Thiophene-based Polymers Research Articles

Synthesis and thermal behaviour of thiophene-based oxazine-ring substituted benzoxazine monomers & polymers.

The latest fourth-generation oxazine-ring substituted thiophene-based benzoxazine monomers and polymers with variation in the degree of phenyl substitution (with and without) in the oxazine-ring were synthesized and characterized. Thiophene-based di-substituted benzoxazine undergoes ring-opening polymerization at a low temperature with a minimal mass loss during polymerization as supported by molecular geometry-guided intramolecular interactions. This class of monomers provides ample opportunities to design at the molecular level high-performance polybenzoxazines with promising smart applications.

Vis-to-NIR electrochromism and bright-to-dark electrofluorochromism in a triazine and thiophene-based three-dimensional covalent polymer

Two triazine and substituted thiophene-based donor–acceptor covalent polymeric frameworks are developed to exhibit the Vis-to-NIR electrochromism and bluish-green-to-quenched electrofluorochromism, simultaneously in a +1.8 to −0.9 V potential range.

Side chain engineering of indacenodithieno[3,2-b]thiophene (IDTT)-based wide bandgap polymers for non-fullerene organic photovoltaics

The highest power conversion efficiency of indacenodithieno[3,2-b]thiophene-based polymers blending with non-fullerene acceptors is obtained based on optimal side chain engineering.

Toward the Rational Design of Organic Solar Photovoltaics: Application of Molecular Structure Methods to Donor Polymers.

Conjugated polymers are promising candidates in the design of polymer solar cell materials with suitable electronic properties. Recent studies show that the use of different functional groups as side chain in thiophene-based polymers changes the electronic and conformation structures. Here we design new thiophene-based molecules by replacing the hydrogen attached to the backbone of P3MT with electron-donating and electron-withdrawing groups. We then calculate the HOMO, LUMO, and HOMO–LUMO energy gap to quantify the theoretical merit of the new polymers as solar absorbers and their inter-ring torsional potential to understand their suitability to link together in high conductivity, extended conjugated systems. Calculations are done with first-principles density functional theory (DFT), implemented using B3LYP with dispersion function and 6-31G(d,p) as basis set. Our results show that the HOMO–LUMO gap is sensibly lowered by donating groups and we found that the substitution of the hydrogen with −NH2, and −F gives an energy gap lower than the energy gap of P3MT. The lowest energy gap was found when substituting with −NH2. Electron-withdrawing groups lower the HOMO, with the overall lowest found when −NO2 is used. −COCl, −CONH2, and −Cl give a steric hindrance greater than that of PTB7, which is set as reference. Our calculations show a possible approach to the rational design of donor materials when substituents are inserted systematically in a generic oligomer.

Unveiling the Enzymatic Degradation Process of Biobased Thiophene Polyesters.

In the past 20 years, scientific research focused on the identification of valid alternatives to materials of fossil origin, in particular, related to biobased polymers. Recently, the efforts led to the synthesis of thiophene-based polymers (TBPs), a new class of polyesters based on 2,5-thiophenedicarboxylic acid (TPCA) that can be industrially produced using biomass-derived molecules. In this study, TBPs were synthesized using diols with different chain length (from C4 to C6) leading to poly(butylene 2,5-thiophenedicarboxylate) (PBTF), poly(pentamethylene 2,5-thiophenedicarboxylate) (PPeTF), and poly(hexamethylene 2,5-thiophenedicarboxylate) (PHTF), respectively, that were processed to thin films. To investigate enzymatic hydrolysis of these polymer films, cutinase 1 (Thc_cut1) and cutinase 2 (Thc_cut2) from Thermobifida cellulosilytica were recombinantly expressed in the host E. coli and purified. After 72 h of incubation at 65°C with 5 µM Thc_cut1, weight loss and HPLC analysis indicated 9, 100, and 80% degradation of PBTF, PPeTF, and PHTG with a concomitant release of 0.12, 2.70, and 0.67 mM of TPCA. The SEM analysis showed that tiny holes were formed on the surface of the films and after 72 h PPeTF was completely degraded. The LC-TOF/MS analysis indicated that Thc_cut2 in particular released various oligomers from the polymer during the reaction. In addition, the FTIR analysis showed the formation of novel acid and hydroxyl groups on the polymer surfaces. The results showed that the two used thermostable cutinases are promising biocatalysts for the environmentally friendly degradation of TPCA-based polyesters, in view of a possible sustainable recycling of plastic waste through resynthesis processes.

