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

315 results found

Boufflet P, Bovo G, Occhi L, Fei Z, Han Y, Anthopoulos T, Yuan H, Heeney MJet al., 2018, The influence of backbone fluorination on the dielectric constant of conjugated polythiophenes, Advanced Electronic Materials, Vol: 4, ISSN: 2199-160X

The ability to modify or enhance the dielectric constant of semiconducting polymers can prove valuable for a range of optoelectronic and microelectronic applications. In the case of organic photovoltaics, increasing the dielectric constant of the active layer has often been suggested as a method to control charge generation, recombination dynamics, and ultimately, the power conversion efficiencies. In this contribution, the impact that the degree and pattern of fluorination has on the dielectric constant of poly(3-octylthiophene) (P3OT), a more soluble analogue of the widely studied conjugated material poly(3-hexylthiophene), is explored. P3OT and its backbone-fluorinated analogue, F-P3OT, are compared along with a block and alternating copolymer version of these materials. It is found that the dielectric constant of the polymer thin films increases as the degree of backbone fluorination increases, in a trend consistent with density functional theory calculations of the dipole moment.

Journal article

Paterson AF, Singh S, Fallon KJ, Hodsden T, Han Y, Schroeder BC, Bronstein H, Heeney M, McCulloch I, Anthopoulos TDet al., 2018, Recent progress in high-mobility organic transistors: a reality check, Advanced Materials, Vol: 30, ISSN: 0935-9648

Over the past three decades, significant research efforts have focused on improving the charge carrier mobility of organic thin‐film transistors (OTFTs). In recent years, a commonly observed nonlinearity in OTFT current–voltage characteristics, known as the “kink” or “double slope,” has led to widespread mobility overestimations, contaminating the relevant literature. Here, published data from the past 30 years is reviewed to uncover the extent of the field‐effect mobility hype and identify the progress that has actually been achieved in the field of OTFTs. Present carrier‐mobility‐related challenges are identified, finding that reliable hole and electron mobility values of 20 and 10 cm2 V−1 s−1, respectively, have yet to be achieved. Based on the analysis, the literature is then reviewed to summarize the concepts behind the success of high‐performance p‐type polymers, along with the latest understanding of the design criteria that will enable further mobility enhancement in n‐type polymers and small molecules, and the reasons why high carrier mobility values have been consistently produced from small molecule/polymer blend semiconductors. Overall, this review brings together important information that aids reliable OTFT data analysis, while providing guidelines for the development of next‐generation organic semiconductors.

Journal article

Rodriquez D, Kohl JG, Morel P, Burrows K, Favaro G, Root SE, Ramirez J, Alkhadra MA, Carpenter CW, Fei Z, Boufflet P, Heeney M, Lipomi DJet al., 2018, Measurement of Cohesion and Adhesion of Semiconducting Polymers by Scratch Testing: Effect of Side-Chain Length and Degree of Polymerization, ACS MACRO LETTERS, Vol: 7, Pages: 1003-1009, ISSN: 2161-1653

Journal article

Heeney MJ, Creamer A, Wood C, Howes P, Casey A, Cong S, Marsh A, Godin R, Panidi J, Anthopoulos T, Burgess C, Wu T, Fei Z, McLachlan M, Stevens Met al., 2018, Post-polymerisation functionalisation of conjugated polymer backbones and its application in multi-functional emissive nanoparticles, Nature Communications, Vol: 9, ISSN: 2041-1723

Backbone functionalisation of conjugated polymers is crucial to their performance in many applications, from electronic displays to nanoparticle biosensors, yet there are limited approaches to introduce functionality. To address this challenge we have developed a method for the direct modification of the aromatic backbone of a conjugated polymer, post-polymerisation. This is achieved via a quantitative nucleophilic aromatic substitution (SNAr) reaction on a range of fluorinated electron deficient comonomers. The method allows for facile tuning of the physical and optoelectronic properties within a batch of consistent molecular weight and dispersity. It also enables the introduction of multiple different functional groups onto the polymer backbone in a controlled manner. To demonstrate the versatility of this reaction, we designed and synthesised a range of emissive poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) based polymers for the creation of mono and multifunctional semiconducting polymer nanoparticles (SPNs) capable of two orthogonal bioconjugation reactions on the same surface.

