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Journal articleWarren PR, Hardigree JFM, Lauritzen AE, et al., 2019,
Tuning the ambipolar behaviour of organic field effect transistors via band engineering
, AIP ADVANCES, Vol: 9- Author Web Link
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- Citations: 19
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Journal articleAlberi K, Nardelli MB, Zakutayev A, et al., 2019,
The 2019 materials by design roadmap
, Journal of Physics D: Applied Physics, Vol: 52, ISSN: 0022-3727Advances in renewable and sustainable energy technologies critically depend on our ability to design and realize materials with optimal properties. Materials discovery and design efforts ideally involve close coupling between materials prediction, synthesis and characterization. The increased use of computational tools, the generation of materials databases, and advances in experimental methods have substantially accelerated these activities. It is therefore an opportune time to consider future prospects for materials by design approaches. The purpose of this Roadmap is to present an overview of the current state of computational materials prediction, synthesis and characterization approaches, materials design needs for various technologies, and future challenges and opportunities that must be addressed. The various perspectives cover topics on computational techniques, validation, materials databases, materials informatics, high-throughput combinatorial methods, advanced characterization approaches, and materials design issues in thermoelectrics, photovoltaics, solid state lighting, catalysts, batteries, metal alloys, complex oxides and transparent conducting materials. It is our hope that this Roadmap will guide researchers and funding agencies in identifying new prospects for materials design.
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Journal articleNightingale J, Wade J, Moia D, et al., 2018,
Impact of molecular order on polaron formation in conjugated polymers
, The Journal of Physical Chemistry C, Vol: 122, Pages: 29129-29140, ISSN: 1932-7447The nature of polaron formation has profound implications on the transport of charge carriers in conjugated polymers, but still remains poorly understood. Here we develop in situ electrochemical resonant Raman spectroscopy, a powerful structural probe that allows direct observation of polaron formation. We report that polaron formation in ordered poly(3-hexyl)thiophene (P3HT) polymer domains (crystalline phase) results in less pronounced changes in molecular conformation, indicating smaller lattice relaxation, compared to polarons generated in disordered polymer domains (amorphous phase) for which we observe large molecular conformational changes. These conformational changes are directly related to the effective conjugation length of the polymer. Furthermore, we elucidate how blending the P3HT polymer with phenyl C-61 butyric acid methyl ester (PCBM) affects polaron formation in the polymer. We find that blending disturbs polymer crystallinity, reducing the density of polarons that can form upon charge injection at the same potential, whilst the lost capacity is partly restored during post-deposition thermal annealing. Our study provides direct spectroscopic evidence for a lower degree of lattice reorganisation in crystalline (and therefore more planarised) polymers than in conformationally disordered polymers. This observation is consistent with higher charge carrier mobility and better device performance commonly found in crystalline polymer materials.
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Journal articleCheng W, Moreno-Gonzalez M, Hu K, et al., 2018,
Solution-Deposited Solid-State Electrochromic Windows
, ISCIENCE, Vol: 10, Pages: 80-+- Author Web Link
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- Citations: 30
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Journal articleSachs M, Sprick RS, Pearce D, et al., 2018,
Understanding structure-activity relationships in linear polymer photocatalysts for hydrogen evolution
, Nature Communications, Vol: 9, ISSN: 2041-1723Conjugated polymers have sparked much interest as photocatalysts for hydrogen production. However, beyond basic considerations such as spectral absorption, the factors that dictate their photocatalytic activity are poorly understood. Here we investigate a series of linear conjugated polymers with external quantum efficiencies for hydrogen production between 0.4 and 11.6%. We monitor the generation of the photoactive species from femtoseconds to seconds after light absorption using transient spectroscopy and correlate their yield with the measured photocatalytic activity. Experiments coupled with modeling suggest that the localization of water around the polymer chain due to the incorporation of sulfone groups into an otherwise hydrophobic backbone is crucial for charge generation. Calculations of solution redox potentials and charge transfer free energies demonstrate that electron transfer from the sacrificial donor becomes thermodynamically favored as a result of the more polar local environment, leading to the production of long-lived electrons in these amphiphilic polymers.
