Quaterthiophene Derivatives Research Articles

Conductive gold nanoparticle assembly linked through interactions between the radical cations of ethylene- and propylene-3,4-dioxythiophene mixed tetramer thiolate

Drop-casting of gold nanoparticle (AuNP) with radical cation moiety of a quaterthiophene derivative provided a conductive film. The interparticle π-dimer was considered to act as effective conduction paths in the AuNP assembly.

Dithienylnaphthalenes and quaterthiophenes substituted with electron-withdrawing groups as n-type organic semiconductors for organic field-effect transistors

The synthesis and subsequent complex study of two related series of derivatives with various acceptor groups reveals the first thienylnaphthalene-based n-type semiconductors and compares them with similarly effective quaterthiophene derivatives.

Study on the Dynamics of Phase Formation and Degradation of 2D Layered Hybrid Perovskites and Low‐dimensional Hybrids Containing Mono‐functionalized Oligothiophene Cations

AbstractLow‐dimensional (2D or 1D) hybrid perovskites are receiving increased attention due to their structural flexibility and enhanced stability compared to their 3D counterparts. Understanding the phase formation and degradation behavior of these materials is crucial towards their use in optoelectronic devices, since different crystal phases possess different optical and electronic properties. In this communication, we study the phase formation and degradation of a series of hybrids containing bithiophene, terthiophene and quaterthiophene derivatives. We show that two crystal phases can be formed for each of these systems, depending on the processing conditions. One phase corresponds to a 2D layered perovskite and the other phase has optical properties corresponding to a dimensionality intermediate between a 2D and a 1D hybrid.

(Invited) Light Emission Modulation from Individual Single-Walled Carbon Nanotubes By Chromophore Encapsulation

The one-dimensional structure of single-walled carbon nanotubes (NT) display optical absorption and near-infrared emission (thanks to van Hove singularities). Chromophore encapsulation into host single-walled carbon nanotubes allows to create hybrid nano-systems with tunable opto-electronic properties. Up to now, we have been confining different kinds of chromophores,1-4 absorbing from the blue/ green (400/500 nm) range (tetracyanoquinodimethane (TNCQ), quaterthiophene derivatives (4T) and tetramethyl-paraphenylenediamine (TMPD)) to the red (700 nm) range (phthalocyanine (MPc)). In addition then can be either electron donor (4T, TMPD) or acceptor (TNCQ).In this study, we investigate, at both the macroscopic and the individual scales, the electronic and the optical properties of our hybrid systems by means of Raman and photoluminescence spectroscopies.Photoluminescence experiments clearly demonstrate changes on the emission properties after encapsulation. The intensities can be increased or reduced depending on the nature of the confined chromophores (electron donor or acceptor) and on the NT diameter.From Raman measurements, a significant charge transfer from the confined dye to the nanotube is evidenced. The main relevant parameters that govern the charge transfer are the nanotube diameter and the nature of the chromophores (electron donor or acceptor).Therefore, Raman and photoluminescence experiments strongly suggest charge transfer between the confined molecules and the nanotubes, leading to a Fermi level shift which governs the radiative de-excitation efficiency.

Ab Initio Approach to Femtosecond Stimulated Raman Spectroscopy: Investigating Vibrational Modes Probed in Excited-State Relaxation of Quaterthiophenes.

Femtosecond stimulated Raman spectroscopy (FSRS) is an ultrafast pump-probe technique designed to elucidate excited-state molecular dynamics by means of vibrational spectroscopy. We present a first-principles protocol for the simulation of FSRS that integrates ab initio molecular dynamics with computational resonance Raman spectroscopy. Theoretical calculations can monitor the time-dependent evolution of specific vibrational modes and thus provide insight into the nature of the motion responsible for the experimental FSRS signal, and we apply this technique to study quaterthiophene derivatives. The S1 state of two different quaterthiophene derivatives relaxes via in-phase and out-of-phase stretching modes whose frequencies are coupled to the dihedral backbone angle, such that the spectral evolution reflects the excited-state relaxation toward a planar conformation. The simulated spectra aid in confirming the experimental assignment of the vibrational modes that are probed in the existing FSRS experiments on quaterthiophenes.

