42 results found
Wade J, Brandt J, Reger D, et al., 2020, 500‐fold amplification of small molecule circularly polarized luminescence through circularly polarized FRET, Angewandte Chemie International Edition, ISSN: 1433-7851
Strongly dissymmetric circularly polarised (CP) luminescence from small organic molecules could transform a range of technologies, such as display devices. However, highly dissymmetric emission is usually not possible with small organic molecules, which typically give dissymmetric factors of photoluminescence ( g PL ) less than 10 ‐2 . Here we describe an almost 10 3 ‐fold chiroptical amplification of a π‐extended superhelicene when embedded in an achiral conjugated polymer matrix. This combination increases the |gPL| of the superhelicene from approximately 3 × 10 ‐4 in solution to 0.15 in a blend film in the solid‐state. We propose that the amplification arises not simply through a chiral environment effect, but instead due to electrodynamic coupling between the electric and magnetic transition dipoles of the polymer donor and superhelicene acceptor, and subsequent CP Förster resonance energy transfer. We show that this amplification effect holds across several achiral polymer hosts and thus represents a simple and versatile approach to enhance the g‐factors of small organic molecules.
Wan L, Wade J, Shi X, et al., 2020, Highly efficient inverted circularly polarized organic light-emitting diodes, ACS Applied Materials & Interfaces, Vol: 12, Pages: 39471-39478, ISSN: 1944-8244
Circularly polarized (CP) electroluminescence has been demonstrated as a strategy to improve the performance of organic light emitting diode (OLED) displays. CP emission can be generated from both small molecule and polymer OLEDs (SM-OLEDs and PLEDs), but to date, these devices suffer from low dissymmetry factors (g-factor <0.1), poor device performance, or a combination of the two. Here, we demonstrate the first CP-PLED employing an inverted device architecture. Through this approach, we demonstrate a highly efficient CP-PLED, with a current efficiency (CE) of 16.4 cd/A, a power efficiency (PE) of 16.6 lm/W, a maximum luminance of over 28,500 cd/m2, and a high EL dissymmetry (gEL) of 0.57. We find that the handedness of the emitted light is sensitive to the PLED device architecture: the sign of CP-EL from an identically prepared active layer reverses between inverted and conventional devices. The inverted structure affords the first demonstration of CP-PLEDs exhibiting both high efficiency and high dissymmetry – the two figures of merit which, until now, have been difficult to achieve at the same time. We also highlight device architecture and associated internal electric field to be a previously unexplored means to control the handedness of CP emission. Our findings significantly broaden the versatility of CP emissive devices and should enable their further application in a variety of other CP-dependent technologies.
Rajan G, Morgan JJ, Murphy C, et al., 2020, Low Operating Voltage Carbon-Graphene Hybrid E-textile for Temperature Sensing, ACS APPLIED MATERIALS & INTERFACES, Vol: 12, Pages: 29861-29867, ISSN: 1944-8244
Wade J, 2020, Preface for the Women's perspectives in 2D materials focus issue, JOURNAL OF PHYSICS-MATERIALS, Vol: 3
Wade J, 2020, Radioactive, PHYSICS WORLD, Vol: 33, Pages: 50-51, ISSN: 0953-8585
Ball P, Hengel E, Moriarty P, et al., Gender issues in fundamental physics: Strumia's bibliometric analysis fails to account for key confounders and confuses correlation with causation, Quantitative Science Studies, ISSN: 2641-3337
Alessandro Strumia recently published a survey of gender differences in publications and citations in high-energy physics (HEP). In addition to providing full access to the data, code, and methodology, Strumia (2020) systematically describes and accounts for gender differences in HEP citation networks. His analysis points both to ongoing difficulties in attracting women to high-energy physics and an encouraging—though slow—trend in improvement.
Karim MMS, Ganose AM, Pieters L, et al., 2019, Anion Distribution, Structural Distortion, and Symmetry-Driven Optical Band Gap Bowing in Mixed Halide Cs2SnX6 Vacancy Ordered Double Perovskites, CHEMISTRY OF MATERIALS, Vol: 31, Pages: 9430-9444, ISSN: 0897-4756
Wade J, Radcliffe D, 2019, Tricks and wizardry, PHYSICS WORLD, Vol: 32, Pages: 35-36, ISSN: 0953-8585
Yan H, Limbu S, Wang X, et al., 2019, Efficient charge carrier injection and balance achieved by low electrochemical doping in solution-processed polymer light-emitting diodes, Advanced Functional Materials, Vol: 29, Pages: 1-9, ISSN: 1616-301X
Charge carrier injection and transport in polymer light‐emitting diodes (PLEDs) is strongly limited by the energy level offset at organic/(in)organic interfaces and the mismatch in electron and hole mobilities. Herein, these limitations are overcome via electrochemical doping of a light‐emitting polymer. Less than 1 wt% of doping agent is enough to effectively tune charge injection and balance and hence significantly improve PLED performance. For thick single‐layer (1.2 µm) PLEDs, dramatic reductions in current and luminance turn‐on voltages (VJ = 11.6 V from 20.0 V and VL = 12.7 V from 19.8 V with/without doping) accompanied by reduced efficiency roll‐off are observed. For thinner (<100 nm) PLEDs, electrochemical doping removes a thickness dependence on VJ and VL, enabling homogeneous electroluminescence emission in large‐area doped devices. Such efficient charge injection and balance properties achieved in doped PLEDs are attributed to a strong electrochemical interaction between the polymer and the doping agents, which is probed by in situ electric‐field‐dependent Raman spectroscopy combined with further electrical and energetic analysis. This approach to control charge injection and balance in solution‐processed PLEDs by low electrochemical doping provides a simple yet feasible strategy for developing high‐quality and efficient lighting applications that are fully compatible with printing technologies.