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Journal articleRice B, Guilbert AAY, Frost JM, et al., 2018,
Polaron states in fullerene adducts modeled by coarse-grained molecular dynamics and tight binding
, Journal of Physical Chemistry Letters, Vol: 9, Pages: 6616-6623, ISSN: 1948-7185Strong electron–phonon coupling leads to polaron localization in molecular semiconductor materials and influences charge transport, but it is expensive to calculate atomistically. Here, we propose a simple and efficient model to determine the energy and spatial extent of polaron states within a coarse-grained representation of a disordered molecular film. We calculate the electronic structure of the molecular assembly using a tight-binding Hamiltonian and determine the polaron state self-consistently by perturbing the site energies by the dielectric response of the surrounding medium to the charge. When applied to fullerene derivatives, the method shows that polarons extend over multiple molecules in C60 but localize on single molecules in higher adducts of phenyl-C61-butyric-acid-methyl-ester (PCBM) because of packing disorder and the polar side chains. In PCBM, polarons localize on single molecules only when energetic disorder is included or when the fullerene is dispersed in a blend. The method helps to establish the conditions under which a hopping transport model is justified.
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Journal articleBabacan O, Abdulla A, Hanna R, et al., 2018,
Unintended Effects of Residential Energy Storage on Emissions from the Electric Power System
, ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 52, Pages: 13600-13608, ISSN: 0013-936X -
Journal articleAzzouzi M, Yan J, Kirchartz T, et al., 2018,
Non-radiative energy losses in bulk-heterojunction organic photovoltaics
, Physical Review X, Vol: 8, ISSN: 2160-3308The performance of solar cells based on molecular electronic materials is limited by relatively high nonradiative voltage losses. The primary pathway for nonradiative recombination in organic donor-acceptor heterojunction devices is believed to be the decay of a charge-transfer (CT) excited state to the ground state via energy transfer to vibrational modes. Recently, nonradiative voltage losses have been related to properties of the charge-transfer state such as the Franck-Condon factor describing the overlap of the CT and ground-state vibrational states and, therefore, to the energy of the CT state. However, experimental data do not always follow the trends suggested by the simple model. Here, we extend this recombination model to include other factors that influence the nonradiative decay-rate constant, and therefore the open-circuit voltage, but have not yet been explored in detail. We use the extended model to understand the observed behavior of series of small molecules:fullerene blend devices, where open-circuit voltage appears insensitive to nonradiative loss. The trend could be explained only in terms of a microstructure-dependent CT-state oscillator strength, showing that parameters other than CT-state energy can control nonradiative recombination. We present design rules for improving open-circuit voltage via the control of material parameters and propose a realistic limit to the power-conversion efficiency of organic solar cells.
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Journal articleYang Y, Rice B, Shi X, et al., 2018,
Emergent Properties of an Organic Semiconductor Driven by its Molecular Chirality (vol 11, pg 8329, 2017)
, ACS NANO, Vol: 12, Pages: 6343-6343, ISSN: 1936-0851Chiral molecules exist as pairs of nonsuperimposable mirror images; a fundamental symmetry property vastly underexplored in organic electronic devices. Here, we show that organic field-effect transistors (OFETs) made from the helically chiral molecule 1-aza[6]helicene can display up to an 80-fold difference in hole mobility, together with differences in thin-film photophysics and morphology, solely depending on whether a single handedness or a 1:1 mixture of left- and right-handed molecules is employed under analogous fabrication conditions. As the molecular properties of either mirror image isomer are identical, these changes must be a result of the different bulk packing induced by chiral composition. Such underlying structures are investigated using crystal structure prediction, a computational methodology rarely applied to molecular materials, and linked to the difference in charge transport. These results illustrate that chirality may be used as a key tuning parameter in future device applications.
