Thiophene Units Research Articles

Tuning the charge transfer and optoelectronic properties of tetrathiafulvalene based organic dye-sensitized solar cells: a theoretical approach.

Here, we have designed a series of dyes following the donor–π–acceptor (D–π–A) architecture by incorporating tetrathiafulvalene (TTF) as the donor unit and phthalazine (PTZ), diketopyrrolopyrrole (DPP) and quinoxaline (QNX) as the acceptor units, along with the thiophene unit as a π-bridge. The designed dyes have been designated as TTF-PTZ, TTF-DPP and TTF-QNX respectively. We have used cyanoacrylic acid as the anchoring group for the dyes TTF-PTZ and TTF-DPP, while for the third dye, TTF-QNX, we used a carboxylic group. The structural, electronic and photochemical properties of the designed dyes are investigated under the regime of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. In this regard, the dihedral angle, energies of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), energy difference between the HOMO and LUMO (ΔH–L values), partial density of states (PDOS), ground state oxidation potential (GSOP), excited state oxidation potential (ESOP), ionization potential (IP), electron affinity (EA), molecular electrostatic potential surface (MEPS) analysis, reorganization energy (λ), electronic coupling matrix element (V), charge transfer rate (kCT), hopping mobility (μhop), absorption spectra, exciton binding energy (EBE) and electron density difference (EDD) of the designed dyes are calculated. This study reveals that the dyes TTF-DPP-4 and TTF-DPP-6′ exhibit the lowest ΔH–L values. The study also reveals that the attachment of the –NH2 group at the donor unit and the –NO2 and –CF3 groups at the acceptor units lower the ΔH–L values of all of the designed dyes. We have also observed that the GSOP of all the designed dyes lie below the redox potential of the I−/I3− electrolyte couple. However, the ESOP of the TTF-PTZ and TTF-QNX groups of dyes, along with the most of the dyes belonging to the TTF-DPP group, lie above the conduction band of the TiO2 semiconducting surface. Moreover, the total reorganization energy (λtot) values are low for the TTF-DPP and TTF-QNX groups of dyes, which confirm the better electron–hole separation efficiency in these groups of dyes. Furthermore, the absorption properties of the designed dyes indicate that the TTF-DPP groups of dyes possess the maximum absorption wavelength (λmax) values and attachment of the –CH3 group at the donor part increases the electron density of the dyes, which in turn results into the maximum red-shift. Therefore, the study reveals that the designed dyes are likely to exhibit facile charge transport. Moreover, the electronic properties of the dye–TiO2 clusters strengthen the performance of the dyes compared to those of the isolated dyes. Hence, our study provides good recommendations for the further design of dyes to enhance the performance of dye-sensitized solar cells (DSSCs).

Design of ultra-high luminescent polymers for organic photovoltaic cells with low energy loss.

Here, new polymers named PBTT-Cn (n = 3, 4, or 5) have been designed based on carboxylate-functionalized thieno[3,2-b]thiophene units. The electroluminescence external quantum efficiencies (EQEEL) of pristine PBTT-C4 and C5 films are over 1 × 10-2, which are among the highest results for OPV materials. Through combination with BTP-eC9, the PBTT-C4-based film showed a high EQEEL of 6 × 10-4 and the Vnon-radloss is 0.19 eV. As a result, a high open-circuit voltage of 0.89 V and a satisfactory PCE of 15% were recorded in the PBTT-C4-based OPV cells.

Theoretical Designing of Novel Donor Acceptor Type Copolymer Comprising of Thiophene

Using ab initio band structure results of three novel donor acceptor polymers (A)x PCDT, (B)x PMCT and (C)x PFTh as the input, the electronic structures and conduction properties of their periodic and aperiodic copolymer (AmBnCk)x have been investigated. The method involves using negative factor counting method based on Dean’s negative eigenvalue theorem. In this article, the quasi-one-dimensional Type II staggered copolymers comprising of thiophene units on the basis of the band alignments of the constituent homopolymers were studied. The trends in their electronic structures and conduction properties as a function of (i) block sizes (m, n, k) and (ii) arrangement of the blocks (periodic or aperiodic) in the various copolymer chains are discussed. These trends are important guidelines to the experimentalists for designing novel electrically conducting polymers with tailor made conduction properties.

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.

