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  • Journal article
    Zeidell AM, Filston DS, Waldrip M, Iqbal HF, Chen H, McCulloch I, Jurchescu ODet al., 2020,

    Large-Area Uniform Polymer Transistor Arrays on Flexible Substrates: Towards High-Throughput Sensor Fabrication

    , ADVANCED MATERIALS TECHNOLOGIES, Vol: 5, ISSN: 2365-709X
  • Journal article
    Sachs M, Cha H, Kosco J, Aitchison CM, Francàs L, Corby S, Chiang C-L, Wilson A, Godin R, Fahey-Williams A, Cooper A, Sprick S, McCulloch I, Durrant JRet al., 2020,

    Tracking charge transfer to residual metal clusters in conjugated polymers for photocatalytic hydrogen evolution

    , Journal of the American Chemical Society, Vol: 142, Pages: 14574-14587, ISSN: 0002-7863

    Semiconducting polymers are versatile materials for solar energy conversion and have gained popularity as photocatalysts for sunlight-driven hydrogen production. Organic polymers often contain residual metal impurities such as palladium (Pd) clusters that are formed during the polymerization reaction, and there is increasing evidence for a catalytic role of such metal clusters in polymer photocatalysts. Using transient and operando optical spectroscopies on nanoparticles of F8BT, P3HT, and the dibenzo[b,d]thiophene sulfone homopolymer, P10, we demonstrate how differences in the timescale of electron transfer to Pd clusters translate into hydrogen evolution activity optima at extremely different residual Pd concentrations. For F8BT nanoparticles with common Pd concentrations of >1000 ppm (>0.1 wt. %), we find that residual Pd clusters quench photogenerated excitons via energy and electron transfer on the fs – ns timescale, thus outcompeting reductive quenching. We spectroscopically identify reduced Pd clusters in our F8BT nanoparticles from the µs timescale onwards and show that the predominant location of long-lived electrons gradually shifts to the F8BT polymer when the Pd content is lowered. While a low yield of long-lived electrons limits the hydrogen evolution activity of F8BT, P10 exhibits a substantially higher hydrogen evolution activity which we demonstrate results from higher yields of long-lived electrons due to more efficient reductive quenching. Surprisingly, and despite the higher performance of P10, long-lived electrons reside on the P10 polymer rather than on the Pd clusters in P10 particles, even at very high Pd concentrations of 27,000 ppm (2.7 wt. %). In contrast, long-lived electrons in F8BT already reside on Pd clusters before the typical timescale of hydrogen evolution. This comparison shows that P10 exhibits efficient reductive quenching but slow electron transfer to residual Pd clusters whereas the opposite is the case for F8
  • Journal article
    Cha H, Zheng Y, Dong Y, Lee HH, Wu J, Bristow H, Zhang J, Lee HKH, Tsoi WC, Bakulin AA, McCulloch I, Durrant JRet al., 2020,

    Exciton and charge carrier dynamics in highly crystalline PTQ10:IDIC organic solar cells

    , Advanced Energy Materials, Pages: 1-11, ISSN: 1614-6832

    Herein the morphology and exciton/charge carrier dynamics in bulk heterojunctions (BHJs) of the donor polymer PTQ10 and molecular acceptor IDIC are investigated. PTQ10:IDIC BHJs are shown to be particularly promising for low cost organic solar cells (OSCs). It is found that both PTQ10 and IDIC show remarkably high crystallinity in optimized BHJs, with GIWAXS data indicating pi‐pi stacking coherence lengths of up to 8 nm. Exciton‐exciton annihilation studies indicate long exciton diffusion lengths for both neat materials (19 nm for PTQ10 and 9.5 nm for IDIC), enabling efficient exciton separation with half lives of 1 and 3 ps, despite the high degree of phase segregation in this blend. Transient absorption data indicate exciton separation leads to the formation of two spectrally distinct species, assigned to interfacial charge transfer (CT) states and separated charges. CT state decay is correlated with the appearance of additional separate charges, indicating relatively efficient CT state dissociation, attributed to the high crystallinity of this blend. The results emphasize the potential for high material crystallinity to enhance charge separation and collection in OSCs, but also that long exciton diffusion lengths are likely to be essential for efficient exciton separation in such high crystallinity devices.
  • Journal article
    Melianas A, Quill TJ, LeCroy G, Tuchman Y, v Loo H, Keene ST, Giovannitti A, Lee HR, Maria IP, McCulloch I, Salleo Aet al., 2020,

