Publications
509 results found
Khim D, Lin Y-H, Anthopoulos TD, 2019, Impact of Layer Configuration and Doping on Electron Transport and Bias Stability in Heterojunction and Superlattice Metal Oxide Transistors, ADVANCED FUNCTIONAL MATERIALS, Vol: 29, ISSN: 1616-301X
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- Citations: 38
Panidi J, Kainth J, Paterson AF, et al., 2019, Introducing a nonvolatile N-type dopant drastically improves electron transport in polymer and small-molecule organic transistors, Advanced Functional Materials, Vol: 29, Pages: 1-10, ISSN: 1616-301X
KGaA, Weinheim Molecular doping is a powerful yet challenging technique for enhancing charge transport in organic semiconductors (OSCs). While there is a wealth of research on p-type dopants, work on their n-type counterparts is comparatively limited. Here, reported is the previously unexplored n-dopant (12a,18a)-5,6,12,12a,13,18,18a,19-octahydro-5,6-dimethyl- 13,18[1′,2′]-benzenobisbenzimidazo [1,2-b:2′,1′-d]benzo[i][2.5]benzodiazo-cine potassium triflate adduct (DMBI-BDZC) and its application in organic thin-film transistors (OTFTs). Two different high electron mobility OSCs, namely, the polymer poly[[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8- bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2′-bithiophene)] and a small-molecule naphthalene diimides fused with 2-(1,3-dithiol-2-ylidene)malononitrile groups (NDI-DTYM2) are used to study the effectiveness of DMBI-BDZC as a n-dopant. N-doping of both semiconductors results in OTFTs with improved electron mobility (up to 1.1 cm2 V−1 s−1), reduced threshold voltage and lower contact resistance. The impact of DMBI-BDZC incorporation is particularly evident in the temperature dependence of the electron transport, where a significant reduction in the activation energy due to trap deactivation is observed. Electron paramagnetic resonance measurements support the n-doping activity of DMBI-BDZC in both semiconductors. This finding is corroborated by density functional theory calculations, which highlights ground-state electron transfer as the main doping mechanism. The work highlights DMBI-BDZC as a promising n-type molecular dopant for OSCs and its application in OTFTs, solar cells, photodetectors, and thermoelectrics.
Zheng X, Troughton J, Gasparini N, et al., 2019, Quantum Dots Supply Bulk- and Surface-Passivation Agents for Efficient and Stable Perovskite Solar Cells, JOULE, Vol: 3, Pages: 1963-1976, ISSN: 2542-4351
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- Citations: 195
Lin Y, Yu L, Xia Y, et al., 2019, One-Step Blade-Coated Highly Efficient Nonfullerene Organic Solar Cells with a Self-Assembled Interfacial Layer Enabled by Solvent Vapor Annealing, SOLAR RRL, Vol: 3, ISSN: 2367-198X
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- Citations: 18
Ma C, Liu C, Huang J, et al., 2019, Plasmonic-Enhanced Light Harvesting and Perovskite Solar Cell Performance Using Au Biometric Dimers with Broadband Structural Darkness, SOLAR RRL, Vol: 3, ISSN: 2367-198X
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- Citations: 29
Wu Y, Li M, Wahyudi W, et al., 2019, Performance and Stability Improvement of Layered NCM Lithium-Ion Batteries at High Voltage by a Microporous Al<sub>2</sub>O<sub>3</sub> Sol-Gel Coating, ACS OMEGA, Vol: 4, Pages: 13972-13980, ISSN: 2470-1343
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- Citations: 47
Khan JI, Ashraf RS, Alamoudi MA, et al., 2019, P3HT Molecular Weight Determines the Performance of P3HT:O-IDTBR Solar Cells, SOLAR RRL, Vol: 3, ISSN: 2367-198X
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- Citations: 21
Paterson AF, Faber H, Savva A, et al., 2019, On the Role of Contact Resistance and Electrode Modification in Organic Electrochemical Transistors., Adv Mater, Pages: e1902291-e1902291
Contact resistance is renowned for its unfavorable impact on transistor performance. Despite its notoriety, the nature of contact resistance in organic electrochemical transistors (OECTs) remains unclear. Here, by investigating the role of contact resistance in n-type OECTs, the first demonstration of source/drain-electrode surface modification for achieving state-of-the-art n-type OECTs is reported. Specifically, thiol-based self-assembled monolayers (SAMs), 4-methylbenzenethiol (MBT) and pentafluorobenzenethiol (PFBT), are used to investigate contact resistance in n-type accumulation-mode OECTs made from the hydrophilic copolymer P-90, where the deliberate functionalization of the gold source/drain electrodes decreases and increases the energetic mismatch at the electrode/semiconductor interface, respectively. Although MBT treatment is found to increase the transconductance three-fold, contact resistance is not found to be the dominant factor governing OECT performance. Additional morphology and surface energy investigations show that increased performance comes from SAM-enhanced source/drain electrode surface energy, which improves wetting, semiconductor/metal interface quality, and semiconductor morphology at the electrode and channel. Overall, contact resistance in n-type OECTs is investigated, whilst identifying source/drain electrode treatment as a useful device engineering strategy for achieving state of the art n-type OECTs.
