Publications
379 results found
Creamer A, Lo Fiego A, Agliano A, et al., 2023, Modular synthesis of semiconducting graft co-polymers to achieve ‘clickable’ fluorescent nanoparticles with long circulation and specific cancer targeting, Advanced Materials, ISSN: 0935-9648
He Q, Basu A, Cha H, et al., 2023, Ultra-Narrowband Near-Infrared Responsive J-Aggregates of Fused Quinoidal Tetracyanoindacenodithiophene, ADVANCED MATERIALS, ISSN: 0935-9648
Anies F, Nugraha MI, Fall A, et al., 2023, In Situ Generation of n-Type Dopants by Thermal Decarboxylation, ADVANCED FUNCTIONAL MATERIALS, ISSN: 1616-301X
Aniés F, Furlan F, Qiao Z, et al., 2023, A comparison of para, meta, and ortho-carborane centred non-fullerene acceptors for organic solar cells, Journal of Materials Chemistry C
We report the first examples of carborane-containing non-fullerene acceptors (NFAs), and their use in organic photovoltaic (OPV) devices. NFAs employing an A-D-A′-D-A type design centred around a central electron withdrawing carborane unit (A′), using either para, meta, or ortho-carborane isomers are reported. We demonstrate that the nature of the isomer has a major impact on device performance, despite minor differences in optoelectronic and morphological properties, with the use of ortho-carborane resulting in the highest device efficiencies. We further show that end-group fluorination is an efficient strategy to modulate energy levels and improve device performance of such NFAs.
Hu X, Basu A, Rimmele M, et al., 2022, N-type polymer semiconductors incorporating heteroannulated benzothiadiazole, POLYMER CHEMISTRY, Vol: 14, Pages: 469-476, ISSN: 1759-9954
Marsh AV, Heeney M, 2022, Conjugated polymers based on selenophene building blocks, POLYMER JOURNAL, ISSN: 0032-3896
Eder S, Ding B, Thornton DB, et al., 2022, Squarephaneic tetraanhydride: a conjugated square‐shaped cyclophane for the synthesis of porous organic materials, Angewandte Chemie International Edition, Vol: 61, Pages: 1-8, ISSN: 1433-7851
Aromatic carboxylic anhydrides are ubiquitous building blocks in organic materials chemistry and have received considerable attention in the synthesis of organic semiconductors, pigments, and battery electrode materials. Here we extend the family of aromatic carboxylic anhydrides with a unique new member, a conjugated cyclophane with four anhydride groups. The cyclophane is obtained in a three-step synthesis and can be functionalised efficiently, as shown by the conversion into tetraimides and an octacarboxylate. Crystal structures reveal the high degree of porosity achievable with the new building block. Excellent electrochemical properties and reversible reduction to the tetraanions are shown for the imides; NMR and EPR measurements confirm the global aromaticity of the dianions and evidence the global Baird aromaticity of the tetraanions. Considering the short synthesis and unique properties, we expect widespread use of the new building block in the development of organic materials.
He Q, Kafourou P, Hu X, et al., 2022, Development of non-fullerene electron acceptors for efficient organic photovoltaics, SN Applied Sciences, Vol: 4, ISSN: 2523-3971
Compared to fullerene based electron acceptors, n-type organic semiconductors, so-called non-fullerene acceptors (NFAs), possess some distinct advantages, such as readily tuning of optical absorption and electronic energy levels, strong absorption in the visible region and good morphological stability for flexible electronic devices. The design and synthesis of new NFAs have enabled the power conversion efficiencies (PCEs) of organic photovoltaic (OPV) devices to increase to around 19%. This review summarises the important breakthroughs that have contributed to this progress, focusing on three classes of NFAs, i.e. perylene diimide (PDI), diketopyrrolopyrrole (DPP) and acceptor–donor–acceptor (A-D-A) based NFAs. Specifically, the PCEs of PDI, DPP, and A-D-A series based non-fullerene OPVs have been reported up to 11%, 13% and 19%, respectively. Structure–property relationships of representative NFAs and their impact on OPV performances are discussed. Finally, we consider the remaining challenges and promising directions for achieving high-performing NFAs.