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Journal articleRice B, LeBlanc LM, Otero-de-la-Roza A, et al., 2018,
A computational exploration of the crystal energy and charge-carrier mobility landscapes of the chiral [6]helicene molecule (vol 10, pg 1865, 2018)
, NANOSCALE, Vol: 10, Pages: 9410-9410, ISSN: 2040-3364 -
Journal articleGiovannitti A, Maria I, Hanifi D, et al., 2018,
The role of the side chain on the performance of n-type conjugated polymers in aqueous electrolytes
, Chemistry of Materials, Vol: 30, Pages: 2945-2953, ISSN: 0897-4756We report a design strategy that allows the preparation of solution processable n type materials from low boiling point solvents for organic electrochemical transistors (OECTs). The polymer backbone is based on NDI-T2 copolymers where a branched alkyl side chain is gradually exchanged for a linear ethylene glycol based side chain. A series of random copolymers are prepared with glycol side chain percentages of 0, 10, 25, 50, 75, 90 and 100 with respect to the alkyl side chains. These are characterized in order to study the influence of the polar side chains on interaction with aqueous electrolytes, their electrochemical redox reactions and performance in OECTs when operated in aqueous electrolytes. We observe that glycol side chain percentages of >50 % are required to achieve volumetric charging while lower glycol chain percentages show a mixed operation with high required voltages to allow for bulk charging of the organic semiconductor. A strong dependence of the electron mobility on the fraction of glycol chains was found for copolymers based on NDI-T2, with a significant drop as alkyl side chains are replaced by glycol side chains.
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Journal articleAltendorf SG, Reisner A, Tam B, et al., 2018,
Strong modification of thin film properties due to screening across the interface
, PHYSICAL REVIEW B, Vol: 97, ISSN: 2469-9950- Author Web Link
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- Citations: 3
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Journal articleRohr J, Shi X, Haque S, et al., 2018,
Charge transport in Spiro-OMeTAD investigated through space-charge-limited current measurements
, Physical Review Applied, Vol: 9, ISSN: 2331-7019Extracting charge-carrier mobilities for organic semiconductors from space-charge-limited conduction measurements is complicated in practice by nonideal factors such as trapping in defects and injection barriers. Here, we show that by allowing the bandlike charge-carrier mobility, trap characteristics, injection barrier heights, and the shunt resistance to vary in a multiple-trapping drift-diffusion model, a numerical fit can be obtained to the entire current density–voltage curve from experimental space-charge-limited current measurements on both symmetric and asymmetric 2,2′,7,7′-tetrakis(N,N-di-4-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) single-carrier devices. This approach yields a bandlike mobility that is more than an order of magnitude higher than the effective mobility obtained using analytical approximations, such as the Mott-Gurney law and the moving-electrode equation. It is also shown that where these analytical approximations require a temperature-dependent effective mobility to achieve fits, the numerical model can yield a temperature-, electric-field-, and charge-carrier-density-independent mobility. Finally, we present an analytical model describing trap-limited current flow through a semiconductor in a symmetric single-carrier device. We compare the obtained charge-carrier mobility and trap characteristics from this analytical model to the results from the numerical model, showing excellent agreement. This work shows the importance of accounting for traps and injection barriers explicitly when analyzing current density–voltage curves from space-charge-limited current measurements.
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Journal articleFei Z, Eisner FD, Jiao X, et al., 2018,
Correction: 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 -
SoftwareCalado P, Barnes PRF, Azzouzi M, et al., 2018,
Driftfusion
An open source drift diffusion code based in MATLAB for simulating solar cells.
