Performance Of Electrochromic Devices Research Articles

High-Performance Black Copolymers Enabling Full Spectrum Control in Electrochromic Devices.

Black-to-transparent electrochromism is hailed as the holy grail of organic optoelectronics. Despite its potential, designing black electrochromic materials that fully absorb visible light remains a significant challenge. Electroactive materials that simultaneously possess excellent cyclic stability, fast switching times, and high coloration efficiency are rare. In this study, we successfully designed copolymers that fully absorb the entire visible spectrum byjudiciously selecting four types of monomers. We incorporated two types of polar side chains to synergistically enhance the ionic conductivity of the copolymers, thus improving the performance of electrochromic devices. Among these electrochromic devices, the P2-a device exhibits cycling stability exceeding 105 cycles, and the P2-c device demonstrates a coloring/ bleaching time of 0.82 s/0.86 s and achieves a coloration efficiency of 1078 cm²/C. This study proposes a strategy for designing and synthesizing high-performance black electrochromic copolymers.

Study on Two Inorganic Consumables in PMMA Electrochromic Devices Based on Work Function Differences

In electrochromic devices, the dielectric layer is not only an electrode dielectric, but also can provide compensating ions for electrochromism. In this paper, three composite porous materials, PMMA/SiO2, PMMA/TiO2, and PMMA/SiO2/TiO2, were prepared and assembled using polymethyl cellulose (PMMA) as the polymer matrix, impurity medium (SiO2) and titanium dioxide (TiO2) inorganic polymers, and the effect of doping two inorganic porous materials on the electrochromic performance was studied. The optical recovery and cycle stability of electrochromic wear of the PMMA/SiO2/TiO2 composite structure are significantly improved compared with the loss of other ceramic structures. Cyclic voltammetry analysis shows that the lithium ion diffusion coefficient of the electrochromic device using the PMMA/SiO2/TiO2 composite ceramic structure is the largest, which is 2.5 × 10−14 cm2​ s−1 . The improvement of electrochromic performance is mainly due to the difference in work function between SiO2 and TiO2 on the figure of merit diagram, which leads to the directional movement of the resonator, accelerates the transmission rate of Li+ and further optimizes the electrochemical properties of the composite ceramic. This study provides an effective method to improve the performance of electrochromic devices.

Optimization of photoelectric properties of transparent conductive B and Ga co-doped ZnO films for electrochromic applications

To improve the performance of electrochromic devices, it is urgently necessary to develop transparent indium-free conductive electrodes with high conductivity and transparency. In this study, thin films of Ga-doped ZnO (GZO) and B–Ga co-doped ZnO (BGZO) were prepared on glass substrates using the plasma-assisted atomic layer deposition (PEALD) technique, and their structural and optoelectronic properties were characterized. It is found that all thin films were consistent with hexagonal fibrous ZnO structure, and the surface morphology of the membrane was homogenous at nanoscale. UV spectroscopy analysis showed that the doping of B and Ga elements could increase the transparency of ZnO films. The electrical properties can be remarkably enhanced by doping with B and Ga elements. Further more, tungsten oxide (WO3) was deposited on the as-prepared BGZO films using magnetron sputtering method. We activated the sample by applying voltage and observed a color transition from transparent to dark blue. It has a modulation range of 65 % in the 633 nm spectrum and a coloring efficiency of 37.8 cm2C-1. This work opens up remarkable new opportunities for developing high-performance transparent conductive electrode in electrochromic devices.

Advances in the Study of Gel Polymer Electrolytes in Electrochromic Devices

The electrolytes in electrochromic devices (ECDs) serve as a conduction medium between electrodes and providing compensating ions for electrochromic reactions. Their characteristics directly affect the performance of electrochromic devices. Due to their ease of processing and encapsulation and high ionic conductivity, polymer gel electrolytes are widely used in electrochromic devices. As gel electrolyte polymers, polyethylene oxide (PEO), polymethyl methacrylate (PMMA), and polyvinylidene fluoride (PVDF) are reviewed according to their polymer matrix. Furthermore, future development trends in gel polymer electrolytes are discussed.