Benzothiadiazole-Based Double-Cable Conjugated Polymers for Single-Component Organic Solar Cells with Efficiency over 4%

Double-cable conjugated polymers have been successfully applied into single-component organic solar cells (SCOSCs) in recent years. The chemical structures of conjugated backbones and aromatic cable units, and the rational tuning of nanophase separation between them, are clue factors for double-cable polymers to further enhance the photovoltaic performance. In this work, we introduced a benzothiadiazole (BT) unit into the backbone of double-cable polymers, where BT was conjugated with two linkers, thiophene and thienothiophene, which were used to control the aggregation behavior. The studies reveal that, although thiophene-containing polymer backbones show less aggregation tendency, the corresponding perylene bisimide (PBI) side units form better stacking. Therefore, thiophene-based double-cable polymers had high hole/electron mobilities and hence a high efficiency of 4.35%, while thienothiophene-containing polymer exhibited a low efficiency of 2.35%. These results demonstrate that BT-polymers display a promising application for high performance double-cable conjugated polymers for SCOSCs.

Charge-transfer dynamics in van der Waals heterojunctions formed by thiophene-based semiconductor polymers and exfoliated franckeite investigated from resonantly core-excited electrons.

Organic/inorganic van der Waals heterojunctions formed by a combination of 2D materials with semiconductor polymer films enable the fabrication of new device architectures that are interesting for electronic and optoelectronic applications. Here, we investigated the charge-transfer dynamics at the interface between 2D layered franckeite (Fr) and two thiophene-based conjugated polymers (PFO-DBT and P3HT) from the resonantly core-excited electron. The unoccupied electronic states of PFO-DBT/Fr and P3HT/Fr heterojunctions were studied using near-edge X-ray absorption fine structure (NEXAFS) and resonant Auger (RAS) synchrotron-based spectroscopies. We found evidence of ultrafast (subfemtosecond charge-transfer times) interfacial electron delocalization pathways from specific electronic states. For the interface between the PFO-DBT polymer and exfoliated franckeite, the most efficient interfacial electron delocalization pathways were found through π*(S-N) and π*(S-C) electronic states corresponding to the benzothiadiazole and thiophene units. On the other hand, for the P3HT polymer, we found that electrons excited to π-π* and S1s-π*(C-C) electronic states of the P3HT polymer are the most affected by the presence of exfoliated franckeite and consequently are the main interfacial electron-transfer pathways in this heterojunction. Our results have important implications in understanding how ultrafast electron delocalization is taking place in organic/inorganic van der Waals heterojunctions, which is relevant information in designing new devices involving these systems.

N-Type Polythiophene Synthesized By Electro-Polymerization for Perovskite Solar Cell