Rimmele M, Glöcklhofer F, Heeney M, 2022, Post-polymerisation approaches for the rapid modification of conjugated polymer properties., Materials Horizons, Vol: 9, Pages: 2678-2697, ISSN: 2051-6355
Post-polymerisation functionalisation provides a facile and efficient way for the introduction of functional groups on the backbone of conjugated polymers. Using post-polymerisation functionalisation approaches, the polymer chain length is usually not affected, meaning that the resulting polymers only differ in their attached functional groups or side chains, which makes them particularly interesting for investigating the influence of the different groups on the polymer properties. For such functionalisations, highly efficient and selective reactions are needed to avoid the formation of complex mixtures or permanent defects in the polymer backbone. A variety of suitable synthetic approaches and reactions that fulfil these criteria have been identified and reported. In this review, a thorough overview is given of the post-polymerisation functionalisations reported to date, with the methods grouped based on the type of reaction used: cycloaddition, oxidation/reduction, nucleophilic aromatic substitution, or halogenation and subsequent cross-coupling reaction. Instead of modifications on the aliphatic side chains of the conjugated polymers, we focus on modifications directly on the conjugated backbones, as these have the most pronounced effect on the optical and electronic properties. Some of the discussed materials have been used in applications, ranging from solar cells to bioelectronics. By providing an overview of this versatile and expanding field for the first time, we showcase post-polymerisation functionalisation as an exciting pathway for the creation of new conjugated materials for a range of applications.
Jang S-Y, Kim I-B, Kim Y, et al., 2022, Facile direct C-H arylation polymerization of conjugated polymer, PDCBT, for organic solar cells, Macromolecular Rapid Communications, ISSN: 1022-1336
Direct arylation polymerization (DArP) is a synthetic method for conjugated polymers; in DArP, organometallic functionalization steps are omitted and there are no toxic byproducts. As a result, it is considered a more sustainable alternative compared to conventional methods such as Stille polymerization. To explore the possibility of DArP-based polymers as donor materials in organic solar cells (OSCs), a series of conjugated polymers based on the structure of PDCBT (poly[2,2''''-bis[[(2-butyloctyl)oxy]carbonyl][2,2':5',2'':5'',2'''-quaterthiophene]-5,5'''-diyl]) are synthesized using DArP and Stille polymerization. By controlling the monomer concentration and reaction time in DArP, DArP-5 with the highest Mn (21.9 kDa) can be obtained and its optoelectronic properties, electrochemical properties, and microscopic molecular ordering are comparable to those of Stille-based PDCBT (Stille-P). Analysis of the polymer structure indicates no structural defects such as crosslinking from undesired β-coupling reactions in DArP-5. Upon blending with the PC71BM acceptor molecule, an increase in the crystallite size of DArP-5 is also observed. In OSC devices with a polymer:PC71BM bulk-heterojunction photoactive layer, DArP-5 demonstrates a comparable power conversion efficiency of 5.8% with that of Stille-P (5.5%). These results prove that DArP is suitable for synthesizing PDCBT, and DArP-based PDCBT can be used in OSCs as an alternative of Stille-based one.
Kafourou P, Qiao Z, Toth M, et al., 2022, Low Dark Current Organic Photodetectors Utilizing Highly Cyanated Non-fullerene Acceptors, ACS APPLIED MATERIALS & INTERFACES, ISSN: 1944-8244
Polak DW, do Casal MT, Toldo JM, et al., 2022, Probing the electronic structure and photophysics of thiophene-diketopyrrolopyrrole derivatives in solution, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 24, Pages: 20138-20151, ISSN: 1463-9076
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- Citations: 1
Rotas G, Antoniou G, Papagiorgis P, et al., 2022, Doping-induced decomposition of organic semiconductors: a caveat to the use of Lewis acid p-dopants, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 10, Pages: 12751-12764, ISSN: 2050-7526
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- Citations: 1
Zhang C, Tan WL, Liu Z, et al., 2022, High-Performance Unipolar n-Type Conjugated Polymers Enabled by Highly Electron-Deficient Building Blocks Containing F and CN Groups (vol 55, pg 4429, 2022), MACROMOLECULES, Vol: 55, Pages: 6295-6295, ISSN: 0024-9297
Dou F, Fei Z, Buchaca-Domingo E, et al., 2022, Observing the On-Site Generation of Excitons and Charges by Low- Temperature Spectroscopy, ACS APPLIED MATERIALS & INTERFACES, ISSN: 1944-8244
Nugraha MI, Gedda M, Firdaus Y, et al., 2022, Addition of diquat enhances the electron mobility in various non-fullerene acceptor molecules, Advanced Functional Materials, ISSN: 1616-301X
Molecular doping of organic semiconductors is often used to enhance their charge transport characteristics. Despite its success, however, most studies to date concern p-doping with considerably fewer reports involving n-dopants. Here, n-doping of organic thin-film transistors (OTFTs) based on several non-fullerene acceptor (NFA) molecules using the recently developed diquat (DQ) as a soluble molecular dopant is reported. The low ionization potential of DQ facilitates efficient electron transfer and subsequent n-doping of the NFAs, resulting in a consistent increase in the electron field-effect mobility. Solution-processed BTP-eC9 and N3-based OTFTs exhibit significant increase in the electron mobility upon DQ doping, with values increasing from 0.02 to 0.17 cm2 V–1 s–1 and from 0.2 to 0.57 cm2 V–1 s–1, respectively. A remarkable electron mobility of >1 cm2 V–1 s–1 is achieved for O-IDTBR transistors upon optimal doping with DQ. The enhanced performance originates primarily from synergistic effects on electronic transport and changes in morphology, including: i) significant reduction of contact resistances, ii) formation of larger crystalline domains, iii) change of preferred crystal orientation, and iv) alteration in molecular packing motif. This work demonstrates the universality of DQ as an electronic additive for improving electron transport in OTFTs.
