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Journal articleGiri D, Saha SK, Siemons N, et al., 2023,
Ion Size-Dependent Electrochromism in Air-Stable Napthalenediimide-Based Conjugated Polymers
, ACS APPLIED MATERIALS & INTERFACES, Vol: 15, Pages: 17767-17778, ISSN: 1944-8244- Cite
- Citations: 10
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Journal articleBeath H, Alonso JB, Mori R, et al., 2023,
Maximising the benefits of renewable energy infrastructure in displacement settings: optimising the operation of a solar-hybrid mini-grid for institutional and business users in Mahama Refugee Camp, Rwanda
, Renewable and Sustainable Energy Reviews, Vol: 176, ISSN: 1364-0321Humanitarian organisations typically rely on expensive, polluting diesel generators to provide power for services in refugee camps, whilst camp residents often have no access to electricity. Integrating solar and battery storage capacity into existing diesel-based systems can provide significant cost and emissions savings and offer an opportunity to provide power to displaced communities. By analysing monitored demand data and using computational energy system modelling, we assess the savings made possible by the integration of solar (18.4 kWp) and battery (78 kWh) capacity into the existing diesel-powered mini-grid in Mahama Refugee Camp, Rwanda. We find that the renewables infrastructure reduces fuel expenditure by $41,500 and emissions by 44 tCO2eq (both 74%) over five years under the generator’s current operational strategy. An alternative strategy, with deeper battery cycling, unlocks further savings of $4100 and 12.4 tCO2eq, using 33% of battery lifetime versus 15% under the original strategy. This reduces the cost of electricity by 33% versus diesel generation alone, whilst more aggressive cycling strategies could prove economical if moderate battery price decreases are realised. Extending the system to businesses in the camp marketplace can completely offset the system fuel costs if the mini-grid company charges customers the same tariff as the one it uses in the host community, but not the national grid tariff. Humanitarian organisations and the private sector should explore opportunities to integrate renewables into existing diesel-based infrastructure, and optimise its performance once installed, to reduce costs and emissions and provide meaningful livelihood opportunities to displaced communities.
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Journal articleSandwell P, Winchester B, Beath H, et al., 2023,
CLOVER: A modelling framework for sustainablecommunity-scale energy systems
, The Journal of Open Source Software, Vol: 8, Pages: 1-5, ISSN: 2475-9066Sustainable Development Goal 7 aims to provide sustainable, affordable, reliable and modernenergy access to all by 2030 (United Nations, 2015). In order for this goal to be achieved,sustainable energy interventions in developing countries must be supported with design toolswhich can evaluate the technical performance of energy systems as well as their economic andclimate impacts.CLOVER (Continuous Lifetime Optimisation of Variable Electricity Resources) is a softwaretool for simulating and optimising community-scale energy systems, typically minigrids, tosupport energy access in developing countries (Winchester et al., 2022). CLOVER can be usedto model electricity demand and supply at an hourly resolution, for example allowing users toinvestigate how an electricity system might perform at a given location. CLOVER can alsoidentify an optimally-sized energy system to meet the needs of the community under specifiedconstraints. For example, a user could define an optimum system as one which provides adesired level of reliability at the lowest cost of electricity. CLOVER can provide an insightinto the technical performance, costs, and climate change impact of a system, and allow theuser to evaluate many different scenarios to decide on the best way to provide sustainable,affordable and reliable electricity to a community.CLOVER can be used on both personal computers and high-performance computing facilities.Its design separates its general framework (code, contained in a source src directory) fromuser inputs (data, contained in a directory entitled locations) which are specific to theirinvestigations. The user inputs these data via a combination of .csv and .yaml files. CLOVER’sstraightforward command-line interface provides simple operation for both experienced Pythonusers and those with little prior exposure to coding. An installable package, clover-energy, isavailable for users to download without needing to become familiar with GitHub’s interface.Informat
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Journal articleWang J, Zhao W, Tam B, et al., 2023,
Pseudocapacitive porous amorphous vanadium pentoxide with enhanced multicolored electrochromism
, CHEMICAL ENGINEERING JOURNAL, Vol: 452, ISSN: 1385-8947- Cite
- Citations: 31
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Journal articleSayani R, Ortega-Arriaga P, Sandwell P, et al., 2022,
Sizing solar-based mini-grids for growing electricity demand: Insights from rural India
, The Journal of High Energy Physics, Vol: 5, Pages: 1-26, ISSN: 1029-8479Mini-grids are a critical way to meet electricity access goals according to current and projected electricity demand of communities and so appropriately sizing them is essential to ensure their financial viability. However, estimation of demand for communities awaiting electricity access is uncertain and growth in demand along with the associated cost implications is rarely considered during estimation of mini-grid sizing. Using a case study of two rural communities in India, we assess the implications of demand growth on financial costs and performance of a mini-grid system consisting of solar photovoltaic (PV) panels and battery storage using two different system sizing approaches. We show a cost-saving potential of up to 12% when mini-grids are sized using a multi-stage approach where mini-grids gradually expand in several stages, rather than a single-stage optimisation approach. We perform a sensitivity analysis of the cost of the two sizing approaches by varying six key parameters: demand growth rate, logistics cost, system re-sizing frequency, likelihood of blackouts, solar PV and battery cost, and degradation rate. Of these, we find that system costs are most sensitive to variations in demand growth rates and cost decreases in solar PV and batteries. Our study shows that demand growth scenarios and choice of mini-grid sizing approaches have important financial and operational implications for the design of systems for rural electrification.
