Publications
421 results found
Xue X, Chandler G, Zhang X, et al., 2015, Oriented Liquid Crystalline Polymer Semiconductor Films with Large Ordered Domains, ACS APPLIED MATERIALS & INTERFACES, Vol: 7, Pages: 26726-26734, ISSN: 1944-8244
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- Citations: 37
Snyder CR, Kline RJ, DeLongchamp DM, et al., 2015, Classification of Semiconducting Polymeric Mesophases to Optimize Device Postprocessing, JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS, Vol: 53, Pages: 1641-1653, ISSN: 0887-6266
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- Citations: 24
Collado Fregoso E, Boufflet P, Fei Z, et al., 2015, Increased Exciton Dipole Moment Translates into Charge-transfer Excitons in Thiophene-fluorinated Low-bandgap Polymers for Organic Photovoltaic Applications, Chemistry of Materials, Vol: 27, Pages: 7934-7944, ISSN: 1520-5002
In this study, we investigate the role of thiophene fluorination in a low-bandgap polymer for organic photovoltaic applications. We use a combined theoretical and experimental approach to investigate charge generation and recombination dynamics, and their correlation with blend microstructure and polymer dipole moment. We find that fluorination results in an increased change in the dipole moment upon exciton formation, which is correlated with the appearance of charge-transfer excitons, as evidenced from ultrafast transient absorption studies. Fluorination also results in smaller yet purer domains, evidenced by atomic force microscopy and resonant soft X-ray scattering, and in agreement with photoluminescence quenching measurements. This change in film morphology is correlated with a modest retardation of nongeminate recombination losses. The efficient charge generation and slower recombination are likely to be partly responsible for the enhanced device efficiency in the fluorinated polymer/fullerene devices.
Al-Hashimi M, Han Y, Smith J, et al., 2015, Influence of the heteroatom on the optoelectronic properties and transistor performance of soluble thiophene-, selenophene- and tellurophene-vinylene copolymers, Chemical Science, Vol: 7, Pages: 1093-1099, ISSN: 2041-6539
We report the first soluble poly(3-dodecyl tellurophenylene-vinylene) polymer (P3TeV) by Stille copolymerization and compare its properties to the analogous thiophene and selenophene containing polymers. The optical band gap of the polymers is shown to systematically decrease as the size of the heteroatom is increased, mainly as a result of a stabilization of the LUMO energy, resulting in a small band gap of 1.4 eV for P3TeV. Field effect transistors measurements in variety of architectures demonstrate that the selenophene polymer exhibits the highest mobility, highlighting that increasing the size of the heteroatom is not always beneficial for charge transport.
Heeney MJ, Han Y, Fei Z, et al., 2015, A Novel Alkylated Indacenodithieno[3,2-b]thiophene-based Polymer for High-performance Field Effect Transistors, Advanced Materials, Vol: 28, Pages: 3922-3927, ISSN: 1521-4095
A novel rigid donor monomer, indacenodithieno[3,2-b]thiophene (IDTT), containing linear alkyl chains is reported. Its copolymer with benzothiadiazole is an excellent p-type semiconductor, affording a mobility of 6.6 cm² V⁻¹ s⁻¹ in top-gated field-effect transistors with pentafluorobenzenethiol-modified Au electrodes. Electrode treatment with solution-deposited copper(I) thiocyanate (CuSCN) has a beneficial hole-injection/electron-blocking effect, further enhancing the mobility to 8.7 cm² V⁻¹ s⁻¹.
Boufflet P, Han Y, Fei Z, et al., 2015, Using Molecular Design to Increase Hole Transport: Backbone Fluorination in the Benchmark Material Poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]-thiophene (pBTTT), Advanced Functional Materials, Vol: 25, Pages: 7038-7048, ISSN: 1616-3028
The synthesis of a novel 3,3'-difluoro-4,4'-dihexadecyl-2,2'-bithiophene monomer and its copolymerisation with thieno[3,2-b]thiophene to afford the fluorinated analogue of the well-known poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]-thiophene) (PBTTT) polymer is reported. Fluorination is found to have a significant influence on the physical properties of the polymer, enhancing aggregation in solution and increasing melting point by over 100 °C compared to non-fluorinated polymer. On the basis of DFT calculations these observations are attributed to inter- and intra-molecular S…F interactions. As a consequence, the fluorinated polymer PFBTTT exhibits a four-fold increase in charge carrier mobility compared to the non-fluorinated polymer and excellent ambient stability for a non-encapsulated transistor device.
