307 results found
Twyman NM, Tetzner K, Anthopoulos TD, et al., 2019, Rapid photonic curing of solution-processed In <inf>2</inf> O <inf>3</inf> layers on flexible substrates, Applied Surface Science, Vol: 479, Pages: 974-979, ISSN: 0169-4332
© 2019 Elsevier B.V. In 2 O 3 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 In 2 O 3 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 In 2 O 3 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.
Eisner FD, Azzouzi M, Fei Z, et al., 2019, Hybridization of Local Exciton and Charge-Transfer States Reduces Nonradiative Voltage Losses in Organic Solar Cells., J Am Chem Soc, Vol: 141, Pages: 6362-6374
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
© 2018 Elsevier Ltd Reduced graphene oxide (rGO) has inherited the outstanding electronic, optical, thermal and mechanical properties of graphene to a large extent, while maintaining sufficient chemically active sites. Therefore, it has attracted a great deal of research attention in the fields of energy storage, electronics, photonics, catalysis, environmental engineering, etc. Currently, the most popular way to prepare rGO is to reduce graphene oxide, which is obtained by modified Hummer methods using tedious treatments in a harsh environment, to rGO flakes. Industrial applications demand advanced preparation methods that can mass produce highly uniform rGO sheets on arbitrary substrates. In this work, a one-step growth process is introduced that utilizes cellulose acetate as a precursor, without any catalysts, to produce uniform ultrathin rGO films on various substrates and free-standing rGO powders. Systematic spectroscopic and microscopic studies on the resulting rGO are performed. Prototypes of electronic and optoelectronic devices, such as field effect transistors (FETs), photodetectors, and humidity sensors, are fabricated and tested, demonstrating the intriguing applications of our rGO materials across a wide range of fields.
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
Karuthedath S, Gorenflot J, Firdaus Y, et 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
Barrit D, Cheng P, Tang MC, et 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.
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
© 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The reported power conversion efficiencies (PCEs) of nonfullerene acceptor (NFA) based organic photovoltaics (OPVs) now exceed 14% and 17% for single-junction and two-terminal tandem cells, respectively. However, increasing the PCE further requires an improved understanding of the factors limiting the device efficiency. Here, the efficiency limits of single-junction and two-terminal tandem NFA-based OPV cells are examined with the aid of a numerical device simulator that takes into account the optical properties of the active material(s), charge recombination effects, and the hole and electron mobilities in the active layer of the device. The simulations reveal that single-junction NFA OPVs can potentially reach PCE values in excess of 18% with mobility values readily achievable in existing material systems. Furthermore, it is found that balanced electron and hole mobilities of >10 −3 cm 2 V −1 s −1 in combination with low nongeminate recombination rate constants of 10 −12 cm 3 s −1 could lead to PCE values in excess of 20% and 25% for single-junction and two-terminal tandem OPV cells, respectively. This analysis provides the first tangible description of the practical performance targets and useful design rules for single-junction and tandem OPVs based on NFA materials, emphasizing the need for developing new material systems that combine these desired characteristics.
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
© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 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.
Paterson AF, Anthopoulos TD, 2018, Enabling thin-film transistor technologies and the device metrics that matter, NATURE COMMUNICATIONS, Vol: 9, ISSN: 2041-1723
Semple J, Georgiadou DG, Wyatt-Moon G, et al., 2018, Large-area plastic nanogap electronics enabled by adhesion lithography, npj Flexible Electronics, Vol: 2
Costa JC, Pouryazdan A, Panidi J, et 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.