Investigating the performance of electrochromic device based on nanostructured molybdenum-doped tungsten trioxide and aniline/O-anisidine copolymer

Electrochemical staining (electrochromism) is a phenomenon related to the reversible color change by external potential. In this research, two electrochromic (EC) systems have been studied: molybdenum-doped tungsten trioxide as cathodic material (Mo-WO3) and aniline/O-anisidine copolymer (PANI-co-POA) as anodic material. Both films were synthesized by electrochemical polymerization on indium tin oxide (ITO). In order to fabricate the electrochromic device (ECD), the cell of ITO/Mo-WO3/polyvinyl alcohol (PVA), 0.5 M H2SO4/PANI-co-POA/ITO was provided. Mo-WO3 and PANI-co-POA were characterized using EDS, FT-IR, XRD, FE-SEM and TEM. Structure distortion may be induced by doping of Mo atoms into WO3 structure. The amorphous state of Mo-WO3 has desirable electrochemical behavior due to increasing in active sites and access of electrolyte. In addition, PANI-co-POA as counter electrode material has high electrical conductivity and causes to fast kinetic of charge transfer in ECD. The electrochromic properties of PANI-co-POA and Mo-WO3 films were evaluated by UV–Visible spectroscopy (UV–Vis), cyclic voltammetry (CV) and chronoamperometry (CA). The optical response times of ECD were 1.8 s for coloration (tc) and 2 s for bleaching (tb). The coloration efficiency (CE) of the specimens was also calculated at 633 nm for Mo-WO3 (144.19 cm2 C−1), PANI-co-POA (35.81 cm2 C−1) and ECD (99.70 cm2 C−1). The results showed that the use of both Mo-WO3 (cathode) and PANI-co-POA (anode) leads to improvement in the electrochromic properties of ECD.

Synergistic Electric and Thermal Effects of Electrochromic Devices.

Electrochromic devices are the preferred devices for smart windows because they work independently of uncontrollable environmental factors and rely more on the user's personal feelings to adjust actively. However, in practical applications, the ambient temperature still has an impact on device performance, such as durability, reversibility and switching performance, etc. These technical issues have significantly slowed down the commercialization of electrochromic devices (ECDs). It is necessary to investigate the main reasons for the influence of temperature on the device and make reasonable optimization to enhance the effectiveness of the device and extend its lifetime. In recent years, with the joint efforts of various outstanding research teams, the performance of electrochromic devices has been rapidly improved, with a longer lifetime, richer colors, and better color contrast. This review highlights the important research on temperature-dependent electrochromic properties in recent years. Also, the reported structures, mechanisms, characteristics, and methods for improving electrochromic properties are discussed in detail. In addition, the challenges and corresponding strategies in this field are presented in this paper. This paper will inspire more researchers to enrich the temperature-dependent properties of ECDs and their related fields with innovative means and methods to overcome the technical obstacles faced.

Minimized optical scattering of MXene-derived 2D V2O5 nanosheet-based electrochromic device with high multicolor contrast and accuracy

An electrochromic device (ECD) based on the redoxation of the transition metal oxide (TMO) is a key technology for obtaining a stable and efficient color display. Developing the TMO-based electrochromic layer in a complex nanotexture can effectively acquire additional surface redox sites for improved ECD performance, while the increased roughness compensates the color range and accuracy through the excessive scattering effect. In this paper, we report the fabrication of a two-dimensional (2D) V2O5 nanosheet through the oxidation of single-layer V2CTx MXene. Benefitting from the high aspect-ratio morphology, the 2D V2O5 nanosheet-based electrochromic layer was fabricated in the optimized nanotexture with significantly reduced number of scattering sites such as surface roughness and internal voids, while acquiring large ion capacitance. The 2D V2O5 nanosheet-based ECD exhibited vibrant multicolor transformation with excellent optical contrast (53.98 %), response time (6.5 s for coloration and 5.0 s for bleaching) and coloration efficiency (91.1 cm2 C−1), which were far more superior to those obtained from a commercial V2O5 powder. In our study, we provide a new perspective based on optical engineering for designing electrochromic materials with the desired color variations.

Highly Transparent Conjugated Polymer as the Counter Electrode in Electrochromic Smart Windows

AbstractA highly transmissive counter electrode material (CEM) at both neutral and doped states in the visible range is essential for the optical performance of electrochromic devices (ECDs), but is rarely reported due to the challenge in molecular design. Herein a novel conjugated polymer HTCP is reported, which exhibits a wide bandgap (3.02 eV) and a strong absorption at 300 nm in its neutral state. Upon oxidation, the absorption spectrum is substantially red‐shifted, peaking at 900 nm. Thus HTCP can keep high transparency throughout the whole visible range at both states, making it particularly well‐suited as the CEM in ECDs, which is demonstrated by the excellent optoelectronic performance of a smart window‐type ECD in this work. Furthermore, the geometric and electronic configuration study of its building block reveals that HTCP evolves from a closed‐shell butterfly‐like folded structure into a twisted geometry featuring a quinoidal open‐shell character after oxidation, explaining the nature of its unique optical properties. This work provides new insights and explicit instructions for the structural design of conjugated polymer‐based CEMs. In addition, it offers a clear scenario for the application of open‐shell materials in optoelectronics, not only limited to the chemical fundamental studies.