Journal article

Marsh AV, Cheetham NJ, Little M, Dyson M, White AJP, Beavis P, Warriner CN, Swain AC, Stavrinou PN, Heeney Met al., 2018, Carborane‐Induced Excimer Emission of Severely Twisted Bis‐ o ‐Carboranyl Chrysene, Angewandte Chemie, Vol: 130, Pages: 10800-10805, ISSN: 0044-8249

Journal article

Heeney MJ, Stavrinou P, Anthony S, Colin W, Beaves P, White A, Dyson M, Little M, Cheetham N, Marsh Aet al., 2018, Carborane induced excimer emission of severely twisted Bis-o-carboranyl chrysene, Angewandte Chemie, Vol: 57, Pages: 10640-10645, ISSN: 1521-3757

The synthesis of a highly twisted chrysene derivative incorporating two electron deficient o‐carboranyl groups is reported. The molecule exhibits a complex, excitation‐dependent photoluminescence, including aggregation‐induced emission (AIE) with good quantum efficiency and an exceptionally long singlet excited state lifetime. Through a combination of detailed optical studies and theoretical calculations, the excited state species are identified, including an unusual excimer induced by the presence of o‐carborane. This is the first time that o‐carborane has been shown to induce excimer formation ab initio, as well as the first observation of excimer emission by a chrysene‐based small molecule in solution. Bis‐o‐carboranyl chrysene is thus an initial member of a new family of o‐carboranyl phenacenes exhibiting a novel architecture for highly‐efficient multi‐luminescent fluorophores.

Journal article

Patra D, Lee J, Dey S, Lee J, Kalin AJ, Putta A, Fei Z, McCarthy-Ward T, Bazzi HS, Fang L, Heeney M, Yoon M-H, Al-Hashimi Met al., 2018, Chalcogen Bridged Thieno- and Selenopheno[2,3-d:5,4-d ']bisthiazole and Their Diketopyrrolopyrrole Based Low-Bandgap Copolymers, MACROMOLECULES, Vol: 51, Pages: 6076-6084, ISSN: 0024-9297

Journal article

Nieuwendaal RC, DeLongchamp DM, Richter LJ, Snyder CR, Jones RL, Engmann S, Herzing A, Heeney M, Fei Z, Sieval AB, Hummelen JCet al., 2018, Characterization of Interfacial Structure in Polymer-Fullerene Bulk Heterojunctions via C-13 {H-2} Rotational Echo Double Resonance NMR, PHYSICAL REVIEW LETTERS, Vol: 121, ISSN: 0031-9007

Journal article

Eisner F, Seitkhan A, Han Y, Khim D, Yengel E, Kirmani AR, Xu J, de Arquer FPG, Sargent EH, Amassian A, Fei Z, Heeney M, Anthopoulos TDet al., 2018, Solution-processed In2O3/ZnO heterojunction electron transport layers for efficient organic bulk heterojunction and inorganic colloidal quantum-dot solar cells, Solar RRL, Vol: 2, ISSN: 2367-198X

We report the development of a solution‐processed In2O3/ZnO heterojunction electron transport layer (ETL) and its application in high efficiency organic bulk‐heterojunction (BHJ) and inorganic colloidal quantum dot (CQD) solar cells. Study of the electrical properties of this low‐dimensional oxide heterostructure via field‐effect measurements reveals that electron transport along the heterointerface is enhanced by more than a tenfold when compared to the individual single‐layer oxides. Use of the heterojunction as the ETL in organic BHJ photovoltaics is found to consistently improve the cell's performance due to the smoothening of the ZnO surface, increased electron mobility and a noticeable reduction in the cathode's work function, leading to a decrease in the cells’ series resistance and a higher fill factor (FF). Specifically, non‐fullerene based organic BHJ solar cells based on In2O3/ZnO ETLs exhibit very high power conversion efficiencies (PCE) of up to 12.8%, and high FFs of over 70%. The bilayer ETL concept is further extended to inorganic lead‐sulphide CQD solar cells. Resulting devices exhibit excellent performance with a maximum PCE of 8.2% and a FF of 56.8%. The present results highlight the potential of multilayer oxides as novel ETL systems and lay the foundation for future developments.

