Imperial College London

ProfessorThomasAnthopoulos

Faculty of Natural SciencesDepartment of Physics

Visiting Professor
 
 
 
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Contact

 

+44 (0)20 7594 6669thomas.anthopoulos Website

 
 
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Assistant

 

Mrs Carolyn Dale +44 (0)20 7594 7579

 
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Location

 

1111Blackett LaboratorySouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

323 results found

Paterson AF, Faber H, Savva A, Nikiforidis G, Gedda M, Hidalgo TC, Chen X, McCulloch I, Anthopoulos TD, Inal Set al., 2019, On the Role of Contact Resistance and Electrode Modification in Organic Electrochemical Transistors., Adv Mater

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.

Journal article

Bristow H, Thorley KJ, White AJP, Wadsworth A, Babics M, Hamid Z, Zhang W, Paterson AF, Kosco J, Panidi J, Anthopoulos TD, McCulloch Iet al., 2019, Impact of Nonfullerene Acceptor Side Chain Variation on Transistor Mobility, ADVANCED ELECTRONIC MATERIALS, ISSN: 2199-160X

Journal article

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.

Working paper

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, ISSN: 1616-301X

Journal article

Choi HH, Paterson AF, Fusella MA, Panidi J, Solomeshch O, Tessler N, Heeney M, Cho K, Anthopoulos TD, Rand BP, Podzorov Vet al., 2019, Hall Effect in Polycrystalline Organic Semiconductors: The Effect of Grain Boundaries, ADVANCED FUNCTIONAL MATERIALS, ISSN: 1616-301X

Journal article

Georgiadou DG, Lin Y, Lim J, Ratnasingham S, McLachlan MA, Snaith HJ, Anthopoulos TDet 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

Journal article

Tang M-C, Barrit D, Munir R, Li R, Barbe JM, Smilgies D-M, Del Gobbo S, Anthopoulos TD, Amassian Aet 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

Journal article

Chaudhry MU, Wang N, Tetzner K, Seitkhan A, Miao Y, Sun Y, Petty MC, Anthopoulos TD, Wang J, Bradley DDCet 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

Journal article

Panidi J, Kainth J, Paterson AF, Wang S, Tsetseris L, Emwas AH, McLachlan MA, Heeney M, Anthopoulos TDet al., 2019, Introducing a nonvolatile N-type dopant drastically improves electron transport in polymer and small-molecule organic transistors, Advanced Functional Materials, 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.

Journal article

Wang K, Neophytou M, Aydin E, Wang M, Laurent T, Harrison GT, Liu J, Liu W, De Bastiani M, Khan JI, Anthopoulos TD, Laquai F, De Wolf Set al., 2019, Triarylphosphine Oxide as Cathode Interfacial Material for Inverted Perovskite Solar Cells, ADVANCED MATERIALS INTERFACES, Vol: 6, ISSN: 2196-7350

Journal article

Paterson AF, Tsetseris L, Li R, Basu A, Faber H, Emwas A-H, Panidi J, Fei Z, Niazi MR, Anjum DH, Heeney M, Anthopoulos TDet 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.

Journal article

Firdaus Y, Le Corre VM, Khan JI, Kan Z, Laquai F, Beaujuge PM, Anthopoulos TDet al., 2019, Key Parameters Requirements for Non-Fullerene-Based Organic Solar Cells with Power Conversion Efficiency > 20%, ADVANCED SCIENCE, Vol: 6, ISSN: 2198-3844

Journal article

Sun G, Shahid M, Fei Z, Xu S, Eisner FD, Anthopoulos TD, McLachlan MA, Heeney Met 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

Journal article

Petromichelaki E, Gagaoudakis E, Moschovis K, Tsetseris L, Anthopoulos TD, Kiriakidis G, Binas Vet al., 2019, Highly sensitive and room temperature detection of ultra-low concentrations of O-3 using self-powered sensing elements of Cu2O nanocubes, NANOSCALE ADVANCES, Vol: 1, Pages: 2009-2017, ISSN: 2516-0230

Journal article

Eisner F, Azzouzi M, Fei Z, Hou X, Anthopoulos T, Dennis TJ, Heeney M, Nelson Jet 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.

Journal article

Eisner FD, Azzouzi M, Fei Z, Hou X, Anthopoulos TD, Dennis TJS, Heeney M, Nelson Jet al., 2019, Hybridization of Local Exciton and Charge-Transfer States Reduces Nonradiative Voltage Losses in Organic Solar Cells., J Am Chem Soc

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.

Journal article

He Q, Shahid M, Panidi J, Marsh AV, Huang W, Daboczi M, Kim J-S, Fei Z, Anthopoulos TD, Heeney Met al., 2019, A versatile star-shaped organic semiconductor based on benzodithiophene and diketopyrrolopyrrole, Journal of Materials Chemistry C, 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.