MoS2 nano-flower incorporation for improving organic-organic solid state electrochromic device performance

A solid state electrochromic device has been fabricated using molybdenum disulfide (MoS2) doped Ethyl viologen (EV) and polythiophene (P3HT) layers. The MoS2 nano flower has been synthesized by one-step hydrothermal method and characterized by electron spectroscopy, X-ray diffraction and Raman spectroscopy. The prepared solid state electrochromic device shows its improved electrochromic performance like switching speed, cycle life and coloration efficiency while showing color modulation between magenta and blue colors. A very small external (±1.4 V) bias is sufficient to switch the device very quickly by taking time as low as 400 ms and shows the transmittance modulation of 42%. It is proposed that the MoS2 having graphene like 2D layered structure and the weak van der Waals force present between layers facilitates large amount of charge movement between the film and electrolyte, hence, promoting the high transfer rate of electrons, which plays the key role to enhance the performance of electrochromic device. Incorporation of MoS2 makes one of the most efficient devices in the family of polythiophene-viologen based devices and opened up a new avenues for other hybrid electrochromic device as graphene alternatives by exhibiting coloration efficiencies of as high as 580 cm2/C.

Robust non-complementary electrochromic device based on WO3 film and CoS catalytic counter electrode with TMTU/TMFDS2+ redox couple

To realize the long-term stability of the WO3-based electrochromic devices (ECDs), the ECDs based on CoS catalytic counter electrodes (CCEs) and a transparent electrolyte containing tetramethylthiourea/tetramethylformaminium disulfide (TMTU/TMFDS2+) redox couple are newly designed. The incorporation of CoS CCEs effectively enhances the reactivity of TMTU/TMFDS2+ redox couple and the electrochromic performance of ECDs. Electrocatalytic activities of the CoS films were systematically investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization measurements. Among CoS CCEs with different electrodeposition times, CoS-15 (electrodeposition for 15 times) electrode exhibits excellent catalytic activity for TMTU/TMFDS2+ redox couple, and simultaneously maintains high transmittance (~80%). The assembled WTC-15 (WO3//TMTU/TMFDS2+//CoS-15) device can achieve low driven voltage (−1.2 V for coloring and 1.0 V for bleaching), rapid switching speed (7.3 s for coloring and 5.9 s for bleaching), and high coloration efficiency (71.2 cm2 C−1). Additionally, the device shows a high transmittance contrast of 67.8% at 648 nm and can be stably switched for >100,000 cycles with <5% contrast attenuation. To our best knowledge, this is the best cycling performance for hybrid WO3-based ECDs ever reported. Meanwhile, this research expands the list of potential counter electrodes (CoS, NiS, and MoS2) in ECDs, which can solve the problem of charge mismatch between electrodes. Moreover, it is the first time that the electrocatalytic ability of transition-metal sulfides on TMTU/TMFDS2+ redox couple has been reported.

Highly-concentrated electrolyte incorporating Li-ion solvation sheath interphase for encapsulation-free organic electrochromic devices

Electrolytes play an essential role in boosting the performance of electrochromic devices (ECDs), nevertheless, the detailed impact of highly-concentrated electrolytes (HCEs) on electrochromism remains elusive. In this work, we creatively report an eco-friendly, aqueous HCE based on lithium bis (trifluoromethanesul-phonyl)-imide (TFSILi), and investigate the potential of developed electrolyte for ECD applications through combining experimental and molecular dynamic simulation approaches. The radial distribution function calculations reveal that the primary solvation sheath of Li-ion is greatly alterd by the concentration of electrolyte. The formation of Li-ion solvation sheath containing TFSI− in electrolyte protects the electrochromic (EC) layer from being destroyed by free water. Mean squared displacement shows that the diffusion coefficient of Li-ion in 15 M HCE reaches up to 8.5 × 10−11 m2/s, indicating that high ion mobility enables faster charge transfer and efficient transport of Li-ion promotes interfacial reaction kinetics, which correlates-well with the experimental conductivity results. These findings demonstrate that HCEs can substantially improve the performance of organic ECDs, especially in terms of device stability, optical memory and switching rate. Notably, the solvation sheath nature of the developed HCE enables the development of encapsulation-free devices, which is greatly attractive for the industrialization of EC technology.