Hu X, Datt R, He Q, et al., 2022, Facile synthesis of annulated benzothiadiazole derivatives and their application as medium band gap acceptors in organic photovoltaic devices, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 10, Pages: 9249-9256, ISSN: 2050-7526
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- Citations: 2
Zhang C, Tan WL, Liu Z, et al., 2022, High-Performance Unipolar n-Type Conjugated Polymers Enabled by Highly Electron-Deficient Building Blocks Containing F and CN Groups, MACROMOLECULES, ISSN: 0024-9297
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- Citations: 6
Firdaus Y, He Q, Muliani L, et al., 2022, Charge transport and recombination in wide-bandgap Y6 derivatives-based organic solar cells, ADVANCES IN NATURAL SCIENCES-NANOSCIENCE AND NANOTECHNOLOGY, Vol: 13, ISSN: 2043-6254
Jacoutot P, Scaccabarozzi AD, Zhang T, et al., 2022, Infrared organic photodetectors employing ultralow bandgap polymer and non-fullerene acceptors for biometric monitoring, Small, Vol: 18, Pages: 1-10, ISSN: 1613-6810
Recent efforts in the field of organic photodetectors (OPD) have been focused on extending broadband detection into the near-infrared (NIR) region. Here, two blends of an ultralow bandgap push–pull polymer TQ-T combined with state-of-the-art non-fullerene acceptors, IEICO-4F and Y6, are compared to obtain OPDs for sensing in the NIR beyond 1100 nm, which is the cut off for benchmark Si photodiodes. It is observed that the TQ-T:IEICO-4F device has a superior IR responsivity (0.03 AW-1 at 1200 nm and −2 V bias) and can detect infrared light up to 1800 nm, while the TQ-T:Y6 blend shows a lower responsivity of 0.01 AW-1. Device physics analyses are tied with spectroscopic and morphological studies to link the superior performance of TQ-T:IEICO-4F OPD to its faster charge separation as well as more favorable donor–acceptor domains mixing. In the polymer blend with Y6, the formation of large agglomerates that exceed the exciton diffusion length, which leads to high charge recombination, is observed. An application of these devices as biometric sensors for real-time heart rate monitoring via photoplethysmography, utilizing infrared light, is demonstrated.
Pletzer M, Plasser F, Rimmele M, et al., 2022, [2.2.2.2]Paracyclophanetetraenes (PCTs): cyclic structural analogues of poly(p‑phenylene vinylene)s (PPVs), Open Research Europe, Vol: 1, Pages: 1-19, ISSN: 2732-5121
Background: Poly(p-phenylene vinylene)s (PPVs) and [2.2.2.2]paracyclophanetetraene (PCT) are both composed of alternating π-conjugated para-phenylene and vinylene units. However, while the former constitute a class of π-conjugated polymers that has been used in organic electronics for decades, the latter is a macrocycle that only recently revealed its potential for applications such as organic battery electrodes. The cyclic structure endows PCT with unusual properties, and further tuning of these may be required for specific applications. Methods: In this article, we adopt an approach often used for tuning the properties of PPVs, the introduction of alkoxy (or alkylthio) substituents at the phenylene units, for tuning the optoelectronic properties of PCT. The resulting methoxy- and methylthio-substituted PCTs, obtained by Wittig cyclisation reactions, are studied by UV-vis absorption, photoluminescence, and cyclic voltammetry measurements, and investigated computationally using the visualisation of chemical shielding tensors (VIST) method. Results: The measurements show that substitution leads to slight changes in terms of absorption/emission energies and redox potentials while having a pronounced effect on the photoluminescence intensity. The computations show the effect of the substituents on the ring currents and chemical shielding and on the associated local and global (anti)aromaticity of the macrocycles, highlighting the interplay of local and global aromaticity in various electronic states. Conclusions: The study offers interesting insights into the tuneability of the properties of this versatile class of π-conjugated macrocycles.