1. IntroductionRecently, organic solar cells exhibit highly attractive features in realizing large areas, being light-weight, being low-cost and possessing flexible photovoltaic panels compared to traditional silicon-based solar cell. There are mainly two types of organic solar cells, one is dye sensitized solar cell (DSC) and the other one is thin film type. In 2009, new type DSC, Perovskite solar cell (PSC) which consists of lead halide and organic amine, has been developed by Miyasaka1). Initially, photoelectric conversion efficiency was 3.9 %, it has been improving. PSC is composed of electrodes and perovskite, hole transport layer (HTL), electron transport layer (ETL). Generally, spiro-OMeTAD, PEDOT:PSS, or PTAA are used as HTL and mesoporous titanium oxide or mesoporous tin oxide are used as ETL.By the way, conductive polymer, such as PEDOT has electrical characteristic and low cost, is used as new material for energy field. Although, most of them are p-type semiconductor, it can make n-type by electrical or chemical methods that has been clarified from the research until now2). But organic solar cell with n-type conductive polymer used as ETL has not been reported.In this paper, we tried to make n-type conductive polymer by electrochemical method, that is very low cost and simple method. And the performance of PSC with n-type polymer as ETL was evaluated to confirm the property of the polymer.2. Experimental2.1 Electro-polymerization and n-type doping by electrochemical methodThe electrochemical polymerization of polythiophene film was carried out under galvanostatic conditions onto the ITO coating PET film (2.4 cm × 2.4 cm, 10 Ω) by applying a constant current density of 1 mA/cm2 for 8 s or 16 s in acetonitrile solution containing 0.5 M thiophene and 0.2 M tetramethylammonium tetrafluoroborate (TMATFB). After polymerization, thiophene film as cathode and Pt as anode in 0.2 M TMATFB acetonitrile solution, n-type doping was carried out same conditions.2.2 Device fabricationPrepared n-type polymer films were cleaned up for 1 or 10 min with UV-O3. After the cleaning, 80 µL perovskite solution (Cs0.05(FA0.83MA0.17)Pb(I0.83Br0.17)3 in DMF/DMSO) was spin-coated onto the thiophene layer at 1000 rpm for 10 s to 4000 rpm for 30 s in N2 atmosphere. When at 10 s of 4000 rpm, 500 µL chlorobenzene dropped onto the film and then the films were annealed at 100℃ for 1 hour in a glovebox with N2. Then, 50 µL spiro-OMeTAD solution (in acetonitrile) was spin-coated onto the film. After these processes, the cells were dried in dry air overnight. Finally, Au electrodes were evaporated on the surface of the cells with vacuum deposition.2.3 Measurement of cell performancePhotoelectric conversion efficiency for PSC with n-type polymer was measured and J-V curves of the sample cells were recorded.3. Results and Discussion3.1 Characteristics of thiophene polymersElectrically conducting thiophene-based polymers were synthesized by electro-polymerization.Both of conditions, the films were brown only edge and the center was clear. It compared shorter time with longer one, the latter was deeper in color and rougher.3.2 Cell performanceCell performance of the PSC with n-type thiophene polymer was evaluated. Photoelectric conversion efficiency for the cell of 8 s polymerization time with n-doping, 10 min UV-O3, was 0.6 %. On the other hand, the performance with 1 min UV-O3 was 4.4 %. It seems that long UV-O3 treatment damaged thiophene structure. Similar results were obtained for solar cells of 16 s polymerization time.Then, we compared the thiophene with different polymerization time with UV-O3 for 1 min. Solar cell performance of thiophene formed by 8 s polymerization (4.4 %) is about three times better than that of 16 s polymerization (1.5 %). As polymerization time decreases, the thickness and resistance of the film decreases. As a result, the electrical characteristic of film was improved.

Thiophene-based Ni-coordination polymer as a catalyst precursor and promoter for multi-walled carbon nanotubes synthesis in CVD

Enormous technological promise of multi-walled carbon nanotubes (MWCNTs) can only be harnessed with the premise of controllable synthesis of MWCNTs, where catalyst precursor and promoter play vital roles. Herein, we have systematically investigated the effects of pre-treatment of catalyst precursor and promoter and growth conditions of MWCNTs. The highest yield of MWCNTs from thiophene-based Ni-coordination polymer is 10 times as that of our previous work. The results indicate that catalyst precursor and promoter can efficiently tune the morphology, yield and quality of MWCNTs.

Thermally Induced Formation of HF4TCNQ- in F4TCNQ-Doped Regioregular P3HT.

The prototypical system for understanding doping in solution-processed organic electronics has been poly(3-hexylthiophene) (P3HT) p-doped with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). Multiple charge-transfer states, defined by the fraction of electron transfer to F4TCNQ, are known to coexist and are dependent on polymer molecular weight, crystallinity, and processing. Less well-understood is the loss of conductivity after thermal annealing of these materials. Specifically, in thermoelectrics, F4TCNQ-doped regioregular (rr) P3HT exhibits significant conductivity losses at temperatures lower than other thiophene-based polymers. Through detailed spectroscopic investigation of progressively heated P3HT films coprocessed with F4TCNQ, we demonstrate that this diminished conductivity is due to formation of the nonchromophoric, weak dopant HF4TCNQ-. This species is likely formed through hydrogen abstraction from the α aliphatic carbon of the hexyl chain at the 3-position of thiophene rings of rr-P3HT. This reaction is eliminated for polymers with ethylene glycol-containing side chains, which retain conductivity at higher operating temperatures. In total, these results provide a critical materials design guideline for organic electronics.

