Publications
423 results found
Ding B, Le V, Yu H, et al., 2024, Development of synthetically accessible glycolated polythiophenes for high-performance organic electrochemical transistors, Advanced Electronic Materials, Vol: 10, ISSN: 2199-160X
Four glycolated polythiophene-based organic mixed ionic-electronic conductors (OMIECs), PE2gTT, PE2gT, PT2gTT, and PT2gT are prepared by atom-efficient direct arylation polymerization, avoiding the need for toxic organometallic precursors. PE2gT, PT2gTT, and PT2gT are operable in p-type accumulation mode organic electrochemical transistors (OECTs), with PT2gT displaying the best device performance with a µC* product figure-of-merit of 290 F cm−1 V−1 s−1. A record volumetric capacitance among p-type glycolated polythiophene OMIECs of 313 F cm−3 is observed for PE2gT, ascribed to the high proportionality of polar components in its materials design. The good OECT performance of PE2gT with µC* = 84.2 F cm−1 V−1 s−1, comparable with state-of-the-art poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) devices, coupled with its synthetic accessibility and favorable accumulation mode operation makes PE2gT an ideal glycolated alternative to PEDOT:PSS in bioelectronics. PE2gT with the least negative threshold voltage also displays the best OECT operational cycling stability, linked to better resistance of its oxidized state against parasitic redox side reactions . Shelf life stability of OECTs stored (without bias) is observed to be better for materials with a more negative threshold voltage and higher average molecular weight (PT2gT), that are less susceptible to ambient auto-oxidation and film delamination.
Ma J, He Q, Xue Z, et al., 2024, Regulation of microstructure and charge transport properties of cyclopentadiene-based conjugated polymers via side-chain engineering, Journal of Materials Chemistry C, Vol: 12, Pages: 3549-3556, ISSN: 2050-7526
Conjugated polymers containing non-aromatic cyclopentadiene (Cp) units have shown great application potential in high performance organic field effect transistors (OFETs). However, the relationship between the structure and properties of Cp-based polymers is underexplored, limiting further improvement of the OFET characteristics of these materials. Herein, we synthesized three copolymers of Cp and diketopyrrolopyrrole (DPP) units with side chains of different branching position and lengths PDPPCp-C4-OD, PDPPCp-C7-OD, and PDPPCp-C7-HO. It is found that the alkyl side chain structure has little effect on the thermal, optical, and electronic properties of the resulting polymers, but significantly influences the thin film microstructure. Among them, PDPPCp-C7-HO with a longer linear alkyl spacer as well as shorter branches adopted the most compact and ordered film microstructure, exhibiting the shortest π–π stacking distance, the largest lamellar coherence length and the highest degree of edge-on orientation in thin film after annealing at 200 °C. As a result, PDPPCp-C7-HO exhibited the highest hole mobility of 2.1 cm2 V−1 s−1 in OFET devices.
Aitchison CM, Albrecht K, Awaga K, et al., 2024, Excitonic organic materials for photochemical and optoelectronic applications: general discussion, Faraday Discussions, Vol: 250, Pages: 298-334, ISSN: 1359-6640
Aitchison CM, Albrecht K, Awaga K, et al., 2024, Organic neuromorphics and bioelectronics: general discussion, Faraday Discussions, Vol: 250, Pages: 83-95, ISSN: 1359-6640
Ding B, Bhosale M, Bennett T, et al., 2024, Reducing undesired solubility of squarephaneic tetraimide for use as an organic battery electrode material, Faraday Discussions, Vol: 250, Pages: 129-144, ISSN: 1359-6640
Locally aromatic alkyl-N-substituted squarephaneic tetraimide (SqTI) conjugated macrocycles are four-electron reducible, owing to global aromaticity and presumed global Baird aromaticity of the dianion and tetraanion states, respectively. However, their good solubility inhibits their application as a battery electrode material. By applying sidechain removal as a strategy to reduce SqTI solubility, we report the development of its unsubstituted derivative SqTI-H, which was obtained directly from squarephaneic tetraanhydride by facile treatment with hexamethyldisilazane and MeOH. Compared to alkyl-N-substituted SqTI-Rs, SqTI-H exhibited further improved thermal stability and low neutral state solubility in most common organic solvents, owing to computationally demonstrated hydrogen-bonding capabilities emanating from each imide position on SqTI-H. Reversible solid state electrochemical reduction of SqTI-H to the globally aromatic dianion state was also observed at -1.25 V vs. Fc/Fc+, which could be further reduced in two stages. Preliminary testing of SqTI-H in composite electrodes for lithium-organic half cells uncovered imperfect cycling performance, which may be explained by persistent solubility of reduced states, necessitating further optimisation of electrode fabrication procedures to attain maximum performance.
