Imperial College London

ProfessorMartinHeeney

Faculty of Natural SciencesDepartment of Chemistry

Professor of Organic Materials
 
 
 
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Contact

 

+44 (0)20 7594 1248m.heeney Website

 
 
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Location

 

401GMolecular Sciences Research HubWhite City Campus

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Summary

 

Publications

Publication Type
Year
to

373 results found

Eder S, Ding B, Thornton DB, Sammut D, White AJP, Plasser F, Stephens IEL, Heeney M, Mezzavilla S, Glöcklhofer Fet al., 2022, Squarephaneic tetraanhydride: a conjugated square‐shaped cyclophane for the synthesis of porous organic materials, Angewandte Chemie International Edition, 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.

Journal article

He Q, Kafourou P, Hu X, Heeney Met 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.

Journal article

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.

Journal article

Jang S-Y, Kim I-B, Kim Y, Lim D-H, Kang H, Heeney M, Kim D-Yet 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.

Journal article

Kafourou P, Qiao Z, Toth M, Anies F, Eisner F, Gasparini N, Heeney Met al., 2022, Low Dark Current Organic Photodetectors Utilizing Highly Cyanated Non-fullerene Acceptors, ACS APPLIED MATERIALS & INTERFACES, ISSN: 1944-8244

Journal article

Polak DW, do Casal MT, Toldo JM, Hu X, Amoruso G, Pomeranc O, Heeney M, Barbatti M, Ashfold MNR, Oliver TAAet 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

Journal article

Rotas G, Antoniou G, Papagiorgis P, Basu A, Panidi J, Ufimkin P, Tsetseris L, Itskos G, Heeney M, Vougioukalakis GC, Anthopoulos TD, Keivanidis PEet 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

Journal article

Zhang C, Tan WL, Liu Z, He Q, Li Y, Ma J, Chesman ASR, Han Y, McNeill CR, Heeney M, Fei Zet 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

Journal article

Dou F, Fei Z, Buchaca-Domingo E, Brosseau C-N, Leonelli R, Heeney M, Zhang Xet al., 2022, Observing the On-Site Generation of Excitons and Charges by Low- Temperature Spectroscopy, ACS APPLIED MATERIALS & INTERFACES, ISSN: 1944-8244

Journal article

Nugraha MI, Gedda M, Firdaus Y, Scaccabarozzi AD, Zhang W, Alshammari S, Anies F, Adilbekova B, Emwas A-H, McCulloch I, Heeney M, Tsetseris L, Anthopoulos TDet 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.

Journal article

Hu X, Datt R, He Q, Kafourou P, Ka Hin Lee H, White AJP, Tsoi WC, Heeney Met 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

Journal article

Zhang C, Tan WL, Liu Z, He Q, Li Y, Ma J, Chesman ASR, Han Y, McNeill CR, Heeney M, Fei Zet 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

Journal article

Firdaus Y, He Q, Muliani L, Rosa ES, Heeney M, Anthopoulos TDet 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

Journal article

Jacoutot P, Scaccabarozzi AD, Zhang T, Qiao Z, Anies F, Neophytou M, Bristow H, Kumar R, Moser M, Nega AD, Schiza A, Dimitrakopoulou-Strauss A, Gregoriou VG, Anthopoulos TD, Heeney M, McCulloch I, Bakulin AA, Chochos CL, Gasparini Net 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.

Journal article

Pletzer M, Plasser F, Rimmele M, Heeney M, Glöcklhofer Fet 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.

Journal article

Scaccabarozzi AD, Basu A, Anies F, Liu J, Zapata-Arteaga O, Warren R, Firdaus Y, Nugraha MI, Lin Y, Campoy-Quiles M, Koch N, Mueller C, Tsetseris L, Heeney M, Anthopoulos TDet al., 2022, Doping Approaches for Organic Semiconductors, CHEMICAL REVIEWS, Vol: 122, Pages: 4420-4492, ISSN: 0009-2665

Journal article

Azzouzi M, Nelson J, Eisner F, Gallop N, Yan J, Zheng X, Cha H, He Q, Fei Z, Heeney M, Bakulin Aet 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.

Journal article

Aniés F, Qiao Z, Nugraha MI, Basu A, Anthopoulos TD, Gasparini N, Heeney Met 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.

Journal article

Hernandez FJ, Fei Z, Osborne C, Crespo-Otero R, Heeney M, Dimitrov SDet 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

Journal article

Liang X, Chen Y, Jiao X, Heeney M, McNeill CR, Dong L, Zhou C, Liu Z, Tan Let 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

Journal article

Kim Y, Kim G, Ding B, Jeong D, Lee I, Park S, Kim BJ, McCulloch I, Heeney M, Yoon M-Het 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.

