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Sample records for 111-oriented perovskite ferrate

  1. Contribution to the analytic study of ferrates

    Preparation and chemical properties of potassium, strontium and barium ferrates are described. Separation by glass-paper chromatography, electrochemical studies and infrared spectra are shown. A polarographic determination of ferrate ion have been worked. The stability of these compounds is studied with differential thermal analysis. (author)

  2. Ordered iodine adsorption as fingerprint of (111) orientation of Pt thin films

    Braunschweig, Bjoern; Mitin, Alexej; Daum, Winfried [Institut fuer Physik und Physikalische Technologien, TU Clausthal, Leibnizstrasse 4, D-38678 Clausthal-Zellerfeld (Germany)

    2009-07-01

    Well-ordered Pt films deposited on re-usable substrates find applications such as inexpensive replacements for bulk single crystals or ultrathin transparent electrodes for spectro-electrochemical applications. While morphological properties of such films - roughness, atomic steps and spatial extent of atomically flat terraces - are easily imaged with the STM, atomic resolution of the Pt surface is often not attainable under environmental conditions. We demonstrate that the atomic surface structure of (111)-oriented Pt thin films deposited on {alpha}-Al{sub 2}O{sub 3}(0001) substrates is clearly revealed after adsorption of ordered iodine adlayers. In comparative STM studies with Pt thin films and with (111)-oriented bulk single crystals we observed the same coexisting (4 x 3{radical}(3)) and ({radical}(43) x {radical}(43)) iodine superstructures which indicates that our Pt films are highly ordered and (111)-oriented.

  3. Potassium ferrate treatment of RFETS' contaminated groundwater

    The potassium ferrate treatment study of Rocky Flats Environmental Technology Site (RFETS) groundwater was performed under the Sitewide Treatability Studies Program (STSP). This study was undertaken to determine the effectiveness of potassium ferrate in a water treatment system to remove the contaminants of concern (COCS) from groundwater at the RFETS. Potassium ferrate is a simple salt where the iron is in the plus six valence state. It is the iron at the plus six valence state (Fe +6) that makes it an unique water treatment chemical, especially in waters where the pH is greater than seven. In basic solutions where the solubility of the oxides/hydroxides of many of the COCs is low, solids are formed as the pH is raised. By using ferrate these solids are agglomerated so they can be effectively removed by sedimentation in conventional water treatment equipment. The objective of this study was to determine the quality of water after treatment with potassium ferrate and to determine if the Colorado Water Quality Control Commission (CWQCC) discharge limits for the COCs listed in Table 1.0-1 could be met. Radionuclides in the groundwater were of special concern

  4. Electronic reconstruction in (001) and (111) oriented LaAlO3/SrTiO3 interfaces

    The observation of a quasi two-dimensional electron gas (q2DEG), superconductivity and magnetism at the (001) interface between the band insulators LaAlO3 (LAO) and SrTiO3 (STO) has opened possibilities for novel electronics applications. Based on density functional calculations, we explore if these multifunctional properties can be extended by changing the crystal orientation from (001) to (111). Despite the difference in stacking with AO and BO2 planes of the perovskite ABO3 structure in (001) oriented superlattices versus AO3 and B layers in the (111) direction, analogous effects such as polar discontinuity arise when the A and B cations are varied across the interface. A further intriguing feature in (111) oriented interfaces is the formation of a buckled honeycomb lattice of the B-site cations. This lattice geometry, well known from graphene, promises to host even more exotic topological phases. The effect of interface termination, thickness of the substrate and strain is discussed.

  5. Fabrication of (111)-oriented Ca{sub 0.5}Sr{sub 0.5}IrO{sub 3}/SrTiO{sub 3} superlattices—A designed playground for honeycomb physics

    Hirai, Daigorou [Department of Physics, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033 (Japan); Matsuno, Jobu [RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198 (Japan); Takagi, Hidenori [Department of Physics, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033 (Japan); Max-Plank-Institute for solid state research, Heisenbergstrasse 1, Stuttgart 70569 (Germany)

    2015-04-01

    We report the fabrication of (111)-oriented superlattice structures with alternating 2m-layers (m = 1, 2, and 3) of Ca{sub 0.5}Sr{sub 0.5}IrO{sub 3} perovskite and two layers of SrTiO{sub 3} perovskite on SrTiO{sub 3}(111) substrates. In the case of m = 1 bilayer films, the Ir sub-lattice is a buckled honeycomb, where a topological state may be anticipated. The successful growth of superlattice structures on an atomic level along the [111] direction was clearly demonstrated by superlattice reflections in x-ray diffraction patterns and by atomically resolved transmission electron microscope images. The ground states of the superlattice films were found to be magnetic insulators, which may suggest the importance of electron correlations in Ir perovskites in addition to the much discussed topological effects.

  6. Degradability of chlorophenols using ferrate(VI) in contaminated groundwater.

    Homolková, M; Hrabák, P; Kolář, M; Černík, M

    2016-01-01

    The production and use of chlorophenolic compounds in industry has led to the introduction of many xenobiotics, among them chlorophenols (CPs), into the environment. Five CPs are listed in the priority pollutant list of the U.S. EPA, with pentachlorophenol (PCP) even being proposed for listing under the Stockholm Convention as a persistent organic pollutant (POP). A green procedure for degrading such pollutants is greatly needed. The use of ferrate could be such a process. This paper studies the degradation of CPs (with an emphasis on PCP) in the presence of ferrate both in a spiked demineralized water system as well as in real contaminated groundwater. Results proved that ferrate was able to completely remove PCP from both water systems. Investigation of the effect of ferrate purity showed that even less pure and thus much cheaper ferrate was applicable. However, with decreasing ferrate purity, the degradability of CPs may be lower. PMID:26370812

  7. Superconducting thin films of (100) and (111) oriented indium doped topological crystalline insulator SnTe

    Si, Weidong, E-mail: wds@bnl.gov, E-mail: qiangli@bnl.gov; Zhang, Cheng; Wu, Lijun; Ozaki, Toshinori; Gu, Genda; Li, Qiang, E-mail: wds@bnl.gov, E-mail: qiangli@bnl.gov [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)

    2015-08-31

    Recent discovery of the topological crystalline insulator SnTe has triggered a search for topological superconductors, which have potential application to topological quantum computing. The present work reports on the superconducting properties of indium doped SnTe thin films. The (100) and (111) oriented thin films were epitaxially grown by pulsed-laser deposition on (100) and (111) BaF{sub 2} crystalline substrates, respectively. The onset superconducting transition temperatures are about 3.8 K for (100) and 3.6 K for (111) orientations, slightly lower than that of the bulk. Magneto-resistive measurements indicate that these thin films may have upper critical fields higher than that of the bulk. With large surface-to-bulk ratio, superconducting indium doped SnTe thin films provide a rich platform for the study of topological superconductivity and potential device applications based on topological superconductors.