Journal article

Datko BD, Walwark DJ, Fei Z, Heeney MJ, Grey JKet al., 2018, Resolving Anomalous Heavy Atom Effects from Discrete Triplet Mediated Photochemistry Events on Single Conjugated Polymer Chains, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 122, Pages: 9718-9725, ISSN: 1932-7447

Journal article

Squeo BM, Gregoriou VG, Han Y, Palma-Cando A, Allard S, Serpetzoglou E, Konidakis I, Stratakis E, Avgeropoulos A, Anthopoulos TD, Heeney M, Scherf U, Chochos CLet al., 2018, alpha,beta-Unsubstituted meso-positioning thienyl BODIPY: a promising electron deficient building block for the development of near infrared (NIR) p-type donor-acceptor (D-A) conjugated polymers, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 6, Pages: 4030-4040, ISSN: 2050-7526

Journal article

Taroni PJ, Santagiuliana G, Wan K, Calado P, Qiu M, Zhang H, Pugno NM, Palma M, Stingelin-Stutzman N, Heeney M, Fenwick O, Baxendale M, Bilotti Eet al., 2018, Toward Stretchable Self-Powered Sensors Based on the Thermoelectric Response of PEDOT:PSS/Polyurethane Blends, ADVANCED FUNCTIONAL MATERIALS, Vol: 28, ISSN: 1616-301X

Journal article

Wijeyasinghe N, Tsetseris L, Regoutz A, Sit WY, Fei Z, Du T, Wang X, Mclachlan MA, Vourlias G, Patsalas PA, Payne DJ, Heeney M, Anthopoulos TDet al., 2018, Copper (I) selenocyanate (CuSeCN) as a novel hole-transport layer for transistors, organic solar cells, and light-emitting diodes, Advanced Functional Materials, Vol: 28, ISSN: 1616-301X

The synthesis and characterization of copper (I) selenocyanate (CuSeCN) and its application as a solution-processable hole-transport layer (HTL) material in transistors, organic light-emitting diodes, and solar cells are reported. Density-functional theory calculations combined with X-ray photoelectron spectroscopy are used to elucidate the electronic band structure, density of states, and microstructure of CuSeCN. Solution-processed layers are found to be nanocrystalline and optically transparent ( > 94%), due to the large bandgap of ≥3.1 eV, with a valence band maximum located at -5.1 eV. Hole-transport analysis performed using field-effect measurements confirms the p-type character of CuSeCN yielding a hole mobility of 0.002 cm 2 V -1 s -1 . When CuSeCN is incorporated as the HTL material in organic light-emitting diodes and organic solar cells, the resulting devices exhibit comparable or improved performance to control devices based on commercially available poly(3,4-ethylenedioxythiophene):polystyrene sulfonate as the HTL. This is the first report on the semiconducting character of CuSeCN and it highlights the tremendous potential for further developments in the area of metal pseudohalides.

Journal article

Datko B, Fei Z, Heeney M, Grey Jet al., 2018, Effect of conformational changes on triplet formation in a heavy heteroatom conjugated polymer: Single polymer molecules and molecular aggregates, 255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727

Conference paper

Charlton RJ, Fogarty R, Bogatko S, Zuehlsdorff TJ, Hine NDM, Heeney MJ, Horsfield AP, Haynes PDet al., 2018, Implicit and explicit host effects on excitons in pentacene derivatives, Journal of Chemical Physics, Vol: 148, ISSN: 0021-9606

Anab initiostudy of the effects of implicit and explicit hosts on the excited state properties ofpentacene and its nitrogen-based derivatives has been performed using ground state density func-tional theory (DFT), time-dependent DFT and ∆SCF. We observe a significant solvatochromicredshift in the excitation energy of the lowest singlet state (S1) of pentacene from inclusion inap-terphenyl host compared to vacuum; for an explicit host consisting of six nearest neighbourp-terphenyls, we obtain a redshift of 65 meV while a conductor-like polarisable continuum model(CPCM) yields a 78 meV redshift. Comparison is made between the excitonic properties of pen-tacene and four of its nitrogen-based analogues, 1,8-, 2,9-, 5,12-, and 6,13-diazapentacene with thelatter found to be the most distinct due to local distortions in the ground state electronic struc-ture. We observe that a CPCM is insufficient to fully understand the impact of the host due tothe presence of a mild charge-transfer (CT) coupling between the chromophore and neighbouringp-terphenyls, a phenomenon which can only be captured using an explicit model. The strengthof this CT interaction increases as the nitrogens are brought closer to the central acene ring ofpentacene.