Casey A, Han Y, Wyatt MF, et al., 2015, Novel soluble thieno[3,2-b]thiophene fused porphyrazine, RSC Advances, Vol: 5, Pages: 90645-90650, ISSN: 2046-2069
The synthesis of the first soluble thieno[3,2-b]thiophene based porphyrazine (ZnTTPz) is reported from the cyclisation of 2,3-dicyano-5-octylthieno[3,2-b]thiophene. ZnTTPz can be considered the all thiophene analogue of naphthalocyanine. ZnTTPz exhibits a red-shifted absorption in solution and thin film, as well as a reduced band gap in comparison to the thiophene analogue due to an increased conjugation length. Films of ZnTTPz processed from solution exhibit p-type semiconducting behaviour in field-effect transistors with low hysteresis and reasonable charge carrier mobility.
Campbell AJ, Higgins SG, Muir BVO, et al., 2015, Indacenodithiophene–benzothiadiazole organic field-effect transistorswith gravure-printed semiconductor and dielectric on plastic, MRS Communications, Vol: 5, Pages: 599-603, ISSN: 2159-6867
We demonstrate the gravure printing of a high-performance indacenodithiophene (IDT) copolymer, indacenodithiophene–benzothiadiazole (C16IDT–BT), onto self-aligned organic field-effect transistor architectures on flexible plastic substrates. We observed that the combination of a gravure-printed dielectric with gravure-printed semiconductor yielded devices with higher mean-effective mobility than devices manufactured using photolithographically patterned dielectric. Peak mobilities of μ = 0.1 cm2 V−1 s−1 were measured, and exceed previous reports for non-printed C16IDT-BT on non-flexible silicon substrates.
Andemach R, Utzat H, Dimitrov SD, et al., 2015, Synthesis and Exciton Dynamics of Triplet Sensitized Conjugated Polymers, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 137, Pages: 10383-10390, ISSN: 0002-7863
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- Citations: 39
Gruber M, Jung S-H, Schott S, et al., 2015, Enabling high-mobility, ambipolar charge-transport in a DPP-benzotriazole copolymer by side-chain engineering, Chemical Science, Vol: 6, Pages: 6949-6960, ISSN: 2041-6539
In this article we discuss the synthesis of four new low band-gap co-polymers based on the diketopyrrolopyrrole (DPP) and benzotriazole (BTZ) monomer unit. We demonstrate that the BTZ unit allows for additional solubilizing side-chains on the co-monomer and show that the introduction of a linear side-chain on the DPP-unit leads to an increase in thin-film order and charge-carrier mobility if a sufficiently solubilizing, branched, side chain is attached to the BTZ. We compare two different synthetic routes, direct arylation and Suzuki-polycondensation, by a direct comparison of polymers obtained via the two routes and show that direct arylation produces polymers with lower electrical performance which we attribute to a higher density of chain Furthermore we demonstrate that a polymer utilizing this design motif and synthesized via Suzuki-polycondensation ((l-C18)-DPP-(b-C17)-BTZ) exhibits exceptionally high and near balanced average electron and hole mobilities >2 cm2 V−1 s−1 which are among the highest, robustly extracted mobility values reported for DPP copolymers in a top-gate configuration to date. Our results demonstrate clearly that linear side chain substitution of the DPP unit together with co-monomers that allow for the use of sufficiently long or branched solubilizing side chains can be an attractive design motif for solution processable, high mobility DPP copolymers.