Scaccabarozzi AD, Basu A, Anies F, et al., 2022, Doping Approaches for Organic Semiconductors, CHEMICAL REVIEWS, Vol: 122, Pages: 4420-4492, ISSN: 0009-2665
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- Citations: 33
Azzouzi M, Nelson J, Eisner F, et al., 2022, Reconciling models of interfacial state kinetics and device performance in organic solar cells: Impact of the energy offsets on the power conversion efficiency, Energy and Environmental Science, Vol: 15, Pages: 156-1270, ISSN: 1754-5692
Achieving the simultaneous increases in the open circuit voltage (Voc), short circuit current (Jsc) and fill factor (FF) necessary to further increase the power conversion efficiency (PCE) of organic photovoltaics (OPV) requires a unified understanding of how molecular and device parameters affect all three characteristics. In this contribution, we introduce a framework that for the first time combines different models that have been used separately to describe the different steps of the charge generation and collection processes in OPV devices: a semi-classical rate model for charge recombination processes in OPV devices, zero-dimensional kinetic models for the photogeneration process and exciton dissociation and one-dimensional semiconductor device models. Using this unified multi-scale model in conjunction with experimental techniques (time-resolved absorption spectroscopy, steady-state and transient optoelectronic measurements) that probe the various steps involved in charge generation we can shed light on how the energy offsets in a series of polymer: non-fullerene devices affect the charge carrier generation, collection, and recombination properties of the devices. We find that changing the energy levels of the donor significantly affects not only the transition rates between local-exciton (LE) and charge-transfer (CT) states, but also significantly changes the transition rates between CT and charge-separated (CS) states, challenging the commonly accepted picture of charge generation and recombination. These results show that in order to obtain an accurate picture of charge generation in OPV devices, a variety of different experimental techniques under different conditions in conjunction with a comprehensive model of processes occurring at different time-scales are required.
Aniés F, Qiao Z, Nugraha MI, et al., 2022, N-type polymer semiconductors incorporating para, meta, and ortho-carborane in the conjugated backbone, Polymer, Vol: 240, Pages: 124481-124481, ISSN: 0032-3861
We report on three novel n-type conjugated polymer semiconductors incorporating carborane in the polymer backbone and demonstrate their applicability in optoelectronic devices. Comparing the optoelectronic properties of para-, meta-, and ortho-carborane isomers revealed similar energetic characteristics between the different polymers, with the carborane unit acting as a “conjugation breaker”, confining electron delocalisation to the conjugated moieties. The fabrication of all-polymer organic photovoltaic (OPV) devices and thin-film transistors (TFTs) revealed some differences in device performance between the polymers, with the meta-carborane based polymer exhibiting superior performance in both OPV and TFT devices.
Hernandez FJ, Fei Z, Osborne C, et al., 2022, Triplet Generation Dynamics in Si- and Ge-Bridged Conjugated Copolymers, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 126, Pages: 1036-1045, ISSN: 1932-7447
Liang X, Chen Y, Jiao X, et al., 2022, Vinylene Flanked Naphtho[1,2-c:5,6-c ']bis[1,2,5]thiadiazole Polymer for Low-Crystallinity Ambipolar Transistors, MACROMOLECULES, Vol: 55, Pages: 331-337, ISSN: 0024-9297
Kim Y, Kim G, Ding B, et al., 2022, High-current-density organic electrochemical diodes enabled by asymmetric active layer design, Advanced Materials, ISSN: 0935-9648
Owing to their outstanding electrical/electrochemical performance, operational stability, mechanical flexibility, and decent biocompatibility, organic mixed ionic–electronic conductors have shown great potential as implantable electrodes for neural recording/stimulation and as active channels for signal switching/amplifying transistors. Nonetheless, no studies exist on a general design rule for high-performance electrochemical diodes, which are essential for highly functional circuit architectures. In this work, generalizable electrochemical diodes with a very high current density over 30 kA cm−2 are designed by introducing an asymmetric active layer based on organic mixed ionic–electronic conductors. The underlying mechanism on polarity-sensitive balanced ionic doping/dedoping is elucidated by numerical device analysis and in operando spectroelectrochemical potential mapping, while the general material requirements for electrochemical diode operation are deduced using various types of conjugated polymers. In parallel, analog signal rectification and digital logic processing circuits are successfully demonstrated to show the broad impact of circuits incorporating organic electrochemical diodes. It is expected that organic electrochemical diodes will play vital roles in realizing multifunctional soft bioelectronic circuitry in combination with organic electrochemical transistors.