Study on the influence of the introduction of the thiophene group on the photocatalytic performance of polymer

Two novel conjugated organic polymers BTTh-1 and BTTh-2 were designed and synthesized. They were prepared by the reaction of two aldehyde units with melamine. Both aldehyde units were based on benzothiadiazole. The difference between the final aldehyde units was the introduction of thiophene groups in the BTTh-2 aldehyde monomer units. The difference between the two materials in the photocatalytic degradation of tetracycline was discussed in the context of the thiophene unit. The degradation efficiency of tetracycline by BTTh-2 (90.9%) was much higher than that of BTTh-1 (40.7%). The characterization results showed that BTTh-2 has a strong charge separation ability and fast transmission rate. After light excitation, the recombination ability of photogenerated holes and electrons becomes weak, and it has better utilization ability for visible light; the bandgap width is narrower.

Deciphering the Electronic Transitions of Thiophene-Based Donor-Acceptor-Donor Pentameric Ligands Utilized for Multimodal Fluorescence Microscopy of Protein Aggregates.

Anionic pentameric thiophene acetates can be used for fluorescence detection and diagnosis of protein amyloid aggregates. Replacing the central thiophene unit by benzothiadiazole (BTD) or quinoxaline (QX) leads to large emission shifts and basic spectral features have been reported [Chem. Eur. J. 2015, 21, 15133‐13137]. Here we present new detailed experimental results of solvent effects, time‐resolved fluorescence and examples employing multi‐photon microscopy and lifetime imaging. Quantum chemical response calculations elucidate how the introduction of the BTD/QX groups changes the electronic states and emissions. The dramatic red‐shift follows an increased conjugation and quinoid character of the π‐electrons of the thiophene backbone. An efficient charge transfer in the excited states S1 and S2 compared to the all‐thiophene analogue makes these more sensitive to the polarity and quenching by the solvent. Taken together, the results guide in the interpretation of images of stained Alzheimer disease brain sections employing advanced fluorescence microscopy and lifetime imaging, and can aid in optimizing future fluorescent ligand development.

Synthesis, characterization, and their field-effect properties of azaisoindigo-based conjugated polymers with versatile alkoxycarbonyl substituents

In this study, versatile alkoxycarbonyl substituents were incorporated onto the azaisoindigo (AIID)-based polymeric π-skeleton, affording two novel polymers PAZPT and PAZPTEt. The PAZPT has the alkoxycarbonyl groups substituted on its thiophene unit, whereas the PAZPTEt has both the thiophene and thieno[3,2-b]thiophene units substituted with alkoxycarbonyl groups. As result, PAZPT has more planar conjugated backbone conformation than that of PAZPTEt. Experimental characterization results indicated that alkoxycarbonyl substituents can effectively pull down the frontier molecular orbital energy levels and optimize the solubility and molecular packing mode of conjugated polymers. All the field-effect transistors based on the two polymers showed ambipolar carrier transport characteristics. Such results show that introducing alkoxycarbonyl substituents on polymeric π-skeleton might be a potential approach in fine-tuning the semiconducting properties of conjugated polymers.

Triphenylamine dyes bearing 5-phenyl-2-(arylthiophen-2-yl)thiazole bridge for dye sensitized solar cells

Three triphenylamine dyes were synthesized with 5-phenyl-2-(arylthiophen-2-yl)thiazole as π bridge and cyanoacrylic acid as the acceptor. Three dyes differ in the aryl ring binding with the acceptor in the π bridge, which leads to different photophysical properties, molecular planarity, energy level and accordingly the photoelectric conversion efficiency. The insertion of furan and thiophene units in π bridge attain broader absorption spectra and better molecular coplanarity, contributing to the distinct improvement of JSC and hence the photovoltaic performance. On the other hand, the presence of benzene unit raises the LUMO level and increases the drive force for the electron injection into TiO2, which enhance VOC. Among three dyes, dye bearing two thiophene units sensitized DSSC achieves a cell efficiency 6.90% due to better JSC (14.09 mA cm2) and VOC (0.73 V).

Design of Thienothiophene-Based Copolymers with Various Side Chain-End Groups for Efficient Polymer Solar Cells.

Three two-dimensional donor–acceptor conjugated copolymers consisting of a benzo[1,2-b:4,5-b′]dithiophene derivative and thieno[3,2-b]thiophene with a conjugated side chain were designed and synthesized for use in bulk heterojunction (BHJ) or nonfullerene polymer solar cells (PSCs). Through attaching various acceptor end groups to the conjugated side chain on the thieno[3,2-b]thiophene moiety, the electronic, photophysical, and morphological properties of these copolymers were significantly affected. It was found that the intermolecular charge transfer interactions were enhanced with the increase in the acceptor strength on the thieno[3,2-b]thiophene moiety. Moreover, a better microphase separation was obtained in the copolymer: PC71BM or ITIC blend films when a strong acceptor end group on the thieno[3,2-b]thiophene moiety was used. As a result, BHJ PSCs based on copolymer:PC71BM blend films as active layers exhibited power conversion efficiencies from 2.82% to 4.41%, while those of nonfullerene copolymer:ITIC-based inverted PSCs ranged from 6.09% to 7.25%. These results indicate the side-chain engineering on the end groups of thieno[3,2-b]thiophene unit through a vinyl bridge linkage is an effective way to adjust the photophysical properties of polymers and morphology of blend films, and also have a significant influence on devices performance.