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Journal articleWade J, Salerno F, Kilbride R, et al., 2022,
Controlling anisotropic properties by manipulating the orientation of chiral small molecules
, Nature Chemistry, Vol: 14, Pages: 1383-1389, ISSN: 1755-4330Chiral π-conjugated molecules bring new functionality to technological applications and represent an exciting, rapidly expanding area of research. Their functional properties, such as the absorption and emission of circularly polarised light or the transport of spin-polarised electrons, are highly anisotropic. As a result, the orientation of chiral molecules criticallydetermines the functionality and efficiency of chiral devices. Here we present a strategy to control the orientation of a small chiral molecule (2,2’-dicyano[6]helicene, CN6H): the use of organic and inorganic templating layers. Such templating layers can either force CN6H molecules to adopt a face-on orientation and self-assemble into upright supramolecular columns oriented with their helical axis perpendicular to the substrate, or an edge-onorientation with parallel-lying supramolecular columns. Through such control, we show that low- and high-energy chiroptical responses can be independently ‘turned on’ or ‘turned off’. The templating methodologies described here provide a simple way to engineer orientational control, and by association, anisotropic functional properties of chiral molecular systems for a range of emerging technologies.
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Journal articleHillman SAJ, Sprick RS, Pearce D, et al., 2022,
Why do sulfone-containing polymer photocatalysts work so well for sacrificial hydrogen evolution from water?
, Journal of the American Chemical Society, Vol: 144, Pages: 19382-19395, ISSN: 0002-7863Many of the highest-performing polymer photocatalysts for sacrificial hydrogen evolution from water have contained dibenzo[b,d]thiophene sulfone units in their polymer backbones. However, the reasons behind the dominance of this building block are not well understood. We study films, dispersions, and solutions of a new set of solution-processable materials, where the sulfone content is systematically controlled, to understand how the sulfone unit affects the three key processes involved in photocatalytic hydrogen generation in this system: light absorption; transfer of the photogenerated hole to the hole scavenger triethylamine (TEA); and transfer of the photogenerated electron to the palladium metal co-catalyst that remains in the polymer from synthesis. Transient absorption spectroscopy and electrochemical measurements, combined with molecular dynamics and density functional theory simulations, show that the sulfone unit has two primary effects. On the picosecond timescale, it dictates the thermodynamics of hole transfer out of the polymer. The sulfone unit attracts water molecules such that the average permittivity experienced by the solvated polymer is increased. We show that TEA oxidation is only thermodynamically favorable above a certain permittivity threshold. On the microsecond timescale, we present experimental evidence that the sulfone unit acts as the electron transfer site out of the polymer, with the kinetics of electron extraction to palladium dictated by the ratio of photogenerated electrons to the number of sulfone units. For the highest-performing, sulfone-rich material, hydrogen evolution seems to be limited by the photogeneration rate of electrons rather than their extraction from the polymer.