Loganathan K, Scaccabarozzi AD, Faber H, et al., 2022, 14 GHz schottky diodes using a p-doped organic polymer., Advanced Materials, Vol: 34, Pages: 1-8, ISSN: 0935-9648
The low carrier mobility of organic semiconductors and the high parasitic resistance and capacitance often encountered in conventional organic Schottky diodes, hinder their deployment in emerging radio frequency (RF) electronics. Here we overcome these limitations by combining self-aligned asymmetric nanogap electrodes (∼25 nm) produced by adhesion-lithography, with a high mobility organic semiconductor and demonstrate RF Schottky diodes able to operate in the 5G frequency spectrum. We used C16 IDT-BT, as the high hole mobility polymer, and studied the impact of p-doping on the diode performance. Pristine C16 IDT-BT-based diodes exhibit maximum intrinsic and extrinsic cutoff frequencies (fC ) of >100 and 6 GHz, respectively. This extraordinary performance is attributed primarily to the planar nature of the nanogap channel and the diode's small junction capacitance (< 2 pF). Doping of C16 IDT-BT with the molecular p-dopant C60 F48 , improves the diode's performance further by reducing the series resistance resulting to intrinsic and extrinsic fC of >100 and ∼14 GHz respectively, while the DC output voltage of a RF rectifier circuit increases by a tenfold. Our work highlights the importance of the planar nanogap architecture and paves the way for the use of organic Schottky diodes in large-area radio frequency electronics of the future. This article is protected by copyright. All rights reserved.
Kafourou P, Nugraha MI, Nikitaras A, et al., 2021, Near-IR absorbing molecular semiconductors incorporating cyanated benzothiadiazole acceptors for high performance semi-transparent n-type organic field-effect transistors, ACS Materials Letters, Vol: 4, Pages: 165-174, ISSN: 2639-4979
Small band gap molecular semiconductors are of interest for the development of transparent electronics. Here we report two near-infrared (NIR), n-type small molecule semiconductors, based upon an acceptor-donor-acceptor (A-D-A) approach. We show that the inclusion of molecular spacers between the strong electron accepting end group, 2,1,3-benzothiadiazole-4,5,6-tricarbonitrile, and the donor core affords semiconductors with very low band gaps down to 1 eV. Both materials were synthesised by a one-pot, sixfold nucleophilic displacement of a fluorinated precursor by cyanide. Significant differences in solid-state ordering and charge carrier mobility are observed depending on the nature of the spacer, with a thiophene spacer resulting in solution processed organic field-effect transistors (OFETs) exhibiting excellent electron mobility up to 1.1 cm2 V-1s-1. The use of silver nanowires as the gate electrodes enables the fabrication of semi-transparent OFET device with average visible transmission of 71% in the optical spectrum.
Allen JDW, Adlem K, Heeney M, 2021, The synthesis and application of novel benzodithiophene based reactive mesogens with negative wavelength dispersion birefringence, Journal of Materials Chemistry C, Vol: 9, Pages: 17419-17426, ISSN: 2050-7526
Optical corrective retardation films are widely used in the display industry to compensate for a variety of imperfections such as off-axis contrast reduction, grey-scale inversion and colour shifts in LCDs and backplane reflections in OLEDs. A wide variety of these films have been produced by multiple methods, however, obtaining ideal wavelength dispersion remains difficult and costly to achieve in thin, single-layer systems. In this work, we report the synthesis of a novel series of reactive mesogen materials designed to exhibit negative wavelength dispersion birefringence. This series of photopolymerisable materials based on a benzodithiophene core exhibiting either an ‘X’-shaped or ‘T’-shaped geometry were synthesised. Their negative wavelength dispersion birefringence properties were investigated in aligned films prepared from photo-polymerised reactive mesogen host mixtures. The nature of the substituents on the BDT core was found to have a significant impact on performance, and materials with an X-shaped geometry were found to exhibit much higher performance than those with a T-shape.
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