EDOT Units Research Articles

Effect of EDOT contribution on the electrochromic and capacitive properties of edot-carbazole based electrochromic polymer: Electrochromic and supercapacitor device applications

3,4-ethylenedioxythiophene (EDOT) based donor-acceptor-donor (DAD) type conjugated polymers generally have extraordinary electrochromic properties due to the excellent nature of the EDOT unit. This work investigates the electrochromic properties of such a system; EDOT-Carbazole-EDOT (ECE) based DAD type of conjugated polymer. Electrochemically synthesized homopolymer film (PECE) showed multichromic behavior with excellent optical properties such as 34 % of optical contrast, subsecond switching response (0.96 s at 478 nm), high coloration efficiency (519 cm2/C at 478 nm) and remarkable specific capacitance (3.04 F/cm2). Inserting more EDOT units into the polymer matrix of PECE via electrochemical synthesis altered the spectral and capacitive behaviors of the resulting copolymers. 2:1 (ECE:EDOT) feeded copolymer exhibited better electrochromic performance than equal feeded copolymer. On the other hand, the capacitive range and capacitance stability were significantly enhanced as the EDOT unit increased in the copolymer matrix.PECE and its copolymers were used to construct dual-type electrochromic devices with poly(3, 4-ethylenedioxythiophene) (PEDOT). ECDs of PECE and copolymers exhibited superior stability upon many switchings, with subsecond switching responses. Furthermore, ECDs can be switched effectively even at the scan rate of 500 mV/s without any loss in charge/discharge amounts. Finally, electrochromic supercapacitor device applications were performed, and a 1.5 V-LED was lighted for up to 25 s with the copolymer supercapacitor device.

Nitrated benzothiadiazole-based D-A electrochromic polymers with tunable spectral properties

Nitrated benzothiadiazole (BT) is the promising acceptor units in constructing D-A-D electrochromic polymers, but its researches in the electrochromic field was very limited so far. In this work, four kinds of nitrated polymer precursors (Th-NO2-BT, EDOT-NO2-BT, Th-2NO2-BT, and EDOT-2NO2-BT) were synthesized by Stille coupling reaction with EDOT and thiophene units as the end groups (electron donor units) and mono-nitrated benzothiadiazole and di-nitrated benzothiadiazole as the core groups (electron acceptor units). The chemical structure and optical properties of the precursor were investigated by means of 1H NMR, UV–vis absorption and fluorescence spectra; the corresponding mono-nitrated polymer films were obtained in CH2Cl2-Bu4NPF6 system by electrochemical deposition method. The optical band gap of di-nitrated polymer precursor is obviously larger than the corresponding mono-nitrated polymer precursor (both ultraviolet and fluorescence spectra are obviously blue-shifted), accompanied with the obvious increased initial oxidation potential. Due to the fluorescence quenching effect of -NO2 group, their absolute quantum yields are all very low (0.0006–0.015). The spectroelectrochemistry and electrochromic kinetics of mono-nitrated polymer films (P(Th-NO2-BT) and P(EDOT-NO2-BT)) were studied. It was found that P(EDOT-NO2-BT) can show better electrochromic performance than P(Th-NO2-BT), with dark green in the neutral state and more obvious electrochromic performance in the near-infrared region (optical contrast: 38.4 %, coloration efficiency: 129.1 cm2/C, and fast response time: 1.4 s). This systematically study about the effects of nitro substitution effect on the properties of D-A electrochromic polymers, which will further expand the selection of the new acceptor units and the application prospect of nitrated electrochromic materials.

Modulating Surface Cation Concentration via Tuning the Molecular Structures of Ethylene Glycol-Functionalized PEDOT for Improved Alkaline Hydrogen Evolution Reaction.