Zhong H, Han Y, Shaw J, et al., 2015, Fused ring cyclopentadithienothiophenes as novel building blocks for high field effect mobility conjugated polymers, Macromolecules, Vol: 48, Pages: 5605-5613, ISSN: 0024-9297
Hu H, Zhao K, Fernandes N, et al., 2015, Entanglements in marginal solutions: a means of tuning pre-aggregation of conjugated polymers with positive implications for charge transport, Journal of Materials Chemistry C, Vol: 3, Pages: 7394-7404, ISSN: 2050-7534
The solution-processing of conjugated polymers, just like commodity polymers, is subject to solvent and molecular weight-dependent solubility, interactions and chain entanglements within the polymer, all of which can influence the crystallization and microstructure development in semi-crystalline polymers and consequently affect charge transport and optoelectronic properties. Disentanglement of polymer chains in marginal solvents was reported to work via ultrasonication, facilitating the formation of photophysically ordered polymer aggregates. In this contribution, we explore how a wide range of technologically relevant solvents and formulations commonly used in organic electronics influence chain entanglement and the aggregation behaviour of P3HT using a combination of rheological and spectrophotometric measurements. The specific viscosity of the solution offers an excellent indication of the degree of entanglements in the solution, which is found to be related to the solubility of P3HT in a given solvent. Moreover, deliberately disentangling the solution in the presence of solvophobic driving forces, leads consistently to formation of photophysically visible aggregates which is indicative of local and perhaps long range order in the solute. We show for a broad range of solvents and molecular weights that disentanglement ultimately leads to significant ordering of the polymer in the solid state and a commensurate increase in charge transport properties. In doing so we demonstrate a remarkable ability to tune the microstructure which has important implications for transport properties. We discuss its potential implications in the context of organic electronics and photovoltaics.
Fei Z, Boufflet P, Wood S, et al., 2015, Influence of backbone fluorination in regioregular poly(3-alkyl-4-fluoro)thiophenes, Journal of the American Chemical Society, Vol: 137, Pages: 6866-6879, ISSN: 1520-5126
We report two strategies toward the synthesis of 3-alkyl-4-fluorothiophenes containing straight (hexyl and octyl) and branched (2-ethylhexyl) alkyl groups. We demonstrate that treatment of the dibrominated monomer with 1 equiv of alkyl Grignard reagent leads to the formation of a single regioisomer as a result of the pronounced directing effect of the fluorine group. Polymerization of the resulting species affords highly regioregular poly(3-alkyl-4-fluoro)thiophenes. Comparison of their properties to those of the analogous non-fluorinated polymers shows that backbone fluorination leads to an increase in the polymer ionization potential without a significant change in optical band gap. Fluorination also results in an enhanced tendency to aggregate in solution, which is ascribed to a more co-planar backbone on the basis of Raman and DFT calculations. Average charge carrier mobilities in field-effect transistors are found to increase by up to a factor of 5 for the fluorinated polymers.
Buchaca-Domingo E, Vandewal K, Fei Z, et al., 2015, Direct correlation of charge transfer absorption with molecular donor: acceptor interfacial area via photothermal deflection spectroscopy, Journal of the American Chemical Society, Vol: 137, Pages: 5256-5259, ISSN: 0002-7863
Here we show that the charge transfer (CT) absorption signal in bulk-heterojunction solar cell blends, measured by photothermal deflection spectroscopy, is directly proportional to the density of molecular donor:acceptor interfaces. Since the optical transitions from the ground state to the interfacial CT state are weakly allowed at photon energies below the optical gap of both the donor and acceptor, we can exploit the use of this sensitive linear absorption spectroscopy for such quantification. Moreover, we determine the absolute molar extinction coefficient of the CT transition for an archetypical polymer:fullerene interface. The latter is ∼100 times lower than the extinction coefficient of the donor chromophore involved, allowing us to experimentally estimate the transition dipole moment as 0.3 D and the electronic coupling between the ground and CT states to be on the order of 30 meV.
