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51 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4, 5, 6 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I09-Surface and Interface Structural Analysis	Amorphous tin-gallium oxide buffer layers in (Ag,Cu)(In,Ga)Se2 solar cells F. Larsson , J. Keller , J. Olsson , O. Donzel-gargand , N. M. Martin , M. Edoff , T. Torndahl Solar Energy Materials And Solar Cells 215 DOI: 10.1016/j.solmat.2020.110647 Diamond Proposal Number(s): [21742] Open Access Show Abstract ▼ Abstract: Amorphous tin-gallium oxide (a-SGO) grown with atomic layer deposition was evaluated as a buffer layer in (Ag,Cu)(In,Ga)Se2 thin-film solar cells in search for a new material that is compatible with a variety of absorber band gaps. Hard and soft X-ray photoelectron spectroscopy on absorber/a-SGO stacks combined with J–V characterization of solar cells that were fabricated, showed that the conduction band alignment at the absorber/a-SGO interface can be tuned by varying the cation composition and/or growth temperature. Here, the surface band gap was 1.1 eV for the absorber. However, optical band gap data for a-SGO indicate that a suitable conduction band alignment can most likely be achieved even for wider absorber band gaps relevant for tandem top cells. A best efficiency of 17.0% was achieved for (Ag,Cu)(In,Ga)Se2/a-SGO devices, compared to η = 18.6% for the best corresponding CdS reference. Lower fill factor and open-circuit voltage values were responsible for lower cell efficiencies. The reduced fill factor is explained by a larger series resistance, seemingly related to interface properties, which are yet to be optimized. Some layer constellations resulted in degradation in fill factor during light soaking as well. This may partly be explained by light-induced changes in the electrical properties of a-SGO, according to analysis of Al/SGO/n-Si metal-oxide-semiconductor capacitors that were fabricated and characterized with J–V and C–V. Moreover, the introduction of a 1 nm thick Ga2O3 interlayer between the absorber and a-SGO improved the open-circuit voltage, which further indicates that the absorber/a-SGO interface can be improved.	Sep 2020
I11-High Resolution Powder Diffraction	In situ phase transformation on nickel-based selenides for enhanced hydrogen evolution reaction in alkaline medium Lingling Zhai , Tsz Woon Benedict Lo , Zheng-long Xu , Jonathan Potter , Jiaying Mo , Xuyun Guo , Chiu Chung Tang , Shik Chi Edman Tsang , Shu Ping Lau Acs Energy Letters DOI: 10.1021/acsenergylett.0c01385 Diamond Proposal Number(s): [23230] Show Abstract ▼ Abstract: Identification of the active species in electrocatalysts toward hydrogen evolution reaction (HER) is of great significance for the development of the catalytic industry; however, it is still the subject of considerable controversy. Herein, we applied operando synchrotron X-ray powder diffraction (SXRD) in the NiSe2 electrocatalyst system, and an in situ phase transformation from cubic NiSe2 to hexagonal NiSe was revealed. The NiSe phase showed an enhanced catalytic activity. Operando Raman spectroscopy verified the decomposition of NiSe2 during HER. Theoretical calculations suggested that the charge transfers from the Se site to Ni site during this evolution process, leading to an increased conductivity and a shifting up of d-band center, which is attributed to the enhanced activity. The generated NiSe phase acts as the “real” active species. Our work unravels the underlying phase transition of the electrocatalyst on reductive conditions in alkaline medium and highlights the significance of identifying the intrinsic active sites under realistic reaction conditions.	Jul 2020