The sluggish catalytic kinetics of nonprecious metal-based electrocatalysts often hinder them from achieving efficient hydrogen evolution reactions (HERs). Poly(3,4-ethylenedioxythiophene) (PEDOT) and its derivatives have been promising materials for various electrochemical applications. Nevertheless, previous studies have demonstrated that PEDOT coatings can be detrimental to HER performance. In this study, we investigated the alkaline HER efficiency of nickel foam coated with three types of ethylene glycol (EG)-functionalized EDOT. Specifically, EDOT derivatives bearing hydroxyl (-OH) and methoxy (-OCH3) end groups on the EG side chain and molecules containing two EDOT units are interconnected via EG moieties. EG groups are selected due to their strong interaction with alkali metal cations. Intriguingly, improved HER performance is observed on all electrodes coated with EG-functionalized EDOTs. Electrochemical impedance spectroscopy, electrochemical quartz crystal microbalance with dissipation, and XPS analysis are employed to explore the origin of enhanced HER efficiency. The results suggest the EG moieties can induce locally concentrated ions near the electrode surface and facilitate water dissociation through noncovalent interactions. The influence of EG chain length is systematically investigated by synthesizing molecules with di-EG, tetra-EG, and hexa-EG functionalities. This study highlights the importance of molecular design in modifying electrode surface properties to promote alkaline HER.

3D Conjugated Hole Transporting Materials for Efficient and Stable Perovskite Solar Cells and Modules.

The orthogonal structure of the widely used hole transporting material (HTM) 2,2',7,7'-tetrakis(N, N-di-p-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD)imparts isotropic conductivity and excellent film-forming capability. However, inherently weak intra- and inter-molecular π-π interactions result in low intrinsic hole mobility. Herein, a novel HTM, termed FTPE-ST, with a twist conjugated dibenzo(g,p)chrysene core and coplanar 3,4-ethylenedioxythiophene (EDOT) as extended donor units, is designed to enhance π-π interactions, without compromising on solubility. The three-dimensional (3D) configuration provides the material multi-direction charge transport as well as excellent solubility even in 2-methylanisole, and its large conjugated backbone endows the HTM with a high hole mobility. Moreover, the sulfur donors in EDOT units coordinate with lead ions on the perovskite surface, leading to stronger interfacial interactions and the suppression of defects at the perovskite/HTM interface. As a result, perovskite solar cells (PSCs) employing FTPE-ST achieve a champion power conversion efficiency (PCE) of 25.21% with excellent long-time stability, one of the highest PCEs for non-spiro HTMs in n-i-p PSCs. In addition, the excellent film-forming capacity of the HTM enables the fabrication of FTPE-ST-based large-scale PSCs (1.0cm2) and modules (29.0cm2), which achieve PCEs of 24.21% (certificated 24.17%) and 21.27%, respectively.

Enhancement of thermoelectric performance of thienoisoindigo based D‐A conjugated polymers through the incorporation of 3,4‐ethylenedioxythiophene as donor unit

AbstractWith the good planarity of conjugated backbone and high charge carrier mobilities, thienoisoindigo (TIIG)‐based polymers show great potential in organic electronic devices. In this work, two TIIG‐based D‐A conjugated polymers (PTIIG‐3T and PTIIG‐2T‐EDOT) were designed and synthesized, which exhibit high lying highest occupied molecular orbital (HOMO) energy level and can be facilely doped by FeCl3. Compared with PTIIG‐3T, one thiophene unit in the donor building block is replaced by 3,4‐ethylenedioxythiophene (EDOT) in PTIIG‐2T‐EDOT, and PTIIG‐2T‐EDOT shows a higher HOMO level with slightly higher coplanarity than PTIIG‐3T, which induce an enhancement in electrical conductivity after oxidation doping. After proper doping, doped PTIIG‐2T‐EDOT film achieved a higher TE power factor of 17.9 μW m−1 K−2 than that of PTIIG‐3T due to its higher conductivity. The results indicate that TIIG unit is a promising building block for future high‐performance conjugated polymers for thermoelectric applications, and incorporation of the EDOT unit into D‐A conjugated polymers could be an effective way to develop high performance thermoelectric polymers.

