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Fuxiang Zhang, Jianqi Xi, Yanwen Zhang, Yang Tong, Haizhou Xue, Rong Huang, Christina Trautmann, William J Weber
The modification of the local structure in cubic perovskite KTaO3 irradiated with 3 MeV and 1.1 GeV Au ions is studied by Raman and X-ray absorption spectroscopy, complemented by density functional theory (DFT) calculations. In the case of irradiation with 3 MeV Au ions where displacement cascade processes are dominant, the Ta L3-edge X-ray absorption measurements suggest that a peak corresponding to the Ta-O bonds in the TaO6 octahedra splits, which is attributed to the formation of TaK antisite defects that are coupled with oxygen vacancies, VO...
February 22, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Zhenye Xu, Yu Liu, Wei Zhou, Moses O Tade, Zongping Shao
Perovskite oxides are highly promising electrodes for oxygen-ion-intercalation-type supercapacitors owing to their high oxygen vacancy concentration, oxygen diffusion rate and tap density. Based on the anion intercalation mechanism, the capacitance is contributed by surface redox reactions and oxygen ion intercalation in the bulk materials. A high concentration of oxygen vacancies is needed because it is the main charge carrier. In this study, we propose B-site cation-ordered Ba2Bi0.1Sc0.2Co1.7O6-δ as an electrode material with an extremely high oxygen vacancy concentration and oxygen diffusion rate...
February 22, 2018: ACS Applied Materials & Interfaces
Zhelu Hu, Hengyang Xiang, Mathilde Schoenauer Sebag, Laurent Billot, Lionel Aigouy, Zhuoying Chen
Thickness-tunable and compact FA0.83 Cs0.17 Pb(I0.6 Br0.4 )3 perovskite thin films are achieved with a large grain size up to 12 microns. They are then employed to fabricate functional solar cells with a simplified planar structure without the use of electron-transport (ETL) layers. These results are highly encouraging for the future large-scale fabrication of FA0.83 Cs0.17 Pb(I0.6 Br0.4 )3 -based solar cells.
February 21, 2018: Chemical Communications: Chem Comm
Weining Zhang, Yilu Chen, Xiaohong Wang, Xiaoxia Yan, Jiaqiang Xu, Zhigang Zeng
MASnI3 /TiO2 composites (MA represents CH3 NH3 + ) are prepared via a solvothermal method and characterized by various techniques. The results indicate that n-n type heterojunction structures and different ohmic contact interfaces are formed for the composites with different contents of MASnI3 and TiO2 before and after calcination, resulting in different optical and photocatalytic performances. Generally speaking, n-n type heterojunctions play roles in photocatalytic applications through two different mechanisms: the heterojunction mechanism and the Z-type mechanism...
February 21, 2018: Physical Chemistry Chemical Physics: PCCP
Lingling Mao, Weijun Ke, Laurent Pedesseau, Yilei Wu, Claudine Katan, Jacky Even, Michael R Wasielewski, Constantinos C Stoumpos, Mercouri G Kanatzidis
The three-dimensional hybrid organic-inorganic perovskites have shown huge potential for use in photovoltaics and other optoelectronic devices. Although these materials are under intense investigation, derivative materials with lower dimensionality are emerging offering higher tunability of physical properties and new capabilities. Here we present a new class of hybrid two-dimensional (2D) perovskite material: Dion-Jacobson lead iodide perovskites, adopting a general formula A'An-1PbnI3n+1 (A' = 3-(aminomethyl)piperidinium (3AMP) or 4-(aminomethyl)piperidinium (4AMP), A = methylammonium (MA))...
February 21, 2018: Journal of the American Chemical Society
Lan Chen, Bin Li, Chunfeng Zhang, Xinyu Huang, Xiaoyong Wang, Min Xiao
Perovskite semiconductor nanocrystals with different compositions have shown promise for applications in light-emitting devices. Dark excitonic states may suppress light emission from such nanocrystals by providing an additional non-radiative recombination channel. Here, we study the composition dependence of dark exciton dynamics in nanocrystals of lead halides by time-resolved photoluminescence spectroscopy at cryogenic temperatures. The presence of spin-related dark states is revealed by magneto-optical spectroscopy...
February 21, 2018: Nano Letters
Zhixiang Zhang, Longhui Zeng, Xiaowei Tong, Yang Gao, Chao Xie, Yuen Hong Tsang, Linbao Luo, Yu Cheng Wu
In this work, we reported on the large-scale synthesis of polycrystalline multilayer PtSe2 film with typical semimetallic characteristics. With the availability of the large-area film, we constructed a heterojunction composed of multilayer PtSe2 and Cs doped FAPbI3 , which can function as a self-driven photodetector in a broadband wavelength from the ultraviolet (UV) to NIR region. Further photoresponse analysis revealed that the heterojunction device showed outstanding photosensitive characteristics with a large Ilight /Idark ratio of 5...