Aitchison CM, Awaga K, Data P, et al., 2024, Organic thermoelectrics: general discussion, Faraday Discussions, Vol: 250, Pages: 400-416, ISSN: 1359-6640
Hu X, Qiao Z, Nodari D, et al., 2024, Remarkable isomer effect on the performance of fully non-fused non-fullerene acceptors in near-infrared organic photodetectors, Advanced Optical Materials, Vol: 12, ISSN: 2195-1071
Two fully non-fused small-molecule acceptors BTIC-1 and BTIC-2 are reported for application in near-infrared organic photodetectors (NIR OPDs). Both acceptors contain the same conjugated backbone but differing sidechain regiochemistry, affording significant differences in their optical properties. The head-to-head arrangement of BTIC-2 results in a reduction of optical band gap of 0.17 eV compared to BTIC-1, which contains a head-to-tail arrangement, with absorption spanning the visible and near-IR regions up to 900 nm. These differences are rationalized on the basis of non-covalent intramolecular interactions facilitating a more co-planar conformation for BTIC-2. OPDs based on PM6:BTIC-2 deliver a low dark current density of 2.4 × 10−7 A cm−2, leading to a superior specific detectivity of 1.7 × 1011 Jones at 828 nm at -2 V. The optimized device exhibits an ultrafast photo response of 2.6 µs and a high -3 dB cut-off frequency of 130 kHz. This work demonstrates that fully non-fused small-molecule acceptors offer competitive device performance for NIR OPDs compared to fused-ring electron acceptors, but with reduced synthetic complexity. Furthermore, the study presents an efficient strategy to enhance device performance by varying conformational locks.
Sharma A, Faber H, AlGhamdi WS, et al., 2024, Label-free metal-oxide transistor biosensors for metabolite detection in human saliva, Advanced Science, ISSN: 2198-3844
Metabolites are essential molecules involved in various metabolic processes, and their deficiencies and excessive concentrations can trigger significant physiological consequences. The detection of multiple metabolites within a non-invasively collected biofluid could facilitate early prognosis and diagnosis of severe diseases. Here, a metal oxide heterojunction transistor (HJ-TFT) sensor is developed for the label-free, rapid detection of uric acid (UA) and 25(OH)Vitamin-D3 (Vit-D3) in human saliva. The HJ-TFTs utilize a solution-processed In2 O3 /ZnO channel functionalized with uricase enzyme and Vit-D3 antibody for the selective detection of UA and Vit-D3, respectively. The ultra-thin tri-channel architecture facilitates strong coupling between the electrons transported along the buried In2 O3 /ZnO heterointerface and the electrostatic perturbations caused by the interactions between the surface-immobilized bioreceptors and target analytes. The biosensors can detect a wide range of concentrations of UA (from 500 nm to 1000 µM) and Vit-D3 (from 100 pM to 120 nm) in human saliva within 60 s. Moreover, the biosensors exhibit good linearity with the physiological concentration of metabolites and limit of detections of ≈152 nm for UA and ≈7 pM for Vit-D3 in real saliva. The specificity is demonstrated against various interfering species, including other metabolites and proteins found in saliva, further showcasing its capabilities.