Mono-chlorinated benzothiadiazole: A new electron-deficient unit for constructing high performance D-A electrochromic polymers

Chlorinated benzothiadiazole (Cl-BT) unit, as a new type of electron-accepting building block with the advantages of easy large-scale synthesis in high yields, has been found to be very promising in designing high performance electroactive polymers with decent optoelectronic properties. Most recently, the Cl-BT unit-based D-A polymers have been applied in many organic electronic devices, but little attention was paid to their electrochromic applications. Herein, in this work, to further evaluate the electrochromic performances of the Cl-BT unit-based chlorinated D-A polymers, two new D-π-A-π-D type chlorinated monomers (Cl-Th and Cl-EDOT) which using mono-chlorinated benzothiadiazole unit as the acceptor unit and thiophene/3,4-ethylenedioxythiophene (EDOT) as the donor unit, was successfully synthesized by Stille coupling reaction and then yield their corresponding chlorinated polymer films (P(Cl-Th) and P(Cl-EDOT)) by electrochemical deposition method. Due to the stronger electron donor ability of EDOT unit, the monomer Cl-EDOT has red-shifted UV–Vis and emission spectra and more significant Stoke's shifts. The lower oxidation potential of Cl-EDOT was very beneficial for improving its resultant D-A chlorinated polymer's optoelectronic properties. As a result, as-formed lower band gap P(Cl-EDOT) (∼1.31 eV) showed reversible color change from the neutral dark green to the oxidized dark blue accompanied with outstanding electrochromic properties, including high optical contrast (24.3%), speedy response time (0.6 s), and high coloration efficiency (170.8 cm2/C), as well as favorable redox stability (70% activity retention after 1000 cycles). The favorable electrochromic performances and good optical stability of P(Cl-EDOT) make it a promising candidate in electrochromic devices. Overall, the chlorinated benzothiadiazole and its derivatives were promising building blocks in constructing high-performance D-A electrochromic polymers.

Different donors' effect on the electrochemical behavior and electrochromic performances of the D-A type chlorinated polymers

Chlorination has proved to be an efficient method in tuning energy levels and optoelectronic properties of organic semiconducting materials with cheaper synthesis and low-cost raw materials when compared with the fluorinated analogues. Herein, in this work, 5-chlorobenzo[c][1,2,5]thiadizole (Cl-BT) unit was chosen as a new acceptor unit to design two new D-A type electrochromic conjugated polymer: P(Cl-T) and P(Cl-EDOT). The electrochemical behavior and electrochromic performances of above-mentioned chlorinated polymers were studied by electrochemical polymerization techniques and spectroelectrochemistry. Thanks to the strong electron-withdrawing ability of Cl-BT unit and the strong electron-donating properties of EDOT unit, the resultant Cl-EDOT precursor could electropolymerize into high quality hybrid polymer films at lower potential (0.71 V vs. Ag/AgCl) with favorable redox activity and better redox stability. Spectroelectrochemistry shown that as-formed lower band gaps P(Cl-EDOT) exhibits reversible color-changing nature from pale blue to gray accompanied with the moderate optical contrast (13.9%), fast response time (0.6 s), and favorable coloration efficiency (126.4 cm2 C−1) in the NIR region that was measured from the kinetic studies. By optimizing the tested electrolyte and solution, its electrochromic performance is further improved (optical contrast: 25.6%, response time: 0.25 s, coloration efficiency: 275.9 C−1 cm2). The favorable redox stability and electrochromic performance of P(Cl-EDOT) make it a good candidate to construct electrochromic device, and Cl-BT unit should be a promising building block in designing high performance near infrared electrochromic materials.

Electrochemical copolymerization of 3,4-ethylenedioxythiophene and dithienothiophene: influence of feed ratio on electrical, optical and electrochromic properties.

