Search Results (19)

Thieno[3,2-b]thiophenes are used as key components in optoelectronic materials, porous hydrogen-storage hosts, organic solar cells, and polymer semiconductors. A step-efficient synthetic protocol was proposed herein for obtaining multisubstituted thieno[3,2-b]thiophene and selenopheno[3,2-b]selenophenes in moderate to good yields via the bisulfur/biselenium cyclization of alkynyl diols with I₂/Na₂S₂O₃ or selenium. Using this strategy, substitution patterns were obtained for backbone modification in functional materials. Full article

The selection of the π-conjugation spacers in semi-conducting polymer backbone is one of the important factors for determining the optoelectrical and morphological properties in organic photodiodes. To study the effects of π-conjugation spacers in donor–acceptor (D-A)-type alternating copolymers on their device performances in all-polymer-based photodiodes (all-PPDs), a series of diketopyrrolopyrrole (DPP)-based copolymers as polymer donors (P_Ds) were designed and synthesized. In detail, three different π-conjugation spacers, thiophene (T for P1), thienothiophene (TT for P2), and bithiophene (BT for P3), were incorporated into the DPP-based copolymer structures. Interestingly, all-PPDs based on the series of P1–P3 as P_Ds and N2200 as a polymer acceptor (P_A) exhibited totally distinct device performances in terms of external quantum efficiency (EQE), dark current density (J_D), and ideal detectivity (D*). The P1-based device showed suppressed J_D (6.1 × 10⁻¹¹ A/cm² at −1 V) compared to those of the P2- and P3-based devices due to the lower lying of the highest occupied molecular orbital (HOMO) level of P1. However, the P3-based all-PPD showed higher EQE (16% at 630 nm wavelength and −1 V) compared to those of the P1- and P2-based devices. And, it mainly originated from the better molecular packing and final blend film morphology, as confirmed by morphological analyses. Full article

Conjugated polymer photocatalysts for hydrogen production have the advantages of an adjustable structure, strong response in the visible light region, adjustable energy levels, and easy functionalization. Using an atom- and step-economic direct C–H arylation method, dibromocyanostilbene was polymerized with thiophene, dithiophene, terthiophene, and fused thienothiophene and dithienothiophene, respectively, to produce donor–acceptor (D-A)-type linear conjugated polymers containing different thiophene derivatives with different conjugation lengths. Among them, the D-A polymer photocatalyst constructed from dithienothiophene could significantly broaden the spectral response, with a hydrogen evolution rate up to 12.15 mmol h⁻¹ g⁻¹. The results showed that the increase in the number of fused rings on thiophene building blocks was beneficial to the photocatalytic hydrogen production of cyanostyrylphene-based linear polymers. For the unfused dithiophene and terthiophene, the increase in the number of thiophene rings enabled more rotation freedom between the thiophene rings and reduced the intrinsic charge mobility, resulting in lower hydrogen production performance accordingly. This study provides a suitable process for the design of electron donors for D-A polymer photocatalysts. Full article

In this study, we developed two novel conjugated polymers that can easily be doped with F4TCNQ organic dopants using a sequential doping method and then studied their organic thermoelectric (OTE) properties. In particular, to promote the intermolecular ordering of OTE polymers in the presence of the F4TCNQ dopant, alkylthiazole-based conjugated building blocks with highly planar backbone structures were synthesized and copolymerized. All polymers showed strong molecular ordering and edge-on orientation in the film state, even in the presence of the F4TCNQ organic dopant. Thus, the sequential doping process barely changed the molecular ordering of the polymer films while making efficient molecular doping. In addition, the doping efficiency was improved in the more π-extended polymer backbones with thienothiophene units due to the emptier space in the polymer lamellar structure to locate ionized F4TCNQ. Moreover, the study of organic thin-film transistors (OTFTs) revealed that higher hole mobility in OTFTs was the key to increasing the electrical conductivity of OTE devices fabricated using the sequential doping method. Full article