(Invited) Modulation of the Fermi Level in Single-Walled Carbon Nanotubes By Chromophore Encapsulation

The one-dimensional structure of single-walled carbon nanotubes renders these materials ideal for optoelectronic applications as they can transport electrons or holes with quasi-ballistic features and as they display optical absorption and near-infrared emission (thanks to van Hove singularities). Nevertheless, functionalities can to be added to nanotube to both improve and control the physical properties. To this aim, chromophore encapsulation into host single-walled carbon nanotubes allows to create hybrid nano-systems with tunable opto-electronic properties. Up to now, we have been confining different kinds of molecules,1-4 either absorbing in the blue/green range, being electron donor (quaterthiophene derivatives (4T) and tetramethyl-paraphenylenediamine (TMPD)) or electron acceptor (tetracyanoquinodimethane (TCNQ)), or absorbing in the red visible range (phthalocyanine (MPc)).In this study, we investigate, at both the macroscopic and the individual scales, the electronic and the optical properties of our hybrid systems by means of Raman and photoluminescence spectroscopies.From Raman measurements, a significant charge transfer from the confined dye to the nanotube is evidenced. Experiments also suggest a photo-activated electron transfer for small diameter (~9 Å) semiconducting and metallic tubes. The main relevant parameters that govern the charge transfer are the nanotube diameter and the electronic properties of both the nanotube (metallic or semiconducting) and the chromophores (electron donor or acceptor).Photoluminescence experiments clearly demonstrate changes on the emission properties after encapsulation. The intensities can be increased or reduced depending on the nature of the confined chromophores (electron donor or acceptor). These behaviors are consistent with a charge transfer.Therefore, Raman and photoluminescence experiments strongly suggest charge transfer between the confined molecules and the nanotubes, leading to a Fermi level shift which governs the radiative de-excitation efficiency and the electron-phonon coupling.

Quasi-Phase Diagrams at Air/Oil Interfaces and Bulk Oil Phases for Crystallization of Small-Molecular Semiconductors by Adjusting Gibbs Adsorption.

The temperature and concentration dependencies of the crystallization of two small-molecular semiconductors were clarified by constructing quasi-phase diagrams at air/oil interfaces and in bulk oil phases. A quinoidal quaterthiophene derivative with four alkyl chains (QQT(CN)4) in 1,1,2,2-tetrachroloethane (TCE) and a thienoacene derivative with two alkyl chains (C8-BTBT) in o-dichlorobenzene were used. The apparent crystal nucleation temperature (Tn) and dissolution temperature (Td) of the molecules were determined based on optical microscopy examination in closed glass capillaries and open dishes during slow cooling and heating processes, respectively. Tn and Td were considered estimates of the critical temperatures for nuclear formation and crystal growth, respectively. The Tn values of QQT(CN)4 and C8-BTBT at the air/oil interfaces were higher than those in the bulk oil phases, whereas the Td values at the air/oil interfaces were almost the same as those in the bulk oil phases. These Gibbs adsorption phenomena were attributed to the solvophobic effect of the alkyl chain moieties. The temperature range between Tn and Td corresponds to suitable supercooling conditions for ideal crystal growth based on the suppression of nucleation. The Tn values at the water/oil and oil/glass interfaces did not shift compared with those of the bulk phases, indicating that adsorption did not occur at the hydrophilic interfaces. Promotion and inhibition of nuclear formation for crystal growth of the semiconductors were achieved at the air/oil and hydrophilic interfaces, respectively.