    Temperature-resilient solid-state organic artificial synapses for neuromorphic computing

    , SCIENCE ADVANCES, Vol: 6, ISSN: 2375-2548
  • Journal article
    Hou L, Leydecker T, Zhang X, Rekab W, Herder M, Cendra C, Hecht S, McCulloch I, Salleo A, Orgiu E, Samori Pet al., 2020,

    Engineering Optically Switchable Transistors with Improved Performance by Controlling Interactions of Diarylethenes in Polymer Matrices

    , JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 142, Pages: 11050-11059, ISSN: 0002-7863
  • Journal article
    Yao L, Liao H, Ravva MK, Guo Y, Duan J, Wang Y, Yu Y, Li Z, McCulloch I, Yue Wet al., 2020,

    Metal-free polymerization: synthesis and properties of fused benzo[1,2-<i>b</i>:4,5-<i>b</i>′]bis[<i>b</i>]benzothiophene (BBBT) polymers

    , POLYMER CHEMISTRY, Vol: 11, Pages: 3695-3700, ISSN: 1759-9954
  • Journal article
    Paterson AF, Savva A, Wustoni S, Tsetseris L, Paulsen BD, Faber H, Emwas AH, Chen X, Nikiforidis G, Hidalgo TC, Moser M, Maria IP, Rivnay J, McCulloch I, Anthopoulos TD, Inal Set al., 2020,

    Water stable molecular n-doping produces organic electrochemical transistors with high transconductance and record stability

    , NATURE COMMUNICATIONS, Vol: 11, ISSN: 2041-1723
  • Journal article
    Xiao M, Kang B, Lee SB, Perdigao LMA, Luci A, Warr DA, Senanayak SP, Nikolka M, Statz M, Wu Y, Sadhanala A, Schott S, Carey R, Wang Q, Lee M, Kim C, Onwubiko A, Jellett C, Liao H, Yue W, Cho K, Costantini G, McCulloch I, Sirringhaus Het al., 2020,

    Anisotropy of Charge Transport in a Uniaxially Aligned Fused Electron-Deficient Polymer Processed by Solution Shear Coating

    , ADVANCED MATERIALS, Vol: 32, ISSN: 0935-9648
    • Cite
    • Citations: 54
  • Journal article
    Muellen K, McCulloch I, Reetz MT, 2020,

    New EurASC Members

    , ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 59, Pages: 8327-8327, ISSN: 1433-7851
  • Journal article
    Matta M, Wu R, Paulsen BD, Petty A, Sheelamanthula R, McCulloch I, Schatz GC, Rivnay Jet al., 2020,

    Ion Coordination and Chelation in a Glycolated Polymer Semiconductor: Molecular Dynamics and X-Ray Fluorescence Study

    <jats:p>&lt;p&gt;Organic electrochemical transistors (OECTs) are based on the doping of a semiconducting polymer by an electrolyte. Due to their ability to conjugate volumetric ion penetration with high hole mobility and charge density, polythiophenes bearing glycolated side chains have rapidly surged as the highest performing materials for OECTs; amongst them, p(g2T-TT) is amongst those with the highest figure of merit. While recent studies have shown how different doping anions tend to affect the polymer microstructure, only a handful of electrolytes have been tested in mixed conduction devices. Our work provides an atomistic picture of the p(g2T-TT) -electrolyte interface in the ‘off’ state of an OECT, expected to be dominated by cation-polymer interactions. Using a combination of molecular dynamics simulations and X-ray fluorescence, we show how different anions effectively tune the coordination and chelation of cations by glycolated polymers. At the same time, softer and hydrophobic anions such as TFSI and ClO&lt;sub&gt;4&lt;/sub&gt; are found to preferentially interact with the p(g2T-TT) phase, further enhancing polymer-cation coordination. Besides opening the way for a full study of electrolyte doping mechanisms in operating devices, our results suggest that tailoring the electrolyte for different applications and materials might be a viable strategy to tune the performance of mixed conducting devices.&lt;/p&gt;</jats:p>
  • Journal article
    Matta M, Wu R, Paulsen BD, Petty A, Sheelamanthula R, McCulloch I, Schatz GC, Rivnay Jet al., 2020,