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Journal articleLee HKH, Telford AM, Rohr JA, et al., 2018,
The role of fullerenes in the environmental stability of polymer: fullerene solar cells
, Energy and Environmental Science, Vol: 11, Pages: 417-428, ISSN: 1754-5692Environmental stability is a common challenge for the commercialisation of low cost, encapsulation-free organic opto-electronic devices. Understanding the role of materials degradation is the key to address this challenge, but most such studies have been limited to conjugated polymers. Here we quantitatively study the role of the common fullerene derivative PCBM in limiting the stability of benchmark organic solar cells, showing that a minor fraction (<1%) of photo-oxidised PCBM, induced by short exposure to either solar or ambient laboratory lighting conditions in air, consistent with typical processing and operating conditions, is sufficient to compromise device performance severely. We identify the effects of photo-oxidation of PCBM on its chemical structure, and connect this to specific changes in its electronic structure, which significantly alter the electron transport and recombination kinetics. The effect of photo-oxidation on device current–voltage characteristics, electron mobility and density of states could all be explained with the same model of photoinduced defects acting as trap states. Our results demonstrate that the photochemical instability of PCBM and chemically similar fullerenes remains a barrier for the commercialisation of organic opto-electronic devices.
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Journal articleRohr JA, Moia D, Haque SA, et al., 2018,
Exploring the validity and limitations of the Mott-Gurney law for charge-carrier mobility determination of semiconducting thin-films
, Journal of Physics: Condensed Matter, Vol: 30, ISSN: 0953-8984Using drift-diffusion simulations, we investigate the voltage dependence of the dark current in single carrier devices, typically used to determine charge-carrier mobilities. For both low and high voltages, the current increases linearly with the applied voltage. Whereas the linear current at low voltages is mainly due to space charge in the middle of the device, the linear current at high voltage is caused by charge-carrier saturation due to a high degree of injection. As a consequence, the current density at these voltages does not follow the classical square law derived by Mott and Gurney, and we show that for trap-free devices, only for intermediate voltages, a space-charge-limited drift current can be observed with a slope that approaches two. We show that, depending on the thickness of the semiconductor layer and the size of the injection barriers, the two linear current-voltage regimes can dominate the whole voltage range, and the intermediate Mott-Gurney regime can shrink or disappear. In this case, which will especially occur for thicknesses and injection barriers typical for single-carrier devices used to probe organic semiconductors, a meaningful analysis using the Mott-Gurney law will become unachievable, because a square-law fit can no longer be achieved, resulting in the mobility being substantially underestimated. General criteria for when to expect deviations from the Mott-Gurney law when used for analysis of intrinsic semiconductors are discussed.
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Journal articleFei 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
, Advanced Materials, Vol: 30, Pages: 1-7, ISSN: 0935-9648A new synthetic route, to prepare an alkylated indacenodithieno[3,2-b]thiophene-based nonfullerene acceptor (C8-ITIC), is reported. Compared to the reported ITIC with phenylalkyl side chains, the new acceptor C8-ITIC exhibits a reduction in the optical band gap, higher absorptivity, and an increased propensity to crystallize. Accordingly, blends with the donor polymer PBDB-T exhibit a power conversion efficiency (PCE) up to 12.4%. Further improvements in efficiency are found upon backbone fluorination of the donor polymer to afford the novel material PFBDB-T. The resulting blend with C8-ITIC shows an impressive PCE up to 13.2% as a result of the higher open-circuit voltage. Electroluminescence studies demonstrate that backbone fluorination reduces the energy loss of the blends, with PFBDB-T/C8-ITIC-based cells exhibiting a small energy loss of 0.6 eV combined with a high JSCof 19.6 mA cm-2.