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Journal articlePulignani C, Mesa C, Hillman S, et al., 2022,
Rational design of carbon nitride photoelectrodes with high activity toward organic oxidations
, Angewandte Chemie International Edition, ISSN: 1433-7851Carbon nitride (CNx) is a scalable polymeric light-absorber with excellent performance in photocatalytic suspension systems, but the activity of CNx photoelectrodes has remained low. Here, cyanamide-functionalized CNx (NCNCNx) has been co-deposited with ITO nanoparticles on a 1.8 Å thick alumina-coated FTO-glass electrode. Transient spectroscopy and impedance measurements support that ITO acts as conductive binder and improves the electron extraction from the NCNCNx, whilst the alumina underlayer reduces the electrical resistance between the ITO and the FTO-coated electrode. The Al2O3|ITO:NCNCNx electrode displays a new benchmark performance for CNx-based photoanodes with a remarkably low onset of –0.4 V vs the reversible hydrogen electrode (RHE) and an outstanding 1.4 ± 0.2 mA cm–2 at 1.23 V vs RHE for the selective oxidation of 4-methylbenzyl alcohol to the corresponding aldehyde. This facile assembly will enable the exploration of CNx in fundamental and applied PEC studies, paving the way for the development of high-performance photoelectrodes using other semiconductor powders
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Journal articleSiemons N, Pearce D, Cendra C, et al., 2022,
Impact of side chain hydrophilicity on packing, swelling and ion interactions in oxy-bithiophene semiconductors.
, Advanced Materials, Vol: 34, ISSN: 0935-9648Exchanging hydrophobic alkyl-based side chains to hydrophilic glycol-based side chains is a widely adopted method for improving mixed-transport device performance, despite the impact on solid state packing and polymer-electrolyte interactions being poorly understood. Presented here is a Molecular Dynamics (MD) force field for modelling alkoxylated and glycolated polythiophenes. The force field is validated against known packing motifs for their monomer crystals. MD simulations, coupled with X-ray Diffraction (XRD), show that alkoxylated polythiophenes will pack with a 'tilted stack' and straight interdigitating side chains, whilst their glycolated counterpart will pack with a 'deflected stack' and an s-bend side chain configuration. MD simulations reveal water penetration pathways into the alkoxylated and glycolated crystals - through the π-stack and through the lamellar stack respectively. Finally, the two distinct ways tri-ethylene glycol polymers can bind to cations are revealed, showing the formation of a meta-stable single bound state, or an energetically deep double bound state, both with a strong side chain length dependance. The minimum energy pathways for the formation of the chelates are identified, showing the physical process through which cations can bind to one or two side chains of a glycolated polythiophene, with consequences for ion transport in bithiophene semiconductors. This article is protected by copyright. All rights reserved.
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Journal articleCalado P, Gelmetti I, Hilton B, et al., 2022,
Driftfusion: an open source code for simulating ordered semiconductor devices with mixed ionic-electronic conducting materials in one dimension
, JOURNAL OF COMPUTATIONAL ELECTRONICS, Vol: 21, Pages: 960-991, ISSN: 1569-8025- Cite
- Citations: 14
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Journal articleWard MD, Shi W, Gasparini N, et al., 2022,
Best practices in the measurement of circularly polarised photodetectors
, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 10, Pages: 10452-10463, ISSN: 2050-7526- Cite
- Citations: 6
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Journal articleTan E, Kim J, Stewart K, et al., 2022,
The role of long-alkyl-group spacers in glycolated copolymers for high performance organic electrochemical transistors
, Advanced Materials, Vol: 34, ISSN: 0935-9648Semiconducting polymers with oligoethylene glycol sidechains have attracted strong research interest for organic electrochemical transistor (OECT) applications. However, key molecular design rules for high-performance OECTs via efficient mixed electronic/ionic charge transport are still unclear. Herein, we synthesize and characterize new glycolated copolymers (gDPP-TTT and gDPP-TTVTT) with diketopyrrolopyrrole (DPP) acceptor and thiophene-based (TTT or TTVTT) donor units for accumulation mode OECTs, where a long-alkyl-group (C12 ) attached to DPP unit acts as a spacer distancing the oligoethylene glycol from the polymer backbone. gDPP-TTVTT shows the highest OECT transconductance (61.9 S cm-1 ) and high operational stability, compared to gDPP-TTT and their alkylated counterparts. Surprisingly, gDPP-TTVTT also shows high electronic charge mobility in field-effect transistor, suggesting efficient ion injection/diffusion without hindering its efficient electronic charge transport. The elongated donor unit (TTVTT) facilitates the hole polaron formation more localized to the donor unit, leading to faster and easier polaron formation with less impact on polymer structure during OECT operation, as opposed to the TTT unit. This is supported by molecular dynamics (MD) simulation. We conclude that these simultaneously high electronic and ionic charge transport properties are achieved due to the long-alkyl-group spacer in amphipathic sidechains, providing an important molecular design rule for glycolated copolymers. This article is protected by copyright. All rights reserved.