Development and analysis of nanomaterial membrane device

In the contemporary era of research and development, energy efficient gadgets like electrochromic devices (ECD) drag an eye for their functionality and suitability. Modern world of Nanomaterials looks forward to enhance the electrochromic device performance for their unique physical and chemical properties. In this paper, an innovative nanomaterial membrane (NMM) device with ITO coated glass is employed along with WO3, NiO and Li doped NiO is developed, characterized and analyzed for transmittance modulation, optical density and switching time. The transmittance at colouration and bleaching conditions is also compared with an existing ECD of a similar material based device structure. The newly developed NMM device showed a transmittance enhancement reaching a peak of ∼88% at bleaching condition in the visible spectrum range. Additionally, optical density and switching time are also investigated and the NMM outshined proving to be extremely beneficial.

Redox Electrolytes for Hybrid Type II Electrochromic Devices with Fe−MEPE or Ni1−xO as Electrode Materials

AbstractThe use of redox electrolytes in electrochromic devices (ECDs) based on cathodically coloring metallopolymers (MEPEs) and various redox mediators, including potassium hexacyanoferrate(II)/(III) (KHCF(II)/(III)), ferrocene/ferrocenium (Fc0/+) and tetramethyl thiourea/tetramethylformaminium disulfide (TMTU/TMFDS2+), was investigated. By decreasing the concentration of KHCF(III) in the electrolyte, it was possible to significantly reduce the loss current. Although the unpleasant yellow tint could be diminished with lower concentrations, Prussian blue (PB, Fe4[Fe(CN)6]3) was formed during cycling. Fc0/+ and TMTU/TMFDS2+ were studied as the basis of alternative redox electrolytes and characterized in terms of their electrochemical and optical properties. The maximum visible light transmittance changes (Δτv) of 50 % and 48 % were reached with the MEPE reference ECD and the MEPE‐ECD with 0.001 M TMTU/TMFDS2+, respectively. Finally, an ECD combining an anodically coloring non‐stoichiometric nickel oxide (Ni1−xO) electrode with a TMTU/TMFDS2+ (molar ratio: 1/0.1) containing electrolyte exhibits a maximum Δτv of 32 %, with τv ranging from 38 % in the dark state to 70 % in the bright state. These results imply that incorporating redox mediators into the electrolyte provides a straightforward and effective means of simplifying device structures and improving the performance of ECDs based on MEPEs and metal oxides.

Synergistic Effect of Al3+/Li+-Based All-Solid-State Electrochromic Devices with Robust Performance

In the electrochromic devices (ECDs), the commonly employed active ions are monovalent ions, such as Li+, for the advantages of small ionic radius and high ion transportation. However, monovalent ions still show several disadvantages, including poor chemical stability, expensive costs, difficult waste disposal, and so on. Here, we proposed a synergistic Al3+/Li+ all-solid-state electrochromic device prepared by magnetron sputtering, which extracts the essence of trivalent ion Al3+ and monovalent ion Li+ and remove their dross. It has been demonstrated that the introduction of Li+ ions can activate the Al3+ ions in the solid electrolyte, and both Al3+ and Li+ ions can induce the electrochromic reaction in the all-solid-state ECDs. The synergistic effect of Al3+/Li+ can promote the performance of ECDs, which includes high optical contrast of 56%, fast coloration time of 9.73 s and bleaching time of 2.98 s, and relatively high coloration efficiency of 62.81 cm2·C–1. Our findings are expected to provide a novel strategy for the utilization of trivalent ions in all-solid-state electrochromic devices.