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Journal articleRice B, LeBlanc LM, Otero-de-la-Roza A, et al., 2018,
A computational exploration of the crystal energy and charge-carrier mobility landscapes of the chiral [6]helicene molecule
, Nanoscale, Vol: 10, Pages: 1865-1876, ISSN: 2040-3364The potential of a given π-conjugated organic molecule in an organic semiconductor device is highly dependent on molecular packing, as it strongly influences the charge-carrier mobility of the material. Such solid-state packing is sensitive to subtle differences in their intermolecular interactions and is challenging to predict. Chirality of the organic molecule adds an additional element of complexity to intuitive packing prediction. Here we use crystal structure prediction to explore the lattice-energy landscape of a potential chiral organic semiconductor, [6]helicene. We reproduce the experimentally observed enantiopure crystal structure and explain the absence of an experimentally observed racemate structure. By exploring how the hole and electron-mobility varies across the energy–structure–function landscape for [6]helicene, we find that an energetically favourable and frequently occurring packing motif is particularly promising for electron-mobility, with a highest calculated mobility of 2.9 cm2 V−1 s−1 (assuming a reorganization energy of 0.46 eV). We also calculate relatively high hole-mobility in some structures, with a highest calculated mobility of 2.0 cm2 V−1 s−1 found for chains of helicenes packed in a herringbone fashion. Neither the energetically favourable nor high charge-carrier mobility packing motifs are intuitively obvious, and this demonstrates the utility of our approach to computationally explore the energy–structure–function landscape for organic semiconductors. Our work demonstrates a route for the use of computational simulations to aid in the design of new molecules for organic electronics, through the a priori prediction of their likely solid-state form and properties.
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Journal articleFew SPM, Schmidt O, Offer GJ, et al., 2018,
Prospective improvements in cost and cycle life of off-grid lithium-ion battery packs: An analysis informed by expert elicitations
, Energy Policy, Vol: 114, Pages: 578-590, ISSN: 0301-4215This paper presents probabilistic estimates of the 2020 and 2030 cost and cycle life of lithium-ion battery (LiB) packs for off-grid stationary electricity storage made by leading battery experts from academia and industry, and insights on the role of public research and development (R&D) funding and other drivers in determining these. By 2020, experts expect developments to arise chiefly through engineering, manufacturing and incremental chemistry changes, and expect additional R&D funding to have little impact on cost. By 2030, experts indicate that more fundamental chemistry changes are possible, particularly under higher R&D funding scenarios, but are not inevitable. Experts suggest that significant improvements in cycle life (eg. doubling or greater) are more achievable than in cost, particularly by 2020, and that R&D could play a greater role in driving these. Experts expressed some concern, but had relatively little knowledge, of the environmental impact of LiBs. Analysis is conducted of the implications of prospective LiB improvements for the competitiveness of solar photovoltaic + LiB systems for off-grid electrification.
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Book chapterTam B, Garbarino S, Guay D, 2018,
NH<inf>3</inf> oxidation on well-defined surfaces and proxies of the same
, Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry, Pages: 752-760The current state of knowledge for the electrooxidation of ammonia on Pt electrodes with well-defined surfaces is discussed. From seminal studies on single crystal electrodes in alkaline media, the reaction is known to be highly dependent upon the surface structure. Pt surfaces with (100) orientation are the most active, while surfaces with (111) and (110) orientation have greatly reduced reactivity. Wide terraces of (100) orientation are also found to be significantly more active than (100) step domains. We describe NH3 electrooxidation on cubic nanoparticles enclosed with six facets of (100) atoms and highlight convenient methods which produce Pt catalysts with sufficiently tuned (100) surface structure such as epitaxial growth of Pt thin layers and Pt electrodeposition; both methods offer a low cost alternative to proxy the synthesis of single crystal (100) Pt catalysts. Emerging, bimetallic catalysts are anticipated to shed light on the ammonia oxidation reaction mechanism and further improve the reaction by reducing self-poisoning of the reaction.
