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  • Journal article
    Abelha TF, Phillips TW, Bannock JH, Nightingale AM, Dreiss CA, Kemal E, Urbano L, deMello JC, Green M, Dailey LAet al., 2017,

    Bright conjugated polymer nanoparticles containing a biodegradable shell produced at high yields and with tuneable optical properties by a scalable microfluidic device

    , NANOSCALE, Vol: 9, Pages: 2009-2019, ISSN: 2040-3364
  • Journal article
    Westacott P, Treat ND, Martin J, Bannock JH, de Mello JC, Chabinyc M, Sieval AB, Michels JJ, Stingelin Net al., 2016,

    Origin of fullerene-induced vitrification of fullerene: donor polymer photovoltaic blends and its impact on solar cell performance

    , Journal of Materials Chemistry A, Vol: 5, Pages: 2689-2700, ISSN: 2050-7488

    Organic solar cell blends comprised of an electron donating polymer and electron accepting fullerene typically form upon solution casting a thin-film structure made up of a complex mixture of phases. These phases can vary greatly in: composition, order and thermodynamic stability; and they are dramatically influenced by the processing history. Understanding the processes that govern the formation of these phases and their subsequent effect on the efficiency of photo-generating and extracting charge carriers is of utmost importance to enable rational design and processing of these blends. Here we show that the vitrifying effect of three fullerene derivatives ([60]PCBM, bis[60]PCBM, and [60]ICBA) on the prototypical donor polymer (rr-P3HT) can dominate microstructure formation of fullerene/donor polymer blends cast from solution. Using a dynamic crystallization model based on an amalgamation of Flory–Huggins and Lauritzen–Hoffman theory coupled to solvent evaporation we demonstrate that this vitrification, which can result in a large fraction of highly intermixed amorphous solid solution of the fullerene and the polymer, is due to kinetic and thermodynamic reasons. The former is partly determined by the glass transition temperature of the individual components while donor polymer:fullerene miscibility, strongly influenced by the chemical nature of the donor and the fullerene and leading to thermodynamic mixing, dictates the second phenomena. We show that our approximate dynamic crystallization model assists understanding the different solid-state structure formation of rr-P3HT:fullerene blends. Due to the generality of the assumptions used, our model should be widely applicable and assist to capture the influence of the different vitrification mechanisms also of other photovoltaic blends, including the high-efficiency systems based on the strongly aggregating PCE11 (PffBT4T-2OD), which also feature clear signs of vitirfication upon blending with, e.g., [60

  • Journal article
    Nightingale AM, deMello JC, 2016,

    Improving the ensemble optical properties of InP quantum dots by indium precursor modification

    , Journal of Materials Chemistry C, Vol: 4, Pages: 8454-8458, ISSN: 2050-7526

    Indium phosphide quantum dots typically exhibit broad and poorly defined ensemble optical properties due to a highly pronounced nucleation period that consumes virtually all phosphorus precursors, leading to subsequent growth by Ostwald ripening and poor final size distributions. Previous attempts to reduce the reactivity of the phosphorus precursor, and thereby limit its consumption during the nucleation phase, have not led to appreciably better optical properties due to an unwanted increase in the duration of nucleation. Here we present an alternative approach to reducing initial precursor consumption using a simple modification of the indium precursor, in which the widely used carboxylate ligand is replaced by a phosphine. The change of ligand leaves residual precursor available for size-focusing growth after nucleation, leading to significantly improved spectral features. Band-edge emission peaks are typically 30% narrower than for the standard method.