Microcrystallization of a Solution-Processable Organic Semiconductor in Capillaries for High-Performance Ambipolar Field-Effect Transistors

We report on the use of microcrystallization in capillaries to fabricate patterned crystalline microstructures of the low-bandgap ambipolar quinoidal quaterthiophene derivative (QQT(CN)4) from a chloroform solution. Aligned needle-shaped QQT(CN)4 crystals were formed in thin film microstructures using either open- or closed- capillaries made of polydimethylsiloxane (PDMS). Their charge transport properties were evaluated in a bottom-gate top-contact transistor configuration. Hole and electron mobilities were found to be as high as 0.17 and 0.083 cm(2) V(-1) s(-1), respectively, approaching the values previously obtained in individual QQT(CN)4 single crystal microneedles. It was possible to control the size of the needle crystals and the microline arrays by adjusting the structure of the PDMS mold and the concentration of QQT(CN)4 solution. These results demonstrate that the microcrystallization in capillaries technique can be used to simultaneously pattern organic needle single crystals and control the microcrystallization processes. Such a simple and versatile method should be promising for the future development of high-performance organic electronic devices.

Synthesis and Physical Properties of Asymmetrical Quaterthiophene Derivatives as Organic Thin‐Film Transistor Materials

We report here, synthesis, physical, thermal, and optoelectronic properties of compounds containing anthracene, anthraquinone, and 11,11,12,12‐tetracyano‐9,10‐anthraquinodimethane units connected to quaterthiophene units. Three compounds, TQAO (6), TQAN (7), and TQAM (8) are synthesized by using Stille coupling, reduction, and Knoevenagel condensation reactions. These compounds were thermally stable and exhibited organic thin‐film transistor (OTFT) properties. Among them, TQAM (8)‐based OTFT has shown ambipolar mobility, both hole and electron mobility of 2.0 × 10−6 and 2.43 × 10−7 cm2/Vs, respectively. TQAO (6) and TQAN (7) has shown low electron mobility of 5.58 × 10−6 and 1.22 × 10−5 cm2/Vs, respectively.

A bridged low band gap A–D–A quaterthiophene as efficient donor for organic solar cells

Covalent bridging of the central 2,2′-bithiophene of α,ω-bis(dicyanovinyl)quaterthiophene derivatives leads to a reduced band gap and efficient organic solar cells.

Aryl end-capped quaterthiophenes applied as anode interfacial layers in inverted organic solar cells

Four aryl end-capped quaterthiophene derivatives were synthesized and their material properties were studied by computational, spectroscopic, electrochemical, and thermoanalytical methods. Compounds were applied as interfacial layers between the bulk heterojunction active layer and Ag anode in inverted organic solar cells. Results show that p-cyanophenyl end-capped quaterthiophene with hexyl side chains increases both the short circuit current density and power conversion efficiency notably compared to reference interlayer material, tris-(8-hydroxyquinoline)aluminum. The improved cell performance was attributed to the optimal positions of the highest occupied molecular orbital and the lowest unoccupied molecular orbital (LUMO) of this material, relative to those of the photoactive electron donor poly(3-hexylthiophene) and Ag anode, and evenly distributed LUMO. In addition, the use of these materials as an anode interfacial layer increases the absorption of the solar cell, which could contribute to the formation of excitons and additional current production by the cell.

Simultaneous Visualization of Covalent and Noncovalent Interactions Using Regions of Density Overlap.

We introduce a density-dependent bonding descriptor that enables simultaneous visualization of both covalent and noncovalent interactions. The proposed quantity is tailored to reveal the regions of space, where the total electron density results from a strong overlap of shell, atomic, or molecular densities. We show that this approach is successful in describing a variety of bonding patterns as well as nonbonding contacts. The Density Overlap Regions Indicator (DORI) analysis is also exploited to visualize and quantify the concept of electronic compactness in supramolecular chemistry. In particular, the scalar field is used to compare the compactness in molecular crystals, with a special emphasis on quaterthiophene derivatives with enhanced charge mobilities.