I07-Surface & interface diffraction	Perovskite crystallization dynamics during spin casting: an in situ wide angle X-ray scattering study Noura Alhazmi , Edwin Pineda , Jonathan Rawle , Jonathan R Howse , Alan D. F. Dunbar Acs Applied Energy Materials DOI: 10.1021/acsaem.9b02470 Diamond Proposal Number(s): [14937] Show Abstract ▼ Abstract: In this study in situ wide angle X-ray scattering (WAXS) has been measured during the spin coating process used to make the precursor films required for the formation of thin films of perovskite. A customized hollow axis spin coater was developed to permit the scattered X-rays to be collected in transmission geometry during the deposition process. Spin coating is the technique most commonly used in laboratories to make thin perovskite films. The dynamics of spin casting MAPbI3-xClx and FAPbI3-xClx films have been investigated and compared to investigate the differences between the dynamics of MAPbI3-xClx and FAPbI3-xClx film formation. In particular we focus on the crystallization dynamics of the precursor film formation. When casting MAPbI3-xClx we observed relatively fast 1D crystallization of the intermediate product MA2PbI3Cl. There was an absence of the desired perovskite phase formed directly; it only appeared after an annealing step which converted the MA2PbI3Cl to MAPbI3. In contrast, slower crystallization via a 3D precursor was observed for FAPbI3-xClx film formation compared to MAPbI3-xClx. Another important finding was that some FAPbI3-xClx perovskite was generated directly during spin casting before annealing. These findings indicate that there are significant differences between the crystallization pathways for these two perovskite materials. These are likely to explain the differences in the lifetime of the resulting perovskite solar cell devices produced using FA and MA cations.	Jun 2020
I09-Surface and Interface Structural Analysis	Stabilisation of Li-rich disordered rocksalt oxyfluoride cathodes by particle surface modification Andrew J. Naylor , Ida Kallquist , David Peralta , Jean-frederic Martin , Adrien Boulineau , Jean-francois Colin , Christian Baur , Johann Chable , Maximilian Fichtner , Kristina Edstrom , Maria Hahlin , Daniel Brandell Acs Applied Energy Materials DOI: 10.1021/acsaem.0c00839 Diamond Proposal Number(s): [20870] Show Abstract ▼ Abstract: Promising theoretical capacities and high voltages are offered by Li-rich disordered rocksalt oxyfluoride materials as cathodes in lithium ion batteries. However, as has been discovered for many other Li-rich materials, the oxyfluorides suffer from extensive surface degradation, leading to severe capacity fading. In the case of Li2VO2F, we have previously determined this to be a result of detrimental reactions between an unstable surface layer and the organic electrolyte. Herein, we present the protection of Li2VO2F particles with AlF3 surface modification, resulting in a much enhanced capacity retention over 50 cycles. While the specific capacity for the untreated material drops below 100 mA h g-1 after only 50 cycles, the treated materials retain almost 200 mA h g-1. Photoelectron spectroscopy depth profiling confirms the stabilisation of the active material surface by the surface modification and reveals its suppression of electrolyte decomposition.	May 2020
I09-Surface and Interface Structural Analysis	Effects of nitridation on SiC/SiO2 structures studied by hard x-ray photoelectron spectroscopy Judith Veronika Berens , Sebastian Bichelmaier , Nathalie K. Fernando , Pardeep Kumar Thakur , Tien-lin Lee , Manfred Mascheck , Tomas Wiell , Susanna K. Eriksson , J. Matthias Kahk , Johannes Lischner , Manesh Mistry , Thomas Aichinger , Gregor Pobegen , Anna Regoutz Journal Of Physics: Energy DOI: 10.1088/2515-7655/ab8c5e Diamond Proposal Number(s): [19885] Open Access Show Abstract ▼ Abstract: SiC is set to enable a new era in power electronics impacting a wide range of energy technologies, from electric vehicles to renewable energy. Its physical characteristics outperform silicon in many aspects, including band gap, breakdown field, and thermal conductivity. The main challenge for further development of SiC-based power semiconductor devices is the quality of the interface between SiC and its native dielectric SiO2. High temperature nitridation processes can improve the interface quality and ultimately the device performance immensely, but the underlying chemical processes are still poorly understood. Here, we present an energy-dependent hard X-ray photoelectron spectroscopy (HAXPES) study probing non-destructively SiC and SiO2 and their interface in device stacks treated in varying atmospheres. We successfully combine laboratory- and synchrotron-based HAXPES to provide unique insights into the chemistry of interface defects and their passivation through nitridation processes.	Apr 2020