Ferree M, Kosco J, Alshehri N, et al., 2024, Organic semiconductor nanoparticles for visible-light-driven CO<sub>2</sub> conversion, Sustainable Energy & Fuels
<jats:p>We present an experimental proof-of-concept study of organic semiconductor nanoparticles (NPs) for visible-light-driven carbon dioxide (CO<jats:sub>2</jats:sub>) conversion.</jats:p>
Qiao Z, He Q, Scaccabarozzi AD, et al., 2024, A novel selenophene based non-fullerene acceptor for near-infrared organic photodetectors with ultra-low dark current, Journal of Materials Chemistry C, ISSN: 2050-7526
<jats:p>Organic photodetectors have great potential in near-infrared applications. Here we develop new non-fullerene acceptors with detection above 800 nm and demonstrated large area devices with record performances.</jats:p>
Qiao Z, He Q, Heeney M, et al., 2023, A novel selenophene based non-fullerene acceptor for near-infrared organic photodetectors with ultra-low dark current, MATSUS Spring 2024 Conference, Publisher: FUNDACIO DE LA COMUNITAT VALENCIANA SCITO
Nanayakkara MPA, He Q, Ruseckas A, et al., 2023, Tissue equivalent curved organic X-ray detectors utilizing high atomic number polythiophene analogues, Advanced Science, Vol: 10, ISSN: 2198-3844
Organic semiconductors are a promising material candidate for X-ray detection. However, the low atomic number (Z) of organic semiconductors leads to poor X-ray absorption thus restricting their performance. Herein, the authors propose a new strategy for achieving high-sensitivity performance for X-ray detectors based on organic semiconductors modified with high –Z heteroatoms. X-ray detectors are fabricated with p-type organic semiconductors containing selenium heteroatoms (poly(3-hexyl)selenophene (P3HSe)) in blends with an n-type fullerene derivative ([6,6]-Phenyl C71 butyric acid methyl ester (PC70BM). When characterized under 70, 100, 150, and 220 kVp X-ray radiation, these heteroatom-containing detectors displayed a superior performance in terms of sensitivity up to 600 ± 11 nC Gy−1 cm−2 with respect to the bismuth oxide (Bi2O3) nanoparticle (NP) sensitized organic detectors. Despite the lower Z of selenium compared to the NPs typically used, the authors identify a more efficient generation of electron-hole pairs, better charge transfer, and charge transport characteristics in heteroatom-incorporated detectors that result in this breakthrough detector performance. The authors also demonstrate flexible X-ray detectors that can be curved to a radius as low as 2 mm with low deviation in X-ray response under 100 repeated bending cycles while maintaining an industry-standard ultra-low dark current of 0.03 ± 0.01 pA mm−2.
Huang Y-T, Nodari D, Furlan F, et al., 2023, Fast near-infrared photodetectors based on nontoxic and solution-processable AgBiS2, Small, ISSN: 1613-6810
Solution-processable near-infrared (NIR) photodetectors are urgently needed for a wide range of next-generation electronics, including sensors, optical communications and bioimaging. However, it is rare to find photodetectors with >300 kHz cut-off frequencies, especially in the NIR region, and many of the emerging inorganic materials explored are comprised of toxic elements, such as lead. Herein, solution-processed AgBiS2 photodetectors with high cut-off frequencies under both white light (>1 MHz) and NIR (approaching 500 kHz) illumination are developed. These high cut-off frequencies are due to the short transit distances of charge-carriers in the ultrathin photoactive layer of AgBiS2 photodetectors, which arise from the strong light absorption of this material, such that film thicknesses well below 120 nm are sufficient to absorb >65% of NIR to visible light. It is also revealed that ion migration plays a critical role in the photo-response speed of these devices, and its detrimental effects can be mitigated by finely tuning the thickness of the photoactive layer, which is important for achieving low dark current densities as well. These outstanding characteristics enable the realization of air-stable, real-time heartbeat sensors based on NIR AgBiS2 photodetectors, which strongly motivates their future integration in high-throughput systems.
Yan H, Cong S, Daboczi M, et al., 2023, Ionic density control of conjugated polyelectrolytes via postpolymerization modification to enhance hole-blocking property for highly efficient PLEDs with fast response times, Advanced Optical Materials, Vol: 11, ISSN: 2195-1071
For an ideal electron interlayer, both electron injection and hole-blocking properties are important to achieve better polymer light-emitting devices (PLEDs) performance. Conjugated polyelectrolytes (CPEs) are applied widely in PLEDs to enhance charge injection. Understanding the role of backbone structures and energetic matching between the CPEs and emitters can benefit charge injection and balance. Herein, a postpolymerization approach to introduce varying amounts of alkyl sulfonate groups onto the backbone of a copolymer of 5-fluoro-2,1,3-benzothiadiazole and 9,9′-dioctylfluorene is utilized. This study finds that device performance is dependent on the percentage of sulfonate groups incorporated, with the optimal copolymer (CPE-50%) maintaining efficient ohmic electron injection and gaining enhanced hole-blocking properties, thereby achieving the most balanced hole/electron current. Therefore, the PLED with CPE-50% interlayer exhibits the highest efficiency (20.3 cd A−1, 20.2 lm W−1) and the fastest response time (4.3 µs), which is the highest efficiency among conventional thin (70 nm) F8BT PLEDs with CPEs. These results highlight the importance of balanced charge carrier density in CPEs and highlight that postpolymerization modification is a useful method for fine-tuning ionic content.