  8. Superconducting thin films of (100) and (111) oriented indium doped topological crystalline insulator SnTe

    Recent discovery of the topological crystalline insulator SnTe has triggered a search for topological superconductors, which have potential application to topological quantum computing. The present work reports on the superconducting properties of indium doped SnTe thin films. The (100) and (111) oriented thin films were epitaxially grown by pulsed-laser deposition on (100) and (111) BaF2 crystalline substrates, respectively. The onset superconducting transition temperatures are about 3.8 K for (100) and 3.6 K for (111) orientations, slightly lower than that of the bulk. Magneto-resistive measurements indicate that these thin films may have upper critical fields higher than that of the bulk. With large surface-to-bulk ratio, superconducting indium doped SnTe thin films provide a rich platform for the study of topological superconductivity and potential device applications based on topological superconductors

  9. Removal of Pharmaceutical residues by ferrate(VI.

    Jia-Qian Jiang

    Full Text Available BACKGROUND: Pharmaceuticals and their metabolites are inevitably emitted into the waters. The adverse environmental and human health effects of pharmaceutical residues in water could take place under a very low concentration range; from several µg/L to ng/L. These are challenges to the global water industries as there is no unit process specifically designed to remove these pollutants. An efficient technology is thus sought to treat these pollutants in water and waste water. METHODOLOGY/MAJOR RESULTS: A novel chemical, ferrate, was assessed using a standard jar test procedure for the removal of pharmaceuticals. The analytical protocols of pharmaceuticals were standard solid phase extraction together with various instrumentation methods including LC-MS, HPLC-UV and UV/Vis spectroscopy. Ferrate can remove more than 80% of ciprofloxacin (CIP at ferrate dose of 1 mg Fe/L and 30% of ibuprofen (IBU at ferrate dose of 2 mg Fe/L. Removal of pharmaceuticals by ferrate was pH dependant and this was in coordinate to the chemical/physical properties of pharmaceuticals. Ferrate has shown higher capability in the degradation of CIP than IBU; this is because CIP has electron-rich organic moieties (EOM which can be readily degraded by ferrate oxidation and IBU has electron-withdrawing groups which has slow reaction rate with ferrate. Promising performance of ferrate in the treatment of real waste water effluent at both pH 6 and 8 and dose range of 1-5 mg Fe/L was observed. Removal efficiency of ciprofloxacin was the highest among the target compounds (63%, followed by naproxen (43%. On the other hand, n-acetyl sulphamethoxazole was the hardest to be removed by ferrate (8% only. CONCLUSIONS: Ferrate is a promising chemical to be used to treat pharmaceuticals in waste water. Adjusting operating conditions in terms of the properties of target pharmaceuticals can maximise the pharmaceutical removal efficiency.

  10. Giant isothermal entropy change In (111)-oriented PMN-PT thin film

    Hamad, Mahmoud A.

    2014-11-01

    An isothermal entropy change of 240 nm (111)-oriented PMN-PT 65/35 film near the ferroelectric Curie temperature, relative cooling power (RCP) and change of heat capacity have been investigated. The extracted data characterized giant isothermal entropy change of more than 16 J/kg K in electric field shift ΔE of 455 kV cm-1, which is nearly twice than that found for PbZr0.95Ti0.05O3 thin film at 492 kV cm-1 near the Curie point. Furthermore, the RCP ≈ 700 J/kg and change of heat capacity ≈ 233 J/kg K in electric field shift ΔE of 747 kV cm-1.

  11. Microstructure and shape memory behavior of [111]-oriented NiTiHfPd alloys

    Acar, E.; Tobe, H.; Karaca, H. E.; Noebe, R. D.; Chumlyakov, Y. I.

    2016-03-01

    The relationship between the microstructure and shape memory properties of [111]-oriented Ni45.3Ti29.7Hf20Pd5 (at%) single crystals was explored. In this precipitation-strengthened alloy, the size and volume fraction of precipitates and interparticle distances govern the martensite morphology and the ensuing shape memory responses. Aging of the solution-treated material, leading to a microstructure of fine, closely spaced precipitates, resulted in a material capable of a shape memory strain of 2.15% at 1000 MPa in compression. Larger precipitates formed after aging the as-grown single crystals (without a prior solution treatment) resulting in a shape memory strain of 2.5% at this same stress level in constant-stress thermal cycling experiments. Superelastic strains of 4% in compression without any residual strain were possible under various microstructural conditions and the stress hysteresis could be varied between nearly 500 and 1000 MPa depending on the microstructure.

  12. Preparation of Potassium Ferrate from Spent Steel Pickling Liquid

    Yu-Ling Wei; Yu-Shun Wang; Chia-Hung Liu

    2015-01-01

    Potassium ferrate (K2FeO4) is a multi-functional green reagent for water treatment with considerable combined effectiveness in oxidization, disinfection, coagulation, sterilization, adsorption, and deodorization, producing environment friendly Fe(III) end-products during the reactions. This study uses a simple method to lower Fe(VI) preparation cost by recycling iron from a spent steel pickling liquid as an iron source for preparing potassium ferrate with a wet oxidation method. The recycled ...

  13. Interfacial dislocations in (111) oriented (Ba{sub 0.7}Sr{sub 0.3})TiO{sub 3} films on SrTiO{sub 3} single crystal

    Shen, Xuan [National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, College of Engineering and Applied Science, and Collaborative Innovation Center of Advanced Materials, Nanjing University, Nanjing 210093 (China); Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973 (United States); Yamada, Tomoaki [Department of Materials, Physics and Energy Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Lin, Ruoqian; Xin, Huolin L.; Su, Dong, E-mail: dsu@bnl.gov [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973 (United States); Kamo, Takafumi; Funakubo, Hiroshi [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Wu, Di [National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, College of Engineering and Applied Science, and Collaborative Innovation Center of Advanced Materials, Nanjing University, Nanjing 210093 (China)

    2015-10-05

    We have investigated the interfacial structure of epitaxial (Ba,Sr)TiO{sub 3} films grown on (111)-oriented SrTiO{sub 3} single-crystal substrates using transmission electron microscopy (TEM) techniques. Compared with the (100) epitaxial perovskite films, we observe dominant dislocation half-loop with Burgers vectors of a〈110〉 comprised of a misfit dislocation along 〈112〉, and threading dislocations along 〈110〉 or 〈100〉. The misfit dislocation with Burgers vector of a〈110〉 can dissociate into two ½a〈110〉 partial dislocations and one stacking fault. We found the dislocation reactions occur not only between misfit dislocations, but also between threading dislocations. Via three-dimensional electron tomography, we retrieved the configurations of the threading dislocation reactions. The reactions between threading dislocations lead to a more efficient strain relaxation than do the misfit dislocations alone in the near-interface region of the (111)-oriented (Ba{sub 0.7}Sr{sub 0.3})TiO{sub 3} films.