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Journal articleZhao W, Wang J, Tam B, et al., 2022,
Macroporous Vanadium Oxide Ion Storage Films Enable Fast Switching Speed and High Cycling Stability of Electrochromic Devices
, ACS APPLIED MATERIALS & INTERFACES, Vol: 14, Pages: 30021-30028, ISSN: 1944-8244- Cite
- Citations: 31
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Journal articleSowe J, Varela Barreras J, Schimpe M, et al., 2022,
Model-informed battery current derating strategies: Simple methods to extend battery lifetime in islanded mini-grids
, Journal of Energy Storage, Vol: 51, Pages: 1-9, ISSN: 2352-152XIslanded mini-grids with batteries are crucial to enable universal access to energy. However, batteries are still costly, and how to select and operate them in an optimal manner is often unclear. The combination of variable climates with simple and low-cost passive thermal management also poses a challenge. Many techno-economic sizing tools usually consider simple battery degradation models, which disregard the impact of climatic conditions and operating strategy on battery performance. This study uses a semi-empirical Li-ion battery degradation model alongside an open-source techno-economic model to capture key insights. These are used to inform simple state of charge and temperature-based current derating strategies to increase lifetime. We demonstrate that such strategies can increase battery lifetime by 45% or 5–7 years in commercial systems already operational. It was found that, irrespective of climatic conditions, 80–90% of capacity fade can be attributed to calendar aging, due to low C-rates. SOC-based derating was found to be the most effective strategy, with temperature-based derating being less effective at extending lifetime and also leading to increased blackout periods. These results highlight the importance of accurate degradation modelling to achieve lifetime extension through improved operational strategies.
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Journal articleEisner F, Foot G, Yan J, et al., 2022,
Emissive charge-transfer states at hybrid inorganic/organic heterojunctions enable low non-radiative recombination and high-performance photodetectors
, Advanced Materials, Vol: 34, ISSN: 0935-9648Hybrid devices based on a heterojunction between inorganic and organic semiconductors have offered a means to combine the advantages of both classes of materials in optoelectronic devices, but, in practice, the performance of such devices has often been disappointing. Here, it is demonstrated that charge generation in hybrid inorganic–organic heterojunctions consisting of copper thiocyanate (CuSCN) and a variety of molecular acceptors (ITIC, IT-4F, Y6, PC70BM, C70, C60) proceeds via emissive charge-transfer (CT) states analogous to those found at all-organic heterojunctions. Importantly, contrary to what has been observed at previous organic–inorganic heterojunctions, the dissociation of the CT-exciton and subsequent charge separation is efficient, allowing the fabrication of planar photovoltaic devices with very low non-radiative voltage losses (0.21 ± 0.02 V). It is shown that such low non-radiative recombination enables the fabrication of simple and cost-effective near-IR (NIR) detectors with extremely low dark current (4 pA cm−2) and noise spectral density (3 fA Hz−1/2) at no external bias, leading to specific detectivities at NIR wavelengths of just under 1013 Jones, close to the performance of commercial silicon photodetectors. It is believed that this work demonstrates the possibility for hybrid heterojunctions to exploit the unique properties of both inorganic and organic semiconductors for high-performance opto-electronic devices.