February 21, 2018: Journal of Physical Chemistry Letters
Daria Noferini, Michael M Koza, Seikh M H Rahman, Zach Evenson, Gøran J Nilsen, Sten Eriksson, Andrew R Wildes, Maths Karlsson
Acceptor-doped barium zirconates are currently receiving considerable interest because of their high proton conductivity at intermediate temperatures, making them applicable as electrolytes in various electrochemical devices, but the mechanism of proton conduction is unclear. Here, we investigate the role of the acceptor-dopant level in the localized proton motions, i.e. proton transfers between oxygens and O-H reorientations, in hydrated samples of the proton conducting, acceptor-doped, perovskites BaZr1-x Inx O3-x/2 with x = 0...
February 21, 2018: Physical Chemistry Chemical Physics: PCCP
Lihong Liu, Weihai Fang, Run Long, Oleg V Prezhdo
Non-radiative electron-hole recombination plays a key role in determining photon conversion efficiencies in solar cells. Experiments demonstrate significant reduction in the recombination rate upon passivation of methylammonium lead iodide perovskite with Lewis base molecules. Using non-adiabatic molecular dynamics combined with time-domain density functional theory, we find that the nonradiative charge recombination is decelerated by an order of magnitude upon adsorption of the molecules. Thiophene acts by the traditional passivation mechanism, forcing electron density away from the surface...
February 20, 2018: Journal of Physical Chemistry Letters
Matthew D Smith, Hemamala I Karunadasa
With nearly 20% of global electricity consumed by lighting, more efficient illumination sources can enable massive energy savings. However, effectively creating the high-quality white light required for indoor illumination remains a challenge. To accurately represent color, the illumination source must provide photons with all the energies visible to our eye. Such a broad emission is difficult to achieve from a single material. In commercial white-light sources, one or more light-emitting diodes, coated by one or more phosphors, yield a combined emission that appears white...
February 20, 2018: Accounts of Chemical Research
Kalpana Singh, Wang Hay Kan, Bailey Patton, Ashfia Huq, Venkataraman Thangadurai
Perovskite-type metal oxides are being used in a wide range of technologies, including fuel cells, batteries, electrolyzers, dielectric capacitors, and sensors. One of their remarkable structural properties is cationic ordering in A or B sites, which affects electrical transport properties under different gaseous atmospheres, and chemical stability under CO2 and humid conditions. For example, a simple-perovskite-type Y-doped BaCeO3 forms BaCO3 and ((Ce,Y)O2-δ ) under CO2 at elevated temperature, while B-site-ordered double-perovskite-type Ba3 Ca1...
February 20, 2018: Inorganic Chemistry
Quinten A Akkerman, Gabriele Rainò, Maksym V Kovalenko, Liberato Manna
Lead halide perovskites (LHPs) in the form of nanometre-sized colloidal crystals, or nanocrystals (NCs), have attracted the attention of diverse materials scientists due to their unique optical versatility, high photoluminescence quantum yields and facile synthesis. LHP NCs have a 'soft' and predominantly ionic lattice, and their optical and electronic properties are highly tolerant to structural defects and surface states. Therefore, they cannot be approached with the same experimental mindset and theoretical framework as conventional semiconductor NCs...
February 19, 2018: Nature Materials
Xue-Feng Cheng, Xiang Hou, Jin Zhou, Bi-Jun Gao, Jing-Hui He, Hua Li, Qing-Feng Xu, Na-Jun Li, Dong-Yun Chen, Jian-Mei Lu
Recently, organic-inorganic hybrid perovskites (OIHP) are studied in memory devices, but ternary resistive memory with three states based on OIHP is not achieved yet. In this work, ternary resistive memory based on hybrid perovskite is achieved with a high device yield (75%), much higher than most organic ternary resistive memories. The pseudohalide-induced 2D (CH3 NH3 )2 PbI2 (SCN)2 perovskite thin film is prepared by using a one-step solution method and fabricated into Al/perovskite film/indium-tin oxide (glass substrate as well as flexible polyethylene terephthalate substrate) random resistive access memory (RRAM) devices...