Journal article

Chen M, Yengel E, Zhang J, Zhu C, He X, Zhang C, Huang J-K, Hedhili MN, Anthopoulos T, Zhang Xet al., 2019, One-step growth of reduced graphene oxide on arbitrary substrates, CARBON, Vol: 144, Pages: 457-463, ISSN: 0008-6223

Journal article

Paterson AF, Mottram AD, Faber H, Niazi MR, Fei Z, Heeney M, Anthopoulos TDet al., 2019, Impact of the gate dielectric on contact resistance in high-mobility organic transistors, Advanced Electronic Materials, 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.

Journal article

Sun G, Shahid M, Fei Z, Xu S, Eisner FD, Anthopolous TD, McLachlan MA, Heeney Met 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%.

Journal article

Twyman N, Tetzner K, Anthopoulos T, Payne D, Regoutz Aet al., Rapid photonic curing of solution-processed In2O3 layers on flexible substrates, Applied Surface Science, 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.

Journal article

Karuthedath S, Gorenflot J, Firdaus Y, Sit W-Y, Eisner F, Seitkhan A, Ravva MK, Anthopoulos TD, Laquai Fet al., 2019, Charge and Triplet Exciton Generation in Neat PC70BM Films and Hybrid CuSCN:PC70BM Solar Cells, ADVANCED ENERGY MATERIALS, Vol: 9, ISSN: 1614-6832

Journal article

Karuthedath S, Firdaus Y, Liang RZ, Gorenflot J, Beaujuge PM, Anthopoulos TD, Laquai Fet al., 2019, Impact of Fullerene on the Photophysics of Ternary Small Molecule Organic Solar Cells, Advanced Energy Materials, ISSN: 1614-6832

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Ternary organic solar cells (OSCs) are among the best-performing organic photovoltaic devices to date, largely due to the recent development of nonfullerene acceptors. However, fullerene molecules still play an important role in ternary OSC systems, since, for reasons not well understood, they often improve the device performance, despite their lack of absorption. Here, the photophysics of a prototypical ternary small-molecule OSC blend composed of the donor DR3, the nonfullerene acceptor ICC6, and the fullerene derivative PC71BM is studied by ultrafast spectroscopy. Surprisingly, it is found that after excitation of PC71BM, ultrafast singlet energy transfer to ICC6 competes efficiently with charge transfer. Subsequently, singlets on ICC6 undergo hole transfer to DR3, resulting in free charge generation. Interestingly, PC71BM improves indirectly the electron mobility of the ternary blend, while electrons reside predominantly in ICC6 domains as indicated by fast spectroscopy. The improved mobility facilitates charge carrier extraction, in turn leading to higher device efficiencies of the ternary compared to binary solar cells. Using the (photo)physical parameters obtained from (transient) spectroscopy and charge transport measurements, the device's current–voltage characteristics are simulated and it is demonstrated that the parameters accurately reproduce the experimentally measured device performance.

Journal article

He Q, Shahid M, Wu J, Jiao X, Eisner FD, Hodsden T, Fei Z, Anthopoulos TD, McNeill CR, Durrant JR, Heeney Met al., 2019, Fused Cyclopentadithienothiophene Acceptor Enables Ultrahigh Short-Circuit Current and High Efficiency >11% in As-Cast Organic Solar Cells, Advanced Functional Materials, ISSN: 1616-301X

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim A new method to synthesize an electron-rich building block cyclopentadithienothiophene (9H-thieno-[3,2-b]thieno[2″,3″:4′,5′]thieno[2′,3′:3,4]cyclopenta[1,2-d]thiophene, CDTT) via a facile aromatic extension strategy is reported. By combining CDTT with 1,1-dicyanomethylene-3-indanone endgroups, a promising nonfullerene small molecule acceptor (CDTTIC) is prepared. As-cast, single-junction nonfullerene organic solar cells based on PFBDB-T: CDTTIC blends exhibit very high short-circuit currents up to 26.2 mA cm−2 in combination with power conversion efficiencies over 11% without any additional processing treatments. The high photocurrent results from the near-infrared absorption of the CDTTIC acceptor and the well-intermixed blend morphology of polymer donor PFBDB-T and CDTTIC. This work demonstrates a useful fused ring extension strategy and promising solar cell results, indicating the great potential of the CDTT derivatives as electron-rich building blocks for constructing high-performance small molecule acceptors in organic solar cells.