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Journal articleYan J, Rodríguez-Martínez X, Pearce D, et al., 2022,
Identifying structure-absorption relationships and predicting absorption strength of non-fullerene acceptors for organic photovoltaics
, Energy & Environmental Science, Vol: 15, Pages: 2958-2973, ISSN: 1754-5692Non-fullerene acceptors (NFAs) are excellent light harvesters, yet the origin of their high optical extinction is not well understood. In this work, we investigate the absorption strength of NFAs by building a database of time-dependent density functional theory (TDDFT) calculations of ∼500 π-conjugated molecules. The calculations are first validated by comparison with experimental measurements in solution and solid state using common fullerene and non-fullerene acceptors. We find that the molar extinction coefficient (εd,max) shows reasonable agreement between calculation in vacuum and experiment for molecules in solution, highlighting the effectiveness of TDDFT for predicting optical properties of organic π-conjugated molecules. We then perform a statistical analysis based on molecular descriptors to identify which features are important in defining the absorption strength. This allows us to identify structural features that are correlated with high absorption strength in NFAs and could be used to guide molecular design: highly absorbing NFAs should possess a planar, linear, and fully conjugated molecular backbone with highly polarisable heteroatoms. We then exploit a random decision forest algorithm to draw predictions for εd,max using a computational framework based on extended tight-binding Hamiltonians, which shows reasonable predicting accuracy with lower computational cost than TDDFT. This work provides a general understanding of the relationship between molecular structure and absorption strength in π-conjugated organic molecules, including NFAs, while introducing predictive machine-learning models of low computational cost.
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Journal articleZhu L, Zhang M, Xu J, et al., 2022,
Single-junction organic solar cells with over 19% efficiency enabled by a refined double-fibril network morphology
, Nature Materials, Vol: 21, ISSN: 1476-1122In organic photovoltaics, morphological control of donor and acceptor domains on the nanoscale is the key for enabling efficient exciton diffusion and dissociation, carrier transport and suppression of recombination losses. To realize this, here, we demonstrated a double-fibril network based on a ternary donor–acceptor morphology with multi-length scales constructed by combining ancillary conjugated polymer crystallizers and a non-fullerene acceptor filament assembly. Using this approach, we achieved an average power conversion efficiency of 19.3% (certified 19.2%). The success lies in the good match between the photoelectric parameters and the morphological characteristic lengths, which utilizes the excitons and free charges efficiently. This strategy leads to an enhanced exciton diffusion length and a reduced recombination rate, hence minimizing photon-to-electron losses in the ternary devices as compared to their binary counterparts. The double-fibril network morphology strategy minimizes losses and maximizes the power output, offering the possibility of 20% power conversion efficiencies in single-junction organic photovoltaics.
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Journal articleHou X, Clarke AJ, Azzouzi M, et al., 2022,
Relationship between molecular properties and degradation mechanisms of organic solar cells based on bis-adducts of phenyl-C₆₁ butyric acid methyl ester
, Journal of Materials Chemistry C, Vol: 10, Pages: 7875-7885, ISSN: 2050-7526Environmental stability remains a major challenge for the commercialisation of organic solar cells and degradation pathways remain poorly understood. Designing materials for improved device stability requires an understanding of the relationship between the properties of the donor or acceptor molecule and different degradation mechanisms. Here we study the correlations between various molecular parameters of the fullerene derivative bis-PCBM and the degradation rate of polymer:bis-PCBM organic solar cells, based on the same carbazole-alt-benzothiadiazole polymer, in aerobic and anaerobic conditions. We compare eight high purity bis-PCBM isomers with different electronic, chemical and packing properties along with PCBM and the mixture of bis isomers. In the case of aerobic photodegradation, we find that device degradation rate is positively correlated to the LUMO energy of the bis-PCBM isomer and to the degree of crystallinity of the isomer, while the correlation of degradation with driving force for epoxide formation is unclear. These results support the idea that in these samples, aerobic photodegradation proceeds via superoxide formation by the photogenerated polaron on the fullerene, followed by further chemical reaction. In the absence of air, photodegradation rate is correlated with molecular structure, supporting the mechanism of microstructural degradation via fullerene dimerization. The approach and findings presented here show how control of specific molecular parameters through chemical design can serve as a strategy to enhance stability of organic solar cells.
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Journal articleAzzouzi M, Nelson J, Eisner F, et al., 2022,
Reconciling models of interfacial state kinetics and device performance in organic solar cells: Impact of the energy offsets on the power conversion efficiency
, Energy and Environmental Science, Vol: 15, Pages: 156-1270, ISSN: 1754-5692Achieving the simultaneous increases in the open circuit voltage (Voc), short circuit current (Jsc) and fill factor (FF) necessary to further increase the power conversion efficiency (PCE) of organic photovoltaics (OPV) requires a unified understanding of how molecular and device parameters affect all three characteristics. In this contribution, we introduce a framework that for the first time combines different models that have been used separately to describe the different steps of the charge generation and collection processes in OPV devices: a semi-classical rate model for charge recombination processes in OPV devices, zero-dimensional kinetic models for the photogeneration process and exciton dissociation and one-dimensional semiconductor device models. Using this unified multi-scale model in conjunction with experimental techniques (time-resolved absorption spectroscopy, steady-state and transient optoelectronic measurements) that probe the various steps involved in charge generation we can shed light on how the energy offsets in a series of polymer: non-fullerene devices affect the charge carrier generation, collection, and recombination properties of the devices. We find that changing the energy levels of the donor significantly affects not only the transition rates between local-exciton (LE) and charge-transfer (CT) states, but also significantly changes the transition rates between CT and charge-separated (CS) states, challenging the commonly accepted picture of charge generation and recombination. These results show that in order to obtain an accurate picture of charge generation in OPV devices, a variety of different experimental techniques under different conditions in conjunction with a comprehensive model of processes occurring at different time-scales are required.
