Publications
641 results found
Seitkhan A, Neophytou M, Kirkus M, et al., 2019, Use of the Phen-NaDPO:Sn(SCN)<sub>2</sub> Blend as Electron Transport Layer Results to Consistent Efficiency Improvements in Organic and Hybrid Perovskite Solar Cells, ADVANCED FUNCTIONAL MATERIALS, Vol: 29, ISSN: 1616-301X
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- Citations: 39
Chen H, Wadsworth A, Ma C, et al., 2019, The Effect of Ring Expansion in Thienobenzo[<i>b</i>]indacenodithiophene Polymers for Organic Field-Effect Transistors, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 141, Pages: 18806-18813, ISSN: 0002-7863
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- Citations: 38
Xiang H, Hu Z, Billot L, et al., 2019, Heavy-Metal-Free Flexible Hybrid Polymer-Nanocrystal Photodetectors Sensitive to 1.5 μm Wavelength, ACS APPLIED MATERIALS & INTERFACES, Vol: 11, Pages: 42571-42579, ISSN: 1944-8244
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- Citations: 10
Ugur E, Khan JI, Aydin E, et al., 2019, Carrier Extraction from Perovskite to Polymeric Charge Transport Layers Probed by Ultrafast Transient Absorption Spectroscopy, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, Vol: 10, Pages: 6921-6928, ISSN: 1948-7185
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- Citations: 19
Zheng Y, Wang G-JN, Kang J, et al., 2019, An Intrinsically Stretchable High-Performance Polymer Semiconductor with Low Crystallinity, ADVANCED FUNCTIONAL MATERIALS, Vol: 29, ISSN: 1616-301X
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- Citations: 103
Neophytou M, De Bastiani M, Gasparini N, et al., 2019, Enhancing the Charge Extraction and Stability of Perovskite Solar Cells Using Strontium Titanate (SrTiO<sub>3</sub>) Electron Transport Layer, ACS APPLIED ENERGY MATERIALS, Vol: 2, Pages: 8090-8097, ISSN: 2574-0962
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- Citations: 42
Lin Y, Adilbekova B, Firdaus Y, et al., 2019, 17% Efficient Organic Solar Cells Based on Liquid Exfoliated WS<sub>2</sub> as a Replacement for PEDOT:PSS, ADVANCED MATERIALS, Vol: 31, ISSN: 0935-9648
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- Citations: 464
Wustoni S, Combe C, Ohayon D, et al., 2019, Membrane-Free Detection of Metal Cations with an Organic Electrochemical Transistor, ADVANCED FUNCTIONAL MATERIALS, Vol: 29, ISSN: 1616-301X
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- Citations: 66
Liao H, Xiao C, Ravva MK, et al., 2019, Fused Pyrazine- and Carbazole-Containing Azaacenes: Synthesis and Properties, CHEMPLUSCHEM, ISSN: 2192-6506
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
Schott S, Chopra U, Lemaur V, et al., 2019, Polaron spin dynamics in high-mobility polymeric semiconductors, NATURE PHYSICS, Vol: 15, Pages: 814-+, ISSN: 1745-2473
Savva A, Ohayon D, Surgailis J, et al., 2019, Solvent Engineering for High-Performance n-Type Organic Electrochemical Transistors, ADVANCED ELECTRONIC MATERIALS, Vol: 5, ISSN: 2199-160X
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
Cha H, Fish G, Luke J, et al., 2019, Suppression of Recombination Losses in Polymer:Nonfullerene Acceptor Organic Solar Cells due to Aggregation Dependence of Acceptor Electron Affinity, ADVANCED ENERGY MATERIALS, Vol: 9, ISSN: 1614-6832
Khan J, Ugur E, Aydin E, et al., 2019, Probing Carrier Extraction from Lead Halide Perovskite to Polymeric Charge Transport Layers by Ultrafast Transient Absorption Spectroscopy, nanoGe Fall Meeting 2019, Publisher: Fundació Scito
Wang S-J, Venkateshvaran D, Mahani MR, et al., 2019, Long spin diffusion lengths in doped conjugated polymers due to enhanced exchange coupling (vol 2, pg 98, 2019), NATURE ELECTRONICS, Vol: 2, Pages: 313-313, ISSN: 2520-1131
McCulloch I, 2019, New synthetic methodology paves the way to prepare electron deficient semiconducting mesopolymers with very high performance, SCIENCE CHINA-CHEMISTRY, Vol: 62, Pages: 885-886, ISSN: 1674-7291
Thomas TH, Harkin DJ, Gillett AJ, et al., 2019, Short contacts between chains enhancing luminescence quantum yields and carrier mobilities in conjugated copolymers, NATURE COMMUNICATIONS, Vol: 10, ISSN: 2041-1723