Designing a copolymer is an efficient and alternative method to generate new chemical and physical properties compared to parent homopolymers without complex synthesis and structural modification. We herein report the electrochemical deposition of copolymer using two monomers 3,4-ethylenedioxythiophene (EDOT) and dithieno[3,2-b:2',3'-d]thiophene (DTT). Three different copolymers P[EDOT-co-DTT] were synthesized by using different feed ratios of monomers (EDOT and DTT molar ratios in solution are 2 : 1, 1 : 1 and 1 : 2) in acetonitrile containing 0.1 M tetrabutylammonium perchlorate (TBAClO4) as a supporting electrolyte. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and UV-vis-NIR spectroscopy were employed to characterize the obtained copolymers. Energy dispersive X-ray spectroscopy (EDX) analysis was used to estimate the composition of EDOT and DTT units in copolymers. The electrochemical and morphological properties were analyzed using cyclic voltammetry (CV) and field emission scanning electron microscopy (FESEM). In situ spectroelectrochemistry and electrochromic studies were performed to investigate the optical and switching properties of the resultant copolymers. The homopolymers poly(3,4-ethylenedioxythiophene) (PEDOT) and polydithieno[3,2-b:2',3'-d]thiophene (PDTT) were also prepared using similar electrochemical conditions and made comparisons where applicable. Computational calculations were done to understand the structure and energy levels of these polymers. It was found that these copolymers P[EDOT-co-DTT] show new properties as compared to homopolymers PEDOT and PDTT for organic electronic applications. Interesting to note that the resultant copolymers display the property of tunable electrochromism with improved transmittance and redox color change between the neutral and oxidized states.

Multicolor electrochromic polymers based on butterfly-shaped monomers for the visualization of energy storage

Electrochromic supercapacitors (ECSCs) enable visual indication of their energy storage, thus effectively preventing them from being overcharged or insufficient energy. The current studies mainly focus on improving its specific capacitance and cycling stability. Herein, two butterfly-shaped triphenylamine-thiophene derivatives with twisted molecular structures were designed and synthesized featuring an EDOT unit as the central core. Then, two conjugated polymers pBTTPAE and pETPAE were prepared through electrochemical polymerization. Both polymers exhibit distinct multicolor display behavior, faster response time and excellent cycling stability. GCD tests show that pBTTPAE exhibited a higher volumetric specific capacitance (324.4 F·cm−3) and GCD stability due to its high specific area. The prototype device based on pBTTPAE is remarkable for its impressive energy density of 17.94 mWh·cm−3 and power density of 6.32 W·cm−3, which can be switched reversibly from yellow to yellow-green and blue when the potential changes from -0.4 V to 1.5 V. The high-performance electrochromic supercapacitor materials demonstrate their extensive utilizations for intelligent energy-storage devices.

Theoretical and experimental investigation of bridging atom effect on the fluorene and silafluorene based trimeric monomers and their corresponding polymers

A series of monomers bearing fluorene and silafluorene with different bridging atoms and 3,4-ethylenedioxythiophene (EDOT) and 3,4-propylenedioxythiophene (ProDOT) as the donor units were synthesized via Stille coupling. To investigate the effect of different donor units and different bridging atoms, the optical and electrochemical behaviors of the monomers and their corresponding polymers were investigated by some electroanalytical and spectroscopic techniques. Electropolymerization of monomers was carried out potentiodynamically via repetitive cycling. Electrochemical investigations revealed that silafluorene bearing monomers and their corresponding polymers were found to exhibit slightly lower oxidation potentials and lower band gap (Eg) values as compared to their fluorene-containing analogs. Moreover, a comparison between two different donor groups revealed that the Eg of polymers bearing EDOT units was found to be lower (about 0.30 eV) as compared to ProDOT bearing ones due to the twist structure of ProDOT that reduces the overlap between the oxygen lone pairs and the aromatic thiophene ring. The results were further confirmed by DFT calculations.