Journal article

Lu R, Han Y, Zhang W, Zhu X, Fei Z, Hodsden T, Anthopoulos TD, Heeney Met al., 2018, Alkylated indacenodithieno[3,2-b] thiophene-based all donor ladder-type conjugated polymers for organic thin film transistors, Journal of Materials Chemistry C, Vol: 6, Pages: 2004-2009, ISSN: 2050-7534

We report the synthesis of a series of indacenodithieno[3,2-b]thiophene (IDTT) based conjugated polymers by copolymerization with three different electron rich co-monomers [thiophene (T), thieno[3,2-b] thiophene (TT) and dithieno[3,2-b:2′,3′-d]thiophene (DTT)] under Stille coupling conditions. The resulting all-donor polymers show very good solubility in common solvents and exhibit similar optical, thermal and electronic properties. However, the performance of these semiconductors in thin film transistor devices varied and was highly dependent on the nature of the co-monomer. All polymers exhibited unipolar p-type charge transport behaviour, with the mobility values following the trend of IDTT-TT > IDTT-DTT > IDTT-T. The peak saturation mobility value of IDTT-TT was extracted to be 1.1 cm 2 V -1 s -1 , amongst the highest mobility for all-donor conjugated polymers reported to date.

Journal article

Fei Z, Eisner FD, Jiao X, Azzouzi M, Röhr JA, Han Y, Shahid M, Chesman ASR, Easton CD, McNeill CR, Anthopoulos TD, Nelson J, Heeney Met al., 2018, An alkylated indacenodithieno[3,2-b]thiophene-based nonfullerene acceptor with high crystallinity exhibiting single junction solar cell efficiencies greater than 13% with low voltage losses, Advanced Materials, Vol: 30, ISSN: 0935-9648

A new synthetic route, to prepare an alkylated indacenodithieno[3,2-b]thiophene-based nonfullerene acceptor (C8-ITIC), is reported. Compared to the reported ITIC with phenylalkyl side chains, the new acceptor C8-ITIC exhibits a reduction in the optical band gap, higher absorptivity, and an increased propensity to crystallize. Accordingly, blends with the donor polymer PBDB-T exhibit a power conversion efficiency (PCE) up to 12.4%. Further improvements in efficiency are found upon backbone fluorination of the donor polymer to afford the novel material PFBDB-T. The resulting blend with C8-ITIC shows an impressive PCE up to 13.2% as a result of the higher open-circuit voltage. Electroluminescence studies demonstrate that backbone fluorination reduces the energy loss of the blends, with PFBDB-T/C8-ITIC-based cells exhibiting a small energy loss of 0.6 eV combined with a high JSCof 19.6 mA cm-2.

Journal article

Datko BD, Thomas AK, Fei Z, Heeney M, Grey JKet al., 2017, Effect of a heavy heteroatom on triplet formation and interactions in single conjugated polymer molecules and aggregates, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 19, Pages: 28239-28248, ISSN: 1463-9076

Journal article

Panidi J, Paterson AF, Khim D, Fei Z, Han Y, Tsetseris L, Vourlias G, Patsalas PA, Heeney M, Anthopoulos TDet al., 2017, Remarkable Enhancement of the Hole Mobility in Several Organic Small-Molecules, Polymers, and Small-Molecule:Polymer Blend Transistors by Simple Admixing of the Lewis Acid p-Dopant B(C6F5)(3), Advanced Science, Vol: 5, ISSN: 2198-3844