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- Citations: 49
Wadsworth A, Bristow H, Hamid Z, et al., 2019, End Group Tuning in Acceptor–Donor–Acceptor Nonfullerene Small Molecules for High Fill Factor Organic Solar Cells, Advanced Functional Materials, Pages: 1808429-1808429, ISSN: 1616-301X
Hu H, Deng W, Qin M, et al., 2019, Charge carrier transport and nanomorphology control for efficient non-fullerene organic solar cells, Materials Today Energy, Vol: 12, Pages: 398-407, ISSN: 2468-6069
Ghasemi M, Hu H, Peng Z, et al., 2019, Delineation of Thermodynamic and Kinetic Factors that Control Stability in Non-fullerene Organic Solar Cells, JOULE, Vol: 3, Pages: 1328-1348, ISSN: 2542-4351
Moser M, Thorley KJ, Moruzzi F, et al., 2019, Highly selective chromoionophores for ratiometric Na+ sensing based on an oligoethyleneglycol bridged bithiophene detection unit, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 7, Pages: 5359-5365, ISSN: 2050-7526
Nikolka M, Broch K, Armitage J, et al., 2019, High-mobility, trap-free charge transport in conjugated polymer diodes, Nature Communications, Vol: 10, ISSN: 2041-1723
Charge transport in conjugated polymer semiconductors has traditionally been thought to be limited to a low-mobility regime by pronounced energetic disorder. Much progress has recently been made in advancing carrier mobilities in field-effect transistors through developing low-disorder conjugated polymers. However, in diodes these polymers have to date not shown much improved mobilities, presumably reflecting the fact that in diodes lower carrier concentrations are available to fill up residual tail states in the density of states. Here, we show that the bulk charge transport in low-disorder polymers is limited by water-induced trap states and that their concentration can be dramatically reduced through incorporating small molecular additives into the polymer film. Upon incorporation of the additives we achieve space-charge limited current characteristics that resemble molecular single crystals such as rubrene with high, trap-free SCLC mobilities up to 0.2 cm2/Vs and a width of the residual tail state distribution comparable to kBT.
Babics M, Duan T, Balawi AH, et al., 2019, Negligible Energy Loss During Charge Generation in Small-Molecule/Fullerene Bulk-Heterojunction Solar Cells Leads to Open-Circuit Voltage over 1.10 V, ACS APPLIED ENERGY MATERIALS, Vol: 2, Pages: 2717-2722, ISSN: 2574-0962
Luke J, Speller EM, Wadsworth A, et al., 2019, Twist and degrade – Impact of molecular structure on the photostability of non-fullerene acceptors and their photovoltaic blends, Advanced Energy Materials, Vol: 9, Pages: 1-14, ISSN: 1614-6832
Non-fullerene acceptors (NFAs) dominate organic photovoltaic (OPV) research due to their promising efficiencies and stabilities. However, there is very little investigation into the molecular processes of degradation, which is critical to guiding design of novel NFAs for long-lived, commercially viable OPVs. Here we investigate the important role of molecular structure and conformation on NFA photostability in air by comparing structurally similar but conformationally different promising NFAs; planar O-IDTBR and non-planar O-IDFBR. We identify a three-phase degradation process: (i) initial photo-induced conformational change (i.e. torsion about the Core-BT dihedral), induced by non-covalent interactions with environmental molecules, (ii) followed by photo-oxidation and fragmentation, leading to chromophore bleaching and degradation product formation, and (iii) finally complete chromophore bleaching.Initial conformational change is a critical prerequisite for further degradation, providing fundamental understanding of the relative stability of IDTBR and IDFBR, where the alreadytwisted IDFBR is more prone to degradation. When blended with the donor polymer P3HT, both NFAs exhibit improved photostability whilst the photostability of the polymer itself is significantly reduced by the more miscible twisted NFA. Our findings elucidate the important role of NFA molecular structure on photostability of OPV systems, and provide vital insights into molecular design rules for intrinsically photostable NFAs.