	Transition metal migration can facilitate ionic diffusion in defect garnet based intercalation electrodes Nicholas H Bashian , Samantha Abdel-latif , Mateusz Zuba , Kent J. Griffith , Alex M. Ganose , Joseph W. Stiles , Shiliang Zhou , David O. Scanlon , Louis F. J. Piper , Brent Melot Acs Energy Letters DOI: 10.1021/acsenergylett.0c00376 Show Abstract ▼ Abstract: The importance of metal migration during multi-electron redox activity has been characterized, revealing a competing demand to satisfy bonding requirements and local strains in structures upon alkali intercalation. The local structural evolution required to accommodate intercalation in Y2(MoO4)3 and Al2(MoO4)3 has been contrasted by operando characterization methods, including X-ray absorption spectroscopy and diffraction, along with nuclear magnetic resonance measurements. Computational modeling further rationalized behavioral differences. The local structure of Y2(MoO4)3 was maintained upon lithiation while the structure of Al2(MoO4)3 underwent substantial local atomic rearrangements as the stronger ionic character of the bonds in Al2(MoO4)3 allowed Al to mix off its starting octahedral position to accommodate strain during cycling. However, this mixing was prevented in the more covalent Y2(MoO4)3 which accommodated strain through rotational motion of polyhedral subunits. Knowing that an increased ionic character can facilitate the diffusion of redox-inactive metals when cycling multi-electron electrodes offers a powerful design principle when identifying next-generation intercalation hosts.	Apr 2020
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS E01-JEM ARM 200CF	Multi‐scale investigations of δ‐Ni 0.25 V 2 O 5 ·nH 2 O cathode materials in aqueous zinc‐ion batteries Jianwei Li , Kit Mccoll , Xuekun Lu , Sanjay Sathasivam , Haobo Dong , Liqun Kang , Zhuangnan Li , Siyu Zhao , Andreas G. Kafizas , Ryan Wang , Dan J. L. Brett , Paul R. Shearing , Furio Corà , Guanjie He , Claire J. Carmalt , Ivan P. Parkin Advanced Energy Materials 8 DOI: 10.1002/aenm.202000058 Diamond Proposal Number(s): [24197, 22572] Show Abstract ▼ Abstract: Cost‐effective and environment‐friendly aqueous zinc‐ion batteries (AZIBs) exhibit tremendous potential for application in grid‐scale energy storage systems but are limited by suitable cathode materials. Hydrated vanadium bronzes have gained significant attention for AZIBs and can be produced with a range of different pre‐intercalated ions, allowing their properties to be optimized. However, gaining a detailed understanding of the energy storage mechanisms within these cathode materials remains a great challenge due to their complex crystallographic frameworks, limiting rational design from the perspective of enhanced Zn2+ diffusion over multiple length scales. Herein, a new class of hydrated porous δ‐Ni0.25V2O5.nH2O nanoribbons for use as an AZIB cathode is reported. The cathode delivers reversibility showing 402 mAh g−1 at 0.2 A g−1 and a capacity retention of 98% over 1200 cycles at 5 A g−1. A detailed investigation using experimental and computational approaches reveal that the host “δ” vanadate lattice has favorable Zn2+ diffusion properties, arising from the atomic‐level structure of the well‐defined lattice channels. Furthermore, the microstructure of the as‐prepared cathodes is examined using multi‐length scale X‐ray computed tomography for the first time in AZIBs and the effective diffusion coefficient is obtained by image‐based modeling, illustrating favorable porosity and satisfactory tortuosity.	Feb 2020