Andernach RE, Rossbauer S, Ashraf RS, et al., 2015, Conjugated Polymer-Porphyrin Complexes for Organic Electronics, CHEMPHYSCHEM, Vol: 16, Pages: 1223-1230, ISSN: 1439-4235
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- Citations: 11
Green J, Han Y, Heeney M, 2015, Use of peripherally alkylated dithieno[3,2-b:2,3-d]pyrrole units in conjugated polymers and small molecules for sensing applications, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Casey A, Han Y, Fei Z, et al., 2015, Cyano substituted benzothiadiazoles: Novel acceptor units allowing systematic lowering of conjugated polymer LUMO levels, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Yau CP, Wang S, Treat ND, et al., 2015, Investigation of Radical and Cationic Cross-Linking in High-Efficiency, Low Band Gap Solar Cell Polymers, Advanced Energy Materials, Vol: 5, ISSN: 1614-6840
Scarongella M, De Jonghe-Risse J, Buchaca-Domingo E, et al., 2015, A Close Look at Charge Generation in Polymer:Fullerene Blends with Microstructure Control, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 137, Pages: 2908-2918, ISSN: 0002-7863
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- Citations: 70
Han S, Fei Z, Jayawardena KDGI, et al., 2015, ZnO hybrid photovoltaics with variable side-chain lengths of thienothiophene polymer, THIN SOLID FILMS, Vol: 576, Pages: 38-41, ISSN: 0040-6090
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- Citations: 4
Colella NS, Zhang L, McCarthy-Ward T, et al., 2015, Controlled integration of oligo- and polythiophenes at the molecular scale, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 17, Pages: 26525-26529, ISSN: 1463-9076
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- Citations: 2
Singh R, Pagona G, Gregoriou VG, et al., 2015, The impact of thienothiophene isomeric structures on the optoelectronic properties and photovoltaic performance in quinoxaline based donor-acceptor copolymers, POLYMER CHEMISTRY, Vol: 6, Pages: 3098-3109, ISSN: 1759-9954
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- Citations: 24
De Jonghe-Risse J, Causa M, Buchaca-Domingo E, et al., 2015, Using the Stark effect to understand charge generation in organic solar cells, 14th Conference on Physical Chemistry of Interfaces and Nanomaterials, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
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- Citations: 2
Dou F, Buchaca-Domingo E, Sakowicz M, et al., 2015, The effect of phase morphology on the nature of long-lived charges in semiconductor polymer:fullerene systems, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 3, Pages: 3722-3729, ISSN: 2050-7526
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- Citations: 20
Wood S, Wade J, Shahid M, et al., 2015, Natures of optical absorption transitions and excitation energy dependent photostability of diketopyrrolopyrrole (DPP)-based photovoltaic copolymers, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 8, Pages: 3222-3232, ISSN: 1754-5692
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- Citations: 73
Casey A, Han Y, Fei Z, et al., 2015, Cyano substituted benzothiadiazole: a novel acceptor inducing n-type behaviour in conjugated polymers, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 3, Pages: 265-275, ISSN: 2050-7526
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- Citations: 82
Shaw J, Zhong H, Yau CP, et al., 2014, Alternating Copolymers Incorporating Dithienogemolodithiophene for Field-Effect Transistor Applications, MACROMOLECULES, Vol: 47, Pages: 8602-8610, ISSN: 0024-9297
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- Citations: 21
Fei Z, Ashraf RS, Han Y, et al., 2014, Diselenogermole as a novel donor monomer for low band gap polymers, Journal of Materials Chemistry A, Vol: 3, Pages: 1986-1994, ISSN: 2050-7496
Fei Z, Pattanasattayavong P, Han Y, et al., 2014, Influence of Side-Chain Regiochemistry on the Transistor Performance of High-Mobility, All-Donor Polymers, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 136, Pages: 15154-15157, ISSN: 0002-7863
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- Citations: 92
Himmelberger S, Vandewal K, Fei Z, et al., 2014, Role of Molecular Weight Distribution on Charge Transport in Semiconducting Polymers, MACROMOLECULES, Vol: 47, Pages: 7151-7157, ISSN: 0024-9297
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- Citations: 92
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