Electron Donor‐Acceptor Spirobi[cyclopenta[2,1‐b : 3,4‐b′]dithiophene] Derivatives as Precursors of Electrodeposited Regioregular Thiophene‐based Polymers

AbstractA series of conjugation extended push‐pull derivatives of 4,4′‐spirobi[cyclopenta[2,1‐b : 3,4‐b′]dithiophene] were synthesized and fully characterized, in which each perpendicularly aligned cyclopenta[2,1‐b : 3,4‐b′]dithiophene features a pendant dicyanovinylene as an electron acceptor and a thiophene as an electron donor. The electrochemical and photophysical properties of the new molecules, which differ from each other for the presence and/or location of an additional n‐hexyl chain on the pendant thiophene unit, were investigated, as well as their susceptibility to electrochemical polymerization. The substitution arrangement of the monomers was found to exert significant influence on the outcome of the electropolymerization process and on the optoelectronic properties and morphological film characteristics of the new regioregular materials obtained.

Efficient wide bandgap all-polymer solar cells benefiting from a random n-type copolymers strategy

A series of random donor-acceptor conjugated polymers with naphthalene diimide and thiophene units were designed and synthesized with varying difluorothiophene (FTh) substitution. In comparison with the non-fluorinated polymer F0, FTh-containing random polymers exhibit increased molecular interaction in solution state as well as enhanced solid state ordering. However, higher FTh content leads to unfavorable decrease in polymer solubility. When incorporated into all-polymer solar cells (all-PSCs) using PT8 as the donor, the crystallinity between donor and acceptor polymer was optimized using random copolymer strategy, and a best PCE of 9.04% was achieved with 10% FTh substitution, which is among the highest reports of wide bandgap all-PSCs. We believe that these findings will further provide insight into the control of polymer-polymer blend with desirable optoelectronic properties.

Benzodithiophene-based small molecules with various termini as hole transporting materials in efficient planar perovskite solar cells

In this study we prepared four benzodithiophene (BDT)-based small organic molecules presenting bithiophene (TT), thiophene (FT), carbazole (CB), and triphenylamine (TPA) units, respectively, as termini, and used them as hole transporting materials for perovskite solar cells (PSCs). The high degrees of planarity of these BDT-based small molecules imparted them with high degrees of stacking and charge transport. These small molecules had suitable optical properties and energy level alignments for use in PSCs based on MAPbI 3 , with compact-TiO 2 as the electron transporting layer and a BDT-based material as the hole transporting layer, in a n–i–p structure. Among our tested BDT-based materials, the PSC incorporating BDT-TT had the best performance, with an average power conversion efficiency of 13.63%. The benzodithiophene (BDT) derivatives presenting bithiophene (TT), carbazole (CB), thiophene (FT), and triphenylamine (TPA) units based small molecules used them as hole transporting materials to fabricate planar perovskite solar cells. • We have prepared benzodithiophene (BDT) derivatives presenting bithiophene (TT), carbazole (CB), thiophene (FT), and triphenylamine (TPA) units and then used them as hole transporting materials to fabricate n–i–p PSCs. The power conversion efficiency of the device incorporating BDT-TT was the highest among our tested PSCs. • The film of the small molecule BDT-TT had the best morphology among our tested BDT-based HTMs, suggesting that TT units might be useful components when designing new hole transporting materials for high-performance PSCs. • Additives improved the performance of our PSCs by increasing the mobilities in the hole transporting materials, thereby achieving higher power conversion efficiencies.

Photophysical Behavior and Sensing Response of Chalcone analogue containing pyrene moeity

D–π–A chalcone composed of pyrene and thiophene units wassynthesized and characterized. The solvatochromic response wasinvestigated in different solvents of various polarities. Additionally, theinclusion characteristic of the investigated dye was studied in differentorganized assemblies of three surfactants. The spectral changessuggested the chalcone would be useful to study the critical micelleconcentrations of the studied assemblies systems. Furthermore, theabsorption and emission spectra are sensitive towards H+, Co2+, Ni2+,Cd2+, Pb2+, and Zn2+ owing to acido- and metallo-chromic behaviors.These results suggest that the investigated chalcone would be potentialcandidate for polarity sensors, probes to characterize microenviromentalpolarity of the surfactants, and sensors for metal ions and H+ proton.