Hunting black color via absorption engineering: EDOT and thiophene-benzothiadiazole based black-to-transmissive copolymer and its electrochromic device application

Neutral state black electrochromics are prominent materials for smart applications such as displays, car rear views, e-papers etc. This work has aimed to obtain a neutral state black electrochromic polymer, by tuning the optical absorbance to whole visible region. Two monomers, 4,7-bis(5-(thiophen-2-yl)thiophen-2-yl)benzo[c] [1,2,5]thiadiazole (TTBTT) and 3,4-ethylenedioxythiophene (EDOT), were selected according to their complementary absorbance behaviors, and they were combined in the same polymer backbone via electrochemical copolymerization technique. Copolymerization was performed using three different monomer feed ratios (2:1, 1:1 and 1:2 (EDOT: TTBTT)). Even though all the copolymers exhibited dark to transmissive colors from neutral to oxidized states, changing the monomer feed resulted in different optical contrast, switching response and color hues for each copolymer. The higher optical contrast (from 17% to 27%) and faster switching response (from 3.6 s to 1.8 s) were recorded as EDOT unit increase in the copolymer chain. A dual type electrochromic device was also constructed using the copolymer and the resulting device was successfully changed its color from black to transmissive.

Conjugated Polymers Containing EDOT Units as Novel Materials for Electrochromic and Resistance Memory Devices.

Four new multifunctional polymers (P1, P2, P3, and P4) containing EDOT units were synthesized by the Stille coupling reaction. A PL spectrum test found that the introduction of large conjugated groups led to strong fluorescence emission in all polymers. Among the electrochromic and switch properties, these polymer films exhibited reversible color changes, as well as good coloring efficiency. Electrochemical experiments found that the initial oxidation potentials of the polymers were 1.27 V, 1.67 V, 1.78 V, and 1.58 V, respectively. Among them, P3 showed a higher coloring efficiency (283.3 cm2·C-1), and P2 showed a shorter response time (tc = 2.2 s, tb = 2.8 s). These polymers all exhibited electrochromic and resistive switching storage characteristics. They have good solubility in many organic solvents. In the resistance switch memory characteristics, all polymers had obvious memristive properties, and P4 exhibited a larger switch current ratio (2527.42) and a smaller threshold voltage (0.9 V).

Tetraphenylsilane-based oligo(azomethine)s containing 3,4-ethylenedioxythiophene units along their backbone: Optical, electronic, thermal properties and computational simulations

A series of three new oligo-poly(azomethine)s (o-PAzMs) were successfully synthesized, incorporating tetraphenylsilane (TPS) and 3,4-ethylenedioxythiophene (EDOT) moieties with Mn and Mw between 3.9 and 5.4 kDa and 8.3–11.6 kDa, respectively. The silylated o-PAzMs were highly soluble in low-boiling point solvents such as CHCl3, THF, and CH2Cl2. All three materials are highly thermally stable, with onset temperatures of degradation of at least 250 °C and with TDT10% between 340 and 460 °C. The glass transition temperature values agree with the flexibility of the repetitive units and showed values between 125 and 155 °C. The absorption and emission of the o-PAzMs were observed in the blue-violet UV–vis region (350–550 nm) with moderate Stokes shifts (48–71 nm). The oligomers are π-conjugated wide-band gap materials (2.83–2.73 eV), where the high electronic transitions would be associated with disruption of π-conjugation, which is promoted by the TPS core and (d-p)π orbital interactions. This disruption controls the effect from the EDOT unit rich donor on HOMO (−5.79 eV to −5.71 eV) and LUMO (−2.98 eV to −2.89 eV) energy values. Furthermore, DFT and TDDFT calculations were performed to theoretically characterize the observed UV–Vis transitions and frontier molecular orbitals (MOs) energies.

