTBD, were designed and synthesized by modulating the conjugated length of the monomer backbone based on the benzo[1,2-c:4,5-c']dithiophene-4,8-dione acceptor unit. The corresponding polymers PTTBD and PTTTBD were successfully synthesized through electrochemical polymerization, whereas this method was ineffective for the synthesis of PTBD from its monomer TBD. As the conjugated length of the monomeric backbone increased, the absorption spectra of these three monomers TBD, TTBD and TTTBD exhibited a progressive red-shift, and their onset potentials (Eonset) gradually decreased. In addition, PTTBD demonstrated superior electrochemical stability and electrochromic performance, changing color from purple in the neutral state to grey in the oxidized state, with a higher optical contrast of 45.65 % and a coloration efficiency (CE) value of 570.84 cm2 C-1 at 1100 nm compared to PTTTBD (27.50 % and 265.68 cm2 C-1). These results indicate that the strategy of tuning the conjugated length of the monomer backbone can optimize the electrochromic performance, offering a promising approach to the design of high-performance electrochromic polymers.

Benzo[1,2-c:4,5-c ']dithiophene-4,8-dione (BDD) unit is a promising candidate for D-A-D type conjugated polymers and employed in electrochromic materials. A series of D-A-D type monomers (EBD, EEBD and EEEBD) and the corresponding conjugated polymers (PEEBD and PEEEBD) based on benzo[1,2-c:4,5-c ']dithiophene-4,8-dione acceptor were designed and synthesized by extending the conjugation length of monomeric backbone. EBD, EEBD and EEEBD exhibited progressively red-shifted absorption spectra and decreasing onset oxidation potential (E-onset) as the conjugation length of monomeric backbone increased. In particularly, EEEBD achieved an extremely low onset oxidation potential of 0.11 V, which was beneficial to obtained high-quality polymer film by electrochemical polymerization. Moreover, PEEBD achieved much better optical contrasts of 39.9 % at 660 nm with the coloration efficiency (CE) value of 320.71 cm(2) C--(1) at 660 nm in comparison with PEEEBD. These results indicated that extending the conjugated length of the monomer backbone using EDOT unit can optimize the electrochromic performance, providing a promising approach to the design of high-performance electrochromic polymers.

Li metal batteries with NCM811 cathodes are promising energy storage systems owing to their ultrahigh energy density (>500 Wh kg(-1)), which call for electrolytes with good flame retardance and superior compatibility with electrodes. Herein, multifunctional flame-retardant diluent ethoxy(pentafluoro)cyclotriphosphazene (PFPN) is used to regulate triethyl phosphate (TEP)-based localized high concentration electrolyte (LHCE-PFPN) to realize excellent flame retardance and superb compatibility with high-voltage cathodes and Li metal anodes. PFPN and TEP endow LHCE-PFPN with excellent flame retardance. PFPN cooperates with bis(fluorosulfonyl)imide (FSI-) anions to form robust solid electrolyte interphase (SEI) enriched with LiF, effectively enhancing the interface stability and restraining the intrinsic reactions between TEP and Li metal. LHCE-PFPN endows Li metal anodes with dendrite-free, high-efficiency (99.5%) and long-term (1000 h) cycle in Li||Li cells and Li||Cu cells. Meanwhile, PFPN also facilitates the formation of robust cathode-electrolyte interphases (CEIs) enriched with LiF. LHCE-PFPN markedly boosts the cycle performance of Li||NCM811 cells even under harsh conditions, including high voltage (4.5 V) and high temperature (60 degrees C), which retains 87.8% of the initial capacity after 500 cycles. This work presents a promising design strategy of efficient nonflammable electrolytes for high-voltage LMBs.