Improving the charge carrier mobility of solution-processable organic semiconductors is critical for the development of advanced organic thin-film transistors and their application in the emerging sector of printed electronics. Here, a simple method is reported for enhancing the hole mobility in a wide range of organic semiconductors, including small-molecules, polymers, and small-molecule:polymer blends, with the latter systems exhibiting the highest mobility. The method is simple and relies on admixing of the molecular Lewis acid B(C6F5)3 in the semiconductor formulation prior to solution deposition. Two prototypical semiconductors where B(C6F5)3 is shown to have a remarkable impact are the blends of 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene:poly(triarylamine) (diF-TESADT:PTAA) and 2,7-dioctyl[1]-benzothieno[3,2-b][1]benzothiophene:poly(indacenodithiophene-co-benzothiadiazole) (C8-BTBT:C16-IDTBT), for which hole mobilities of 8 and 11 cm2 V−1 s−1, respectively, are obtained. Doping of the 6,13-bis(triisopropylsilylethynyl)pentacene:PTAA blend with B(C6F5)3 is also shown to increase the maximum hole mobility to 3.7 cm2 V−1 s−1. Analysis of the single and multicomponent materials reveals that B(C6F5)3 plays a dual role, first acting as an efficient p-dopant, and secondly as a microstructure modifier. Semiconductors that undergo simultaneous p-doping and dopant-induced long-range crystallization are found to consistently outperform transistors based on the pristine materials. Our work underscores Lewis acid doping as a generic strategy towards high performance printed organic microelectronics.

Journal article

Wade J, Wood S, Collado-Fregoso E, Heeney M, Durrant J, Kim J-Set al., 2017, Impact of Fullerene Intercalation on Structural and Thermal Properties of Organic Photovoltaic Blends, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 121, Pages: 20976-20985, ISSN: 1932-7447

The performance of organic photovoltaic blend devices is critically dependent on the polymer:fullerene interface. These interfaces are expected to impact the structural and thermal properties of the polymer with regards to the conjugated backbone planarity and transition temperatures during annealing/cooling processes. Here, we report the impact of fullerene intercalation on structural and thermal properties of poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene (PBTTT), a highly stable material known to exhibit liquid crystalline behavior. We undertake a detailed systematic study of the extent of intercalation in the PBTTT:fullerene blend, considering the use of four different fullerene derivatives and also varying the loading ratios. Resonant Raman spectroscopy allows direct observation of the interface morphology in situ during controlled heating and cooling. We find that small fullerene molecules readily intercalate into PBTTT crystallites, resulting in a planarization of the polymer backbone, but high fullerene loading ratios or larger fullerenes result in nonintercalated domains. During cooling from melt, nonintercalated blend films are found to return to their original morphology and reproduce all thermal transitions on cooling with minimal hysteresis. Intercalated blend films show significant hysteresis on cooling due to the crystallized fullerene attempting to reintercalate. The strongest hysteresis is for intercalated blend films with excess fullerene loading ratio, which form a distinct nanoribbon morphology and exhibit a reduced geminate recombination rate. These results reveal that careful consideration should be taken during device fabrication, as postdeposition thermal treatments significantly impact the charge generation and recombination dynamics.

Journal article

Wijeyasinghe N, Regoutz A, Eisner F, Du T, Tsetseris L, Lin Y-H, Faber H, Pattanasattayavong P, Li J, Yan F, McLachlan MA, Payne DJ, Heeney M, Anthopoulos TDet al., 2017, Copper(I) Thiocyanate (CuSCN) Hole-Transport Layers Processed from Aqueous Precursor Solutions and Their Application in Thin-Film Transistors and Highly Efficient Organic and Organometal Halide Perovskite Solar Cells, ADVANCED FUNCTIONAL MATERIALS, Vol: 27, ISSN: 1616-301X

This study reports the development of copper(I) thiocyanate (CuSCN) hole-transport layers (HTLs) processed from aqueous ammonia as a novel alternative to conventional n-alkyl sulfide solvents. Wide bandgap (3.4–3.9 eV) and ultrathin (3–5 nm) layers of CuSCN are formed when the aqueous CuSCN–ammine complex solution is spin-cast in air and annealed at 100 °C. X-ray photoelectron spectroscopy confirms the high compositional purity of the formed CuSCN layers, while the high-resolution valence band spectra agree with first-principles calculations. Study of the hole-transport properties using field-effect transistor measurements reveals that the aqueous-processed CuSCN layers exhibit a fivefold higher hole mobility than films processed from diethyl sulfide solutions with the maximum values approaching 0.1 cm2 V−1 s−1. A further interesting characteristic is the low surface roughness of the resulting CuSCN layers, which in the case of solar cells helps to planarize the indium tin oxide anode. Organic bulk heterojunction and planar organometal halide perovskite solar cells based on aqueous-processed CuSCN HTLs yield power conversion efficiency of 10.7% and 17.5%, respectively. Importantly, aqueous-processed CuSCN-based cells consistently outperform devices based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate HTLs. This is the first report on CuSCN films and devices processed via an aqueous-based synthetic route that is compatible with high-throughput manufacturing and paves the way for further developments.