Self-organization polymer consisting of quinacridone and quaterthiophene units: Coplanar structure between benzene and thiophene linkage

Poly[quinacridone-co-quaterthiophene] (PQCQT) was synthesized through a Suzuki coupling reaction by introducing the characterization and self-assembly of quinacridone and quaterthiophene derivatives. The PQCQT was dissolved in a common organic solvent with an Mn value of 52.9kg/mol. The optical band gap energy of the PQCQT was similar to the P3HT at 2.12eV. The energy of the HOMO of the PQCQT was −5.10eV, and the energy of the LUMO was −2.98eV. The results of the X-ray diffraction measurement showed that the Lamellar d-spacing (d1) of the out-of-plane PQCQT was 23.2Å, and the π–π stacking distance (dπ) between the layers was 3.5Å. A bulk-heterojunction type of polymer solar cell was produced with a structure of ITO/PEDOT:PSS/active-layer/PFN/Al. When the ratio of the PQCQT and PC71BM was 1:2, the device performed best with a power conversion efficiency (PCE) of 2.3%.

Molecular aggregation–performance relationship in the design of novel cyclohexylethynyl end-capped quaterthiophenes for solution-processed organic transistors

Abstract The synthesis and characterization of cyclohexylethenyl end-capped quaterthiophenes is reported. Additionally, an investigation of the performance of organic field-effect transistors based on these quaterthiophenes in view of the relationship between the solid-state (or aggregate) order and the electronic performance is described. UV–vis absorption measurements revealed that the quaterthiophene with an asymmetrically substituted cyclohexylethynyl end-group induced the formation of H-type aggregates, whereas the quaterthiophene with a symmetrically substituted cyclohexylethynyl end-groups favored the formation of J-type aggregates. Two-dimensional grazing-incidence wide-angle X-ray scattering studies were performed to support the molecular structure-dependent packing of films of the new quaterthiophenes. Solution-processed quaterthiophenes were tested as the active layers of p-type organic field-effect transistors with a bottom gate/top contact geometry. The field-effect mobility of devices that incorporated asymmetric quaterthiophene molecules was quite high, exceeding 0.02 cm2/V s, due to H-aggregation and good in-plane ordering. In contrast, the field-effect mobility of devices that incorporated symmetrical quaterthiophenes, was low, above 5 × 10−4 cm2/(V s), due to the formation of J-aggregates and poor in-plane ordering. A comparison of the symmetrical and asymmetrical quaterthiophene derivatives revealed that the molecular aggregation-dependent packing, determined by the cyclohexylethynyl end groups, was responsible for influencing the organic field-effect transistor performance.

Temperature Activation of the Photoinduced Charge Carrier Generation Efficiency in Quaterthiophene:C60 Mixed Films

We measure photoinduced excitations in a dicyanovinyl end-capped methylated quaterthiophene derivative in blends with the electron acceptor C60, as already employed in organic photovoltaics. By usi...

Effect of Molecular Structure of α,α′-Dialkylquaterthiophenes and Their Organosilicon Multipods on Ordering, Phase Behavior, and Charge Carrier Mobility

We report on bulk structures of a family of quaterthiophene (4T) derivatives with linear and branched end groups such as α,α′-dihexylquaterthiophene (Hex-4T-Hex), α,α′-didecyl-quaterthiophene (Dec-4T-Dec) and α,α′-bis(2-ethylhexyl)quaterthiophene (EH-4T-EH), tetramethyldisiloxane-based dimers D2-Und-4T-EH and D2-Und-4T-Hex, and carbosilane-siloxane-based tetramers D4-Und-4T-EH and D4-Und-4T-Hex. The dimers and tetramers contain undecylenic (Und) spacers between the disiloxane and 4T- units of the molecule. The impact of the molecular architecture on the bulk structure at different temperatures is addressed with X-ray diffraction and differential scanning calorimetry. For all of the studied quaterthiophene-containing organosilicon multipods the formation of 4T-crystal sublattice is observed. The alkyl periphery plays an important role in the molecular packing and thermal stability of the ordered phase. They can stabilize or destabilize the crystal phase, depending on their length and architecture. The quat...