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Journal articleFew S, Barton J, Sandwell P, et al., 2022,
Electricity demand in populations gaining access: Impact of rurality and climatic conditions, and implications for microgrid design
, Energy for Sustainable Development, Vol: 66, Pages: 151-164, ISSN: 0973-0826Almost 800 million people currently lack access to reliable electricity, for many of whom solar microgrid systems are expected to be the most cost-effective solution. Quantifying current and future electricity demand is crucial for cost-effective design of reliable microgrids. However, electricity usage is connected to a wide range of social and economic factors alongside climatic conditions, making estimation of demand challenging. This paper presents a framework facilitating each stage of solar microgrid design from demand estimation through to cost-optimal sizing of the microgrid and its economic and environmental characterisation. Household demand is simulated based upon (1) climatic conditions, (2) appliance ratings and usage patterns, and (3) rates of growth in appliance ownership based upon the Multi-Tier Framework for measuring household electricity access. Microgrid demands are simulated based on the combination of these with (4) nondomestic demand based upon locally available data. The framework is demonstrated across four rates of domestic demand growth and two climatic conditions (‘tropical savanna’ and ‘humid subtropical’), alongside nondomestic demand based upon two operational microgrids (one rural and one peri-urban). When growth rates are high, newly introduced appliances tend to dominate, with differing impacts on the demand profile depending on power and usage times. Cooling represents a modest contribution to demand in the tropical savanna climate. However, in the hotter and more seasonally varying humid subtropical climate, cooling becomes the dominant driver of demand, increasing seasonality and proportion of demand at night. Nondomestic demand in the rural microgrid is primarily agricultural, and exhibits more seasonality and better alignment with daylight hours than demand in the peri-urban setting, which is more service-based. Across cases, increased seasonality and proportion of demand at night lead to poorer alignme
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Journal articleWard MD, Wade J, Shi X, et al., 2022,
Highly selective high-speed circularly polarized photodiodes based on π-conjugated polymers
, Advanced Optical Materials, Vol: 10, ISSN: 2195-1071Chiral π-conjugated molecular systems that are intrinsically sensitive to the handedness of circularly polarized (CP) light potentially allow for miniaturized, low-cost CP detection devices. Such devices promise to transform several technologies, including biosensing, quantum optics, and communication of data encrypted by exploiting the spin angular momentum of light. Here a simple, bilayer organic photodiode (CP OPD) comprising an achiral π-conjugated polymer–chiral additive blend as the electron donor layer and an achiral C60 electron acceptor layer is realized. These devices exhibit considerable photocurrent dissymmetry gph, with absolute values as high as 0.85 and dark currents as low as 10 pA. Impressively, they showcase a linear dynamic range of 80 dB, and rise and fall times of ≈7 µs, which significantly outperforms all previously reported CP selective photodetectors. Mechanistically, it is shown that the gph is sensitive to the thickness of both the chiral donor and achiral acceptor layers and that a trade-off exists between the external quantum efficiency and gph. The fast-switching speeds of these devices, coupled with their large dynamic range and highly selective response to CP light, opens up the possibility of their direct application in CP sensing and optical communications.