PEDOT-graphene counter-electrode for solar and improved artificial light conversion in regular, bifacial and FTO-less cobalt mediated DSSCs

Dye-sensitized solar cells (DSSC) are emerging as an attractive indoor photovoltaic technology to address the challenge of sustainable powering wireless sensor nodes for Internet of Things (IoTs) and low power consuming electronics. This study reports on new highly electrochemically active PEDOT:PSS (PP) and graphene nanoplatelets (GNPs) composite layer with protruding morphology as counter-electrode for Co(III/II) mediated DSSCs. The PP:GNP counter-electrode layer displays an apparent activation energy (Ea) for charge transfer with Co(bpy)3+/2+ ions of 6.2 kJ•mol−1, almost twofold lower than pristine PP. The fraction of oxidized EDOT units in the polymer increased upon graphene nanoplatelets doping; the work function of PP:GNPs catalyst was best suited to the Co(bpy)3+/2+ redox potential than pristine PP. Despite the significant difference in the catalytic activity, conventional DSSCs with PP and PP:GNP counter-electrodes display similar power conversion efficiency (PCE) of 11.0% and 10.7%, respectively, under 1-Sun illumination. A considerable advantage of the PP:GNP counter-electrode layer emerges under artificial light; DSSCs with PP:GNP cathode render PCE of 29.7% at 1000 lx, surpassing the counterparts with PP counter-electrode. Protruding from the PP matrix film, GNPs particles shorten the effective diffusion path for Cobalt ions and decrease the device resistance; higher photocurrent is possible under low power illumination. Transparency of ca. 65% in the visible region and superior electrical conductivity of the PP:GNP films allow using them in FTO-less bifacial devices; DSSCs with bare soda-lime glass substrates for the cathode displayed a PCE of 9.4% under 1-Sun and 21.9% and 18.7% under 1000 lx, for front and back illumination respectively. This makes PP:GNP counter-electrode very attractive for the cost-effective DSSCs targeting indoor light conversion.

Synthesis and fast switching electrochromic properties of conjugated microporous polymers based on carbazole-thiophene derivatives

To study the relationship between chemical structure and switching time of electrochromic polymer materials, four star-shape monomers, 3,6-di(thiophen-2-yl)-9-(4-(thiophen-2-yl)phenyl)-9H-carbazole (M1), 2,7-di(thiophen-2-yl)-9-(4-(thiophen-2-yl)phenyl)-9H-carbazole(M2), 3,6-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9-(4-(thiophen-2-yl) phenyl)-9H-carbazole(M3) and 2,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9-(4-(thiophen-2-yl)phenyl)-9H-carbazole(M4) were designed and synthesized successfully, their chemical structure were characterized by nuclear magnetic resonance (NMR) and high resolution mass spectrum (HRMS). Their resulting polymer films could be obtained by electropolymerization, all the polymer films showed well-defined electrochemical properties except for PM2, the PM3 and PM4 revealed wider electrochemical response due to the existence of EDOT units. The surface morphology results indicated that all the polymer films consisted of many particles, and PM1 and PM3 showed smaller grain than that of PM2 and PM4 due to the different aggregation structure, which might benefit for the transport of doped ions. Electrochromic kinetic studies confirmed such hypothesis furtherly, PM3 revealed fastest switching time (Tc: 0.72 s and Tb: 0.61 s), the reason could be explained by electrochemical impedance spectroscopy, which indicated that PM3 possessed the smallest charge transfer resistance (Rct) and fastest diffusion coefficient values at the oxidation state. We hope these findings will provide a little effect on designing and synthesizing high performance electrochromic materials and devices.

Influence of alkyne spacers on the performance of thiophene-based donors in bulk-heterojunction organic photovoltaic cells