  14. Preparation of Potassium Ferrate from Spent Steel Pickling Liquid

    Yu-Ling Wei

    2015-09-01

    Full Text Available Potassium ferrate (K2FeO4 is a multi-functional green reagent for water treatment with considerable combined effectiveness in oxidization, disinfection, coagulation, sterilization, adsorption, and deodorization, producing environment friendly Fe(III end-products during the reactions. This study uses a simple method to lower Fe(VI preparation cost by recycling iron from a spent steel pickling liquid as an iron source for preparing potassium ferrate with a wet oxidation method. The recycled iron is in powder form of ferrous (93% and ferric chlorides (7%, as determined by X-ray Absorption Near Edge Spectrum (XANES simulation. The synthesis method involves three steps, namely, oxidation of ferrous/ferric ions to form ferrate with NaOCl under alkaline conditions, substitution of sodium with potassium to form potassium ferrate, and continuously washing impurities with various organic solvents off the in-house ferrate. Characterization of the in-house product with various instruments, such as scanning electron microscopy (SEM, ultraviolet-visible (UV-Vis, X-ray diffraction (XRD, and X-ray absorption spectroscopy (XAS, proves that product quality and purity are comparative to a commercialized one. Methylene blue (MB de-colorization tests with in-house potassium ferrate shows that, within 30 min, almost all MB molecules are de-colorized at a Fe/carbon mole ratio of 2/1.

  15. Induced Superconductivity and Engineered Josephson Tunneling Devices in Epitaxial (111)-Oriented Gold/Vanadium Heterostructures.

    Wei, Peng; Katmis, Ferhat; Chang, Cui-Zu; Moodera, Jagadeesh S

    2016-04-13

    We report a unique experimental approach to create topological superconductors by inducing superconductivity into epitaxial metallic thin film with strong spin-orbit coupling. Utilizing molecular beam epitaxy technique under ultrahigh vacuum conditions, we are able to achieve (111) oriented single phase of gold (Au) thin film grown on a well-oriented vanadium (V) s-wave superconductor film with clean interface. We obtained atomically smooth Au thin films with thicknesses even down to below a nanometer showing near-ideal surface quality. The as-grown V/Au bilayer heterostructure exhibits superconducting transition at around 3.9 K. Clear Josephson tunneling and Andreev reflection are observed in S-I-S tunnel junctions fabricated from the epitaxial bilayers. The barrier thickness dependent tunneling and the associated subharmonic gap structures (SGS) confirmed the induced superconductivity in Au (111), paving the way for engineering thin film heterostructures based on p-wave superconductivity and nano devices exploiting Majorana Fermions for quantum computing. PMID:26943807

  16. Deposition of highly (111)-oriented PZT thin films by using metal organic chemical deposition

    Bu, K H; Choi, D K; Seong, W K; Kim, J D

    1999-01-01

    Lead zirconate titanate (PZT) thin films have been grown on Pt/Ta/SiNx/Si substrates by using metal organic chemical vapor deposition with Pb(C sub 2 H sub 5) sub 4 , Zr(O-t-C sub 4 H sub 9) sub 4 , and Ti(O-i-C sub 3 H sub 7) sub 4 as source materials and O sub 2 as an oxidizing gas. The Zr fraction in the thin films was controlled by varying the flow rate of the Zr source material. The crystal structure and the electrical properties were investigated as functions of the composition. X-ray diffraction analysis showed that at a certain range of Zr fraction, highly (111)-oriented PZT thin films with no pyrochlore phases were deposited. On the other hand, at low Zr fractions, there were peaks from Pb-oxide phases. At high Zr fractions, peaks from pyrochlore phase were seen. The films also showed good electrical properties, such as a high dielectric constant of more than 1200 and a low coercive voltage of 1.35 V.

  17. Structural and magnetic properties of (111) oriented annealed ultrathin Co/Pt multilayers

    Sharma, A.; Tripathi, S.; Tripathi, J.

    2016-05-01

    The effect of annealing on the structural and magnetic properties of Co/Pt multilayers was studied as a function of annealing temperature. The ultrathin layers of Pt and Co were deposited to make [Pt 1nm/Co 1nm]x20 multilayer on Si (100) substrate using MBE technique. The structural, magnetic and electronic properties were recorded using XRD, SQUID and XPS techniques, respectively. M-H loop of as deposited sample shows soft magnetic nature with coercivity value of 350 Oe which increases to 974 Oe in 500°C annealed film. When studied at low temperature (5K), the coercivity of 592 Oe is obtained in the as deposited sample which increases to 1626 Oe after annealing. In addition, as revealed by X-ray photoelectron spectroscopy, modifications in core level and valance band are observed. The observed changes in magnetic and electronic properties are attributed to structural modifications in correlation with the changes in (111) orientation of the films seen by X-ray diffraction.

  18. Epitaxial growth of (111)-oriented LaAlO$_3$/LaNiO$_3$ ultra-thin superlattices

    Middey, S.; Meyers, D.; Kareev, M.; Moon, E.J.; Gray, B. A.; Liu, X.; Freeland, J. W.; Chakhalian, J.

    2012-01-01

    The epitaxial stabilization of a single layer or superlattice structures composed of complex oxide materials on polar (111) surfaces is severely burdened by reconstructions at the interface, that commonly arise to neutralize the polarity. We report on the synthesis of high quality LaNiO$_3$/mLaAlO$_3$ pseudo cubic (111) superlattices on polar (111)-oriented LaAlO$_3$, the proposed complex oxide candidate for a topological insulating behavior. Comprehensive X-Ray diffraction measurements, RHEE...

  19. Ferrate(VI) and ferrate(V) oxidation of cyanide, thiocyanate, and copper(I) cyanide

    Cyanide (CN-), thiocyanate (SCN-), and copper(I) cyanide (Cu(CN)43-) are common constituents in the wastes of many industrial processes such as metal finishing and gold mining, and their treatment is required before the safe discharge of effluent. The oxidation of CN-, SCN-, and Cu(CN)43- by ferrate(VI) (FeVIO42-; Fe(VI)) and ferrate(V) (FeVO43-; Fe(V)) has been studied using stopped-flow and premix pulse radiolysis techniques. The rate laws for the oxidation of cyanides were found to be first-order with respect to each reactant. The second-order rate constants decreased with increasing pH because the deprotonated species, FeO42-, is less reactive than the protonated Fe(VI) species, HFeO4-. Cyanides react 103-105 times faster with Fe(V) than with Fe(VI). The Fe(V) reaction with CN- proceeds by sequential one-electron reductions from Fe(V) to Fe(IV) to Fe(III). However, a two-electron transfer process from Fe(V) to Fe(III) occurs in the reaction of Fe(V) with SCN- and Cu(CN)43-. The toxic CN- species of cyanide wastes is converted into relatively non-toxic cyanate (NCO-). Results indicate that Fe(VI) is highly efficient in removing cyanides from electroplating rinse water and gold mill effluent

  20. SYNTHESIS OF POTASSIUM FERRATE FOR USE IN TEXTILE WASTEWATER TREATMENT

    F Vaezi; A. Mesdaghinia; H. Jamani

    1999-01-01

    Potassium ferrate has been used as a multi-purpose chemical in treatment of wastewaters. With the formula of K2Fe04 it has 3 excellent characters for water treatment, so by using it alone, it would be possible to confine all reactivity, it is essential to prepare ferrate at the point of use. In this study, K2Fe04 was synthesized, then it has been employed for chlorine gas with an alkaline solution of ferric chloride, then it has been employed for textile wastewater treatment. Textile is one o...