  • Journal article
    Bannock JH, Xu W, Baïssas T, Heeney M, de Mello JCet al., 2016,

    Rapid flow-based synthesis of poly(3-hexylthiophene) using 2-methyltetrahydrofuran as a bio-derived reaction solvent

    , European Polymer Journal, Vol: 80, Pages: 240-246, ISSN: 1873-1945

    We report the synthesis of poly(3-hexylthiophene) (P3HT) by Grignard metathesis (GRIM) polymerization using the bio-derived ‘green’ solvent 2-methyltetrahydrofuran (2-MeTHF). Using a standard flask-based reaction, the molecular weight distribution, regioregularity and product yield were found to be similar to those obtained under equivalent conditions using tetrahydrofuran (THF) as a reaction solvent. The synthesis was subsequently adapted to a novel “tube-in-shell” droplet-based flow reactor, using a newly developed high-solubility catalyst derived from nickel(II) bromide ethylene glycol dimethyl ether complex (Ni(dme)Br2) and 1,3-bis(diphenylphosphino)propane (dppp). Use of the new catalyst together with an increased reaction temperature of 65 oC (enabled by the higher boiling point of 2-MeTHF) resulted in an approximate four-fold increase in reaction rate compared to a standard THF- based synthesis at 55 oC, with full conversion reached within one minute. The purified flow- synthesized polymer had an Mw of 46 kg mol-1, a low PDI of 1.4, and a regioregularity of 93 %, indicating the suitability of flow-based GRIM polymerization in 2-MeTHF for the high- throughput synthesis of high quality P3HT.

  • Journal article
    Bannock JH, Treat N, Chabinyc M, Stingelin N, Heeney M, de Mello JCet al., 2016,

    The influence of polymer purification on the efficiency of poly(3-hexylthiophene):fullerene organic solar cells

    , Scientific Reports, Vol: 6, ISSN: 2045-2322

    We report the influence of different polymer purification procedures on the photovoltaic performance ofbulk heterojunction solar cells formed from binary blends of poly(3-hexylthiophene) (P3HT) andfullerenes. Selective Soxhlet extractions and metal scavenging agents were used to remove residualmonomer, magnesium salt by-products and catalyst from high-weight P3HT (Mw 121 kg/mol, PDI 1.8,RR 99%) synthesised by the Grignard metathesis (GRIM) polymerization route. Using phenyl-C61-butyric acid methyl ester (PC60BM) as an electron acceptor, we observed an increase in average powerconversion efficiency from 2.3 to 4.8 % in going from crude to fully purified material. Using indene-C60bisadduct (IC60BA) in place of PC60BM, we observed a further increase to an average value of 6.6 %,which is high for a bulk heterojunction formed from a binary blend of P3HT and C60 fullerene derivatives.

  • Journal article
    Falco A, Matarese B, Feyen P, Benfenati F, Lugli P, de Mello JCet al., 2016,

    Investigation of the Stability and Biocompatibility of Commonly Used Electrode Materials in Organic Neurooptoelectronics

    , IEEE TRANSACTIONS ON NANOTECHNOLOGY, Vol: 15, Pages: 746-753, ISSN: 1536-125X
  • Conference paper
    Matarese BFE, 2015,

    Investigation of the stability and biocompatibility of commonly used electrode materials in organic neuro-optoelectronics

    , Nanotechnology (IEEE-NANO) , 2015 IEEE 15th International Conference on, Publisher: IEEE, Pages: 1539-1542

    We have investigated the stability of key electro-optical properties (Conductivity, Work Function, Transmittance) of several commonly used electrode materials for organic optoelectronics (Indium-Tin Oxide, Gold, Silver, Aluminum) in different media (Air, DI water, Phosphate Buffered Saline and Dulbecco's Modified Eagle Medium). By comparing the electrode materials side by side, we aimed to identify their advantages and drawbacks for use in solid/liquid devices. Since many applications of such devices involve the direct contact with biological species, we also investigated their biocompatibility by evaluating cytotoxicity of HEK293 cells cultured on the candidate materials.

  • Journal article
    Hu H, Zhao K, Fernandes N, Boufflet P, Bannock JH, Yu L, de Mello JC, Stingelin N, Heeney M, Giannelise EP, Amassian Aet 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.