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Journal articleWadsworth A, Hamid Z, Bidwell M, et al., 2018,
Progress in Poly (3-Hexylthiophene) Organic Solar Cells and the Influence of Its Molecular Weight on Device Performance
, ADVANCED ENERGY MATERIALS, Vol: 8, ISSN: 1614-6832 -
Journal articlePrashanthan K, Thivakarasarma T, Ravirajan P, et al., 2017,
Enhancement of hole mobility in hybrid titanium dioxide/poly(3-hexylthiophene) nanocomposites by employing an oligothiophene dye as an interface modifier
, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 5, Pages: 11758-11762, ISSN: 2050-7526 -
Working paperMoia D, Giovannitti A, Szumska AA, et al., 2017,
A salt water battery with high stability and charging rates made from solution processed conjugated polymers with polar side chains
, Publisher: arXivWe report a neutral salt water based battery which uses p-type and n-typesolution processed polymer films as the cathode and the anode of the cell. Thespecific capacity of the electrodes (approximately 30 mAh cm-3) is achieved viaformation of bipolarons in both the p-type and n-type polymers. By engineeringethylene glycol and zwitterion based side chains attached to the polymerbackbone we facilitate rapid ion transport through the non-porous polymerfilms. This, combined with efficient transport of electronic charge via theconjugated polymer backbones, allowed the films to maintain constant capacityat high charge and discharge rates (>1000 C-rate). The electrodes also showgood stability during electrochemical cycling (less than 30% decrease incapacity over >1000 cycles) and an output voltage up to 1.4 V. The performanceof these semiconducting polymers with polar side-chains demonstrates thepotential of this material class for fast-charging, water based electrochemicalenergy storage devices.
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Journal articleSchmidt O, Gambhir A, Staffell IL, et al., 2017,
Future cost and performance of water electrolysis: An expert elicitation study
, International Journal of Hydrogen Energy, Vol: 42, Pages: 30470-30492, ISSN: 0360-3199The need for energy storage to balance intermittent and inflexible electricity supply with demand is driving interest in conversion of renewable electricity via electrolysis into a storable gas. But, high capital cost and uncertainty regarding future cost and performance improvements are barriers to investment in water electrolysis. Expert elicitations can support decision-making when data are sparse and their future development uncertain. Therefore, this study presents expert views on future capital cost, lifetime and efficiency for three electrolysis technologies: alkaline (AEC), proton exchange membrane (PEMEC) and solid oxide electrolysis cell (SOEC). Experts estimate that increased R&D funding can reduce capital costs by 0–24%, while production scale-up alone has an impact of 17–30%. System lifetimes may converge at around 60,000–90,000 h and efficiency improvements will be negligible. In addition to innovations on the cell-level, experts highlight improved production methods to automate manufacturing and produce higher quality components. Research into SOECs with lower electrode polarisation resistance or zero-gap AECs could undermine the projected dominance of PEMEC systems. This study thereby reduces barriers to investment in water electrolysis and shows how expert elicitations can help guide near-term investment, policy and research efforts to support the development of electrolysis for low-carbon energy systems.
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Journal articleBabacan O, Ratnam EL, Disfani VR, et al., 2017,
Distributed energy storage system scheduling considering tariff structure, energy arbitrage and solar PV penetration
, Applied Energy, Vol: 205, Pages: 1384-1393, ISSN: 0306-2619We develop a new convex optimization (CO)-based charge/discharge scheduling algorithm for distributed energy storage systems (ESSs) co-located with solar photovoltaic (PV) systems. The CO-based scheduling algorithm minimizes the monthly electricity expenses of a customer who owns an ESS and incorporates both a time-of-use volumetric tariff and a demand charge tariff. Further, we propose the novel idea of a “supply charge” tariff that incentivizes ESS customers to store excess solar PV generation that may otherwise result in reverse power flow in the distribution grid. By means of a case study we observe the CO-based daily charge/discharge schedules reduce (1) peak net demand (that is, load minus PV generation) of the customer, (2) power fluctuations in the customer net demand profile, and (3) the reliance of the customer on the grid by way of promoting energy self-consumption of local solar PV generation. Two alternate methods for behind-the-meter ESS scheduling are considered as benchmarks for cost minimization, peak net demand reduction, and mitigation of net demand fluctuations. The algorithm is tested using real 30-min interval residential load and solar data of 53 customers over 2-years. Results show that the CO-based scheduling algorithm provides mean peak net demand reductions between 46% and 64%, reduces mean net demand fluctuations by 25–49%, and increases the mean solar PV self-consumption between 24% and 39% when compared to a customer without an ESS. Introduction of a supply charge reduces the maximum solar PV power supply to the grid by 19% on average and does not financially impact ESS owners.