  1. Helicoidal Ordering in Iron Perovskites

    Mostovoy, Maxim

    2005-04-01

    We study the double exchange in transition metal oxides with itinerant and localized electrons. We show that the charge transfer energy Δ and the oxygen-oxygen hopping amplitude tpp have a strong effect on magnetic ordering: while for Δ>0 the ground state is ferromagnetic, for negative Δ and large tpp the double exchange gives rise to an incommensurate helicoidal ordering of local spins, observed, e.g., in the iron perovskites SrFeO3 and CaFeO3. For negative Δ, the metal-insulator transition into a charge-ordered state has little effect on magnetic ordering. This explains the difference in magnetic and transport properties of ferrates and manganites.

  2. Investigation of electrochemical synthesis of ferrate - Part II: Optimization of the process parameters of ferrate(VI electrochemical synthesis

    Čekerevac Milan I.

    2010-01-01

    Full Text Available In part I [1] of the investigation the behavior of iron and selected low carbon steels in concentrated (10M - 15 M water solution of NaOH and KOH in wide range of electrode potentials, between hydrogen evolution reaction and oxygen evolution reaction, is investigated and discussed. On the base of experimental data obtained by LSV and galvanostatic pulse methods, it is concluded [1] that efficient synthesis of ferrate (VI can be expected in the region of anodic potentials between + 0,55 V and + 0,75 V against Hg|HgO reference electrode. In this paper optimization of electrolysis parameters of the electrochemical synthesis of ferrate(VI is elaborated. The most important parameters chosen for optimization process were: anode material, alkaline electrolyte concentration, regime of electrical potential control, current density and electrolyte temperature. The best current efficiency and yield of ferrate(VI synthesis of the explored anode materials (electrical steel, low carbon cold rolled steel plate, and structural steel is obtained when electrical steel with 3 wt% of silicon is applied. The worst current efficiency is obtained with anodes made of structural steel with higher concentration of manganese, chromium and nickel. The influence of alloying elements on the process of electrochemical synthesis of ferrate(VI is discussed in terms of their influence on formation and stability of anodic passive layer and oxygen evolution reaction. The increase of electrolyte concentration from 10M to 15M NaOH and KOH provided the increase of current efficiency with maximum obtained for 14M NaOH. The yield of ferrate(VI synthesis increases with temperature raise, having maximal value at about +50°C, and after that, at higher temperatures, instability of ferrate(VI increases and the yield of synthesis lessens. Considering the influence of electrical regime control it is concluded that the biggest yield of ferrate(VI can be expected with constant anodic potential

  3. Effect of post-treatment on photocatalytic oxidation activity of (111 oriented NaNbO3 film

    Feng Zhang

    2015-10-01

    Full Text Available We investigate the impact of post-treatment on photocatalytic oxidation activity of (111 oriented NaNbO3 film prepared by pulse laser deposition. Some impurities such as Na2Nb4O11 and bigger particles appear in the treated samples. The activity of rhodamine B degradation with N2 purge increases with the amount of ⋅OH, the sample treated under H2/Ar(7% being the highest activity, followed by under air and untreated one; the opposite trend is observed when the system was without N2 purge.

  4. Structural and dielectric properties of (001) and (111)-oriented BaZr0.2Ti0.8O3 epitaxial thin films

    We have grown and characterized BaZr0.2Ti0.8O3 (BZT) epitaxial thin films deposited on (001) and (111)-oriented SrRuO3-buffered SrTiO3 substrates by pulsed laser deposition. Structural and morphological characterizations were performed using X-ray diffractometry and atomic force microscopy, respectively. A cube-on-cube epitaxial relationship was ascertained from the θ-2θ and φ diffractograms in both (001) and (111)-oriented films. The (001)-oriented films showed a smooth granular morphology, whereas the faceted pyramid-like crystallites of the (111)-oriented films led to a rough surface. The dielectric response of BZT at room temperature was measured along the growth direction. The films were found to be ferroelectric, although a well-saturated hysteresis loop was obtained only for the (001)-oriented films. High leakage currents were observed for the (111) orientation, likely associated to charge transport along the boundaries of its crystallites. The remanent polarization, coercive field, dielectric constant, and relative change of dielectric permittivity (tunability) of (111)-oriented BZT were higher than those of (001)-oriented BZT.

  5. SYNTHESIS OF POTASSIUM FERRATE FOR USE IN TEXTILE WASTEWATER TREATMENT

    F. Vaezi

    1999-12-01

    Full Text Available Potassium ferrate has been used as a multi-purpose chemical in treatment of wastewaters. With the formula of K2Fe04 it has 3 excellent characters for water treatment, so by using it alone, it would be possible to confine all reactivity, it is essential to prepare ferrate at the point of use. In this study, K2Fe04 was synthesized, then it has been employed for chlorine gas with an alkaline solution of ferric chloride, then it has been employed for textile wastewater treatment. Textile is one of the industries with high significance for water pollution. Comparison of results with a conventional coagulant (FeC13 has shown that total COD and SS removal were about 27 to 29 and 0.7 to 2 percent more and the sludge volume was 2.5 times less, also, the required dose of K2Fe04 for this treatment. Another advantage of using ferrate is its ability in reducing bacterial content of wastewater. All the simplex treated by synthesized chemical was well disinfected.

  6. Electronic structures of [001]- and [111]-oriented InSb and GaSb free-standing nanowires

    We report on a theoretical study of the electronic structures of InSb and GaSb nanowires oriented along the [001] and [111] crystallographic directions. The nanowires are described by atomistic, tight-binding models, including spin-orbit interaction. The band structures and the wave functions of the nanowires are calculated by means of a Lanczos iteration algorithm. For the [001]-oriented InSb and GaSb nanowires, the systems with both square and rectangular cross sections are considered. Here, it is found that all the energy bands are doubly degenerate. Although the lowest conduction bands in these nanowires show good parabolic dispersions, the top valence bands show rich and complex structures. In particular, the topmost valence bands of the nanowires with a square cross section show a double maximum structure. In the nanowires with a rectangular cross section, this double maximum structure is suppressed, and the top valence bands gradually develop into parabolic bands as the aspect ratio of the cross section is increased. For the [111]-oriented InSb and GaSb nanowires, the systems with hexagonal cross sections are considered. It is found that all the bands at the Γ-point are again doubly degenerate. However, some of them will split into non-degenerate bands when the wave vector moves away from the Γ-point. Although the lowest conduction bands again show good parabolic dispersions, the topmost valence bands do not show the double maximum structure. Instead, they show a single maximum structure with its maximum at a wave vector slightly away from the Γ-point. The wave functions of the band states near the band gaps of the [001]- and [111]-oriented InSb and GaSb nanowires are also calculated and are presented in terms of probability distributions in the cross sections. It is found that although the probability distributions of the band states in the [001]-oriented nanowires with a rectangular cross section could be qualitatively described by one-band effective

  7. Vertically Aligned Ge Nanowires on Flexible Plastic Films Synthesized by (111)-Oriented Ge Seeded Vapor-Liquid-Solid Growth.