The ever-increasing demand for renewable energy has led to the intensification of research focused upon harnessing the abundant energy from sunlight. Solution processed organic solar cells fabricated using conjugated polymer donor materials dominated the early development of organic photovoltaics (OPV). More recently, organic solar cells fabricated using small molecule donors have become increasingly attractive due to the advantages these systems have over their polymeric counterparts. These include reproducible synthesis and the ability to more accurately develop structure-activity relationships. Here, we report the synthesis of thiophene based small molecule donors that have been used to investigate the influence of alkyne π-spacers on the optical, electronic and photovoltaic properties of solution-processable bulk-heterojunction (BHJ) organic OPV cells. Additionally, we compare the addition of 3,4-ethylenedioxythiophene (EDOT) units in place of the end-thiophene of these derivatives. We found that the compounds featuring alkyne moieties displayed poor charge transfer and blue-shifted UV–vis spectra, whereas the incorporation of the EDOT units increased charge transfer for the non-alkyne derivative resulting in red-shifted absorbance. DFT calculations predicted higher charge separation/mobility and lower charge generation for the compounds without alkyne units. Indeed, greater Jsc values and higher PCEs were found for the compounds lacking alkyne spacers. EDOT containing compounds showed poor performance which is likely due to an unfavourable morphology and higher HOMO level, leading to lower Voc. Hence, the simplest 5T-1 molecule showed the highest performance of 3.24%, which is c.a. 1.6x that of the alkyne-containing 5TA-1 and c.a. 2.9x that of the EDOT-containing derivative. This study demonstrates that alkyne spacers can be detrimental to orbital interactions, charge transfer and OPV performance, and that the EDOT unit can be added to provide greater charge transfer due to its auxiliary donating ability. However, careful design is required to ensure higher Voc values and a favourable morphology in thiophene-based solution-processable OPVs.

Synthesis and third-order nonlinear optical properties of low band gap 3,4-ethylenedioxythiophene-thiophene copolymers

Alternate donor–acceptor 3,4-ethylenedioxythiophene (EDOT) based copolymers with thiophene and 3-methyl thiophene were designed by employing density functional theory (DFT) in the periodic boundary condition using HSE06 exchange correlation functional and 6-31G basis set. The designed copolymers were synthesized via a simple and facile route, i.e., direct arylation and their third-order nonlinear optical properties were investigated by Z-scan technique. The resultant copolymers, P(EDOT-THP) and P(EDOT-MeTHP) were characterized by spectroscopic analysis. The photophysical and electrochemical properties of EDOT-thiophene copolymers were investigated by UV–visible spectra and cyclic voltammetry, respectively. The copolymers revealed low band gap and better electronic properties as compared to the homopolymers. The introduction of EDOT unit in the polythiophene leads to decreased HOMO-LUMO energy levels, and the absorption spectra was red shifted when compared with that of the parent compound. The nonlinear absorption and nonlinear refraction coefficient of copolymers have been investigated at 532 nm. The optical limiting properties of copolymers have also been measured. The copolymers exhibited strong optical nonlinearity owing to the presence of alternate donor-π-acceptor scheme in the polymers.

The synthesis of alternating donor-acceptor polymers based on pyrene-4,5,9,10-tetraone and thiophene derivatives, their composites with carbon, and their lithium storage performances as anode materials.

Two conjugated polymer@activated carbon composites were synthesized by the in situ polymerization of two donor–acceptor type polymers including poly[(thiophene-2,5-yl)-((pyrene-4,5,9,10-tetraone)-2,7-yl)] (PTPT) and poly[((2,3-dihydrothieno[3,4-b][1,4]dioxine)-5,7-yl)-((pyrene-4,5,9,10-tetraone)-2,7-yl)] (POTPT) on activated carbon (AC) by one-step cross-coupling reaction catalyzed by an organometallic catalyst. Cyclic voltammetry showed that both polymers exhibited ambipolar properties, low bandgaps, and low electrode potentials, which could be useful for their application as anodes in lithium-ion battery cells (LIBs). For PTPT@AC and POTPT@AC anodes, they showed a high capacity of 253.9 and 370.5 mA h g−1 at 100 mA g−1. Besides, the capacities of pure polymers were calculated to be 693.5 and 1276.5 mA h g−1 for PTPT and POTPT, respectively, at 100 mA g−1. Compared with PTPT, the introduction of the 3,4-ethylenedioxy unit into the side chain of the thiophene unit leads to substantially improved performance of POTPT due to the lowered LUMO energy levels of POTPT and the electron-rich feature of the EDOT unit. It is suggested that the structure-tuning strategy might be an effective method to prepare the new polymer-based anode for next generation LIBs with high performance and high safety.