Henderson C, Luke J, Bicalho I, et al., 2023, Charge transfer complex formation between organic interlayers drives light-soaking in large area perovskite solar cells, Energy and Environmental Science, Vol: 16, Pages: 5891-5903, ISSN: 1754-5692
Light soaking (LS) is a well-known but poorly understood phenomenon in perovskite solar cells (PSCs) which significantly affects device efficiency and stability. LS is greatly reduced in large-area inverted PSCs when a PC61BM electron transport layer (ETL) is replaced with C60, where the ETL is commonly in contact with a thin bathocuproine (BCP) interlayer. Herein, we identify the key molecular origins of this LS effect using a combination of surface photovoltage, ambient photoemission spectroscopy, Raman spectroscopy, integrated with density functional theory simulations. We find that BCP forms a photoinduced charge-transfer (CT) complex with both C60 and PC61BM. The C60/BCP complex accelerates C60 dimer formation, leading to a favourable cascading energetic landscape for electron extraction and reduced recombination loss. In contrast, the PC61BM/BCP complex suppresses PC61BM dimer formation, meaning that PC61BM dimerisation is not the cause of LS. Instead, it is the slow light-induced formation of the PC61BM/BCP CT complex itself, and the new energetic transport levels associated with it, which cause the much slower and stronger LS effect of PC61BM based PSCs. These findings provide key understanding of photoinduced ETL/BCP interactions and their impact on the LS effect in PSCs.
Tang Y, Tan WL, Fei Z, et al., 2023, Different energetics at donor:acceptor interfaces in bilayer and bulk-heterojunction polymer:non-fullerene organic solar cells, Solar RRL, Vol: 7, ISSN: 2367-198X
To understand the limitations placed on the open-circuit voltage of bulk heterojunction (BHJ) organic solar cells, the energy levels of neat donor and acceptor samples are often characterized and applied to study BHJ blends. However, energy levels derived from neat samples may not necessarily reflect those at the donor:acceptor interface in blends. The properties of organic semiconductors are sensitive to microstructural changes, with non-fullerene acceptors (NFAs) in particular known to exhibit different thin-film polymorphs. To investigate the influence of differences in molecular packing in neat and blend films, temperature-dependent current–voltage characteristics are measured for bilayer (BL) and BHJ devices. Herein, the fullerene acceptor PC71BM is compared—whose energy levels are expected to be less sensitive to molecular packing—with the NFA ITIC, paired with the same donor polymer PTB7-Th. It is found that the interfacial energy levels differ for BL and BHJ devices for the PTB7-Th:ITIC system but remain the same for the PTB7-Th:PC71BM system. Furthermore, X-ray scattering measurements identify that ITIC exhibits a different packing mode in neat films and in BHJ blends. Such microstructure-dependent differences between neat and blend samples need to be considered when studying energy losses in NFA BHJ solar cells.