    Toko, Kaoru; Nakata, Mitsuki; Jevasuwan, Wipakorn; Fukata, Naoki; Suemasu, Takashi

    2015-08-19

    Transfer-free fabrication of vertical Ge nanowires (NWs) on a plastic substrate is demonstrated using a vapor-liquid-solid (VLS) method. The crystal quality of Ge seed layers (50 nm thickness) prepared on plastic substrates strongly influenced the VLS growth morphology, i.e., the density, uniformity, and crystal quality of Ge NWs. The metal-induced layer exchange yielded a (111)-oriented Ge seed layer at 325 °C, which allowed for the VLS growth of vertically aligned Ge NWs. The Ge NW array had almost the same quality as that formed on a bulk Ge(111) substrate. Transmission electron microscopy demonstrated that the Ge NWs were defect-free single crystals. The present investigation paves the way for advanced electronic optical devices integrated on a low-cost flexible substrate. PMID:26230716

  8. (111)-oriented Zn3N2 growth on a-plane sapphire substrates by molecular beam epitaxy

    (111)-oriented Zn3N2 thin films were grown on a-plane (112-bar0) sapphire substrates by plasma-assisted molecular beam epitaxy. Zn3N2/sapphire exhibits orientational relationships of out-of-plane parallel [112-bar0] and in-plane almost parallel [0001] and parallel [0001]. These specific orientations result from similar surface configurations of N atoms in Zn3N2 and Al atoms in sapphire at the interface. Under the optimum growth conditions, the film showed a full width at half maximum of 185 arcsec for an X-ray (222) diffraction rocking curve and a root-mean-square roughness of 8.5 A in an atomic force microscope image. These results suggest that a-plane sapphire is a suitable heteroepitaxial substrate for high-quality Zn3N2 thin films. (author)

  9. Settleability and characteristics of ferrate(VI)-induced particles in advanced wastewater treatment.

    Zheng, Lei; Deng, Yang

    2016-04-15

    Ferrate(VI) as an emerging water treatment agent has recently recaptured interests for advanced wastewater treatment. A large number of studies were published to report ferrate(VI)-driven oxidation for various water contaminants. In contrast, very few efforts were made to characterize ferrate(VI) resultant particles in water and wastewater. In this study, jar tests were performed to examine the settleability and characteristics of ferrate(VI)-induced iron oxide particles, particularly the non-settable fraction of these particles, after ferrate(VI) reduction in a biologically treated municipal wastewater. The particle settleability was evaluated through the measurement of turbidity and particulate iron concentration in the supernatant with the settling time. Results showed that a majority of ferrate(VI)-induced iron oxide aggregates remained suspended and caused an increased turbidity. For example, at a Fe(VI) dose of 5.0 mg/L and pH 7.50, 82% of the added iron remained in the supernatant and the turbidity was 8.97 NTU against the untreated sample turbidity (2.33 NTU) after 72-h settling. The poor settling property of these particles suggested that coagulation and flocculation did not perform well in the ferrate(VI) treatment. Particle size analysis and transmission electron microscopy (TEM) revealed that nano-scale particles were produced after ferrate(VI) decomposition, and gradually aggregated to form micro-scale larger particles in the secondary effluent. Zeta potentials of the non-settable ferrate(VI) resultant aggregates varied between -7.36 and -8.01 mV at pH 7.50 during the 72-h settling. The negative surface charges made the aggregates to be relatively stable in the wastewater matrix. PMID:26900976

  10. Treatment of selected pharmaceuticals by ferrate(VI): performance, kinetic studies and identification of oxidation products.

    Zhou, Zhengwei; Jiang, Jia-Qian

    2015-03-15

    The performance of ferrate(VI) in treating sulfamethoxazole (SMX), diclofenac (DCF), carbamazepine (CBZ) and bezafibrate (BZF) in test solutions containing the four compounds was investigated. A series of jar-test experiments was performed on a bench-scale at pH 6-9 and at a ferrate(VI) dose of 1-5 mg Fe/L. The results suggested that ferrate(VI) can effectively remove SMX, DCF and CBZ from the test solutions, with greater than 80% removal under optimum conditions. However, the removal efficiency of BZF was very low, less than 25% under the studied conditions. Increasing the dose of ferrate(VI) improved the treatment performance, while the influence of solution pH on ferrate(VI) performance varied among the different target compounds. Ferrate(VI) demonstrated the highest reactivity with SMX at pH 8 and pH 9 (20 °C), with apparent second-order rate constants of 360±17 M(-1) s(-1) and 1.26±0.02 M(-1) s(-1), respectively. However, BZF showed the lowest removal by ferrate(VI) with the smallest rate constants (less than 0.5 M(-1) s(-1)) at pH 8 and pH 9. Furthermore, a number of oxidation products (OPs) of SMX, DCF and CBZ during ferrate(VI) oxidation were detected by liquid chromatography and mass spectrometry (LC-MS), and their degradation pathways were tentatively proposed. No OPs of BZF were detected during ferrate(VI) oxidation. PMID:25063450

  11. STUDI DEGRADASI ZAT PEWARNA AZO, METIL ORANYE MENGGUNAKAN FERRAT (FeO42-)

    Dian Windy Dwiasi; Mardiyah Kurniasih

    2008-01-01

    Synthesis of ferrate and its application to azo dyes degradation have been investigated. The synthesis was carried out by reacting Fe(NO3)3 solution with NaOCl in alkaline condition. Oxidation reaction of azo dyes was carried out by adjusting the molar ratio of ferrate to azo dyes. When ferrate reacted with azo dyes, its absorbance was monitored using UV-Vis spectrophotometer at pH condition that had been optimized. Kinetics study for azo dyes degradation was carried out at the absorbance max...

  12. Efficient iodination of aromatic compounds using potassium ferrate supported on montmorillonite

    Hoda Keipour; Mohammad A. Khalilzadeh; Bita Mohtat; Abolfazl Hosseini; Daryoush Zareyee

    2011-01-01

    Potassium ferrate impregnated on montmorillonite is a mild, cheap, and non-toxic reagent for the iodination of phenols, including naphthol, aromatic amines, and heterocyclic substrates in fair to excellent yields by a simple isolation procedure.