Design of twisted conjugated molecular systems towards stable multi-colored electrochromic polymers

Promising advancement of conjugated polymers in electrochromic devices require to design high-performance electrochromic polymers with rich color conversion and long-term stability under cyclic electrical loads. Here we report a new strategy in developing multi-colored electrochromic polymers with good stability via twisted conjugated molecular engineering. A series of twisted hybrid precursors are synthesized by coupling ortho-alkylenedioxybenzenes with EDOT units, and their corresponding polymers are facilely electrosynthesized at relatively low polymerization potentials. The structure-property relationships of such ortho-alkylenedioxybenzene-EDOT hybrid precursors and polymers are systematically elucidated via DFT calculations, spectral, morphological, electrochemical and spectroelectrochemical analysis, etc. We demonstrate that the dihedral angle between ortho-alkylenedioxybenzenes and EDOT moieties can substantially affect the electrochemical and electrochromic properties of polymers. As the dihedral angle and electron cloud density increases, these hybrid polymers display distinct multiple color switching nature and good overall performance including high coloration efficiency (>200 cm2 C−1), decent optical contrast (>45%), fast switching (<1 s), and excellent switching stability (96% of optical contrast after 3500 cycling) under cyclic electrical loads. With these findings, this work will provide novel insights for rational design of stable and highly efficient multi-colored electrochromic polymers.

Enhancing electrochemical and electrochromic performances of carbazole comprising monomer via copolymerization with 3,4-ethylenedioxythiophene (EDOT)

In this study, two novel electrochromic copolymers (CoP1.3 and CoP1.5) were synthesized via electrochemical methods and characterized. The comonomers used in the synthesis were 3,4-ethylenedioxythiophene (EDOT) and a carbazole comprising monomer; 9-(2-(4-(Phenyldiazenyl) phenoxy) ethyl)-3,6-di(thiophen-2-yl)-9H-carbazole (M1). Carbazole containing monomer (M1) and EDOT were combined with two different comonomer feed ratios, 1: 3 and 1: 5 respectively in order to investigate the effect of increasing EDOT amount on electrochemical, spectroelectrochemical and electrochromic behaviors. The electrochemical and spectroelectrochemical characterizations of the electrochemically obtained copolymers were performed by cyclic voltammetry (CV) and UV–vis-NIR spectrophotometry. Both copolymers exhibited p-type doping with reversible oxidation potentials reported at 0.23 V/0.93 V for CoP1.3 and 0.30 V/0.98 V for CoP1.5. The difference between these oxidation potentials could be dedicated to the difference in electron density in the copolymer chains. Optical band gap values were calculated from neutral state absorptions as 1.21 eV and 1.18 eV for CoP1.3 and CoP1.5, respectively. Due to the higher EDOT amount in the copolymer backbone, the band gap for CoP1.5 is lower than that of CoP1.3. Both CoP1.3 and CoP1.5 exhibited multichromic behavior with different colors in the neutral and oxidized states. While both copolymers (CoP1.3 and CoP1.5) exhibited purple color in the neutral states, the colors turned to blue colors upon applied potentials. Optical contrast values were calculated as 31 % (at 555 nm), 55 % (at 1050 nm) and 38 % (at 1240 nm) for CoP1.3 and 34 % (at 565 nm), 25 % (at 975 nm) and 45 % (at 1170 nm) for CoP1.5. As a result of electrochromic switching studies, switching times (oxidation) were calculated as 2.5 s, 1.7 s, 1.9 s for CoP1.3 and 1.9 s, 1.8 s, 2.7 s for CoP1.5. Furthermore, addition of EDOT unit into copolymer backbone resulted in the obvious improvements in electrochemical, optical, electrochromic and kinetic properties. Copolymers exhibited full visible absorption with red-shifted neutral state absorption, lower optical band gap values compared to those of homopolymers.