Journal article

Barrit D, Cheng P, Tang MC, Wang K, Dang H, Smilgies DM, Liu S, Anthopoulos TD, Zhao K, Amassian Aet al., 2019, Impact of the Solvation State of Lead Iodide on Its Two-Step Conversion to MAPbI <inf>3</inf> : An In Situ Investigation, Advanced Functional Materials, ISSN: 1616-301X

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Producing high efficiency solar cells without high-temperature processing or use of additives still remains a challenge with the two-step process. Here, the solution processing of MAPbI 3 from PbI 2 films in N,N-dimethylformamide (DMF) is investigated. In-situ grazing incidence wide-angle X-ray scattering (GIWAXS) measurements reveal a sol–gel process involving three PbI 2 -DMF solvate complexes—disordered (P 0 ) and ordered (P 1 , P 2 )—prior to PbI 2 formation. When the appropriate solvated state of PbI 2 is exposed to MAI (methylammonium Iodide), it can lead to rapid and complete room temperature conversion into MAPbI 3 with higher quality films and improved solar cell performance. Complementary in-situ optical reflectance, absorbance, and quartz crystal microbalance with dissipation (QCM-D) measurements show that dry PbI 2 can take up only one third of the MAI taken up by the solvated-crystalline P 2 phase of PbI 2 , requiring additional annealing and yet still underperforming. The perovskite solar cells fabricated from the ordered P 2 precursor show higher power conversion efficiency (PCE) and reproducibility than devices fabricated from other cases. The average PCE of the solar cells is greatly improved from 13.2(±0.53)% (from annealed PbI 2 ) to 15.7(±0.35)% (from P 2 ) reaching up to 16.2%. This work demonstrates the importance of controlling the solvation of PbI 2 as an effective strategy for the growth of high-quality perovskite films and their application in high efficiency and reproducible solar cells.

Journal article

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.

Journal article

Paterson AF, Lin Y-H, Mottram AD, Fei Z, Niazi MR, Kirmani AR, Amassian A, Solomeshch O, Tessler N, Heeney M, Anthopoulos TDet 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

Journal article

Costa JC, Pouryazdan A, Panidi J, Anthopoulos T, Liedke MO, Schneider C, Wagner A, Munzenrieder Net al., 2018, Low temperature and radiation stability of flexible IGZO TFTs and their suitability for space applications, Pages: 98-101, ISSN: 1930-8876

© 2018 IEEE. In this paper, Low Earth Orbit radiation and temperature conditions are mimicked to investigate the suitability of flexible Indium-Gallium-Zinc-Oxide transistors for lightweight space-wearables. Such wearable devices could be incorporated into spacesuits as unobtrusive sensors such as radiation detectors or physiological monitors. Due to the harsh environment to which these space-wearables would be exposed, they have to be able to withstand high radiation doses and low temperatures. For this reason, the impacts of high energetic electron irradiation with fluences up to 10 12 e - /cm 2 and low operating temperatures down to 78 K, are investigated. This simulates 278 h in a Low Earth Orbit. The threshold voltage and mobility of transistors that were exposed to e-irradiation are found to shift by +0.09 0.05 V and-0.6 0.5 cm 2 V -1 s -1 . Subsequent low temperature exposure resulted in additional shifts of +0.38V and-5.95 cm 2 V -1 s -1 for the same parameters. These values are larger than the ones obtained from non-irradiated reference samples. If this is considered during the systems' design, these devices can be used to unobtrusively integrate sensor systems into space-suits.

Conference paper

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

Wyatt-Moon G, Georgiadou DG, Zoladek-Lemanczyk A, Castro FA, Anthopoulos TDet al., 2018, Flexible nanogap polymer light-emitting diodes fabricated via adhesion lithography (a-Lith), Journal of Physics: Materials, Vol: 1, ISSN: 2515-7639

We report the development of coplanar green colour organic light-emitting diodes (OLEDs) based on asymmetric nanogap electrodes fabricated on different substrates including glass and plastic. Using adhesion lithography (a-Lith) we pattern Al and Au layers acting as the cathode and anode electrodes, respectively, separated by an inter-electrode distance of <15 nm with an aspect ratio of up to 106. Spin-coating the organic light-emitting polymer poly(9,9-dioctylfluorene-alt-bithiophene) (F8T2) on top of the asymmetric Al–Au nanogap electrodes results in green light-emitting nanogap OLEDs with promising operating characteristics. We show that the scaling of the OLED's width from 4 to 200 mm can substantially improve the light output of the device without any adverse effects on the manufacturing yield. Furthermore, it is found that the light-emitting properties in the nanogap area differ from the bulk organic film, an effect attributed to confinement of the conjugated polymer chains in the nanogap channel. These results render a-Lith particularly attractive for low cost facile fabrication of nanoscale light-emitting sources and arrays on different substrates of arbitrary size.

Journal article

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