  • Journal article
    Phillips T, Bannock JH, de Mello JC, 2015,

    Microscale extraction and phase separation using a porous capillary

    , Lab on a Chip, Vol: 15, Pages: 2960-2967, ISSN: 1473-0197

    We report the use of a porous polytetrafluoroethylene capillary for the inline separation of liquid–liquid segmented flows, based on the selective wetting and permeation of the porous capillary walls by one of the liquids. Insertion of a narrow flow restriction at the capillary outlet allows the back pressure to be tuned for multiple liquid–liquid combinations and flow conditions. In this way, efficient separation of aqueous–organic, aqueous–fluorous and organic–fluorous segmented flows can be readily achieved over a wide range of flow rates. The porous-capillary-separator enables the straightforward regeneration of a continuous flow from a segmented flow, and may be applied to various applications, including inline analysis, biphasic reactions, and purification. As a demonstration of the latter, we performed a simple inline aqueous–organic extraction of the pH indicator 2,6-dichloroindophenol. An aqueous solution of the conjugate base was mixed with hydrochloric acid in continuous flow to protonate the indicator and render it organic-soluble. The indicator was then extracted from the aqueous feed into chloroform using a segmented flow. The two liquids were finally separated inline using a porous PTFE capillary, with the aqueous phase emerging as a continuous stream from the separator outlet. UV-visible absorption spectroscopy showed the concentration of indicator in the outflowing aqueous phase to be less than one percent of its original value, confirming the efficacy of the extraction and separation process.

  • Journal article
    Buchaca-Domingo E, Vandewal K, Fei Z, Watkins SE, Scholes FH, Bannock JH, de Mello JC, Richter LJ, DeLongchamp DM, Amassian A, Heeney M, Salleo A, Stingelin Net 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.

  • Journal article
    de Mello J, Anthony J, Lee S, 2015,

    Organic electronics: recent developments.

    , Chemphyschem, Vol: 16, Pages: 1099-1100
  • Journal article
    Pang C, Chellappan V, Yim JH, Tan MJ, Goh GTW, Lee S, Zhang J, de Mello Jet al., 2015,

    Enhanced Performance Using an SU-8 Dielectric Inter layer in a Bulk Heterojunction Organic Solar Cell

    , ACS APPLIED MATERIALS & INTERFACES, Vol: 7, Pages: 5219-5225, ISSN: 1944-8244
  • Journal article
    Hellmann C, Treat ND, Scaccabarozzi AD, Hollis JR, Fleischli FD, Bannock JH, de Mello J, Michels JJ, Kim J-S, Stingelin Net al., 2015,

    Solution Processing of Polymer Semiconductor: Insulator Blends-Tailored Optical Properties Through Liquid-Liquid Phase Separation Control

    , JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS, Vol: 53, Pages: 304-310, ISSN: 0887-6266
  • Journal article
    Dattani R, Telling MTF, Lopez CG, Krishnadasan SH, Bannock JH, Terry AE, de Mello JC, Cabral JT, Nedoma AJet al., 2015,

    Rapid precipitation: An alternative to solvent casting for organic solar cells

    , Chemphyschem, Vol: 16, Pages: 1231-1238, ISSN: 1439-7641

    Rapid precipitation, immersion of a liquid formulation into a nonsolvent, is compared with drop casting for fabricating organic solar cells. Blends comprising poly-3-hexylthiophene (P3HT), phenyl-C61-butyric acid methyl ester (PCBM), and chlorobenzene were processed into bulk samples by using two distinct routes: rapid precipitation and drop casting. The resulting structure, phases, and crystallinity were analyzed by using small-angle neutron scattering, X-ray diffraction, differential scanning calorimetry, and muon spin resonance. Rapid precipitation was found to induce a finely structured phase separation between PCBM and P3HT, with 65 wt % crystallinity in the P3HT phase. In contrast, solvent casting resulted in a mixed PCBM/P3HT phase with only 43 wt % P3HT crystallinity. The structural advantages conferred by rapid precipitation were shown to persist following intense thermal treatments.