  13. Treatment of combined sewer overflows using ferrate (VI).

    Gandhi, Rohan; Ray, Ajay K; Sharma, Virender K; Nakhla, George

    2014-11-01

    This paper presents the results of a study conducted on the treatment of combined sewer overflows using ferrate (VI) [Fe (VI)]. At a Fe (VI) dose of 0.24 mg/L, total chemical oxygen demand (TCOD), soluble chemical oxygen demand (SCOD), total biochemical oxygen demand (TBOD5), soluble biochemical oxygen demand (SBOD5), total suspended solids (TSS), volatile suspended solids (VSS), total phosphorus (TP), total nitrogen (TN), and soluble TN removal efficiencies of 71, 75, 69, 68, 72, 83, 64, 38, and 36%, respectively, were achieved. Kinetic studies revealed that a contact time of only 15 minutes is sufficient to achieve secondary effluent criteria. An innovative technique of using primary sludge (PS) and thickened waste activated sludge as a source for the in situ synthesis of ferrate was developed. A comparative study of treatment efficiencies achieved by Fe (VI) generated from different sources was done. At 0.1 mg/L dose of Fe (VI) synthesized from PS, TCOD, SCOD, TSS, VSS, TP, and TN removal efficiencies of 60, 62, 63, 67, 30, and 25%, respectively, were achieved. PMID:25509525

  14. Anàlisi de l'obra narrativa de Ferrater Mora des de la seva filosofia

    Bardera Poch, Damià

    2015-01-01

    In this thesis we offer a philosophical reading of Josep Ferrater Mora’s narrative work, starting from Ferrater Mora’s philosophical thought. Thus, this is an intraferraterian doctoral thesis, which aims at proving that Ferrater Mora’s narrative work literarily reflects some of the key concepts and proposals of his thought: integrationism, the dispositions of being and meaning, some aspects of applied ethics, his philosophical anthropology and the importance of death. Regarding the secondary ...

  15. STUDI DEGRADASI ZAT PEWARNA AZO, METIL ORANYE MENGGUNAKAN FERRAT (FeO42-

    Dian Windy Dwiasi

    2008-05-01

    Full Text Available Synthesis of ferrate and its application to azo dyes degradation have been investigated. The synthesis was carried out by reacting Fe(NO33 solution with NaOCl in alkaline condition. Oxidation reaction of azo dyes was carried out by adjusting the molar ratio of ferrate to azo dyes. When ferrate reacted with azo dyes, its absorbance was monitored using UV-Vis spectrophotometer at pH condition that had been optimized. Kinetics study for azo dyes degradation was carried out at the absorbance maximum of azo dyes, as a function of time. Ferrate can oxidize azo dyes, methyl oranye effectively in optimum pH of 9.6. With the molar ratio of ferrate/azo dyes 5/1, it showed that the percentages of methyl oranye degradation reached 100%. The azo dyes degradation followed first order of kinetics. Analysis using UV-Vis spectrofotometry suggests that the products of azo dyes degradation are nitrate, ammonia, and benzene. This results showed that ferrate is an alternative and green oxidizing agent which can be used for azo dyes degradation.

  16. Magnetism and electronic structure of (001)- and (111)-oriented LaTiO{sub 3} bilayers sandwiched in LaScO{sub 3} barriers

    Weng, Yakui; Dong, Shuai, E-mail: sdong@seu.edu.cn [Department of Physics and Jiangsu Key Laboratory of Advanced Metallic Materials, Southeast University, Nanjing 211189 (China)

    2015-05-07

    In this study, the magnetism and electronic structure of LaTiO{sub 3} bilayers along both the (001) and (111) orientations are calculated using the density functional theory. The band insulator LaScO{sub 3} is chosen as the barrier layer and substrate to obtain the isolating LaTiO{sub 3} bilayer. For both the (001)- and (111)-oriented cases, LaTiO{sub 3} demonstrates the G-type antiferromagnetism as the ground state, similar to the bulk material. However, the electronic structure is significantly changed. The occupied bands of Ti are much narrower in the (111) case, giving a nearly flat band. As a result, the exchange coupling between nearest-neighbor Ti ions is reformed in these superlattices, which will affect the Néel temperature significantly.

  17. Enhanced ferroelectric and dielectric properties of (111)-oriented highly cation-ordered PbSc0.5Ta0.5O3 thin films

    Cation-ordered (111)-oriented epitaxial PbSc0.5Ta0.5O3 (PST) thin films were deposited by pulsed laser deposition on SrRuO3-electroded SrTiO3 (111) substrates at three different temperatures of 525 °C, 550 °C, and 575 °C. All the films were well crystalline and (111)-oriented at all the three growth temperatures; however, the films deposited at the temperatures other than 550 °C exhibited the presence of a pyrochlore phase. X-ray diffraction analysis and transmission electron microscopy measurements revealed that the films were epitaxial and highly cation-ordered. In comparison to (001)-oriented PST films, (111)-oriented films on SrRuO3/SrTiO3 (111) exhibited enhanced ferroelectric and dielectric properties with a broad size distribution of cation-ordered domains (5–100 nm). At a measurement temperature of 100 K, the remnant polarization of PST (111) films is almost √3 times larger than the remnant polarization observed for (001)-oriented PST films, which is attributed to the (111) orientation of the films, as the spontaneous polarization in PST lies close to the [111] direction. The observed dielectric constant and loss at 1 kHz were around 1145 and 0.11, respectively. The dielectric constant is thus almost three times higher than for previously reported (001)-oriented PST thin films, most probably due to the enhancement in cation-ordering

  18. Magnetic field-dependent polarization of (111)-oriented PZT–Co ferrite nanobilayer: Effect of Co ferrite composition

    The perfect (111)-oriented PZT/CFO (CFO=CoFe2O4, Co0.8Fe2.2O4 and Co0.6Mn0.2Fe2.2O4) bilayer multiferroic thin films were grown on Pt(111)/Si substrate at 600 °C using pulsed laser deposition technique. The precision X-ray diffraction analysis (avoiding the shift of peak due to the sample misalignment) revealed that the CFO films on Pt(111)/Si substrate were under an out-of-plane contraction and deposition of PZT top layer led to more increase in the out-of-plane contraction, i.e. increase in the residual stresses. The PZT and CFO layers have significant effects on magnetic and ferroelectric properties of PZT/CFO bilayer films, respectively, leading to an enhanced in-plane magnetic anisotropy as well as increased and asymmetric polarization. The effect of composition of CFO layer on magnetic field-dependent polarization of PZT/CFO bilayer films was investigated by applying the magnetic field during P-E measurement. The polarization of PZT films were increased by applying the magnetic field as a result of strain transferred from magnetostrictive CFO underlayer. This increase in polarization for PZT/Co0.6Mn0.2Fe2.2O4 was higher than that for PZT/Co0.8Fe2.2O4 and both of them were significantly higher than that for PZT/CoFe2O4 bilayer film, which was discussed based on their magnetostriction properties. - Highlights: • The effect of composition of CFO on P–E characteristics of PZT/CFO films was investigated. • The polarization of PZT films were increased by applying the magnetic field. • The increasing polarization was a result of strain from magnetostrictive CFO underlayer

  19. Magnetic field-dependent polarization of (111)-oriented PZT–Co ferrite nanobilayer: Effect of Co ferrite composition

    Khodaei, M. [Advanced Magnetic Materials Research Center, School of Metallurgy and Materials, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Faculty of Materials Science and Engineering, K. N. Toosi University of Technology, Tehran (Iran, Islamic Republic of); Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of); Seyyed Ebrahimi, S.A., E-mail: saseyyed@ut.ac.ir [Advanced Magnetic Materials Research Center, School of Metallurgy and Materials, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Jun Park, Yong [Pohang Accelerator Laboratory, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of); Son, Junwoo; Baik, Sunggi [Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of)