    Ion Coordination and Chelation in a Glycolated Polymer Semiconductor: Molecular Dynamics and X-Ray Fluorescence Study

    <jats:p> Organic electrochemical transistors (OECTs) are based on the doping of a semiconducting polymer by an electrolyte. Due to their ability to conjugate volumetric ion penetration with high hole mobility and charge density, polythiophenes bearing glycolated side chains have rapidly surged as the highest performing materials for OECTs; amongst them, p(g2T-TT) is amongst those with the highest figure of merit. While recent studies have shown how different doping anions tend to affect the polymer microstructure, only a handful of electrolytes have been tested in mixed conduction devices. Our work provides an atomistic picture of the p(g2T-TT) -electrolyte interface in the ‘off’ state of an OECT, expected to be dominated by cation-polymer interactions. Using a combination of molecular dynamics simulations and X-ray fluorescence, we show how different anions effectively tune the coordination and chelation of cations by glycolated polymers. At the same time, softer and hydrophobic anions such as TFSI and ClO <jats:sub>4</jats:sub> are found to preferentially interact with the p(g2T-TT) phase, further enhancing polymer-cation coordination. Besides opening the way for a full study of electrolyte doping mechanisms in operating devices, our results suggest that tailoring the electrolyte for different applications and materials might be a viable strategy to tune the performance of mixed conducting devices. </jats:p>
  • Journal article
    Gasparini N, Paleti HK, Bertrandie J, Cai G, Zhang G, Wadsworth A, Lu X, Yip H-L, McCulloch I, Baran Det al., 2020,

    Exploiting Ternary Blends for Improved Photostability in High-Efficiency Organic Solar Cells

    , ACS ENERGY LETTERS, Vol: 5, Pages: 1371-1379, ISSN: 2380-8195
    • Cite
    • Citations: 153
  • Journal article
    Woods DJ, Hillman S, Pearce D, Wilbraham L, Flagg L, Duffy W, Mcculloch I, Durrant J, Guilbert A, Zwijnenburg M, Sprick RS, Nelson J, Cooper Aet al., 2020,

    Side-chain tuning in conjugated polymer photocatalysts for improved hydrogen production from water

    , Energy & Environmental Science, Vol: 13, Pages: 1843-1855, ISSN: 1754-5692

    Structure–property–activity relationships in solution processable polymer photocatalysts for hydrogen production from water were probed by varying the chemical structure of both the polymer side-chains and the polymer backbone. In both cases, the photocatalytic performance depends strongly on the inclusion of more polar groups, such as dibenzo[b,d]thiophene sulfone backbone units or oligo(ethylene glycol) side-chains. We used optical, spectroscopic, and structural characterisation techniques to understand the different catalytic activities of these systems. We find that although polar groups improve the wettability of the material with water in all cases, backbone and side-chain modifications affect photocatalytic performance in different ways: the inclusion of dibenzo[b,d]thiophene sulfone backbone units improves the thermodynamic driving force for hole transfer to the sacrificial donor, while the inclusion of oligo ethylene glycol side-chains aids the degree of polymer swelling and also extends the electron polaron lifetime. The best performing material, FS-TEG, exhibits a HER of 72.5 μmol h−1 for 25 mg photocatalyst (2.9 mmol g−1 h−1) when dispersed in the presence of a sacrificial donor and illuminated with λ > 420 nm light, corresponding to a hydrogen evolution EQE of 10% at 420 nm. When cast as a thin film, this HER was further boosted to 13.9 mmol g−1 h−1 (3.0 mmol m−2 h−1), which is among the highest rates in this field.
  • Journal article
    Wu X, Surendran A, Moser M, Chen S, Muhammad BT, Maria IP, McCulloch I, Leong WLet al., 2020,

    Universal Spray-Deposition Process for Scalable, High-Performance, and Stable Organic Electrochemical Transistors

    , ACS APPLIED MATERIALS & INTERFACES, Vol: 12, Pages: 20757-20764, ISSN: 1944-8244
    • Cite
    • Citations: 66
  • Journal article
    Han D, Khan Y, Ting J, Zhu J, Combe C, Wadsworth A, McCulloch I, Arias ACet al., 2020,

    Pulse Oximetry Using Organic Optoelectronics under Ambient Light

    , ADVANCED MATERIALS TECHNOLOGIES, Vol: 5, ISSN: 2365-709X

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