Wade J, Pugh H, Nightingale J, et al., 2019, Colour in bivalve shells: Using resonance Raman spectroscopy to compare pigments at different phylogenetic levels, Journal of Raman Spectroscopy, Vol: 50, Pages: 1527-1536, ISSN: 0377-0486
Several studies have suggested that shell colour may be phylogenetically distributed within the phylum Mollusca, but this pattern is confounded by our ignorance of the homology of colour and lack of understanding about the identity of most molluscan pigments. We use resonance Raman spectroscopy to address this problem by examining bivalve pigments producing a range of colours and compare spectra from taxa at different phylogenetic levels. The spectra of most shell pigments exhibited a skeletal signature typical of partially methylated polyenes, possibly modified carotenoids, with the strongest peaks occurring between 1,501–1,540 cm−1 and 1,117–1,144 cm−1 due to the C═C (ν1) and C–C (ν2) stretching modes, respectively. Neither pigment class nor mineral structure differentiated Imparidentia and Pteriomorphia. Spectral acquisitions for purple pigments for two species of Asaphis suggest that identical or nearly identical pigments are shared within this genus, and some red pigments from distantly related species have similar spectra. Conversely, two species with brown shells have distinctly different pigments, highlighting the difficulty in determining the homology of colour even within a single class of pigments. Curiously, we were unable to detect any Raman activity for green‐coloured shell or pigment peaks for the yellow area of Codakia paytenorum, suggesting that these colours are due to structural elements or a pigment that is quite different from those observed in other taxa examined to date. Our results are consistent with the idea that classes of pigments are evolutionarily ancient but heritable modifications may be specific to clades.
Wade J, Zaringhalam M, 2019, Why we need to keep talking about equality in physics, PHYSICS WORLD, Vol: 32, Pages: 34-38, ISSN: 0953-8585
Britton B, Jackson C, Wade J, 2019, The reward and risk of social media for academics, Nature Reviews Chemistry, Vol: 3, Pages: 459-461, ISSN: 2397-3358
We are three academics who are active on social media. We explore the motivations for and benefits of engaging with social media, as well as its costs and risks. Overall, we believe this engagement to be a net benefit for us, our employers and for wider society.
Wan L, Wade J, Salerno F, et al., 2019, Inverting the handedness of circularly polarized luminescence from light-emitting polymers using film thickness, ACS Nano, Vol: 13, Pages: 8099-8105, ISSN: 1936-0851
The emission of circularly polarized light is central to many applications, including data storage, optical quantum computation, biosensing, environmental monitoring, and display technologies. An emerging method to induce (chiral) circularly polarized (CP) electroluminescence from the active layer of polymer light-emitting diodes (polymer OLEDs; PLEDs) involves blending achiral polymers with chiral small-molecule additives, where the handedness/sign of the CP light is controlled by the absolute stereochemistry of the small molecule. Through the in-depth study of such a system we report an interesting chiroptical property: the ability to tune the sign of CP light as a function of active layer thickness for a fixed enantiomer of the chiral additive. We demonstrate that it is possible to achieve both efficient (4.0 cd/A) and bright (8000 cd/m2) CP-PLEDs, with high dissymmetry of emission of both left-handed (LH) and right-handed (RH) light, depending on thickness (thin films, 110 nm: gEL = 0.51, thick films, 160 nm: gEL = -1.05, with the terms "thick" and "thin" representing the upper and lower limits of the thickness regime studied), for the same additive enantiomer. We propose that this arises due to an interplay between localized CP emission originating from molecular chirality and CP light amplification or inversion through a chiral medium. We link morphological, spectroscopic, and electronic characterization in thin films and devices with theoretical studies in an effort to determine the factors that underpin these observations. Through the control of active layer thickness and device architecture, this study provides insights into the mechanisms that result in CP luminescence and high performance from CP-PLEDs, as well as demonstrating new opportunities in CP photonic device design.