Ferree M, Kosco J, De Castro C, et al., 2023, Unleashing the Potential of Organic Semiconductor Nanoparticles towards CO2 Photoreduction, Catalyst Design Strategies for Photo- and Electrochemical Fuel Synthesis, Publisher: FUNDACIO DE LA COMUNITAT VALENCIANA SCITO
Sharma A, AlGhamdi WS, Faber H, et al., 2023, Non-invasive, ultrasensitive detection of glucose in saliva using metal oxide transistors, BIOSENSORS & BIOELECTRONICS, Vol: 237, ISSN: 0956-5663
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Rimmele M, Qiao Z, Panidi J, et al., 2023, A polymer library enables the rapid identification of a highly scalable and efficient donor material for organic solar cells, Materials horizons, Vol: 10, Pages: 4202-4212, ISSN: 2051-6347
The dramatic improvement of the PCE (power conversion efficiency) of organic photovoltaic devices in the past few years has been driven by the development of new polymer donor materials and non-fullerene acceptors (NFAs). In the design of such materials synthetic scalability is often not considered, and hence complicated synthetic protocols are typical for high-performing materials. Here we report an approach to readily introduce a variety of solubilizing groups into a benzo[c][1,2,5]thiadiazole acceptor comonomer. This allowed for the ready preparation of a library of eleven donor polymers of varying side chains and comonomers, which facilitated a rapid screening of properties and photovoltaic device performance. Donor FO6-T emerged as the optimal material, exhibiting good solubility in chlorinated and non-chlorinated solvents and achieving 15.4% PCE with L8BO as the acceptor (15.2% with Y6) and good device stability. FO6-T was readily prepared on the gram scale, and synthetic complexity (SC) analysis highlighted FO6-T as an attractive donor polymer for potential large scale applications.
Ling Z, Nugraha MI, Hadmojo WT, et al., 2023, Over 19% Efficiency in Ternary Organic Solar Cells Enabled by n-Type Dopants, ACS ENERGY LETTERS, Vol: 8, Pages: 4104-4112, ISSN: 2380-8195
Xu W, Hart LJF, Moss B, et al., 2023, Impact of Interface Energetic Alignment and Mobile Ions on Charge Carrier Accumulation and Extraction in p-i-n Perovskite Solar Cells, ADVANCED ENERGY MATERIALS, Vol: 13, ISSN: 1614-6832
He Q, Shaw J, Firdaus Y, et al., 2023, p-type conjugated polymers containing electron-deficient pentacyclic azepinedione, Macromolecules, Vol: 56, Pages: 5825-5834, ISSN: 0024-9297
Bisthienoazepinedione (BTA) has been reported for constructing high-performing p-type conjugated polymers in organic electronics, but the ring extended version of BTA is not well explored. In this work, we report a new synthesis of a key building block to the ring expanded electron-deficient pentacyclic azepinedione (BTTA). Three copolymers of BTAA with benzodithiophene substituted by different side chains are prepared. These polymers exhibit similar energy levels and optical absorption in solution and solid state, while significant differences are revealed in their film morphologies and behavior in transistor and photovoltaic devices. The best-performing polymers in transistor devices contained alkylthienyl side chains on the BDT unit (pBDT-BTTA-2 and pBDT-BTTA-3) and demonstrated maximum saturation hole mobilities of 0.027 and 0.017 cm2 V–1 s–1. Blends of these polymers with PC71BM exhibited a best photovoltaic efficiency of 6.78% for pBDT-BTTA-3-based devices. Changing to a low band gap non-fullerene acceptor (BTP-eC9) resulted in improved efficiency of up to 13.5%. Our results are among the best device performances for BTA and BTTA-based p-type polymers and highlight the versatile applications of this electron-deficient BTTA unit.
Cong S, Chen J, Ding B, et al., 2023, Tunable control of the performance of aqueous-based electrochemical devices by post-polymerization functionalization., Materials horizons, Vol: 10, Pages: 3090-3100, ISSN: 2051-6347
Functionalized polymeric mixed ionic-electronic conductors (PMIECs) are highly desired for the development of electrochemical applications, yet are hindered by the limited conventional synthesis techniques. Here, we propose a "graft-onto-polymer" synthesis strategy by post-polymerization functionalization (GOP-PPF) to prepare a family of PMIECs sharing the same backbone while functionalized with varying ethylene glycol (EG) compositions (two, four, and six EG repeating units). Unlike the typical procedure, GOP-PPF uses a nucleophilic aromatic substitution reaction for the facile and versatile attachment of functional units to a pre-synthesized conjugated-polymer precursor. Importantly, these redox-active PMIECs are investigated as a platform for energy storage devices and organic electrochemical transistors (OECTs) in aqueous media. The ion diffusivity, charge mobility and charge-storage capacity can be significantly improved by optimizing the EG composition. Specifically, g2T2-gBT6 containing the highest EG density gives the highest charge-storage capacity exceeding 180 F g-1 among the polymer series, resulting from the improved ion diffusivity. Moreover, g2T2-gBT4 with four EG repeating units exhibits a superior performance compared to its two analogues in OECTs, associated with a high μC* up to 359 F V-1 cm-1 s-1, owing to the optimal balance between ionic-electronic coupling and charge mobility. Through the GOP-PPF, PMIECs can be tailored to access desirable performance metrics at the molecular level.