Thermoelectric properties of a semicrystalline polymer doped beyond the insulator-to-metal transition by electrolyte gating.

Conducting polymer thin films containing inherent structural disorder exhibit complicated electronic, transport, and thermoelectric properties. The unconventional power-law relation between the Seebeck coefficient (S) and the electrical conductivity (σ) is one of the typical consequences of this disorder, where no maximum of the thermoelectric power factor (P = S 2σ) has been observed upon doping, unlike conventional systems. Here, it is demonstrated that a thiophene-based semicrystalline polymer exhibits a clear maximum of P through wide-range carrier doping by the electrolyte gating technique. The maximum value appears around the macroscopic insulator-to-metal transition upon doping, which is firmly confirmed by the temperature dependence of σ and magnetoresistance measurements. The effect of disorder on charge transport is suppressed in the metallic state, resulting in the conventional S-σ relation described by the Mott equation. The present results provide a physical background for controlling the performance of conducting polymers toward the application to thermoelectric devices.

Thiophene-Based Aldehyde Derivatives for Functionalizable and Adhesive Semiconducting Polymers.

The pursuit for novelty in the field of (bio)electronics demands for new and better-performing (semi)conductive materials. Since the discovery of poly(3,4-ethylenedioxythiophene) (PEDOT), the ubiquitous golden standard, many studies have focused on its applications but only few on its structural modification and/or functionalization. This lack of structural variety strongly limits the versatility of PEDOT, thus hampering the development of novel PEDOT-based materials. In this paper, we present a short and simple strategy for introducing an aldehyde functionality in thiophene-based semiconducting polymers. First, through a two-step synthesis, an EDOT-aldehyde derivative was prepared and polymerized, both chemically and electrochemically. Next, to overcome the inability of thiophene-aldehyde to be polymerized by any means, we synthesized a trimer in which thiophene-aldehyde is enclosed between two EDOT groups. The successful chemical and electrochemical polymerization of this new trimer is presented. The polymer suspensions were characterized by ultraviolet-visible-near-infrared spectroscopy, while the corresponding films were characterized by Fourier transform infrared and four-point-probe conductivity measurements. Afterward, insoluble semiconducting films were formed by using ethylenediamine as a cross-linker, demonstrating in this way the suitability of the aldehyde group for the easy chemical modification of our material. The efficient reactivity conferred by aldehyde groups was also exploited for grafting fluorescent polyamine nanoparticles on the film surface, creating a fluorescent semiconducting polymer film. The films prepared by electropolymerization, as shown by means of a sonication test, exhibit strong surface adhesion on pristine indium tin oxide (ITO). This property paves the way for the application of these polymers as conductive electrodes for interfacing with living organisms. Thanks to the high reactivity of the aldehyde group, the aldehyde-bearing thiophene-based polymers prepared herein are extremely valuable for numerous applications requiring the facile incorporation of a functional group on thiophene, such as the functionalization with labile molecules (thermo-, photo-, and electro-labile, pH sensitive, etc.).

The Effect of Oligo(Ethylene Oxide) Side Chains: A Strategy to Improve Contrast and Switching Speed in Electrochromic Polymers.

Solution-processable electrochromic polymers (ECPs) with high performance are urgently needed for extensive applications. Nevertheless, they suffer from slow switching speed because of low ionic conductivities. Herein, we present an effective strategy to improve the contrast and switching speed in ECPs via facile side-chain engineering. A novel electrochromic thieno[3,2-b]thiophene-based polymer (PmOTTBTD) is designed and successfully synthesized by introducing oligo(ethylene oxide) side chains with high ionic conductivity. Compared to the counterpart POTTBTD without modification by oligo(ethylene oxide) chains, PmOTTBTD demonstrates nearly double contrast (42 % vs. 24 %) with a fast oxidation switching process that just takes half of the time when detected under 400 nm, as well as much higher coloration efficiencies (e. g. 239.04 cm2 C-1 vs. 226.26 cm2 C-1 @ 400 nm and 314.04 cm2 C-1 vs. 174.00 cm2 C-1 @ 650∼700 nm). Besides, PmOTTBTD exhibits excellent stability with negligible decay after 3000 cycles. Our work suggests a facile strategy that could be adopted to realize high-performance ECPs via molecular design tuning.