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Journal articleMiller TS, Suter TM, Telford AM, et al., 2017,
Single crystal, luminescent carbon nitride nanosheets formed by spontaneous dissolution
, Nano Letters, Vol: 17, Pages: 5891-5896, ISSN: 1530-6984A primary method for the production of 2D nanosheets is liquid-phase delamination from their 3D layered bulk analogues. Most strategies currently achieve this objective by significant mechanical energy input or chemical modification but these processes are detrimental to the structure and properties of the resulting 2D nanomaterials. Bulk poly(triazine imide) (PTI)-based carbon nitrides are layered materials with a high degree of crystalline order. Here, we demonstrate that these semiconductors are spontaneously soluble in select polar aprotic solvents, that is, without any chemical or physical intervention. In contrast to more aggressive exfoliation strategies, this thermodynamically driven dissolution process perfectly maintains the crystallographic form of the starting material, yielding solutions of defect-free, hexagonal 2D nanosheets with a well-defined size distribution. This pristine nanosheet structure results in narrow, excitation-wavelength-independent photoluminescence emission spectra. Furthermore, by controlling the aggregation state of the nanosheets, we demonstrate that the emission wavelengths can be tuned from narrow UV to broad-band white. This has potential applicability to a range of optoelectronic devices.
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Journal articleNelson J, 2017,
A map to find winners
, NATURE MATERIALS, Vol: 16, Pages: 969-970, ISSN: 1476-1122 -
Conference paperSandwell P, Ekins-Daukes N, Nelson J, 2017,
What are the greatest opportunities for PV to contribute to rural development?
, SNEC 11th International Photovoltaic Power Generation Conference and Exhibition (SNEC), Publisher: Elsevier Science BV, Pages: 139-146, ISSN: 1876-6102Minigrid systems powered by solar photovoltaics and battery storage are being deployed around the world to provide basic energy access and facilitate economic development. We use a minigrid simulation and optimisation tool that we have developed to assess various minigrid options in meeting the growing electricity demand of a community in rural Uttar Pradesh, India, in terms of the reliability of the service they provide, the cost of electricity, and total greenhouse gas emissions. We assess the breakeven distance at which off-grid minigrids are favourable in comparison to extending an unreliable grid network with a minigrid backup system, both with and without a carbon price. We suggest that policy recommendations that would encourage the use of minigrids for sustainable rural development, for example allowing subsidies to be available for system expansions and minimum service reliability requirements.
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Journal articleGuilbert AAY, Zbiri M, Dunbar ADF, et al., 2017,
Quantitative Analysis of the Molecular Dynamics of P3HT:PCBM Bulk Heterojunction
, Journal of Physical Chemistry B, Vol: 121, Pages: 9073-9080, ISSN: 1520-5207The optoelectronic properties of blends of conjugated polymers and small molecules are likely to be affected by the molecular dynamics of the active layer components. We study the dynamics of regioregular poly(3-hexylthiophene) (P3HT):phenyl-C61-butyric acid methyl ester (PCBM) blends using molecular dynamics (MD) simulation on time scales up to 50 ns and in a temperature range of 250–360 K. First, we compare the MD results with quasi-elastic neutron-scattering (QENS) measurements. Experiment and simulation give evidence of the vitrification of P3HT upon blending and the plasticization of PCBM by P3HT. Second, we reconstruct the QENS signal based on the independent simulations of the three phases constituting the complex microstructure of such blends. Finally, we found that P3HT chains tend to wrap around PCBM molecules in the amorphous mixture of P3HT and PCBM; this molecular interaction between P3HT and PCBM is likely to be responsible for the observed frustration of P3HT, the plasticization of PCBM, and the partial miscibility of P3HT and PCBM.
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Contact
Jenny Nelson
Professor of Physics
1007, Huxley Building
South Kensington, London, SW7 2AZ