  • Journal article
    Edwards AN, Yamazaki M, Krishnadasan SH, Phillips TW, Rowlands L, Jourdain R, Nightingale AM, de Mello JCet al., 2015,

    Photostable phosphorescent polymer nanospheres for high sensitivity detection

    , JOURNAL OF MATERIALS CHEMISTRY C, Vol: 3, Pages: 6565-6572, ISSN: 2050-7526
  • Journal article
    Dattani R, Bannock JH, Fei Z, MacKenzie RCI, Guilbert AAY, Vezie MS, Nelson J, de Mello JC, Heeney M, Cabral JT, Nedoma AJet al., 2014,

    A general mechanism for controlling thin film structures in all-conjugated block copolymer: fullerene blends

    , JOURNAL OF MATERIALS CHEMISTRY A, Vol: 2, Pages: 14711-14719, ISSN: 2050-7488
  • Journal article
    Bannock JH, Krishnadasan SH, Heeney M, de Mello JCet al., 2014,

    A gentle introduction to the noble art of flow chemistry

    , MATERIALS HORIZONS, Vol: 1, Pages: 373-378, ISSN: 2051-6347
  • Journal article
    Phillips TW, Lignos IG, Maceiczyk RM, deMello AJ, de Mello JCet al., 2014,

    Nanocrystal synthesis in microfluidic reactors: where next?

    , Lab on a Chip
  • Journal article
    Nightingale AM, Phillips TW, Bannock JH, de Mello JCet al., 2014,

    Controlled multistep synthesis in a three-phase droplet reactor

    , Nature Communications, Vol: 5, Pages: 1-8, ISSN: 2041-1723

    Channel-fouling is a pervasive problem in continuous flow chemistry, causing poor productcontrol and reactor failure. Droplet chemistry, in which the reaction mixture flows as discretedroplets inside an immiscible carrier liquid, prevents fouling by isolating the reaction from thechannel walls. Unfortunately, the difficulty of controllably adding new reagents to an existingdroplet stream has largely restricted droplet chemistry to simple reactions in which allreagents are supplied at the time of droplet formation. Here we describe an effective methodfor repeatedly adding controlled quantities of reagents to droplets. The reagents are injectedinto a multiphase fluid stream, comprising the carrier liquid, droplets of the reaction mixtureand an inert gas that maintains a uniform droplet spacing and suppresses new dropletformation. The method, which is suited to many multistep reactions, is applied to a five-stagequantum dot synthesis wherein particle growth is sustained by repeatedly adding freshfeedstock.

  • Journal article
    Georgiev YM, Petkov N, McCarthy B, Yu R, Djara V, O'Connell D, Lotty O, Nightingale AM, Thamsumet N, deMello JC, Blake A, Das S, Holmes JDet al., 2014,

    Fully CMOS-compatible top-down fabrication of sub-50 nm silicon nanowire sensing devices

    , MICROELECTRONIC ENGINEERING, Vol: 118, Pages: 47-53, ISSN: 0167-9317
  • Conference paper
    Phillips TW, 2014,

    Flow synthesis of silver nanowires for low cost and high performance transparent conducting electrodes

    , Materials Research Society Spring 2014
  • Conference paper
    Fagas G, Nolan M, Georgiev YM, Yu R, Lotty O, Petkov N, Holmes JD, Jia G, Eisenhawer B, Gawlik A, Falk F, Khosropour N, Buitrago E, Badia MF-B, Krummenacher F, Ionescu AM, Kayal M, Nightingale AM, de Mello JC, Puik E, van der Bent F, Lafeber R, Ramaneti R, Hien DT, van Rijn Cet al., 2014,

    Component design and testing for a miniaturised autonomous sensor based on a nanowire materials platform

    , Conference on Smart Sensors, Actuators and MEMS within the SPIE EUROPE Symposium on Microtechnologies, Publisher: SPRINGER HEIDELBERG, Pages: 971-988, ISSN: 0946-7076
  • Journal article
    Yim JH, Joe S-Y, Pang C, Lee KM, Jeong H, Park J-Y, Ahn YH, de Mello JC, Lee Set al., 2014,