The synthesis of some novel donor-acceptor and acceptor-donor-acceptor systems containing a 2,2′-bi[3,2-b]thienothiophene donor block and various electron-accepting units is described alongside their photophysical properties studied using electrochemistry, optical spectroscopy and theoretical calculations. The obtained results show that the energy levels can be modulated by changing the strength of the acceptor unit. Among the three investigated end-groups, 1,1-dicyanomethylene-3-indanone exhibited the largest bathochromic shift and the lowest band gap suggesting the strongest electron-withdrawing character. Moreover, the emissive properties of the investigated systems vary greatly with the nature of the terminal group and are generally lower compared to their precursor aldehyde derivatives. Full article

Thieno[3,2-b]thiophene and isomeric thieno[2,3-b]thiophene represent fused, bicyclic and electron rich heterocycles. These small planar organic compounds belong to the remarkable family of annulated building blocks for various organic materials. The first part of this review focuses on the synthesis of the primary unsubstituted thienothiophene scaffolds. All synthetic pathways available in the literature, dating from the 19th century, are summarized. The second part is devoted to the applications of the thienothiophene-derived materials across (opto)electronics. Organic light emitting diodes, organic solar cells, organic field-effect transistors and nonlinear optics were identified as the most successful application areas of both thienothiophenes. The fundamental structure-property relationships were evaluated for each particular group of derivatives. Full article

The fabrication of colorless and see-through dye-sensitized solar cells (DSCs) requires the photosensitizers to have little or no absorption in the visible light region of the solar spectrum. However, a trade-off between transparency and power conversion efficiency (PCE) has to be tackled, since most transparent DSCs are showing low PCE when compared to colorful and opaque DSCs. One strategy to increase PCE is applying two cosensitizers with selective conversion of the UV and NIR radiation, therefore, the non-visible part only is absorbed. In this study, we report synthesis of novel five UV-selective absorbers, based on diimide and Schiff bases incorporating carboxyl and pyridyl anchoring groups. A systematic computational investigation using density functional theory (DFT) and time-dependent DFT approaches was employed to evaluate their prospect of application in transparent DSCs. Experimental UV/Vis absorption spectra showed that all dyes exhibit an absorption band covering the mid/near-UV region of solar spectrum, with a bathochromic shift and a hyperchromic shifts for Py-1 dye. Computational results showed that the studied dyes satisfied the basic photophysical and energetics requirements of operating DSC as well as the stability and thermodynamical spontaneity of adsorption onto surface of TiO₂. However, results revealed outperformance of the thienothiophene core-containing Py-1 UV-dye, owing to its advantageous structural attributes, improved conjugation, intense emission, large Stokes shift and maximum charge transferred to the anchor. Chemical compatibility of Py-1 dye was then theoretically investigated as a potential cosensitizer of a reference VG20-C2 NIR-dye. By the judicious selection of pyridyl anchor-based UV-absorber (Py-1) and carboxyl anchor-based NIR-absorber (VG20), the advantage of the optical complementarity and selectivity of different TiO₂-adsorption-site (Lewis- and Bronsted-acidic) can be achieved. An improved overall PCE is estimated accordingly. Full article