Simultaneous detection of nitrophenol isomers using an easy-to-fabricate thiophene-based microporous polymer film modified electrode

A thiophene-based microporous polymer film modified glassy carbon electrode (GCE) was simply fabricated via one-step template-free electropolymerization in dichloromethane without any surfactant. The prepared electrode exhibited remarkably increased electrochemical responses for nitrophenol (NP) isomers compared to non-modified GCE. The phenomenon could be ascribed to the strong intermolecular interactions between electron-rich, broad-surface-area thiophene-based conjugated microporous polymer film and electron-poor nitro-analytes. The proposed sensor was systematically characterized for its application in the simultaneous determination of nitrophenol isomers. At optimum conditions, the sensor displayed satisfactory linear ranges: 0.3–10 µmol L−1, 0.3–12.5 µmol L−1 and 0.3–15 µmol L−1 for o, m, p-NP, respectively. Excellent detection limits of 0.04 µmol L−1 for o-NP, 0.05 µmol L−1 for m-NP and p-NP were showed. Our results proved that the thiophene-based microporous polymer films obtained by electropolymerization are truly promising in developing electrochemical sensors.

13.9%-Efficiency and Eco-Friendly Nonfullerene Polymer Solar Cells Obtained by Balancing Molecular Weight and Solubility in Chlorinated Thiophene-Based Polymer Backbones.

To industrialize nonfullerene polymer solar cells (NFPSCs), the molecular design of the donor polymers must feature low-cost materials and a high overall yield. Two chlorinated thiophene-based polymers, P(F-Cl) and P(Cl-Cl), are synthesized by introducing halogen effects like fluorine (F) and chlorine (Cl) to the previously reported P(Cl), which exhibits low complexity. However, the molecular weights of these polymers are insufficient owing to their low solubility, which in turn is caused by introducing rigid halogen atoms during the polymerization. Thus, they show relatively low power conversion efficiencies (PCEs) of 11.8% and 10.3%, respectively. To overcome these shortcomings, two new terpolymers are designed and synthesized by introducing a small amount of 1,3-bis(5-bromothiophen-2-yl)-5,7-bis(2-ethylhexyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione (BDD) unit into each backbone, namely, P(F-Cl)(BDD = 0.2) and P(Cl-Cl)(BDD = 0.2). As a result, both polymers remain inexpensive and show a better molecular weight-solubility balance, achieving high PCEs of 12.7% and 13.9%, respectively, in NFPSCs processed using eco-friendly solvents.

Chemistry at the Interface of α-Sexithiophene and Vapor-Deposited Ag, Al, Mg, and Ca: A Molecular View

Interfacial chemistry of thiophene-based polymers and oligomers in contact with low work function metals is of interest for organic electronic devices. Herein, interfacial reactions of the model thiophene-based oligomer, α-sexithiophene (α-6T), in ultrathin (5 ML) films with vapor-deposited Ag, Al, Mg, and Ca are investigated using surface Raman spectroscopy and X-ray photoelectron spectroscopy under ultrahigh vacuum conditions. Although typically considered an electron donor, results indicate that α-6T is reduced by Al and Ca. The reduction product with Al is the tetrahydrothiophene, whereas complete degradation of the thiophene cores occurs with Ca with the formation of calcium sulfide. In contrast, for the higher work function Ag, contact doping from α-6T to Ag nanoparticles is observed, inducing the formation of polaron states at the interface. Inter-ring torsion by the C–C bond rotation is also induced by electron sharing between α-6T and Ag. Mg, which is expected to undergo electron transfer in a ma...