Bristow H, Thorley KJ, White AJP, et al., 2019, Impact of Nonfullerene Acceptor Side Chain Variation on Transistor Mobility, ADVANCED ELECTRONIC MATERIALS, ISSN: 2199-160X
Bottacchi F, Bottacchi S, Anthopoulos TD, 2019, A novel method for surface coverage spectroscopy with atomic force microscope: theory, modeling and experimental results for cylindrical nanostructures
A novel method for measuring the surface coverage of randomly distributedcylindrical nanoparticles such as nanorods and nanowires, using atomic forcemicroscopy (AFM), is presented. The method offers several advantages overexisting techniques such as particle beam and x-ray diffraction spectroscopy.These include, subnanometer vertical and lateral resolution, non destructiveinteraction with the sample surface allowing repeated measurements,user-friendly setup and ambient operating conditions. The method relies on theuse of a statistical model to describe the variations of the nanoparticlesaggregates height as a function of x,y position on the sample surface measuredby AFM. To verify the validity of the method we studied two types of randomlyoriented networks of carbon nanotubes (CNTs) and silver nanowires (Ag NWs) bothprocessed from solution phase. Experimental results are found to be inexcellent agreement with model predictions whilst analysis of the measuredsurface height density, together with the nanoparticle diameter statisticaldistribution, allow the extraction of the coverage coefficients for alldetected nanoparticle aggregates as well as for the total surface coverage. Themethod can be seen as a new powerful tool for the quantitative surface coverageanalysis of arbitrary nanoscale systems.
Choi HH, Paterson AF, Fusella MA, et al., 2019, Hall Effect in Polycrystalline Organic Semiconductors: The Effect of Grain Boundaries, ADVANCED FUNCTIONAL MATERIALS, ISSN: 1616-301X
Georgiadou DG, Lin Y, Lim J, et al., 2019, High Responsivity and Response Speed Single‐Layer Mixed‐Cation Lead Mixed‐Halide Perovskite Photodetectors Based on Nanogap Electrodes Manufactured on Large‐Area Rigid and Flexible Substrates, Advanced Functional Materials, Vol: 29, Pages: 1901371-1901371, ISSN: 1616-301X
Tang M-C, Barrit D, Munir R, et al., 2019, Bismuth-Based Perovskite-Inspired Solar Cells: In Situ Diagnostics Reveal Similarities and Differences in the Film Formation of Bismuth- and Lead-Based Films, SOLAR RRL, Vol: 3, ISSN: 2367-198X
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- Citations: 39
Chaudhry MU, Wang N, Tetzner K, et al., 2019, Light-Emitting Transistors Based on Solution-Processed Heterostructures of Self-Organized Multiple-Quantum-Well Perovskite and Metal-Oxide Semiconductors, ADVANCED ELECTRONIC MATERIALS, Vol: 5, ISSN: 2199-160X
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- Citations: 16
Twyman N, Tetzner K, Anthopoulos T, et al., 2019, Rapid photonic curing of solution-processed In2O3 layers on flexible substrates, Applied Surface Science, Vol: 479, Pages: 974-979, ISSN: 0169-4332
In2O3 is one of the most important semiconducting metal oxides primarily because of its wide band gap, high electron mobility and processing versatility. To this end, high-quality thin films of In2O3 can be prepared using scalable and inexpensive solution-based deposition methods, hence making it attractive for application in a number of emerging electronic applications. However, traditional solution processing often requires high temperature and lengthy annealing steps, making it impossible to use in combination with temperature-sensitive plastic substrates, which would be desired for numerous emerging flexible device applications. Here, rapid photonic curing of In2O3 layers is explored as an alternative to thermal annealing. Oxide thin films are successfully prepared on a range of substrates, including glass, polyimide, and polyethylene naphthalate. The effect of substrate and post-processing treatment on the morphology, surface chemistry, and electronic properties is investigated by atomic force microscopy and X-ray photoelectron spectroscopy. Systematic trends are identified, particularly in the degree of conversion of the precursor and its influence on the electronic structure.