Wade J, 2019, 30 years of the Web, PHYSICS WORLD, Vol: 32, Pages: 38-38, ISSN: 0953-8585
Wade J, 2019, Let's fight sexism with data, NEW SCIENTIST, Vol: 241, Pages: 24-25, ISSN: 0262-4079
Gabrys BJ, Wade J, Dyer J, et al., 2019, Women in Physics in the UK: On the Road to Equality, 6th IUPAP International Conference on Women in Physics (ICWIP), Publisher: AMER INST PHYSICS, ISSN: 0094-243X
Meza-Montes L, Betacchy M, Hodari A, et al., 2019, Workshop Report: Cultural Bias and Perception, 6th IUPAP International Conference on Women in Physics (ICWIP), Publisher: AMER INST PHYSICS, ISSN: 0094-243X
Nightingale 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: 1932-7447
The 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.
Wade J, Wood S, 2018, Materials for the 21st century, Europhysics News, Vol: 49, Pages: 14-17, ISSN: 0531-7479
Wade J, 2018, Balance the equation, NEW SCIENTIST, Vol: 240, Pages: 26-27, ISSN: 0262-4079
Wade J, 2018, Making health digital, PHYSICS WORLD, Vol: 31, Pages: 27-30, ISSN: 0953-8585
Wade J, 2018, Rooted in physics, PHYSICS WORLD, Vol: 31, Pages: 38-41, ISSN: 0953-8585
Wade J, Wood S, Collado-Fregoso E, et al., 2017, Impact of Fullerene Intercalation on Structural and Thermal Properties of Organic Photovoltaic Blends, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 121, Pages: 20976-20985, ISSN: 1932-7447
The performance of organic photovoltaic blend devices is critically dependent on the polymer:fullerene interface. These interfaces are expected to impact the structural and thermal properties of the polymer with regards to the conjugated backbone planarity and transition temperatures during annealing/cooling processes. Here, we report the impact of fullerene intercalation on structural and thermal properties of poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene (PBTTT), a highly stable material known to exhibit liquid crystalline behavior. We undertake a detailed systematic study of the extent of intercalation in the PBTTT:fullerene blend, considering the use of four different fullerene derivatives and also varying the loading ratios. Resonant Raman spectroscopy allows direct observation of the interface morphology in situ during controlled heating and cooling. We find that small fullerene molecules readily intercalate into PBTTT crystallites, resulting in a planarization of the polymer backbone, but high fullerene loading ratios or larger fullerenes result in nonintercalated domains. During cooling from melt, nonintercalated blend films are found to return to their original morphology and reproduce all thermal transitions on cooling with minimal hysteresis. Intercalated blend films show significant hysteresis on cooling due to the crystallized fullerene attempting to reintercalate. The strongest hysteresis is for intercalated blend films with excess fullerene loading ratio, which form a distinct nanoribbon morphology and exhibit a reduced geminate recombination rate. These results reveal that careful consideration should be taken during device fabrication, as postdeposition thermal treatments significantly impact the charge generation and recombination dynamics.
Tesh S, Wade J, 2017, 'Look happy dear, you've just made a discovery', PHYSICS WORLD, Vol: 30, Pages: 31-33, ISSN: 0953-8585
Boufflet P, Wood S, Wade J, et al., 2016, Comparing blends and blocks: Synthesis of partially fluorinated diblock polythiophene copolymers to investigate the thermal stability of optical and morphological properties, Beilstein Journal of Organic Chemistry, Vol: 12, Pages: 2150-2163, ISSN: 1860-5397
The microstructure of the active blend layer has been shown to be a critically important factor in the performance of organic solar devices. Block copolymers provide a potentially interesting avenue for controlling this active layer microstructure in solar cell blends. Here we explore the impact of backbone fluorination in block copolymers of poly(3-octyl-4-fluorothiophene)s and poly(3-octylthiophene) (F-P3OT-b-P3OT). Two block co-polymers with varying block lengths were prepared via sequential monomer addition under Kumada catalyst transfer polymerisation (KCTP) conditions. We compare the behavior of the block copolymer to that of the corresponding homopolymer blends. In both types of system, we find the fluorinated segments tend to dominate the UV–visible absorption and molecular vibrational spectral features, as well as the thermal behavior. In the block copolymer case, non-fluorinated segments appear to slightly frustrate the aggregation of the more fluorinated block. However, in situ temperature dependent Raman spectroscopy shows that the intramolecular order is more thermally stable in the block copolymer than in the corresponding blend, suggesting that such materials may be interesting for enhanced thermal stability of organic photovoltaic active layers based on similar systems.
Fernando B, Wade J, Tazi K, 2016, Sowing seeds from space, ASTRONOMY & GEOPHYSICS, Vol: 57, Pages: 11-11, ISSN: 1366-8781
Fernando B, Wade J, Tazi K, 2016, Sowing seeds from space, Astronomy and Geophysics, Vol: 57, ISSN: 1366-8781
Wood S, Kim J-H, Wade J, et al., 2016, Systematic control of heteroatoms in donor-acceptor copolymers and its effects on molecular conformation and photovoltaic performance, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 4, Pages: 7966-7978, ISSN: 2050-7526
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