Journal article

Green JP, Cryer SJ, Marafie J, White AJP, Heeney Met al., 2017, Synthesis of a Luminescent Arsolo[2,3-d:5,4-d']bis(thiazole) Building Block and Comparison to Its Phosphole Analogue, Organometallics, Vol: 36, Pages: 2632-2636, ISSN: 0276-7333

The synthesis of 4-phenyl-4H-arsolo[2,3-d:5,4-d′]bis(thiazole) is reported, and its properties are compared to those of the previously prepared phosphole analogue. By comparison of their single-crystal structures, the harmonic oscillator model of heterocyclic electron delocalization (HOMHED) was used to directly compare the aromatic character of the two systems. The findings demonstrate that, although both compounds can be considered aromatic, the phosphole-containing compound had a greater degree of aromatic character than its arsole analogue. The arsole derivative exhibited excellent stability in ambient air with no formation of the arsole oxide observed upon storage. The absorption and photoluminescence spectra of the arsole derivate were subtly altered in comparison to the phosphole derivative, suggesting that changing pnictogenic atoms in such fused-ring systems to heavier analogues could be a viable way of tuning both the ambient stability and optoelectronic properties of such materials.

Journal article

Fei Z, Chen L, Han Y, Gann E, Chesman ASR, McNeill CR, Anthopoulos TD, Heeney M, Pietrangelo Aet al., 2017, Alternating 5,5-Dimethylcyclopentadiene and Diketopyrrolopyrrole Copolymer Prepared at Room Temperature for High Performance Organic Thin-Film Transistors, Journal of the American Chemical Society, Vol: 139, Pages: 8094-8097, ISSN: 1520-5126

We report that the inclusion of nonaromatic 5,5-dimethylcyclopentadiene monomer into a conjugated backbone is an attractive strategy to high performance semiconducting polymers. The use of this monomer enables a room temperature Suzuki copolymerization with a diketopyrrolopyrrole comonomer to afford a highly soluble, high molecular weight material. The resulting low band gap polymer exhibits excellent photo and thermal stability, and despite a large π–π stacking distance of 4.26 Å, it demonstrates excellent performance in thin-film transistor devices.

Journal article

Fei Z, Han Y, Gann E, Hodsden T, Chesman ASR, McNeill CR, Anthopoulos TD, Heeney MJet al., 2017, Alkylated selenophene-based ladder-type monomers via a facileroute for high performance thin-film transistor applications, Journal of the American Chemical Society, Vol: 139, Pages: 8552-8561, ISSN: 1943-2984

We report the synthesis of two new selenophene-containing ladder-type monomers, cyclopentadiselenophene (CPDS) and indacenodiselenophene (IDSe), via a 2-fold and 4-fold Pd-catalyzed coupling with a 1,1-diborylmethane derivative. Copolymers with benzothiadiazole were prepared in high yield by Suzuki polymerization to afford materials which exhibited excellent solubility in a range of nonchlorinated solvents. The CPDS copolymer exhibited a band gap of just 1.18 eV, which is among the lowest reported for donor–acceptor polymers. Thin-film transistors were fabricated using environmentally benign, nonchlorinated solvents, with the CPDS and IDSe copolymers exhibiting hole mobility up to 0.15 and 6.4 cm2 V–1 s–1, respectively. This high performance was achieved without the undesirable peak in mobility often observed at low gate voltages due to parasitic contact resistance.