Speller EM, Clarke AJ, Aristidou N, et al., 2019, Toward improved environmental stability of polymer:fullerene and polymer:non-fullerene organic solar cells: a common energetic origin of light and oxygen induced degradation, ACS Energy Letters, Vol: 4, Pages: 846-852, ISSN: 2380-8195
With the emergence of nonfullerene electron acceptors resulting in further breakthroughs in the performance of organic solar cells, there is now an urgent need to understand their degradation mechanisms in order to improve their intrinsic stability through better material design. In this study, we present quantitative evidence for a common root cause of light-induced degradation of polymer:nonfullerene and polymer:fullerene organic solar cells in air, namely, a fast photo-oxidation process of the photoactive materials mediated by the formation of superoxide radical ions, whose yield is found to be strongly controlled by the lowest unoccupied molecular orbital (LUMO) levels of the electron acceptors used. Our results elucidate the general relevance of this degradation mechanism to both polymer:fullerene and polymer:nonfullerene blends and highlight the necessity of designing electron acceptor materials with sufficient electron affinities to overcome this challenge, thereby paving the way toward achieving long-term solar cell stability with minimal device encapsulation.
Moia D, Giovannitti A, Szumska AA, et al., 2019, Design and evaluation of conjugated polymers with polar side chains as electrode materials for electrochemical energy storage in aqueous electrolytes, Energy & Environmental Science, Vol: 12, Pages: 1349-1357, ISSN: 1754-5692
We report the development of redox-active conjugated polymers that have potential applications in electrochemical energy storage. Side chain engineering enables processing of the polymer electrodes from solution, stability in aqueous electrolytes and efficient transport of ionic and electronic charge carriers. We synthesized a 3,3′-dialkoxybithiophene homo-polymer (p-type polymer) with glycol side chains and prepared naphthalene-1,4,5,8-tetracarboxylic-diimide-dialkoxybithiophene (NDI-gT2) copolymers (n-type polymer) with either a glycol or zwitterionic side chain on the NDI unit. For the latter, we developed a post-functionalization synthesis to attach the polar zwitterion side chains to the polymer backbone to avoid challenges of purifying polar intermediates. We demonstrate fast and reversible charging of solution processed electrodes for both the p- and n-type polymers in aqueous electrolytes, without using additives or porous scaffolds and for films up to micrometers thick. We apply spectroelectrochemistry as an in operando technique to probe the state of charge of the electrodes. This reveals that thin films of the p-type polymer and zwitterion n-type polymer can be charged reversibly with up to two electronic charges per repeat unit (bipolaron formation). We combine thin films of these polymers in a two-electrode cell and demonstrate output voltages of up to 1.4 V with high redox-stability. Our findings demonstrate the potential of functionalizing conjugated polymers with appropriate polar side chains to improve the accessible capacity, and to improve reversibility and rate capabilities of polymer electrodes in aqueous electrolytes.
Haque MA, Gandi AN, Mohanraman R, et al., 2019, A 0D Lead-Free Hybrid Crystal with Ultralow Thermal Conductivity, ADVANCED FUNCTIONAL MATERIALS, Vol: 29, ISSN: 1616-301X
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- Citations: 28
Dimitrov SD, Azzouzi M, Wu J, et al., 2019, Spectroscopic investigation of the effect of microstructure and energetic offset on the nature of interfacial charge transfer states in polymer: fullerene blends, Journal of the American Chemical Society, Vol: 141, Pages: 4634-4643, ISSN: 0002-7863
Despite performance improvements of organic photovoltaics, the mechanism of photoinduced electron-hole separation at organic donor-acceptor interfaces remains poorly understood. Inconclusive experimental and theoretical results have produced contradictory models for electron-hole separation in which the role of interfacial charge-transfer (CT) states is unclear, with one model identifying them as limiting separation and another as readily dissociating. Here, polymer-fullerene blends with contrasting photocurrent properties and enthalpic offsets driving separation were studied. By modifying composition, film structures were varied from consisting of molecularly mixed polymer-fullerene domains to consisting of both molecularly mixed and fullerene domains. Transient absorption spectroscopy revealed that CT state dissociation generating separated electron-hole pairs is only efficient in the high energy offset blend with fullerene domains. In all other blends (with low offset or predominantly molecularly mixed domains), nanosecond geminate electron-hole recombination is observed revealing the importance of spatially localized electron-hole pairs (bound CT states) in the electron-hole dynamics. A two-dimensional lattice exciton model was used to simulate the excited state spectrum of a model system as a function of microstructure and energy offset. The results could reproduce the main features of experimental electroluminescence spectra indicating that electron-hole pairs become less bound and more spatially separated upon increasing energy offset and fullerene domain density. Differences between electroluminescence and photoluminescence spectra could be explained by CT photoluminescence being dominated by more-bound states, reflecting geminate recombination processes, while CT electroluminescence preferentially probes less-bound CT states that escape geminate recombination. These results suggest that apparently contradictory studies on electron-hole separation can be exp
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