    2015-05-15

    The perfect (111)-oriented PZT/CFO (CFO=CoFe{sub 2}O{sub 4}, Co{sub 0.8}Fe{sub 2.2}O{sub 4} and Co{sub 0.6}Mn{sub 0.2}Fe{sub 2.2}O{sub 4}) bilayer multiferroic thin films were grown on Pt(111)/Si substrate at 600 °C using pulsed laser deposition technique. The precision X-ray diffraction analysis (avoiding the shift of peak due to the sample misalignment) revealed that the CFO films on Pt(111)/Si substrate were under an out-of-plane contraction and deposition of PZT top layer led to more increase in the out-of-plane contraction, i.e. increase in the residual stresses. The PZT and CFO layers have significant effects on magnetic and ferroelectric properties of PZT/CFO bilayer films, respectively, leading to an enhanced in-plane magnetic anisotropy as well as increased and asymmetric polarization. The effect of composition of CFO layer on magnetic field-dependent polarization of PZT/CFO bilayer films was investigated by applying the magnetic field during P-E measurement. The polarization of PZT films were increased by applying the magnetic field as a result of strain transferred from magnetostrictive CFO underlayer. This increase in polarization for PZT/Co{sub 0.6}Mn{sub 0.2}Fe{sub 2.2}O{sub 4} was higher than that for PZT/Co{sub 0.8}Fe{sub 2.2}O{sub 4} and both of them were significantly higher than that for PZT/CoFe{sub 2}O{sub 4} bilayer film, which was discussed based on their magnetostriction properties. - Highlights: • The effect of composition of CFO on P–E characteristics of PZT/CFO films was investigated. • The polarization of PZT films were increased by applying the magnetic field. • The increasing polarization was a result of strain from magnetostrictive CFO underlayer.

  20. Oxidation of Oil Sands Process-Affected Water by Potassium Ferrate(VI).

    Wang, Chengjin; Klamerth, Nikolaus; Huang, Rongfu; Elnakar, Haitham; Gamal El-Din, Mohamed

    2016-04-19

    This paper investigates the oxidation of oil sands process-affected water (OSPW) by potassium ferrate(VI). Due to the selectivity of ferrate(VI) oxidation, two-ring and three-ring fluorescing aromatics were preferentially removed at doses removed only at doses ≥100 mg/L Fe(VI). Ferrate(VI) oxidation achieved 64.0% and 78.4% removal of naphthenic acids (NAs) at the dose of 200 mg/L and 400 mg/L Fe(VI) respectively, and NAs with high carbon number and ring number were removed preferentially. (1)H nuclear magnetic resonance ((1)H NMR) spectra indicated that the oxidation of fluorescing aromatics resulted in the opening of some aromatic rings. Electron paramagnetic resonance (EPR) analysis detected signals of organic radical intermediates, indicating that one-electron transfer is one of the probable mechanisms in the oxidation of NAs. The inhibition effect of OSPW on Vibrio fischeri and the toxicity effect on goldfish primary kidney macrophages (PKMs) were both reduced after ferrate(VI) oxidation. The fluorescing aromatics in OSPW were proposed to be an important contributor to this acute toxicity. Degradation of model compounds with ferrate(VI) was also investigated and the results confirmed our findings in OSPW study. PMID:27008571

  1. STUDI PENURUNAN ZAT WARNA ACID ORANGE 7 DENGAN PROSES OKSIDASI MENGGUNAKAN FERRAT (FeO42-

    Dian Windy Dwiasi

    2011-05-01

    Full Text Available Colour removal from textile wastewater has been a matter of considerable interest during the last two decades, not only because of the potential toxicity of certain dyes but often due to their visibility in receiving waters and to their low biodegradability. Due to the limited success of some physical and chemical techniques for the treatment of dye effluents it is necessary to develop destructive systems leading to complete mineralization or, at least, to less harmful or easy-to-treat compounds. Oxidation processes using ferrate (FeO42- have been found to be very effective in the degradation of dye pollutants and for the treatment of waste waters from the textile industry. Acid Orange 7 (AO7 commonly used as a textile dye and could be degraded by ferrate oxidation processes. In the oxidation degradation of dye by ferrate process, effect of some parameters such as time, pH, and molar ratio of dye was examined at experimental condition. AO7 removal by this process was calculated to be equal to 12 minute at experimental condition. Ferrate can oxidize acid orange 7 effectively at optimum pH of 9.8, with the molar ratio of ferrate : acid orange 7 at 4:1. The percentages of acid orange 7 degradation reached to 98.9%.

  2. On Josep Ferrater Mora’s integrationism : the possibility of oscillating

    Sales i Coderch, Jordi R.

    2014-01-01

    En l’escrit que segueix volem posar en joc l’«integracionisme» de Ferrater Mora en una consideració més general de la dicotomia dogmatisme-escepticisme en teoria del coneixement. La clau que significa l’«oscil·lació» en la definició ferrateriana de l’integracionisme se’ns descobrirà com a eina d’aclariment de la tensió irresolta en la dicotomia i també com a dificultat en si mateixa This paper sets Ferrater Mora’s integrationist philosophy against the larger background of the opposition be...

  3. Ferrate(VI): a novel oxidant for degradation of cationic surfactant - cetylpyridinium bromide.

    Yang, Weihua; Lin, Xiaoyan; Wang, Honghui; Yang, Wutao

    2013-01-01

    Ferrate(VI) is an efficient multi-functional water treatment reagent that has several novel properties, such as strong oxidation, absorption, flocculation, disinfection and deodorization. The removal of cationic surfactants based on ferrate (K2FeO4) was performed in the case of cetylpyridinium bromide (CPB). The influence of operating variables on the mineralization efficiency was studied as a function of ferrate dosage, initial pH and reaction time. Total organic carbon (TOC), UV and infrared spectra were performed to gain a better understanding of the degradation process. Results show that the optimal treatment conditions are as follows, solution initial pH is over 5, oxidation time is 5 min and ferrate dosage is 1.5 times that of CPB. The removal efficiency of CPB above 99% and TOC removal percentage of 91.3% can be achieved in minutes. The reaction of CPB with K2FeO4 responds to a second-order kinetic law. PMID:23676386

  4. Synthesis of potassium ferrate using residual ferrous sulfate as iron bearing material

    This paper summarizes the results obtained during potassium ferrate (K2FeVIO4) synthesis which is a high added value material. This compound that contains iron in the rare hexavalent state is becoming a substance of growing importance for the water and effluent treatment industries. This is due to its multi-functional nature (oxidation, flocculation, elimination of heavy metals, decomposition of organic matter, etc.). The most well known synthesis methods for potassium ferrate synthesis are those involving the chemical and/or electrochemical oxidation of iron (II) and (III) from aqueous solutions having a high alkali concentration. These methods are generally characterized by a low FeVI efficiency due to the reaction of the potassium ferrate with water, leading to the reduction of FeVI into FeIII. Concerning the work pertinent to this paper, the synthesis of K2FeVIO4 was achieved by a simultaneous reaction of two solids (iron sulfate and KOH) and one gaseous oxidant (chlorine). The synthesis process is performed in a rotary reactor at room temperature and the global synthesis reaction is exothermic. The effects of different experimental parameters on the potassium ferrate synthesis are investigated to determine the optimal conditions for the process.