Journal article

Costa L, Al-Hashimi M, Heeney M, Terekhov A, Rajput D, Hofmeister W, Verma Aet al., 2017, Template-Synthesis of Conjugated Poly(3-Hexylselenophene) (P3HS) Nanofibers Using Femtosecond Laser Machined Fused Silica Templates, MRS ADVANCES, Vol: 2, Pages: 2957-2960, ISSN: 2059-8521

Journal article

Hu Z, Haws RT, Fei Z, Boufflet P, Heeney M, Rossky PJ, Vanden Bout DAet al., 2017, Impact of backbone fluorination on nanoscale morphology and excitonic coupling in polythiophenes, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 114, Pages: 5113-5118, ISSN: 0027-8424

Journal article

Creamer A, Casey A, Marsh AV, Shahid M, Gao M, Heeney Met al., 2017, Systematic Tuning of 2,1,3-Benzothiadiazole Acceptor Strength by Monofunctionalization with Alkylamine, Thioalkyl, or Alkoxy Groups in Carbazole Donor-Acceptor Polymers, MACROMOLECULES, Vol: 50, Pages: 2736-2746, ISSN: 0024-9297

A simple route to the preparation of alkylamine, thioalkyl, and alkoxy monofunctionalized 4,7-di(thiophen-2-yl)-2,1,3-benzothiadiazole) based monomers is reported from a common fluorinated precursor. Copolymerization with a carbazole comonomer under Suzuki conditions yielded a series of analogous donor–acceptor copolymers in which the only difference was the nature of the heteroatom (N, O, or S) on the benzothiadiazole core. This was shown to have a significant impact on the wavelength and intensity of the intramolecular charge transfer (ICT) absorption peak due to a combination of electronic and steric factors. Substantial differences were also observed in the solar cell performance of blends with PC71BM, with the octylamino substituted polymer exhibiting significantly lower performance than the other two polymers. This polymer also exhibited a reversible change in the optical spectra upon exposure to acid, suggesting potential as a sensing material.

Journal article

Casey A, Green JP, Shakya Tuladhar P, Kirkus M, Han Y, Anthopoulos TD, Heeney MJet al., 2017, Cyano substituted benzotriazole based polymers for use in organic solar cells, Journal of Materials Chemistry A, Vol: 5, Pages: 6465-6470, ISSN: 2050-7496

A new synthetic route to the electron accepting di-cyano substituted benzo[d][1,2,3]triazole (BTz) monomer 2-(2-butyloctyl)-4,7-di(thiophen-2-yl)-2H-benzotriazole-5,6-dicarbonitrile (dTdCNBTz) is reported. The cyano substituents can be easily introduced to the BTz unit in one step via the nucleophilic aromatic substitution of the fluorine substituents of the fluorinated precursor 2-(2-butyloctyl)-4,7-di(thiophen-2-yl)-2H-benzotriazole-5,6-difluoro (dTdFBTz). Co-polymers were prepared with distannylated benzo[1,2-b:4,5-b′]dithiophene (BDT) monomers containing either 2-ethylhexylthienyl (T-EH) side chains or 2-butyloctylthienyl (T-BO) side chains via Stille coupling to yield the novel medium band gap polymers P1 and P2 respectively. Whilst the organic photovoltaic (OPV) performance of P1 was limited by a lack of solubility, the improved solubility of P2 resulted in promising device efficiencies of up to 6.9% in blends with PC61BM, with high open circuit voltages of 0.95 V.

Journal article

Rodriquez D, Kim J-H, Root SE, Fe Z, Boufflet P, Heeney M, Kim T-S, Lipomi DJet al., 2017, Comparison of Methods for Determining the Mechanical Properties of Semiconducting Polymer Films for Stretchable Electronics, ACS APPLIED MATERIALS & INTERFACES, Vol: 9, Pages: 8855-8862, ISSN: 1944-8244

Journal article

Patra D, Lee J, Lee J, Sredojevic DN, White AJP, Bazzi HS, Brothers EN, Heeney M, Fang L, Yoon M-H, Al-Hashimi Met al., 2017, Synthesis of low band gap polymers based on pyrrolo[3,2-d:4,5-d ']bisthiazole (PBTz) and thienylenevinylene (TV) for organic thin-film transistors (OTFTs), JOURNAL OF MATERIALS CHEMISTRY C, Vol: 5, Pages: 2247-2258, ISSN: 2050-7526

Journal article

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