Novel heterocyclic liquid crystalline semiconductors with polymorphism

ABSTRACT Novel heterocyclic liquid crystalline semiconductors incorporating fused thiazolo[5,4-d]thiazole (N, S), thiophene (S), pyridine (N), and/or alkoxy (O) units have been synthesised via simple and high efficient reaction routes and exhibit polymorphic transitions. The correlation between the molecular structures, especially the presence of strong polar and electronegative heteroatoms, and mesomorphic behaviour and transition temperatures was investigated. The energy levels and band gap for heterocyclic liquid crystalline 6 and 10 have also been measured to further evaluate their potentials for use as promising organic semiconductors.

Molecular design of dibenzo[g,p]chrysene-based hole-transporting materials for perovskite solar cells: A theoretical study

Designed with a steric twisted, π-conjugated dibenzochrysene (DBC) core and arylamine-based electron-donating side arms, four small molecules as hole-transporting materials (HTMs) are simulated with density functional theory and Marcus theory of electron transfer. Our results show that, adding the fluorene moiety in auxiliary side arms and extending the π-conjugated structure can make the highest occupied molecular orbital (HOMO) energy levels down-shifted. By tailoring of electron-donating side arms, the HOMO levels of designed HTMs range from −4.95 to −5.24 eV, which affords a chance for the interfacial energy regulation. Meanwhile, we also find that the suitable extension of π-conjugated side arms and the accessorial sulfur-sulfur interaction may be beneficial for promoting the intermolecular electronic coupling. Coupled with the lower reorganization energy, the DBC-4 (7.08 × 10−1 cm2 v−1 s−1) displays the largest hole mobility. In addition, the better solubility can be expected for the DBC-4 due to the larger solvation free energy, whereas its stability may be somewhat lower. Adding thiophene unit in side arms makes the absorption spectra obviously red-shift. Overall, this work provides some useful clues for designing of high-efficient HTMs, and the DBC-4 is proposed as potential HTM.

A new two-dimensional covalent organic framework with intralayer hydrogen bonding as supercapacitor electrode material

Abstract A new two-dimensional covalent organic framework (DBT-MA-COF) is designed and synthesized via Carbon–Nitrogen coupling reaction by using 2,5-dibromothiophene (DBT) and melamine (MA) as the monomers. The C−Hˑ N intralayer hydrogen bonding exists in the structure of DBT-MA-COF so that a plane rigid structure can be maintained. The material exhibits a quasi-reversible redox process caused by triazine units and the transformation of the quinone and aromatic structures to make the DBT-MA-COF possess pseudocapacitive characteristics. DBT-MA-COF has high heteroatom content for the existence of triazine and thiophene units, which can accelerate the transfer of electrolyte ions on the surface of DBT-MA-COF electrode and improve the solution conductivity of the material. The assembled asymmetric supercapacitor DBT-MA-COF//C-CTS ASC has a high energy density of 32.1 W h kg−1 with the power density of 800 W kg−1. The cycle life of the device is excellent which can reach 83% even after 30,000 continuous galvanostatic charge-discharge cycles. The strategy in this work provides a line of thinking to design and prepare new COFs used as long life and pseudocapacitive supercapacitor materials.

Development and Testing of an All-Atom Force Field for Diketopyrrolopyrrole Polymers with Conjugated Substituents.

We develop an all-atom force field for a series of diketopyrrolopyrrole polymers with two aromatic pyridine substituents and a variable number of π-conjugated thiophene units in the backbone (DPP2PymT), used as donor materials in organic photovoltaic devices. Available intrafragment parameterizations of the individual fragment building blocks are combined with interfragment bonded and nonbonded parameters explicitly derived from density functional theory calculations. To validate the force field, we perform classical molecular dynamics simulations of single polymer chains with m = 1, 2, 3 in good and bad solvents and of melts. We observe the expected dependence of the chain conformation on the solvent quality, with the chain collapsing in water, and swelling in chloroform. The glass-transition temperature for the polymer melts is found to be in the range of 340–370 K. Analysis of the mobility of the conjugated segments in the polymer backbone reveals two relaxation processes: a fast one with a characteristic time at room temperature on the order of 10 ps associated with nearly harmonic vibrations and a slow one on the order of 100 ns associated with temperature-activated cis–trans transitions.