    Fully Solution-Processed Semitransparent Organic Solar Cells with a Silver Nanowire Cathode and a Conducting Polymer Anode

    , ACS Nano, Vol: 8, Pages: 2857-2863, ISSN: 1936-0851

    We report the fabrication of efficient indium tin oxide-free organicsolar cells based on poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid methylester (P3HT:PCBM). All layers of the devices from the lowermost silver nanowire cathodeto the uppermost conducting polymer anode are deposited from solution and processedat plastic-compatible temperatures <200 C. Owing to the absence of an opaque metalelectrode, the devices are semitransparent with potential applications in powergeneratingwindows and tandem-cells. The measured power conversion efficiencies(PCEs) of 2.3 and 2.0% under cathode- and anode-side illumination, respectively, matchpreviously reported PCE values for equivalent semitransparent organic solar cells usingindium tin oxide.

  • Journal article
    Bannock JH, Al-Hashimi M, Krishnadasan SH, Halls JJM, Heeney M, de Mello JCet al., 2014,

    Controlled synthesis of conjugated random copolymers in a droplet-based microreactor

    , Materials Horizons
  • Journal article
    Beesley DJ, Semple J, Krishnan Jagadamma L, Amassian A, McLachlan MA, Anthopoulos TD, DeMello JCet al., 2014,

    Sub-15-nm patterning of asymmetric metal electrodes and devices by adhesion lithography

    , Nat Commun, Vol: 5

    Coplanar electrodes formed from asymmetric metals separated on the nanometre length scale are essential elements of nanoscale photonic and electronic devices. Existing fabrication methods typically involve electron-beam lithography—a technique that enables high fidelity patterning but suffers from significant limitations in terms of low throughput, poor scalability to large areas and restrictive choice of substrate and electrode materials. Here, we describe a versatile method for the rapid fabrication of asymmetric nanogap electrodes that exploits the ability of selected self-assembled monolayers to attach conformally to a prepatterned metal layer and thereby weaken adhesion to a subsequently deposited metal film. The method may be carried out under ambient conditions using simple equipment and a minimum of processing steps, enabling the rapid fabrication of nanogap electrodes and optoelectronic devices with aspect ratios in excess of 100,000.

  • Journal article
    Khan FR, Schmuecking K, Krishnadasan SH, Berhanu D, Smith BD, deMello JC, Rainbow PS, Luoma SN, Valsami-Jones Eet al., 2013,


    , ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY, Vol: 32, Pages: 2621-2629, ISSN: 0730-7268
  • Journal article
    Xia R, Leem D-S, Kirchartz T, Spencer S, Murphy C, He Z, Wu H, Su S, Cao Y, Kim JS, deMello JC, Bradley DDC, Nelson Jet al., 2013,

    Investigation of a Conjugated Polyelectrolyte Interlayer for Inverted Polymer:Fullerene Solar Cells

    , ADVANCED ENERGY MATERIALS, Vol: 3, Pages: 718-723, ISSN: 1614-6832
  • Journal article
    Nightingale AM, deMello JC, 2013,

    Segmented Flow Reactors for Nanocrystal Synthesis

    , ADVANCED MATERIALS, Vol: 25, Pages: 1813-1821, ISSN: 0935-9648
  • Journal article
    Nightingale AM, Bannock JH, Krishnadasan SH, O'Mahoney FTF, Haque SA, Sloan J, Drury C, McIntyre R, de Mello JCet al., 2013,

    Large-scale synthesis of nanocrystals in a multichannel droplet reactor

    , Journal of Materials Chemistry A
  • Journal article
    Ong K-H, Lim S-L, Li J, Wong H-K, Tan H-S, Lin T-T, Moh LC-H, de Mello JC, Chen Z-Ket al., 2013,

    Design and synthesis of benzothiadiazole-oligothiophene polymers for organic solar cell applications

    , POLYMER CHEMISTRY, Vol: 4, Pages: 1863-1873, ISSN: 1759-9954

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