The benzoselenadiazole-based D-A-D polymers have demonstrated significant potential in organic solar cells, due to its lower optical band gap, more red-shifted absorption spectra, good processing ability, and higher hole transport. However, its application in the electrochromic field is relatively limited so far. Therefore, this work presents the design and synthesis of four difluorinated D-A-D monomers. These monomers incorporate difluorobenzoselenadiazole as their electron-withdrawing segment, with thiophene and 3,4-ethylenedioxythiophene (EDOT) serving as the electron-donor components. These monomers were polymerized into D-A-D polymers via electrochemical deposition method, and their optoelectronic properties were systematically investigated. The elongation of the it-conjugated systems of monomers, along with the stronger electron donating ability of the EDOT unit, further reduced the oxidation potential of Se-Th-EDOT to 0.65 V. This change was accompanied by a blue shift in the electronic spectra and a red shift in the emission spectra. Among the polymers, those derived from EDOT-containing monomers exhibited superior performance, including enhanced redox stability, and a notable shift in hue, evolving from green to a sky-blue shade when oxidized. Notably, the P(Se-Th-EDOT) exhibited remarkable electrochromic performances, featuring an optical contrast of 33.21 %, response times within the range of 0.4-0.80 s, and a coloration efficiency reaching to 160.08 cm2 C- 1. Devices based on P (Se-Th-EDOT) further shown improved coloration efficiency (228.66 cm2 C-1) and rapid response times (0.05-0.28 s). The research outcomes underscore the suitability of D-A polymers that incorporate difluorinated benzoselenadiazole for the advancement of state-of-the-art electrochromic applications.

In this work, two pairs of D-A-D type isomeric monomers, ETTD, EBDD and EETTD, EEBDD, were designed and synthesized by modifying the orientation of the thiophene ring and the conjugation length of the molecular backbone based on benzodithiophene-4,8-dione acceptor units. We also successfully synthesized polymers PEETTD and PEEBDD via electrochemical polymerization, but failed to obtain PETTD and PEBDD from ETTD and EBDD. These subtle structural changes significantly impacted the optical and electrochemical properties and polymerization of the monomers. Notably, EEBDD exhibited the lowest onset oxidation potential (0.44 V) and the strongest absorption at 486 nm, while EETTD displayed the most red-shifted absorption edge. PEEBDD demonstrated impressive electrochromic properties, including a better optical contrast of 39.9% and a coloration efficiency of 320.7 cm2 C-1 at 660 nm when compared to PEETTD. These results reveal the importance of thiophene ring orientation and conjugation length in tuning the electrochromic performance of polymers, offering a promising approach for designing high-performance electrochromic materials.

In this study, two difluorinated D-A polymers, P(FF-Th) and P(FF-EDOT), were prepared through electrochemical deposition method. The two polymers originated from difluorinated D-it-A-it-D monomers were synthesized via Stille coupling, using thiophene and EDOT as donors. Subsequently, several analytical techniques were employed to evaluate the optoelectronic and electrochromic properties of the two difluorinated D-A polymers. Furthermore, to reveal the intrinsic mechanisms influencing their performance, the impact of the thiophene donor units' structure on the electrochromic properties of the synthesized polymers was thoroughly explored. Contrary to FFTh, FF-EDOT features a lower initial oxidation potential, thereby easing the synthesis of superior-quality difluorinated polymers with a diminished polymerization potential. In addition, the difluorinated P(FF-EDOT) films retain an impressive 77.4 % of their redox activity even after 1000 cycles. The fluorescence spectra and UV of FF-EDOT show a redshift after introducing the EDOT unit. Studies using electrochemical and spectroelectrochemical methods indicate that both polymers have hole-doping and electron-doping characteristics. Notably, P(FF-EDOT) has a smaller optical band gap, lower oxidation potential, and better dynamic stability. The optical band gap of these two newly developed difluorinated D-A polymers can be adjusted, with their electrochromic properties being significantly influenced by the differing electron-donating capacities of their thiophene-based donor units.

We designed and synthesized two monomers, TTTPA and TETPA, by inserting the EDOT and thiophene unit as it-bridges between thiophene unit and nitro-substituted triphenylamine (TPA) through Stille coupling reaction, and the corresponding polymers PTTTPA and PTETPA were also prepared by electrochemical polymerization. Both TTTPA and TETPA displayed the red-shifted absorption spectra and lower onset oxidation potential, in particular, TETPA possessed a much lower initial oxidation potential of 0.68 V than its counterpart TTPA (1.00 V) without it-bridges. In addition, PTTTPA possessed the reversible and stable color change from yellow to gray between the neutral and oxidized state with a higher optical contrast of 27.1 %, and exhibited a higher coloration efficiency of 134.43 cm2 C-1 when compared with PTTPA and PTETPA. These results demonstrated that the reasonable introduction of it-bridges could optimize the electrochromic performance of TPA- based polymer.