February 19, 2018: Small
Haifeng Yuan, Elke Debroye, Eva Bladt, Gang Lu, Masoumeh Keshavarz, Kris P F Janssen, Maarten B J Roeffaers, Sara Bals, Edward H Sargent, Johan Hofkens
Organic-inorganic halide perovskites (OIHPs) have demonstrated outstanding energy conversion efficiency in solar cells and light-emitting devices. In spite of intensive developments in both materials and devices, electronic traps and defects that significantly affect their device properties remain under-investigated. Particularly, it remains challenging to identify and to resolve traps individually at the nanoscopic scale. Here, photo-active traps (PATs) are mapped over OIHP nanocrystal morphology of different crystallinity by means of correlative optical differential super-resolution localization microscopy (Δ-SRLM) and electron microscopy...
February 19, 2018: Advanced Materials
Miriam Ezbiri, Michael Takacs, Boris Stolz, Jeffrey Lungthok, Aldo Steinfeld, Ronald Michalsky
Perovskites are attractive redox materials for thermo/electrochemical fuel synthesis. To design perovskites with balanced redox energetics for thermochemically splitting CO2 , the activity of lattice oxygen vacancies and stability against crystal phase changes and detrimental carbonate formation are predicted for a representative range of perovskites by electronic structure computations. Systematic trends in these materials properties when doping with selected metal cations are described in the free energy range defined for isothermal and temperature-swing redox cycles...
August 7, 2017: Journal of Materials Chemistry. A, Materials for Energy and Sustainability
A Scrimshire, A Lobera, A M T Bell, A H Jones, I Sterianou, S D Forder, P A Bingham
Lanthanide orthoferrites have wide-ranging industrial uses including solar, catalytic and electronic applications. Here a series of lanthanide orthoferrite perovskites, LnFeO 3 (Ln = La; Nd; Sm; Eu; Gd), prepared through a standard stoichiometric wet ball milling route using oxide precursors, has been studied. Characterisation through x-ray diffraction and x-ray fluorescence confirmed the synthesis of phase-pure or near-pure LnFeO 3 compounds. 57 Fe Mössbauer spectroscopy was performed over a temperature range of 10 K-293 K to observe hyperfine structure and to enable calculation of the recoil-free fraction and Debye temperature (θ D ) of each orthoferrite...
February 16, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Bo Wei, Michael Schroeder, Manfred Martin
The surface chemistry and the Cr tolerance ability of oxygen electrodes play a vital role in the performance and long-term stability of solid oxide cells (SOCs). In this paper, the surface cation segregations on the double perovskite oxide PrBaCo2O5+δ (PBCO) and its relationship with Cr deposition are reported. During high temperature annealing in an O2 atmosphere, the elements Ba and Co diffuse out of the lattice and form many BaO and Co3O4 precipitates on the surface, mainly located at grain boundaries. In the presence of volatile Cr species, the observation of BaCrO4 but not CoCr2O4 on a segregated PBCO surface reveals that the Cr deposition preferentially takes place on segregated BaO rather than on Co3O4 precipitates...
February 16, 2018: ACS Applied Materials & Interfaces
Anthony K Cheetham, G Kieslich, H H-M Yeung
The evolution of metal-organic frameworks (MOFs) has been one of the most exciting aspects of materials chemistry over the last 20 years. In this Account, we discuss the development during this period in our understanding of the factors that control the crystallization of MOFs from solution. Both classical porous MOFs and dense MOF phases are considered. This is an opportune time at which to examine this complex area because the experimental tools now available to interrogate crystallization processes have matured significantly in the last 5 years, particularly with the use of in situ synchrotron X-ray diffraction...
February 16, 2018: Accounts of Chemical Research
Soyun Park, Min-Sung Kim, Woongsik Jang, Jin Kuen Park, Dong Hwan Wang
Herein, solvent-treated bandgap-tunable covalent organic nanosheets (CONs) were prepared via the Stille cross-coupling reaction. These materials are considered useful as interlayers in photovoltaic devices upon the alignment of energy levels between other components. Among various types of solar cells, according to the organic-interlayer study, inverted planar perovskite solar cells (PSCs) are mostly demanded to effectively transport and collect charge carriers due to their high performance. At first, the C-V analysis proved the energy levels of the frontier orbitals for CON-10 and CON-16 nanosheets; this verified the suitability of these nanosheets as hole transport layers (HTLs) with the PEDOT:PSS upon casting both films from DMSO...
February 16, 2018: Nanoscale
Hao Huang, Jia Li, Ya Yi, Jiahong Wang, Yihong Kang, Paul K Chu, H C Ong, Xue-Feng Yu
This communication describes a novel low-dimensional nanohybrid structure consisting of all-inorganic perovskite nanocrystals (NCs) growing in situ on two-dimensional (2D) black phosphorus (BP) nanosheets. Such a nanohybrid structure promises synergetic properties by combining the respective strengths of perovskite materials and BP, which opens new opportunities for next-generation optoelectronic devices.
February 16, 2018: Chemical Communications: Chem Comm
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