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
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
Xu Y, Ji D, Song H, et al., 2018, Light-Matter Interaction within Extreme Dimensions: From Nanomanufacturing to Applications, ADVANCED OPTICAL MATERIALS, Vol: 6, ISSN: 2195-1071
Wyatt-Moon G, Georgiadou DG, Zoladek-Lemanczyk A, et al., 2018, Flexible nanogap polymer light-emitting diodes fabricated via adhesion lithography (a-Lith), Journal of Physics: Materials, Vol: 1, Pages: 01LT01-01LT01
Paterson AF, Singh S, Fallon KJ, et al., 2018, Recent Progress in High-Mobility Organic Transistors: A Reality Check, ADVANCED MATERIALS, Vol: 30, ISSN: 0935-9648
Wahyudi W, Cao Z, Kumar P, et al., 2018, Phase Inversion Strategy to Flexible Freestanding Electrode: Critical Coupling of Binders and Electrolytes for High Performance Li-S Battery, ADVANCED FUNCTIONAL MATERIALS, Vol: 28, ISSN: 1616-301X
Creamer A, Wood CS, Howes PD, et al., 2018, Post-polymerisation functionalisation of conjugated polymer backbones and its application in multifunctional emissive nanoparticles, NATURE COMMUNICATIONS, Vol: 9, ISSN: 2041-1723
Wijeyasinghe N, Eisner F, Tsetseris L, et al., 2018, p-Doping of Copper(I) Thiocyanate (CuSCN) Hole-Transport Layers for High-Performance Transistors and Organic Solar Cells, ADVANCED FUNCTIONAL MATERIALS, Vol: 28, ISSN: 1616-301X
Firdaus Y, Seitkhan A, Eisner F, et al., 2018, Charge Photogeneration and Recombination in Mesostructured CuSCN-Nanowire/PC70BM Solar Cells, SOLAR RRL, Vol: 2, ISSN: 2367-198X
Eisner F, Seitkhan A, Han Y, et al., 2018, Solution-Processed In2O3/ZnO Heterojunction Electron Transport Layers for Efficient Organic Bulk Heterojunction and Inorganic Colloidal Quantum-Dot Solar Cells, SOLAR RRL, Vol: 2, ISSN: 2367-198X
Choi HH, Rodionov YI, Paterson AF, et al., 2018, Accurate Extraction of Charge Carrier Mobility in 4-Probe Field-Effect Transistors, ADVANCED FUNCTIONAL MATERIALS, Vol: 28, ISSN: 1616-301X
Chaudhry MU, Tetzner K, Lin Y-H, et al., 2018, Low-Voltage Solution-Processed Hybrid Light-Emitting Transistors, ACS APPLIED MATERIALS & INTERFACES, Vol: 10, Pages: 18445-18449, ISSN: 1944-8244
Mottram AD, Pattanasattayavong P, Isakov I, et al., 2018, Electron mobility enhancement in solution-processed low-voltage In2O3 transistorsvia channel interface planarization, AIP ADVANCES, Vol: 8, ISSN: 2158-3226
Squeo BM, Gregoriou VG, Han Y, et al., 2018, alpha,beta-Unsubstituted meso-positioning thienyl BODIPY: a promising electron deficient building block for the development of near infrared (NIR) p-type donor-acceptor (D-A) conjugated polymers, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 6, Pages: 4030-4040, ISSN: 2050-7526
Nam S, Hahm SG, Khim D, et al., 2018, Pronounced Side Chain Effects in Triple Bond-Conjugated Polymers Containing Naphthalene Diimides for n-Channel Organic Field-Effect Transistors, ACS APPLIED MATERIALS & INTERFACES, Vol: 10, Pages: 12921-12929, ISSN: 1944-8244
Wijeyasinghe N, Tsetseris L, Regoutz A, et al., 2018, Copper (I) Selenocyanate (CuSeCN) as a Novel Hole-Transport Layer for Transistors, Organic Solar Cells, and Light-Emitting Diodes, ADVANCED FUNCTIONAL MATERIALS, Vol: 28, ISSN: 1616-301X
Sit W-Y, Eisner FD, Lin Y-H, et al., 2018, High-Efficiency Fullerene Solar Cells Enabled by a Spontaneously Formed Mesostructured CuSCN-Nanowire Heterointerface, ADVANCED SCIENCE, Vol: 5, ISSN: 2198-3844
Huang W, Lin Y-H, Anthopoulos TD, 2018, High Speed Ultraviolet Phototransistors Based on an Ambipolar Fullerene Derivative, ACS APPLIED MATERIALS & INTERFACES, Vol: 10, Pages: 10202-10210, ISSN: 1944-8244
Fei Z, Eisner FD, Jiao X, et al., 2018, An Alkylated Indacenodithieno[3,2-b] thiophene-Based Nonfullerene Acceptor with High Crystallinity Exhibiting Single Junction Solar Cell Efficiencies Greater than 13% with Low Voltage Losses (vol 30, 2018), ADVANCED MATERIALS, Vol: 30, ISSN: 0935-9648
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