He Q, Shahid M, Panidi J, et al., 2019, A versatile star-shaped organic semiconductor based on benzodithiophene and diketopyrrolopyrrole, Journal of Materials Chemistry C, Vol: 7, Pages: 6622-6629, ISSN: 2050-7526
We report the synthesis of a new star-shaped π-conjugated oligomer, BDT(DPP)4, containing a benzodithiophene core and four diketopyrrolopyrrole arms. The thermal, electrochemical and optical properties are characterized and the results complemented by computational studies. The utility of the molecule is demonstrated in both solar cell and field-effect transistor devices. In the former, BDT(DPP)4 displays low efficiency when used as an acceptor in blends with poly(3-hexylthiophene) but exhibits promising performance as a donor, in blends with either a fullerene or a non-fullerene acceptor. In field-effect transistors BDT(DPP)4 exhibits typical p-type transistor behavior, which is in accordance with its better donor performance in solar cell devices.
Wang K, Neophytou M, Aydin E, et al., 2019, Triarylphosphine Oxide as Cathode Interfacial Material for Inverted Perovskite Solar Cells, ADVANCED MATERIALS INTERFACES, Vol: 6, ISSN: 2196-7350
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- Citations: 14
Paterson AF, Tsetseris L, Li R, et al., 2019, Addition of the lewis acid Zn(C6 F5 )2 enables organic transistors with a maximum hole mobility in excess of 20 cm2 V-1 s-1, Advanced Materials, Vol: 31, ISSN: 0935-9648
Incorporating the molecular organic Lewis acid tris(pentafluorophenyl)borane [B(C6 F5 )3 ] into organic semiconductors has shown remarkable promise in recent years for controlling the operating characteristics and performance of various opto/electronic devices, including, light-emitting diodes, solar cells, and organic thin-film transistors (OTFTs). Despite the demonstrated potential, however, to date most of the work has been limited to B(C6 F5 )3 with the latter serving as the prototypical air-stable molecular Lewis acid system. Herein, the use of bis(pentafluorophenyl)zinc [Zn(C6 F5 )2 ] is reported as an alternative Lewis acid additive in high-hole-mobility OTFTs based on small-molecule:polymer blends comprising 2,7-dioctyl[1]benzothieno [3,2-b][1]benzothiophene and indacenodithiophene-benzothiadiazole. Systematic analysis of the materials and device characteristics supports the hypothesis that Zn(C6 F5 )2 acts simultaneously as a p-dopant and a microstructure modifier. It is proposed that it is the combination of these synergistic effects that leads to OTFTs with a maximum hole mobility value of 21.5 cm2 V-1 s-1 . The work not only highlights Zn(C6 F5 )2 as a promising new additive for next-generation optoelectronic devices, but also opens up new avenues in the search for high-mobility organic semiconductors.
Firdaus Y, Le Corre VM, Khan JI, et al., 2019, Key Parameters Requirements for Non-Fullerene-Based Organic Solar Cells with Power Conversion Efficiency >20%, ADVANCED SCIENCE, Vol: 6
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- Citations: 138
Sun G, Shahid M, Fei Z, et al., 2019, Highly-efficient semi-transparent organic solar cells utilising non-fullerene acceptors with optimised multilayer MoO3/Ag/MoO3 electrodes (vol 3, pg 450, 2019), MATERIALS CHEMISTRY FRONTIERS, Vol: 3, Pages: 955-955
Paterson AF, Mottram AD, Faber H, et al., 2019, Impact of the gate dielectric on contact resistance in high-mobility organic transistors, Advanced Electronic Materials, Vol: 5, ISSN: 2199-160X
The impact of the gate dielectric on contact resistance in organic thin-film transistors (OTFTs) is investigated using electrical characterization, bias-stress stability measurements, and bandgap density of states (DOS) analysis. Two similar dielectric materials, namely Cytop and poly[4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole-co-tetrafluoroethylene] (Teflon AF2400), are tested in top-gate bottom-contact OTFTs. The contact resistance of Cytop-based OTFTs is found to be greater than that of the AF2400-based devices, even though the metal/OSC interface remains identical in both systems. The Cytop devices are also found to perform worse in bias-stress stability tests which, along with the DOS calculations, suggests that charge trapping at the OSC/dielectric interface is more prevalent with Cytop than AF2400. This increased charge trapping at the Cytop OSC/dielectric interface appears to be associated with the higher contact resistance in Cytop OTFTs. Differences in the molecular structure between Cytop and AF2400 and the large difference in the glass transition temperature of the two polymers may be responsible for the observed difference in the transistor performance. Overall, this study highlights the importance of the gate dielectric material in the quest for better performing OTFTs and integrated circuits.