Journal article

Loganathan K, Scaccabarozzi AD, Faber H, Ferrari F, Bizak Z, Yengel E, Naphade DR, Gedda M, He Q, Solomeshch O, Adilbekova B, Yarali E, Tsetseris L, Salama KN, Heeney M, Tessler N, Anthopoulos TDet 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.

Journal article

Kafourou P, Nugraha MI, Nikitaras A, Tan L, Firdaus Y, Aniés F, Eisner F, Ding B, Wenzel J, Holicky M, Tsetseris L, Anthopoulos TD, Heeney Met 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.

Journal article

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.

Journal article

Lin Y-H, Han Y, Sharma A, AlGhamdi WS, Liu C-H, Chang T-H, Xiao X-W, Lin W-Z, Lu P-Y, Seitkhan A, Mottram AD, Pattanasattayavong P, Faber H, Heeney M, Anthopoulos TDet al., 2021, A tri-channel oxide transistor concept for the rapid detection of biomolecules including the SARS-CoV-2 spike protein, Advanced Materials, Pages: 1-14, ISSN: 0935-9648

Solid-state transistor sensors that can detect biomolecules in real time are highly attractive for emerging bioanalytical applications. However, combining upscalable manufacturing with the required performance remains challenging. Here, an alternative biosensor transistor concept is developed, which relies on a solution-processed In2O3/ZnO semiconducting heterojunction featuring a geometrically engineered tri-channel architecture for the rapid, real-time detection of important biomolecules. The sensor combines a high electron mobility channel, attributed to the electronic properties of the In2O3/ZnO heterointerface, in close proximity to a sensing surface featuring tethered analyte receptors. The unusual tri-channel design enables strong coupling between the buried electron channel and electrostatic perturbations occurring during receptor–analyte interactions allowing for robust, real-time detection of biomolecules down to attomolar (am) concentrations. The experimental findings are corroborated by extensive device simulations, highlighting the unique advantages of the heterojunction tri-channel design. By functionalizing the surface of the geometrically engineered channel with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody receptors, real-time detection of the SARS-CoV-2 spike S1 protein down to am concentrations is demonstrated in under 2 min in physiological relevant conditions.

Journal article

Pletzer M, Plasser F, Rimmele M, Heeney M, Glöcklhofer Fet al., 2021, [2.2.2.2]Paracyclophanetetraenes (PCTs): cyclic structural analogues of poly(p‑phenylene vinylene)s (PPVs), Publisher: F1000Research

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.

Working paper

Allen TG, Kafourou P, Larson BW, Heeney M, Reid OG, Rumbles Get al., 2021, Reconciling the Driving Force and the Barrier to Charge Separation in Donor-Nonfullerene Acceptor Films, ACS ENERGY LETTERS, Vol: 6, Pages: 3572-3581, ISSN: 2380-8195

Journal article

Huang Y, Lukito Tjhe DH, Jacobs IE, Jiao X, He Q, Statz M, Ren X, Huang X, McCulloch I, Heeney M, McNeill C, Sirringhaus Het al., 2021, Design of experiment optimization of aligned polymer thermoelectrics doped by ion-exchange, APPLIED PHYSICS LETTERS, Vol: 119, ISSN: 0003-6951

Journal article

Ding B, Kim G, Kim Y, Eisner FD, GutiérrezFernández E, Martín J, Yoon M, Heeney Met al., 2021, Influence of backbone curvature on the organic electrochemical transistor performance of glycolated donor–acceptor conjugated polymers, Angewandte Chemie, Vol: 133, Pages: 19831-19836, ISSN: 0044-8249

Two new glycolated semiconducting polymers PgBT(F)2gT and PgBT(F)2gTT of differing backbone curvatures were designed and synthesised for application as p-type accumulation mode organic electrochemical transistor (OECT) materials. Both polymers demonstrated stable and reversible oxidation, accessible within the aqueous electrochemical window, to generate polaronic charge carriers. OECTs fabricated from PgBT(F)2gT featuring a curved backbone geometry attained a higher volumetric capacitance of 170 F cm−3. However, PgBT(F)2gTT with a linear backbone displayed overall superior OECT performance with a normalised peak transconductance of 3.00×104 mS cm−1, owing to its enhanced order, expediting the charge mobility to 0.931 cm2 V−1 s−1.

Journal article

Dey S, Attar S, Manley EF, Moncho S, Brothers EN, Bazzi HS, Bronstein H, Marks TJ, Heeney M, Schroeder BC, Al-Hashimi Met al., 2021, Transition-Metal-Free Homopolymerization of Pyrrolo[2,3-d:5,4-d']bisthiazoles via Nucleophilic Aromatic Substitution, ACS APPLIED MATERIALS & INTERFACES, Vol: 13, Pages: 41094-41101, ISSN: 1944-8244

Journal article

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