Implementation of high-performance electrochromic device based on all-solution-fabricated Prussian blue and tungsten trioxide thin film

Electrochromic devices (ECDs) rely on interfacial charge-transfer and ion transport. They generally suffer from a decline in their operational performance, which is caused by irreversible redox reactions, ion accumulation, or overpotential at the solution/electrode interface. Herein, we implement high-performance ECDs with excellent optical modulation (45.9%), fast switching speed (3 s), high coloring efficiency (98.1 cm2/C), and excellent long-term performance (>1000 cycles) under the bias of 0.7 V through in-depth optimization of device components and modulation of its driving characteristics. Three requirements for device structure and operation were considered to implement high-performance ECDs; i) uniformity and robustness of the electrochromic (EC) film in the working electrode (WE), ii) high surface area and fast redox properties of the complementary electrode, iii) total offsetting of the charge applied in the device during the coloring/bleaching process. Various electrodeposition methods such as galvanostatic, potentiostatic, pulsed potential, and triple pulse potential application were exploited to fabricate the active layers, and the active layers produced under optimized conditions through individual studies on the most stable film stability, electrochemical behavior, EC and ion storage characteristics were assembled in the devices. Under all optimized conditions, we constructed high-performance ECDs composed of electrodeposited Prussian blue (PB) as an EC layer and tungsten trioxide (WO3) as a complementary layer, respectively. In particular, the offset of the charge applied to the device between the coloring and bleaching processes drastically improved the long-term stability of EC performance under low operating bias. The results provide a useful basis for enhancing the performance of ECDs and can be widely applied to various ECDs.

Facile sol–gel fabrication of MoS2 bulk, flake and quantum dot for electrochromic device and their enhanced performance with WO3

Low–temperature fabrication of electrochromic device (ECD) is an attractive characteristic, supporting their use in smart windows and flexible devices. In this study, different MoS2 morphologies (bulk, flake and quantum dots) are fabricated onto indium tin oxide using the sol–gel method. The ECD performance of the fabricated MoS2 devices is optimized, and then the MoS2 bulk, flake and quantum dots are used as electrochromic anodic layers, with WO3 as cathodic layer to prepare MoS2/WO3–based ECDs. The fabricated MoS2/WO3 ECDs are found to exhibit high optical contrasts (59–75%) at 1.5–0 V and 700 nm. In addition, the stability, switching time and coloration efficiency of the MoS2 devices are found to be improved by the WO3 layer. When MoS2 quantum dot film is used as an electrochromic layer, it shows better ECD performance with WO3 than films prepared with either bulk or flake MoS2. It could be expected that the MoS2 quantum dot morphology allows more Li+ ions to penetrate the crystal lattice, promoting a greater charge transfer, which is crucial for the enhanced electrochromic property. This work provides an encouraging support for the application of cost effective, solution–processed MoS2/WO3–based ECDs, working at low temperature and low voltage, to the processing of flexible and optical devices.

The electrochromic device performance with DNA based electrolyte

The influence of the DNA based electrolyte on the electrochromic device performance designed with two different working electrodes is presented. The novelty of the present research consists in the use of DNA membrane with different LiClO4 ratios in order to achieve new electrochromic windows with good performances. For this purpose, two different working electrodes and the same counter electrode were used and compared for assembling different devices as glass/ITO/Prussian Blue (PB)/DNA membrane/CeO2–TiO2/ITO/glass and glass/ITO/WO3/DNA membrane/CeO2–TiO2/ITO/glass. The main goal is to find the optimum LiClO4 ratio into the membrane's composition, which promotes the best ionic conductivity required for a good ECD performance. In the selection of the best DNA membrane the FT-IR, UV-VIS spectroscopy, and the ionic conductivity results were used. The two working electrodes were analyzed by contact angle and surface free energy. The electrochromic devices were evaluated by charge density measurements, cyclic voltammetry, and chronoamperometric cycling coupled with UV-VIS spectroscopy. The obtained results showed that the best composition of the DNA based membranes is 1 wt% of LiClO4 (DNA1GLY1LP1), and the electrochemical and spectroscopic performance of ECDs were similar for PB and WO3 as working electrodes. Nevertheless, the Prussian Blue electrode showed an almost constant transmission variation after a number of consecutive cycles of colour change.

High-performance electrochromic device based on polythiothene/poly(3-thiophene boronic acid) bilayer film

Abstract In this article, electrochromic polymer bilayer film on indium tin oxide (ITO) coated glass is built as electrode to facilitate the diffusion and migration of ions in electrochromic devices (ECDs). We investigate the performance of device based on the bilayer film using polythiothene (PT) and poly(3-thiophene boronic acid) (P3TBA) as model polymers. Notably, the incorporation of thin P3TBA layer (P3TBA has a high polarity) can change the surface morphology of PT film (rough and uncompacted), and increase the surface area of PT/P3TBA film, which will benefit the diffusion and migration of ions in ECD based on PT/P3TBA bilayer film on ITO glass (PT/P3TBA/ITO). As a result, the performance of ECD based on PT/P3TBA/ITO is significantly improved, which exhibits a highly optical contrast (48%), coloration efficiency (298 cm2/C), short response time (the coloration time and bleaching time are 5.27 and 0.48 s), and stable cycling. Compared with ECD based on PT film on ITO glass (PT/ITO), the optical contrast of ECD based on PT/P3TBA/ITO increases 200% (16% → 48%), and its coloration efficiency increases 54% (193 → 298 cm2/C). This study suggests that rational design of bilayer film micromorphology on electrode level might be a useful strategy for fabricating high performance polymer ECDs.