As an electron donor group, alkoxy was very effective in improving the optoelectronic properties of conjugated polymers. To investigate the impact of incorporating alkoxy groups on the electrochromic characteristics of hybrid electrochromic polymers, in the course of this study, three methoxylated monomers, namely EOMeE, E2OMeE, and EMeE, were readily synthesized via the Stille coupling reaction. The fabrication of the respective methoxylated polymers, specifically P(EOMeE) and P(E2OMeE), was accomplished utilizing the electrochemical deposition method. Subsequently, a comprehensive investigation was conducted to analyze their molecular configurations, optical characteristics, electrochemical behavior, and electrochromic attributes. Notably, aside from EMeE, which is challenging to electro-polymerize into stable films, the other two methoxylated monomers exhibit low initial oxidation potentials ranging from 0.55 to 0.6 V. This feature is highly advantageous for fabricating high-quality electrochromic polymers at reduced potentials. With the increase of methoxy substitution numbers, the ultraviolet and fluorescence of the monomer have a certain degree of red shift trend, accompanied by the decrease of fluorescence quantum yield. As prepared methoxylated polymer also possesses excellent redox activity and outstanding redox stability. It is marked by reliably high and steady variations in transmittance throughout the near-infrared range, in conjunction with excellent optical stability and a beneficial memory effect. Concurrently, the addition of methoxy groups markedly decreases the response time of the hybrid methoxylated polymers to below 1 s and preserves a high coloration efficiency of over 164.52 cm2 C-1 across the full wavelength range. These findings suggest that the synthesized methoxylated hybrid polymers are highly promising for use in electrochromic devices.

In this paper, two di-nitrated D-pi-A-pi-D type monomers with di-nitrated benzothiadiazole as the acceptor unit, EDOT as the donor unit, and EDOT and 3-dodecylthiophene as the pi-bridge units, respectively, were successfully synthesized by Stille coupling reactions, and their corresponding di-nitrated polymers (P(2EDOT-2NO2-BT) and P (EDOT-C12Th-2NO2-BT)) were obtained by electrochemical polymerization method. Through optical, cyclic voltammetry, spectroelectrochemistry and kinetic studies, the effects of pi-bridge units on the optoelectronic properties, electrochemical and electrochromic properties of di-nitrated monomers and their corresponding D-A polymers were systematically discussed, and the structure-property relationship was further revealed. Compared to the monomer 2EDOT-2NO2-BT that using EDOT as the pi-bridge unit, the absorption and fluorescence spectra of EDOT-C12Th-2NO2-BT that using 3-dodecylthiophene as the pi-bridge unit are blue-shifted, with a larger Stokes shift (196 nm) and optical band gap (1.76 eV). Both of these di-nitrated monomers have very low fluorescence quantum yields and onset oxidation potentials (0.74-0.77 V), which make them ideal for electrodepositing high-quality electrochromic polymer films. Due to the loose and porous surface morphology, both these two di-nitrated polymers exhibit favorable redox activity and redox stability (the retained electroactivity of them were both over 80 % after 1000 cycle), as well as favorable electrochromic performance with obvious and reversible multicolor color change, good optical stability, decent optical contrast (33.24 %), short response time (as low as 1.5 s), good coloration efficiency (152.47 C-1 cm2) and memory effect. Overall, both these two di-nitrated polymers have good redox stability and electrochromic properties, opens new possibilities for electrochromic devices based on the di-nitrated polymers.

To investigate the effects of heteroatom substitution and fluorination, two novel D-pi-A-pi-D type monomers (BSeT-E and FBSe-T-E) were synthesized by replacing the S atom in benzothiadiazole with Se and introducing a F atom. The polymers, P(BSe-T-E) and P(FBSe-T-E), were prepared via electrochemical deposition. The resulting monomers and polymers exhibited lower band gaps and red-shifted absorption spectra compared to sulfur-based analogs, alongside a reduced onset oxidation potential due to selenium substitution (slightly countered by fluorination). P(BSe-T-E) exhibited excellent redox stability, retaining 99 % electrochemical activity after 1000 cycles. Both of them exhibited distinct color changes: P(BSe-T-E) switched from brownish-yellow to sapphire blue, and P(FBSe-T-E) from deep black to deep blue. Notably, at 1100 nm, P(BSe-T-E) demonstrated a high optical contrast of 34.66 %, a coloration efficiency of 133.08 cm2 C- 1, and a rapid response time of 0.63 s. Additionally, it exhibited a significant memory effect. These findings not only highlight the promising application potential of BSe-based acceptors, but also expand the application of benzene heterocyclic compounds in the electrochromic field.