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Journal articleAlmora O, Baran D, Bazan GC, et al., 2021,
Device performance of emerging photovoltaic materials (version 2)
, Advanced Energy Materials, Vol: 11, Pages: 1-41, ISSN: 1614-6832Following the 1st release of the “Emerging photovoltaic (PV) reports”, the best achievements in the performance of emerging photovoltaic devices in diverse emerging photovoltaic research subjects are summarized, as reported in peer-reviewed articles in academic journals since August 2020. Updated graphs, tables, and analyses are provided with several performance parameters, e.g., power conversion efficiency, open-circuit voltage, short-circuit current density, fill factor, light utilization efficiency, and stability test energy yield. These parameters are presented as a function of the photovoltaic bandgap energy and the average visible transmittance for each technology and application and are put into perspective using, e.g., the detailed balance efficiency limit. The 2nd instalment of the “Emerging PV reports” extends the scope toward tandem solar cells and presents the current state-of-the-art in tandem solar cell performance for various material combinations.
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Journal articleBozal-Ginesta C, Rao RR, Mesa CA, et al., 2021,
Redox-state kinetics in water-oxidation IrOx electrocatalysts measured by operando spectroelectrochemistry
, ACS Catalysis, Vol: 11, Pages: 15013-15025, ISSN: 2155-5435Hydrous iridium oxides (IrOx) are the best oxygen evolution electrocatalysts available for operation in acidic environments. In this study, we employ time-resolved operando spectroelectrochemistry to investigate the redox-state kinetics of IrOx electrocatalyst films for both water and hydrogen peroxide oxidation. Three different redox species involving Ir3+, Ir3.x+, Ir4+, and Ir4.y+ are identified spectroscopically, and their concentrations are quantified as a function of applied potential. The generation of Ir4.y+ states is found to be the potential-determining step for catalytic water oxidation, while H2O2 oxidation is observed to be driven by the generation of Ir4+ states. The reaction kinetics for water oxidation, determined from the optical signal decays at open circuit, accelerates from ∼20 to <0.5 s with increasing applied potential above 1.3 V versus reversible hydrogen electrode [i.e., turnover frequencies (TOFs) per active Ir state increasing from 0.05 to 2 s–1]. In contrast, the reaction kinetics for H2O2 is found to be almost independent of the applied potential (increasing from 0.1 to 0.3 s–1 over a wider potential window), indicative of a first-order reaction mechanism. These spectroelectrochemical data quantify the increase of both the density of active Ir4.y+ states and the TOFs of these states with applied positive potential, resulting in the observed sharp turn on of catalytic water oxidation current. We reconcile these data with the broader literature while providing a unique kinetic insight into IrOx electrocatalytic reaction mechanisms, indicating a first-order reaction mechanism for H2O2 oxidation driven by Ir4+ states and a higher-order reaction mechanism involving the cooperative interaction of multiple Ir4.y+ states for water oxidation.
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Journal articleEisner F, Tam B, Belova V, et al., 2021,
Color-tunable hybrid heterojunctions as semi-transparent photovoltaic windows for photoelectrochemical water splitting
, Cell Reports Physical Science, Vol: 2, Pages: 1-16, ISSN: 2666-3864The strong but narrow-bandwidth absorption spectra of organic semiconductors make them excellent candidates for semi-transparent solar cell applications in which color specificity is important. In this study, using a hybrid heterojunction combining the transparent inorganic semiconductor copper thiocyanate (CuSCN) with organic semiconductors (C70, PC70BM, C60, ITIC, IT-4F, or Y6), we show that simple color-tunable solar cells can be fabricated in which the transmission spectrum is determined solely by choice of the organic semiconductor. Using a joint electrical-optical model, we show that it is possible to combine the unique attributes of high photovoltage and color tunability to use these heterojunctions as photovoltaic windows in tandem photoelectrochemical (PEC)-photovoltaic (PV) cells. We demonstrate that this configuration can lead to a reduction in the parasitic absorption losses in the PEC-PV cells and, thus, to solar-to-hydrogen efficiencies (>3%) that are higher than that predicted using the traditionally used architecture in which the PV is placed behind the PEC.