Shear coating is a promising deposition method for upscaling device fabrication and enabling high throughput, and is furthermore suitable for translating to roll-to-roll processing. Although common polymer semiconductors (PSCs) are solution processible, they are still prone to mechanical failure upon stretching, limiting applications in e.g., electronic skin and health monitoring. Progress made towards mechanically compliant PSCs, e.g., the incorporation of soft segments into the polymer backbone, could not only allow such applications, but also benefit advanced fabrication methods, like roll-to-roll printing on flexible substrates, to produce the targeted devices. Tri-block copolymers (TBCs), consisting of an inner rigid semiconducting poly-diketo-pyrrolopyrrole-thienothiophene (PDPP-TT) block flanked by two soft elastomeric poly(dimethylsiloxane) (PDMS) chains, maintain good charge transport properties, while being mechanically soft and flexible. Potentially aiming at the fabrication of TBC-based wearable electronics by means of cost-efficient and scalable deposition methods (e.g., blade-coating), a tolerance of the electrical performance of the TBCs to the shear speed was investigated. Herein, we demonstrate that such TBCs can be deposited at high shear speeds (film formation up to a speed of 10 mm s⁻¹). While such high speeds result in increased film thickness, no degradation of the electrical performance was observed, as was frequently reported for polymer−based OFETs. Instead, high shear speeds even led to a small improvement in the electrical performance: mobility increased from 0.06 cm² V⁻¹ s⁻¹ at 0.5 mm s⁻¹ to 0.16 cm² V⁻¹ s⁻¹ at 7 mm s⁻¹ for the TBC with 24 wt% PDMS, and for the TBC containing 37 wt% PDMS from 0.05 cm² V⁻¹ s⁻¹ at 0.5 mm s⁻¹ to 0.13 cm² V⁻¹ s⁻¹ at 7 mm s⁻¹. Interestingly, the improvement of mobility is not accompanied by any significant changes in morphology. Full article

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. Full article

3-(2-Octyldodecyl)thieno[3,2-b]thiophen was successfully synthesized as a new π-bridge with a long branched side alkyl chain. Two donor-π-bridge-acceptor type copolymers were designed and synthesized by combining this π-bridge structure, a fluorinated benzothiadiazole acceptor unit, and a thiophene or thienothiophene donor unit, (PT-ODTTBT or PTT-ODTTBT respectively) through Stille polymerization. Inverted OPV devices with a structure of ITO/ZnO/polymer:PC₇₁BM/MoO₃/Ag were fabricated by spin-coating in ambient atmosphere or N₂ within a glovebox to evaluate the photovoltaic performance of the synthesized polymers (effective active area: 0.09 cm²). The PTT-ODTTBT:PC₇₁BM-based structure exhibited the highest organic photovoltaic (OPV) device performance, with a maximum power conversion efficiency (PCE) of 7.05 (6.88 ± 0.12)%, a high short-circuit current (J_sc) of 13.96 mA/cm², and a fill factor (FF) of 66.94 (66.47 ± 0.63)%; whereas the PT-ODTTBT:PC₇₁BM-based device achieved overall lower device performance. According to GIWAXS analysis, both neat and blend films of PTT-ODTTBT exhibited well-organized lamellar stacking, leading to a higher charge carrier mobility than that of PT-ODTTBT. Compared to PT-ODTTBT containing a thiophene donor unit, PTT-ODTTBT containing a thienothiophene donor unit exhibited higher crystallinity, preferential face-on orientation, and a bicontinuous interpenetrating network in the film, which are responsible for the improved OPV performance in terms of high J_sc, FF, and PCE. Full article

We report the simple synthesis of two organic chromophores featuring an ethynyl-thienothiophene linker with an n-hexyl chain (CSD-03 and CSD-04), their optical and electrochemical properties, and their use as photosensitizers in dye-sensitized solar cells (DSSCs). Our theoretical and experimental studies show that adding the second thienothiophene allows for narrowing the bandgap of the molecule and thus ensuring more light harvesting in the visible region. The efficiencies of both CSD-03 (5.46 ± 0.03%) and CSD-04 (5.20 ± 0.03%) are comparable to that of N719 (5.92 ± 0.01%) in translucent DSSCs fabricated with 5 μm-thick TiO₂ photoanodes. Full article

A new family of fluorescent thiophene and thienothiophene-containing squaraine dyes is described with tunable wavelengths that cover the absorption/emission range of 600–800 nm. The deep-red and near-infrared fluorescent compounds were easily prepared by simple synthesis and purification methods. Spectral studies showed that each squaraine was rapidly encapsulated by a tetralactam macrocycle, with nanomolar affinity in water, to produce a threaded supramolecular complex with high chemical stability, increased fluorescence quantum yield, and decreased fluorescence quenching upon dye self-aggregation. Energy transfer within the supramolecular complex permitted multiplex emission. That is, two separate dyes with fluorescence emission bands that match the popular Cy5 and Cy7 channels, could be simultaneously excited with a beam of 375 nm light. A broad range of practical applications is envisioned in healthcare diagnostics, microscopy, molecular imaging, and fluorescence-guided surgery. Full article