Task-specific synthesis of cost-effective electron-rich thiophene-based hypercrosslinked polymer with perylene for efficient iodine capture

An electron-rich thiophene-based hypercrosslinked polymer knitting with perylene moieties was obtained in the presence of anhydrous ferric chloride. The resultant polymer possessed a specific surface area of 612.83 m2 g−1 and high thermal stability. Taking advantage of electron-rich structure and microporosity as well as high surface area, the material showed high iodine vapor uptake capacity up to 360 wt%. The performance was 13-fold higher than that of the representative porous silver-based zeolite mordenite and was the highest value among the reported thiophene-based porous organic polymers. X-ray photoelectron spectrometer and Raman analysis results demonstrated that the form of captured iodine was polyiodide anions. We envisage practical application of such promising and cost-effective materials in the field of iodine capture.

Ternary Solar Cells Employing Thieno[3,4-b]thiophene-Based Copolymer Offer High Performance with Large Current Density and Fine-Tuned Morphology

A novel thieno[3,4-b]thiophene-based donor polymer PTBTz-2 was used to construct ternary organic solar cells with two classical acceptors 3,9-bis(2-methylene-(3-(1,1-dicyano-methylene)-indanone)-5,...

Conjugation-broken thiophene-based electropolymerized polymers with well-defined structures: effect of conjugation lengths on electrochromic properties.

A series of monomers containing tetraphenylsilane connected to different thiophenes such as thiophene, bithiophene and terthiophene were designed and synthesized and were further used to prepare the corresponding polymers via electrochemical polymerization (pSiTPTP, pSiTPBTP and pSiTPTTP). From the polymers, the effective conjugate elements were well defined as bithiophene, quaterthiophene and sexithiophene because the sp3 Si atom can block the conjugation between the thiophene units in the polymer backbone. The spectroelectrochemical results indicated that pSiTPTP is incapable of electrochromism, which may be attributed to the insufficient conjugation length of the independent bithiophene. In contrast, both pSiTPBTP and pSiTPTTP exhibited obvious electrochromic properties and furthermore, pSiTPTTP displayed a shorter switching time and better stability. Such different electrochemical behaviors can be ascribed to the looser stacking structure and lower oxidation potential of pSiTPTTP with the independent sexithiophene unit. The EIS measurements also confirmed the lower charge-transfer resistance and higher ion-diffusion rate of pSiTPTTP with the independent sexithiophene unit. Hence, we can conclude that the effects of the electrochromic behavior of the conjugation-broken polythiophene derivatives depend on the increased conjugation length of the thiophene repeating unit, in which the inadequate electrochromism with bithiophene units can change to superior electrochromic properties with increased sexithiophene units.

Monte Carlo Algorithm Based on Internal Bridging Moves for the Atomistic Simulation of Thiophene Oligomers and Polymers

We introduce a powerful Monte Carlo (MC) algorithm for the atomistic simulation of bulk models of oligo- and polythiophenes by redesigning MC moves originally developed for considerably simpler polymer structures and architectures, such as linear and branched polyethylene, to account for the ring structure of the thiophene monomer. Elementary MC moves implemented include bias reptation of an end thiophene ring, flip of an internal thiophene ring, rotation of an end thiophene ring, concerted rotation of three thiophene rings, rigid translation of an entire molecule, rotation of an entire molecule, and volume fluctuation. In the implementation of all moves we assume that thiophene ring atoms remain rigid and strictly coplanar; on the other hand, inter-ring torsion and bond bending angles are left fully flexible subject to suitable potential energy functions. Test simulations with the new algorithm of an important thiophene oligomer, α-sexithiophene (α-6T), at a high enough temperature (above its isotropic-to-nematic phase transition) using a new united atom model specifically developed for the purpose of this work provide predictions for the volumetric, conformational, and structural properties that are remarkably close to those obtained from detailed atomistic molecular dynamics (MD) simulations using an all-atom model. The new algorithm is particularly promising for addressing the rich (and largely unexplored) phase behavior and nanoscale ordering of very long (also more complex) thiophene-based polymers which cannot be accessed by conventional MD methods due to the extremely long relaxation times characterizing chain dynamics in these systems.