Petromichelaki E, Gagaoudakis E, Moschovis K, et al., 2019, Highly sensitive and room temperature detection of ultra-low concentrations of O<sub>3</sub> using self-powered sensing elements of Cu<sub>2</sub>O nanocubes, NANOSCALE ADVANCES, Vol: 1, Pages: 2009-2017, ISSN: 2516-0230
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- Citations: 13
Eisner F, Azzouzi M, Fei Z, et al., 2019, Hybridization of local exciton and charge-transfer states reduces non-radiative voltage losses in organic solar cells, Journal of the American Chemical Society, Vol: 141, Pages: 6362-6374, ISSN: 1520-5126
A number of recent studies have shown that the nonradiative voltage losses in organic solar cells can be suppressed in systems with low energetic offsets between donor and acceptor molecular states, but the physical reasons underpinning this remain unclear. Here, we present a systematic study of 18 different donor/acceptor blends to determine the effect that energetic offset has on both radiative and nonradiative recombination of the charge-transfer (CT) state. We find that, for certain blends, low offsets result in hybridization between charge-transfer and lowest donor or acceptor exciton states, which leads to a strong suppression in the nonradiative voltage loss to values as low as 0.23 V associated with an increase in the luminescence of the CT state. Further, we extend a two-state CT-state recombination model to include the interaction between CT and first excited states, which allows us to explain the low nonradiative voltage losses as an increase in the effective CT to ground state oscillator strength due to the intensity borrowing mechanism. We show that low nonradiative voltage losses can be achieved in material combinations with a strong electronic coupling between CT and first excited states and where the lower band gap material has a high oscillator strength for transitions from the excited state to the ground state. Finally, from our model we propose that achieving very low nonradiative voltage losses may come at a cost of higher overall recombination rates, which may help to explain the generally lower FF and EQE of highly hybridized systems.
Chen M, Yengel E, Zhang J, et al., 2019, One-step growth of reduced graphene oxide on arbitrary substrates, CARBON, Vol: 144, Pages: 457-463, ISSN: 0008-6223
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- Citations: 11
Sun G, Shahid M, Fei Z, et al., 2019, Highly-efficient semi-transparent organic solar cells utilising non-fullerene acceptors with optimised multilayer MoO3/Ag/MoO3 electrodes, Materials Chemistry Frontiers, Vol: 3, Pages: 450-455, ISSN: 2052-1537
We report the optimisation of a semi-transparent solar cell based on a blend of a recently reported high performance donor polymer (PFBDB-T) with a non-fullerene acceptor derivative (C8-ITIC). The performance is shown to strongly depend on the nature of the semi-transparent electrode, and we report the optimal fabrication conditions for a multilayer MoO3/Ag/MoO3 electrode. The effect of deposition rate and layer thickness of both the Ag and the outer MoO3 on transparency and sheet resistance is investigated, and is shown to have a significant impact on the overall device performance. The optimised PFBDB-T:C8-ITIC based devices exhibit an average power conversion efficiency (PCE) of 9.2% with an average visible transmittance (AVT) of 22%.
Karuthedath S, Gorenflot J, Firdaus Y, et al., 2019, Charge and Triplet Exciton Generation in Neat PC<sub>70</sub>BM Films and Hybrid CuSCN:PC<sub>70</sub>BM Solar Cells, ADVANCED ENERGY MATERIALS, Vol: 9, ISSN: 1614-6832
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- Citations: 19
Cheng F, Verrelli E, Alharthi FA, et al., 2019, Lyotropic 'hairy' TiO<sub>2</sub> nanorods, NANOSCALE ADVANCES, Vol: 1, Pages: 254-264, ISSN: 2516-0230
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- Citations: 8
Paterson AF, Anthopoulos TD, 2018, Enabling thin-film transistor technologies and the device metrics that matter, Nature Communications, Vol: 9, ISSN: 2041-1723
The field-effect transistor kickstarted the digital revolution that propelled our society into the information age. One member of the now large family of field-effect devices is the thin-film transistor (TFT), best known for its enabling role in modern flat-panel displays. TFTs can be used in all sorts of innovative applications because of the broad variety of materials they can be made from, which give them diverse electrical and mechanical characteristics. To successfully utilize TFT technologies in a variety of rapidly emerging applications, such as flexible, stretchable and transparent large-area microelectronics, there are a number of metrics that matter.
Paterson AF, Lin Y-H, Mottram AD, et al., 2018, The Impact of Molecular p-Doping on Charge Transport in High-Mobility Small-Molecule/Polymer Blend Organic Transistors, ADVANCED ELECTRONIC MATERIALS, Vol: 4, ISSN: 2199-160X
Boufflet P, Bovo G, Occhi L, et 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.
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