Fluorescent Organic Nanoparticles (FONs), prepared by self-aggregation of dedicated dyes in water, represent a promising green alternative to the toxic quantum dots (QDs) for bioimaging purposes. In the present paper, we describe the synthesis and photophysical properties of new dipolar push-pull derivatives built from thieno[3,2-b]thiophene as a π-conjugated bridge that connects a triphenylamine moiety bearing various bulky substituents as electron-releasing moiety to acceptor end-groups of increasing strength (i.e., aldehyde, dicyanovinyl and diethylthiobarbiturate). All dyes display fluorescence properties in chloroform, which shifts from the green to the NIR range depending on the molecular polarization (i.e., strength of the end-groups) as well as a large two-photon absorption (TPA) band response in the biological spectral window (700–1000 nm). The TPA bands show a bathochromic shift and hyperchromic effect with increasing polarization of the dyes with maximum TPA cross-section reaching 2000 GM for small size chromophore. All dyes are found to form stable and deeply colored nanoparticles (20–45 nm in diameter) upon nanoprecipitation in water. Although their fluorescence is strongly reduced upon aggregation, all nanoparticles show large one-photon (up to 10⁸ M⁻¹·cm⁻¹ in the visible region) and two-photon (up to 10⁶ GM in the NIR) brightness. Interestingly, both linear and non-linear optical properties are significantly affected by interchromophoric interactions, which are promoted by the molecular confinement and modulated by both the dipolar strength and the presence of the bulky groups. Finally, we exploited the photophysical properties of the FONs to design optimized core-shell nanoparticles built from a pair of complementary dipolar dyes that promotes an efficient core-to-shell FRET process. The resulting molecular-based core-shell nanoparticles combine large two-photon absorption and enhanced emission both located in the NIR spectral region, thanks to a major amplification (by a factor of 20) of the core fluorescence quantum yield. These novel nanoparticles, which combine huge one-and two-photon brightness, hold major promise for in vivo optical bioimaging. Full article

Several series of novel substituted thienothiophene derivatives were synthesized by reacting the synthone 1 with different reagents. The newly synthesized compounds were characterized by means of different spectroscopic methods such as IR, NMR, mass spectrometry and by elemental analyses. The new compounds displayed significant activity against both Gram-positive and Gram negative bacteria, in addition to fungi. Molecular docking and POM analyses show the crucial role and impact of substituents on bioactivity and indicate the unfavorable structural parameters in actual drug design: more substitution doesn’t guaranty more efficiency in bioactivity. Full article

Thioenethiophene derivatives represent an important class of compounds with diverse biological activities. We describe here the synthesis of a new series of thieno[2,3-b]thiophene containing bis-heterocyclic compounds 3–7. All the compounds were evaluated for their in vitro antioxidant potential, α-glucosidase and β-glucuronidase inhibiton and anticancer activity against PC-3 cell lines. Compounds 2b (IC₅₀ = 1.3 ± 0.2 μM), 5a (IC₅₀ = 2.3 ± 0.4 μM) and 5b (IC₅₀ = 8.7 ± 0.1 μM) showed a potent inhibition of β-glucuronidase enzyme, more active than the standard d-saccharic acid 1,4-lactone (IC₅₀ = 45.8 ± 2.5 μM). Compounds 5a (IC₅₀ = 22.0 ± 0.3 μM) and 5b (IC₅₀ = 58.4 ± 1.2 μM) were also found to be potent α-glucosidase inhibitors as compared to standard drug (acarbose, IC₅₀ = 841 ± 1.7 μM). Full article