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ReportPearce D, Pearce A, Gambhir A, et al., 2021,
Research pathways for net-zero transport
The future is uncertain and there are many different pathways ahead for technology and society. Some, but not all, ofthese pathways will deliver the required amount of decarbonisation to comply with the Paris Agreement. Whilst wecannot know for certain which of these pathways will be chosen, research allows us both to identify the patterns andtrends that can help shape the pathways, and ultimately our future, and to develop the technologies and approachesthat can assist decarbonisation
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Journal articleSzumska AA, Maria IP, Flagg LQ, et al., 2021,
Reversible Electrochemical Charging of n-Type Conjugated Polymer Electrodes in Aqueous Electrolytes
, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 143, Pages: 14795-14805, ISSN: 0002-7863- Author Web Link
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- Citations: 97
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Journal articleSchmidt J, Weatherby J, Sugden I, et al., 2021,
Computational screening of organic semiconductors: exploring side-group functionalisation and assembly to optimise charge transport in chiral molecules
, Crystal Growth and Design, Vol: 21, Pages: 5036-5049, ISSN: 1528-7483Molecular materials are challenging to design as their packing arrangement and hence properties are subject to subtle variations in the interplay of soft intermolecular interactions that are difficult to predict. The rational design of new molecular materials with tailored properties is currently hampered by the lack of knowledge of how a candidate molecule will pack in space and how we can control the polymorphs we can experimentally obtain. Here, we develop a simplified approach to aid the material design process, by the development of a screening process that is used to test 1344 helicene molecules that have potential as organic electronic materials. Our approach bridges the gap between single molecule design, molecular assembly, and the resulting charge-carrier mobilities. We find that fluorination significantly improves electron transport in the molecular material by up to 200%; the reference [6]helicene packing showed a mobility of 0.30 cm2 V-1 s-1, fluorination increased the mobility to up to 0.96 and 0.97 (13-fluoro[6]H and 4,13-difluoro[6]H), assuming an outer reorganisation energy of 0.30 eV. Side groups containing triple bonds largely lead to improved transfer integrals. We validate our screening approach through the use of crystal structure prediction to confirm the presence of favourable packing motifs to maximize charge mobility.
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Journal articleJux N, Reger D, Haines P, et al., 2021,
A family of superhelicenes - easily tunable, chiral nanographenes by merging helicity with planar π-systems
, Angewandte Chemie International Edition, Vol: 60, Pages: 18073-18081, ISSN: 1433-7851Incorporating helicity into large polycyclic aromatic hydrocarbons (PAHs) constitutes a new field of research at the interface between chemistry and material sciences. Lately, interest in the design of π-extended helicenes has surged. This new class of twisted, chiral nanographenes not only reveals unique characteristics but also finds its way into emerging applications such as spintronics. Insights into their structure-property relationships and on-demand tuning are scarce. To close these knowledge gaps, we designed a straightforward synthetic route towards a full-fledged family of π-extended helicenes: superhelicenes. Common are two hexa-peri-hexabenzocoronenes (HBCs) connected via a central 5-membered ring. By means of structurally altering this 5-membered ring, we realized a versatile library of molecular building blocks. Not only the superhelicene structure, but also their features are tuned with ease. In-depth physico-chemical characterizations served as a proof of concept thereof. The superhelicene enantiomers were separated, their circular dichroism was measured in preliminary studies and concluded with an enantiomeric assignment. Our work was rounded-off by crystal structure analyses. Mixed stacks of M- and P-isomers led to twisted molecular wires. Using such stacks, charge-carrier mobilities were calculated, giving reason to expect outstanding hole transporting properties.
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Journal articleReger D, Haines P, Amsharov KY, et al., 2021,
A Family of Superhelicenes: Easily Tunable, Chiral Nanographenes by Merging Helicity with Planar π Systems
, Angewandte Chemie, Vol: 133, Pages: 18221-18229, ISSN: 0044-8249<jats:title>Abstract</jats:title><jats:p>We designed a straightforward synthetic route towards a full‐fledged family of π‐extended helicenes: superhelicenes. They have two hexa‐peri‐hexabenzocoronenes (HBCs) in common that are connected via a central five‐membered ring. By means of structurally altering this 5‐membered ring, we realized a versatile library of molecular building blocks. Not only the superhelicene structure, but also their features are tuned with ease. In‐depth physico‐chemical characterizations served as a proof of concept thereof. The superhelicene enantiomers were separated, their circular dichroism was measured in preliminary studies and concluded with an enantiomeric assignment. Our work was rounded‐off by crystal structure analyses. Mixed stacks of M‐ and P‐isomers led to twisted molecular wires. Using such stacks, charge‐carrier mobilities were calculated, giving reason to expect outstanding hole transporting properties.</jats:p>
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Journal articleCilio L, Babacan O, 2021,
Allocation optimisation of rapid charging stations in large urban areas to support fully electric taxi fleets
, APPLIED ENERGY, Vol: 295, ISSN: 0306-2619- Author Web Link
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