Panidi J, Mazzolini E, Eisner F, et al., 2023, Biorenewable solvents for high-performance organic solar cells, ACS Energy Letters, Vol: 8, Pages: 3038-3047, ISSN: 2380-8195
With the advent of nonfullerene acceptors (NFAs), organic photovoltaic (OPV) devices are now achieving high enough power conversion efficiencies (PCEs) for commercialization. However, these high performances rely on active layers processed from petroleum-based and toxic solvents, which are undesirable for mass manufacturing. Here, we demonstrate the use of biorenewable 2-methyltetrahydrofuran (2MeTHF) and cyclopentyl methyl ether (CPME) solvents to process donor: NFA-based OPVs with no additional additives in the active layer. Furthermore, to reduce the overall carbon footprint of the manufacturing cycle of the OPVs, we use polymeric donors that require a few synthetic steps for their synthesis, namely, PTQ10 and FO6-T, which are blended with the Y-series NFA Y12. High performance was achieved using 2MeTHF as the processing solvent, reaching PCEs of 14.5% and 11.4% for PTQ10:Y12 and FO6-T:Y12 blends, respectively. This work demonstrates the potential of using biorenewable solvents without additives for the processing of OPV active layers, opening the door to large-scale and green manufacturing of organic solar cells.
Jiang Z, Du T, Lin C, et al., 2023, Deciphering the role of hole transport layer HOMO level on the open circuit voltage of perovskite Solar cells, Advanced Materials Interfaces, Vol: 10, ISSN: 2196-7350
With the rapid development of perovskite solar cells, reducing losses in open-circuit voltage (Voc) is a key issue in efforts to further improve device performance. Here it is focused on investigating the correlation between the highest occupied molecular orbital (HOMO) of device hole transport layers (HTLs) and device Voc. To achieve this, structurally similar HTL materials with comparable optical band gaps and doping levels, but distinctly different HOMO levels are employed. Using light-intensity dependent Voc and photoluminescence measurements significant differences in the behavior of devices employing the two HTLs are highlighted. Light-induced increase of quasi-Fermi level splitting (ΔEF) in the perovskite layer results in interfacial quasi-Fermi level bending required to align with the HOMO level of the HTL, resulting in the Voc measured at the contacts being smaller than the ΔEF in the perovskite. It is concluded that minimizing the energetic offset between HTLs and the perovskite active layer is of great importance to reduce non-radiative recombination losses in perovskite solar cells with high Voc values that approach the radiative limit.
Jacoutot P, Scaccabarozzi A, Nodari D, et al., 2023, Enhanced Sub-1 eV detection in organic photodetectors through tuning polymer energetics and microstructure, Science Advances, Vol: 9, Pages: 1-9, ISSN: 2375-2548
One of the key challenges facing organic photodiodes (OPD) is increasing the detection into the IR region. Organic semiconductor polymers provide a platform for tuning the bandgap and optoelectronic response to go beyond the traditional 1000 nm benchmark. In this work, we present a NIR polymer with absorption up to 1500 nm. The polymer-based OPD delivers a high specific detectivity D* of 1.03×1010 Jones (-2 V) at 1200 nm and a dark current Jd of just 2.3×10-6 A cm-2 at -2V. We demonstrate a strong improvement of all OPD metrics in the NIR region compared to previously reported NIR-OPD, due to the enhanced crystallinity and optimized energy alignment which leads to reduced charge recombination. The high D* value in the 1100-1300 nm region is particularly promising for biosensing applications. We demonstrate the OPD as a pulse oximeter under NIR illumination, delivering heart rate and blood oxygen saturation readings in real-time without signal amplification.