B18-Core EXAFS	Oxygen redox activity through a reductive coupling mechanism in the P3-type nickel-doped sodium manganese oxide Eun Jeong Kim , Le Anh Ma , Laurent C. Duda , David M. Pickup , Alan V. Chadwick , Reza Younesi , John T. S. Irvine , A. Robert Armstrong Acs Applied Energy Materials DOI: 10.1021/acsaem.9b02171 Diamond Proposal Number(s): [14239] Show Abstract ▼ Abstract: Increasing dependence on rechargeable batteries for energy storage calls for the improvement of energy density of batteries. Toward this goal, introduction of positive electrode materials with high voltage and/or high capacity is in high demand. The use of oxygen chemistry in lithium and sodium layered oxides has been of interest to achieve high capacity. Nevertheless, a complete understanding of oxygen-based redox processes remains elusive especially in sodium ion batteries. Herein, a novel P3-type Na0.67Ni0.2Mn0.8O2, synthesized at low temperature, exhibits oxygen redox activity in high potentials. Characterization using a range of spectroscopic techniques reveals the anionic redox activity is stabilized by the reduction of Ni, because of the strong Ni 3d–O 2p hybridization states created during charge. This observation suggests that different route of oxygen redox processes occur in P3 structure materials, which can lead to the exploration of oxygen redox chemistry for further development in rechargeable batteries.	Jan 2020
I15-1-X-ray Pair Distribution Function (XPDF)	Li2O:Li–Mn–O disordered rock‐salt nanocomposites as cathode prelithiation additives for high‐energy density Li‐ion batteries Maria Diaz-lopez , Philip A. Chater , Pierre Bordet , Melanie Freire , Christian Jordy , Oleg I. Lebedev , Valerie Pralong Advanced Energy Materials 142 DOI: 10.1002/aenm.201902788 Diamond Proposal Number(s): [20893] Open Access Show Abstract ▼ Abstract: The irreversible loss of lithium from the cathode material during the first cycles of rechargeable Li‐ion batteries notably reduces the overall cell capacity. Here, a new family of sacrificial cathode additives based on Li2O:Li2/3Mn1/3O5/6 composites synthesized by mechanochemical alloying is reported. These nanocomposites display record (but irreversible) capacities within the Li–Mn–O systems studied, of up to 1157 mAh g−1, which represents an increase of over 300% of the originally reported capacity in Li2/3Mn1/3O5/6 disordered rock salts. Such a high irreversible capacity is achieved by the reaction between Li2O and Li2/3Mn1/3O5/6 during the first charge, where electrochemically active Li2O acts as a Li+ donor. A 13% increase of the LiFePO4 and LiCoO2 first charge gravimetric capacities is demonstrated by the addition of only 2 wt% of the nanosized composite in the cathode mixture. This result shows the great potential of these newly discovered sacrificial additives to counteract initial losses of Li+ ions and improve battery performance.	Jan 2020
I09-Surface and Interface Structural Analysis	Quantifying the capacity contributions during activation of Li2MnO3 Jatinkumar Rana , Joseph K. Papp , Zachary Lebens-higgins , Mateusz Zuba , Lori A. Kaufman , Anshika Goel , Richard Schmuch , Martin Winter , M. Stanley Whittingham , Wanli Yang , Bryan D. Mccloskey , Louis F. J. Piper Acs Energy Letters DOI: 10.1021/acsenergylett.9b02799 Diamond Proposal Number(s): [22250] Show Abstract ▼ Abstract: Though Li2MnO3 was originally considered to be electrochemically inert, its observed activation has spawned a new class of Li-rich layered compounds that deliver capacities beyond the traditional transition-metal redox limit. Despite progress in our understanding of oxygen redox in Li-rich compounds, the underlying origin of the initial charge capacity of Li2MnO3 remains hotly contested. To resolve this issue, we review all possible charge compensation mechanisms including bulk oxygen redox, oxidation of Mn4+, and surface degradation for Li2MnO3 cathodes displaying capacities exceeding 350 mAh g–1. Using elemental and orbital selective X-ray spectroscopy techniques, we rule out oxidation of Mn4+ and bulk oxygen redox during activation of Li2MnO3. Quantitative gas-evolution and titration studies reveal that O2 and CO2 release accounted for a large fraction of the observed capacity during activation with minor contributions from reduced Mn species on the surface. These studies reveal that, although Li2MnO3 is considered critical for promoting bulk anionic redox in Li-rich layered oxides, Li2MnO3 by itself does not exhibit bulk oxygen redox or manganese oxidation beyond its initial Mn4+ valence.	Jan 2020

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