Development of a robust supramolecular method to prepare well-defined nanofibrils from conjugated molecules

In order to produce materials with tailored structures and functions via supramolecular self-assembly of molecular precursors in a predictable fashion, it is necessary to develop ‘supramolecular methods’ based on structurally simple ‘supramolecular synthons’. Thus, the formation of one-dimensional aggregates from π-conjugated molecules requires a combination of non-covalent interactions that efficiently suppresses lateral aggregation, promotes one-dimensional aggregation, and is also compatible with a productive π–π overlap of the constituent molecules. In the present work, we demonstrate that oligopeptide–polymer derivatives comprising a flexible polymer segment terminally attached to a β-sheet-forming oligopeptide segment are structurally simple substituents that perfectly fulfill these requirements. We synthesized a matrix of diacetylene model compounds that carried oligopeptide–polymer substituents with varying degrees of polymerization of the attached polymers and different length oligopeptide segments. We combined solution-phase IR spectroscopy, AFM imaging and the topochemical diacetylene polymerization as a highly sensitive probe for the molecular arrangement and the degree of order inside aggregates obtained in organic solvents. The thus determined molecular parameters for the reliable formation of well-defined nanoscopic fibrillar structures with uniform diameters, and defined helical ‘core–shell’ morphologies were then successfully transferred to analogous perylene bisimide and quaterthiophene derivatives, demonstrating the versatility and robustness of the chosen molecular design.

A side chain-modified quaterthiophene derivative for enhancing the performance of organic solar cell devices

A conjugated polymer donor material, poly(3,4′′′-di(decylthiophenyl)quaterthiophene) (PDTQT), featuring decylthiophenyl side chains on the polymer backbone, was introduced to reduce the crystallinity of poly(quaterthiophene) (PQT-C12) layers in organic photovoltaic cells. The resulting PDTQT:PC71BM blend active layer formed a well-interpenetrated nanoscale morphology that increased the power conversion efficiency (PCE) relative to devices based on highly crystalline PQT-C12. Bulk heterojunction solar cells fabricated using the PDTQT:PC71BM blend thin films yielded the best photovoltaic performances with a high short-circuit current density of 9.8 mA cm−2, a high open-circuit voltage of 0.91 V, a fill factor of 0.36, and a high PCE of 3.2% under AM 1.5G illumination with an intensity of 100 mW cm−2. Decylthiophenyl side chain substitution appeared to be an effective strategy for obtaining high organic photovoltaic cell device performances.

Charge transfer in conjugated oligomers encapsulated into carbon nanotubes

This study deals with a hybrid system consisting in quaterthiophene derivative encapsulated inside single-walled and multi-walled carbon nanotubes. Investigations of the encapsulation step are performed by transmission electron microscopy. Raman spectroscopy data point out different behaviors depending on the laser excitation energy with respect to the optical absorption of quaterthiophene. At low excitation energy (far from the oligomer resonance window) there is no significant modification of the Raman spectra before and after encapsulation. By contrast, at high excitation energy (close to the oligomer resonance window), Raman spectra exhibit a G-band shift together with an important RBM intensity loss, suggesting a significant charge transfer between the inserted molecule and the host nanotubes. Those results suggest a photo induced process leading to a significant charge transfer.

Influence of gate dielectric on the ambipolar characteristics of solution-processed organic field-effect transistors

Solution-processed ambipolar organic field-effect transistors based on dicyanomethylene-substituted quinoidal quaterthiophene derivative [QQT(CN)4] are fabricated using various gate dielectric materials including cross-linked polyimide and poly-4-vinylphenol. Devices with spin-coated polymeric gate dielectric layers show a reduced hysteresis in their transfer characteristics. Among the insulating polymers examined in this study, a new fluorinated polymer with a low dielectric constant of 2.8 significantly improves both hole and electron field-effect mobilities of QQT(CN)4 thin films to values as high as 0.04 and 0.002 cm2 V−1 s−1. These values are close to the best mobilities obtained in QQT(CN)4 devices fabricated on SiO2 treated with octadecyltrichlorosilane. The influence of the metal used for source/drain metal electrodes on the device performance is also investigated. Whereas best device performances are achieved with gold electrodes, more balanced electron and hole field-effect mobilities could be obtained using chromium.