Bennett TLR, Marsh AV, Turner JM, et al., 2023, Functionalisation of conjugated macrocycles with type I and II concealed antiaromaticity via cross-coupling reactions, Molecular Systems Design & Engineering, Vol: 8, Pages: 713-720, ISSN: 2058-9689
Conjugated macrocycles can exhibit concealed antiaromaticity; that is, despite not being antiaromatic, under specific circumstances, they can display properties typically observed in antiaromatic molecules due to their formal macrocyclic 4n π-electron system. Paracyclophanetetraene (PCT) and its derivatives are prime examples of macrocycles exhibiting this behaviour. In redox reactions and upon photoexcitation, they have been shown to behave like antiaromatic molecules (requiring type I and II concealed antiaromaticity, respectively), with such phenomena showing potential for use in battery electrode materials and other electronic applications. However, further exploration of PCTs has been hindered by the lack of halogenated molecular building blocks that would permit their integration into larger conjugated molecules by cross-coupling reactions. Here, we present two dibrominated PCTs, obtained as a mixture of regioisomers from a three-step synthesis, and demonstrate their functionalisation via Suzuki cross-coupling reactions. Optical, electrochemical, and theoretical studies reveal that aryl substituents can subtly tune the properties and behaviour of PCT, showing that this is a viable strategy in further exploring this promising class of materials.
Polak DW, Andrews I, Farrow G, et al., 2023, Conjugation-length dependence of regioregular oligo 3-alkyl(thienylene-vinylene)s demonstrates polyene-like behaviour with weak electron-electron correlations, Physical Chemistry Chemical Physics, Vol: 25, Pages: 11205-11215, ISSN: 1463-9076
Poly(3-alkyl(thienylene-vinylene)) (P3TV) and its longer oligomers have negligibly low photoluminescence quantum yields, however, the reason for their low yields is currently debated. Here, we prepare a series of regioregular (3-dodecyl)thienylene-vinylene oligomers with n = 2–8 repeat units by iterative Horner–Wadsworth–Emmons reactions, and report their steady-state, transient absorption, and emission spectroscopy. The results presented here demonstrate that 3-alkyl(thienylene-vinylene) oligomers form part of the polyene family. The shortest (n = 2) oligomer emits from the bright 1Bu state, while fluorescence in oligomers with n = 3, 4 is from the formally dark 2Ag state, allowed via Herzberg–Teller vibronic coupling to the nearby bright 1Bu state as described for diphenyl-polyenes. Longer oligomers and the polymer are essentially non-emissive as the 2Ag state can no longer intensity-borrow from the 1Bu state. We demonstrate that the spectral shapes, photoluminescence quantum yield, and transient spectral behaviour can all be explained using a polyene model with weak electronic correlations.
Ding B, Jo I-Y, Yu H, et al., 2023, Enhanced organic electrochemical transistor performance of donor-acceptor conjugated polymers modified with hybrid glycol/ ionic side chains by postpolymerization modification, Chemistry of Materials, Vol: 35, Pages: 3290-3299, ISSN: 0897-4756
Emergent bioelectronic technologies are underpinned by the organic electrochemical transistor (OECT), which employs an electrolyte medium to modulate the conductivity of its organic semiconductor channel. Here we utilize postpolymerization modification (PPM) on a conjugated polymer backbone to directly introduce glycolated or anionic side chains via fluoride displacement. The resulting polymers demonstrated increased volumetric capacitances, with subdued swelling, compared to their parent polymer in p-type enhancement mode OECTs. This increase in capacitance was attributed to their modified side chain configurations enabling cationic charge compensation for thin film electrochemical oxidation, as deduced from electrochemical quartz crystal microbalance measurements. An overall improvement in OECT performance was recorded for the hybrid glycol/ionic polymer compared to the parent, owing to its low swelling and bimodal crystalline orientation as imaged by grazing-incidence wide-angle X-ray scattering, enabling its high charge mobility at 1.02 cm2·V–1·s–1. Compromised device performance was recorded for the fully glycolated derivative compared to the parent, which was linked to its limited face-on stacking, which hindered OECT charge mobility at 0.26 cm2·V–1·s–1, despite its high capacitance. These results highlight the effectiveness of anionic side chain attachment by PPM as a means of increasing the volumetric capacitance of p-type conjugated polymers for OECTs, while retaining solid-state macromolecular properties that facilitate hole transport.
Marsh AV, Heeney M, 2023, Conjugated polymers based on selenophene building blocks, POLYMER JOURNAL, Vol: 55, Pages: 375-385, ISSN: 0032-3896
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