Binding Mode Multiplicity and Multiscale Chirality in the Supramolecular Assembly of DNA and a π-Conjugated Polymer.

Water-soluble π-conjugated polymers are increasingly considered for DNA biosensing. However, the conformational rearrangement, supramolecular organization and dynamics upon interaction with DNA have been overlooked, which prevents the rational design of such detection tools. To elucidate the binding of a cationic polythiophene (CPT) to DNA with atomistic resolution, we performed molecular simulations of their supramolecular assembly. Comparison of replicated simulations show a multiplicity of CPT binding geometries that contribute to the wrapping of CPT around DNA. The different binding geometries are stabilized by both electrostatic interactions between CPT lateral cations and DNA phosphodiesters and van der Waals interactions between the CPT backbone and the DNA grooves. Simulated circular dichroism (CD) spectra show that the induced CD signal stems from a conserved geometrical feature across the replicated simulations, i. e. the presence of segments of syn configurations between thiophene units along the CPT chain. At the macromolecular scale, we inspected the different shapes related to the CPT binding modes around the DNA through symmetry metrics. Altogether, molecular dynamics (MD) simulations, model Hamiltonian calculations of the CD spectra, and symmetry indices provide insights into the origin of induced chirality from the atomic to the macromolecular scale. Our multidisciplinary approach points out the hierarchical aspect of CPT chiral organization induced by DNA.

Thiophene-Bridged Donor-Acceptor sp2 -Carbon-Linked 2D Conjugated Polymers as Photocathodes for Water Reduction.

Photoelectrochemical (PEC) water reduction, converting solar energy into environmentally friendly hydrogen fuel, requires delicate design and synthesis of semiconductors with appropriate bandgaps, suitable energy levels of the frontier orbitals, and high intrinsic charge mobility. In this work, the synthesis of a novel bithiophene-bridged donor-acceptor-based 2D sp2 -carbon-linked conjugated polymer (2D CCP) is demonstrated. The Knoevenagel polymerization between the electron-accepting building block 2,3,8,9,14,15-hexa(4-formylphenyl) diquinoxalino[2,3-a:2',3'-c]phenazine (HATN-6CHO) and the first electron-donating linker 2,2'-([2,2'-bithiophene]-5,5'-diyl)diacetonitrile (ThDAN) provides the 2D CCP-HATNThDAN (2D CCP-Th). Compared with the corresponding biphenyl-bridged 2D CCP-HATN-BDAN (2D CCP-BD), the bithiophene-based 2D CCP-Th exhibits a wide light-harvesting range (up to 674nm), a optical energy gap (2.04eV), and highest energy occupied molecular orbital-lowest unoccupied molecular orbital distributions for facilitated charge transfer, which make 2D CCP-Th a promising candidate for PEC water reduction. As a result, 2D CCP-Th presents a superb H2 -evolution photocurrent density up to ≈7.9 µA cm-2 at 0V versus reversible hydrogen electrode, which is superior to the reported 2D covalent organic frameworks and most carbon nitride materials (0.09-6.0 µA cm-2 ). Density functional theory calculations identify the thiophene units and cyano substituents at the vinylene linkage as active sites for the evolution of H2 .

Robust design of D-π-A model compounds using digital structures for organic DSSC applications

New D−π-spacer−A model compound dye sensitizers (or dyes) are developed using digital structures for organic dyes sensitized solar cells (DSSCs) applications. Based on our previous studies, the model D−π-spacer−A dyes contain building blocks of a di(<i>p</i>-carboxy)-phenylamine as the electron donor and a perylene monoimide as the electron acceptor. The new D−π-spacer−A dyes are constructed through variations of a set of three model π-spacer units, fluorene, 3,4-ethylenedioxythiophene and thiophene. The new dyes are presented by digital structures of π(ijk) in a digital control Π-matrix. If the chromophore database of the π-units is arranged in a defined manner, the new dyes are therefore designed through selecting of the set of three integers (ijk). Properties such as the UV–vis spectra which are calculated using the time-dependent density functional theory (TD-DFT) determine if the new compounds are suitable for organic solar cell purposes. The same strategy can be applied to donors and acceptors in the D−π-spacer−A model compound in order to robust design and build new organic dyes for DSSCs. The digital structures of the organic compounds enhance the machine driven structure-property relationship establishment once the database is sufficiently comprehensive. The present study demonstrates that new compounds obtained through mixing the π-spacer units of fluorene, 3,4-ethylenedioxythiophene and thiophene, e.g. π121 and π211, result in better dyes in DSSC applications. The concise digital structures of the new dyes are able to achieve a more robust design of the organic dyes and other materials.