Effect of trifluoromethyl substituents in benzyl-based viologen on the electrochromic performance: Optical contrast and stability

Viologen (V) based molecules are classic and prestigious electrochromic (EC) materials which have dramatic optical contrast and tunable coloring states in solution-type electrochromic devices (ECDs). However, the stability of viologen based ECDs was significantly reduced by the dimer formation, and the resultant aggregation of viologens, which may occur once viologen dication (V2+) was reduced to viologen radical cation (V+•). To diminish this phenomenon, two novel symmetric benzyl-based viologens including 1,1′-bis(3,5-bis(trifluoromethyl)-benzyl)-4,4′-bipyridine-1,1′-diium (DTFMBzV) and 1,1′-bis(4-(trifluoromethyl)benzyl)-4,4′-bipyridine-1,1′-diium (TFMBzV) with various numbers of trifluoromethyl (CF3) substituents were synthesized and studied in this work. Substituent of CF3 in benzyl-based viologens not only enhance its optical property by increasing the π‒conjugation of bipyridine, but also avoid the aggregation by repulsing the viologen with fluorine atoms. The electrochromic performance of ECDs consisted of benzyl viologen (BzV/Fc ECD) and benzyl-based viologens with various numbers of CF3 substituents (DTFMBzV/Fc ECD and TFMBzV/Fc ECD) incorporated with ferrocene (Fc) were studied. According to the result of UV–vis absorbance spectra, the absorbances of benzyl viologen-based ECDs were strengthened at 399 and 605 nm by increasing the number of CF3 substituents. The DTFMBzV/Fc ECD gives a high transmittance change (ΔT) of 63.5% at 605 nm initially with a short response time (<3 s) by biasing the cell potential from 0 to 1.1 V. As for the stability, the DTFMBzV/Fc ECD exhibits an extremely high retention (97% of its initial ΔT) after switching for 10,000 cycles, which implied the dimerization of viologen was diminished by introducing the CF3 substituents with stronger electrostatic repulsion. As the result, DTFMBzV/Fc ECD exhibited the best electrochromic performance in terms of optical contrast and long-term stability. This study provides a simple yet effective strategy to tailing the electrochromic properties of viologen molecules for further application in electrochromism.

Yellow-to-blue switching of indole[3,2-b]carbazole-based electrochromic polymers and the corresponding electrochromic devices with outstanding photopic contrast, fast switching speed, and satisfactory cycling stability

Three novel π-conjugated indolo[3,2-b]carbazole derivatives, 2,8-di(thiophen-2-yl)-5,11-dioctyl-indolo[3,2-b] carbazole (TICZ), 2,8-bis(4-ethylthiophen-2-yl)-5,11-dioctyl-indolo[3,2-b]carbazole (ETICZ) and 2,8-bis(2-(3,4-ethylenedioxythiophene))-5,11-dioctyl-indolo[3,2-b]carbazole (EDTICZ), were synthesized and electrochemically polymerized to afford the corresponding polymers. The effects of different substituent groups on thiophen units in terms of optical, electrochemical, and electrochromic properties and the performance of electrochromic devices (ECDs) were investigated in detail. Electrochemical and optical analysis demonstrated that incorporation of strong auxochromic groups resulted in polymer PEDTICZ with low oxidation potentials, red-shifted absorption peaks and corresponding narrow band gap values but is unfavorable for incorporating ethyl groups. Spectroelectrochemical studies indicated an evident variation in the absorption spectra as well as significant color changes for all of the polymer films upon application of an external potential. PTICZ had high optical contrast with visible light (58.6%), fast switching speed (0.92 s), and satisfactory coloration efficiency (167 cm2 C−1). Of these three systems, the results for PEDTICZ were next best, and those for PETICZ were third. Also, there was a larger contrast (82.7% and 57.8%) in the NIR region (1500 nm) for the PTICZ and PEDTICZ films, respectively. Along with high coloring efficiencies, these results indicate that these systems are favorable for many NIR applications.