  5. Removal of Estrogenic Compounds in Dairy Waste Lagoons by Ferrate (VI): Oxidation/Coagulation

    Ferrate(VI) was used to break down and/or remove steroidal estrogens (SE) from dairy waste lagoon effluent (DWLE). Dairy lagoon sites were sampled for estrogenic content (EC) and assayed using high performance liquid chromatography coupled to triple quadrupole mass spectrometry. Effects of varying...

  6. Application of electrochemically synthesized ferrate(VI in the purification of wastewater from coal separation plant

    Čekerevac Milan I.

    2010-01-01

    Full Text Available The oxidative and coagulation efficiency of Na2FeO4 solution, electrochemically generated by trans-passive anodic oxidation of electrical steel in 10M NaOH solution, is confirmed in the process of purification of heavily contaminated wastewater from coal separation plant. The decontamination efficiency is evaluated comparing the values of selected contamination parameters obtained by chemical and biochemical analysis of plant effluent water and water obtained after decontamination with ferrate(VI solution in relatively simple laboratory procedure. The sample of 450 ml of wastewater is treated in laboratory conditions with 100cm3 solution of 1 mg dm-3 Na2FeO4 in 10M NaOH. The chemical analysis of effluent water after treatment have shown almost 3 times lower permanganate index, about 3 times lower iron content, 1.45 times lower As3+ content, 7.35 times lower ammonia content. Turbidity and chemical oxygen demand (COD is reduced for more than 5.77and 13.4 times, respectively. The suspended and colloid matter is eliminated from effluent water after treatment with ferrate(VI solution. Also, biochemical exploration has confirmed high efficiency of ferrate(VI in organics and microbial elimination showing 7.1 times lower 5-days bio-chemical oxygen demand (BOD5, and total elimination of aerobic and anaerobic bacteria from effluent water. According to standards on quality of industrial wastewater effluents, it may be concluded that ferrate(VI treatment of wastewater almost completely eliminates excess of dangerous chemicals and pathogen bacteria, with the exemption of arsenic. Thus, ferrate(VI shows capable performance in treatment of coal separation plant wastewater.

  7. Treatment of chemical warfare agents by zero-valent iron nanoparticles and ferrate(VI)/(III) composite

    Highlights: ► Ferrate(VI) has been found to be highly efficient to decontaminate chemical warfare agents. ► Fast degradation of sulfur mustard, soman and compound VX by ferrate(VI). ► Nanoscale zero-valent iron particles are considerably less efficient in degradation of studied warfare agents compared to ferrate(VI). - Abstract: Nanoscale zero-valent iron (nZVI) particles and a composite containing a mixture of ferrate(VI) and ferrate(III) were prepared by thermal procedures. The phase compositions, valence states of iron, and particle sizes of iron-bearing compounds were determined by combination of X-ray powder diffraction, Mössbauer spectroscopy and scanning electron microscopy. The applicability of these environmentally friendly iron based materials in treatment of chemical warfare agents (CWAs) has been tested with three representative compounds, sulfur mustard (bis(2-chlorethyl) sulfide, HD), soman ((3,3′-imethylbutan-2-yl)-methylphosphonofluoridate, GD), and O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX). Zero-valent iron, even in the nanodimensional state, had a sluggish reactivity with CWAs, which was also observed in low degrees of CWAs degradation. On the contrary, ferrate(VI)/(III) composite exhibited a high reactivity and complete degradations of CWAs were accomplished. Under the studied conditions, the estimated first-order rate constants (∼10−2 s−1) with the ferrate(VI)/(III) composite were several orders of magnitude higher than those of spontaneous hydrolysis of CWAs (10−8–10−6 s−1). The results demonstrated that the oxidative technology based on application of ferrate(VI) is very promising to decontaminate CWAs.

  8. Síntese eletroquímica do ion ferrato(VI) Eletrochemical synthesis of iron(VI) ferrate

    Maria Augusta de Luca; Sérgio João de Luca; Maria Alice Santana

    2003-01-01

    The optimization of ferrate(VI) ion generation has been studied due to its favorable characteristics for application in several fields, including environmental quality control. The paper presents the best conditions for electrolytic generation of ferrate(VI) in alkaline media. An appropriate electrolyte was NaOH, 10 mol/L. Circulation of the electrolyte solution was important to avoid acidification close to the anode surface. An anode pre-cleaning with 10% HCl was more efficient than a cathod...

  9. Simultaneous achievement of high dielectric constant and low temperature dependence of capacitance in (111)-oriented BaTiO3-Bi(Mg0.5Ti0.5)O3-BiFeO3 solid solution thin films

    Kimura, Junichi; Chentir, Mohamed-Tahar; Shimizu, Takao; Uchida, Hiroshi; Funakubo, Hiroshi

    2016-01-01

    The temperature dependence of the capacitance of (111)c-oriented (0.90-x)BaTiO3-0.10Bi(Mg0.5Ti0.5)O3-xBiFeO3 solid solution films is investigated. These films are prepared on (111)cSrRuO3/(111)Pt/TiO2/SiO2/(100)Si substrates by the chemical solution deposition technique. All the films have perovskite structures and the crystal symmetry at room temperature varies with increasing x ratio, from pseudocubic when x = 0-0.30 to rhombohedral when x = 0.50-0.90. The pseudocubic phase shows a high relative dielectric constant (ɛr) (ranging between 400 and 560 at room temperature and an operating frequency of 100 kHz) and a low temperature dependence of capacitance up to 400°C, while maintaining a dielectric loss (tan δ) value of less than 0.2 at 100 kHz. In contrast, ɛr for the rhombohedral phase increases monotonically with increasing temperature up to 250°C, and increasingly high tan δ values are recorded at higher temperatures. These results indicate that pseudocubic (0.90-x)BaTiO3-0.10Bi(Mg0.5Ti0.5)O3-xBiFeO3 solid solution films with (111) orientation are suitable candidates for high-temperature capacitor applications.

  10. The Handheld Library: Developments at the Rector Gabriel Ferraté Library, UPC

    Beatriz Benítez Juan; Javier Clavero Campos; Miquel Codina Vila; Andrés Pérez Gálvez

    2011-01-01

    The purpose of this paper is to highlight the mobile services developed by the Rector Gabriel Ferraté Library (BRGF) of the Universitat Politècnica de Catalunya (UPC Barcelona Tech) in Barcelona, Spain. We hope this paper will be of use to other libraries exploring new technologies for communicating and delivering their services to users at a time when mobile services are an emerging topic in librarianship and information science literature. By setting out the successive steps involved in ...

  11. Formation of bromate during ferrate(VI) oxidation of bromide in water.

    Huang, Xin; Deng, Yang; Liu, Shuang; Song, Yali; Li, Nanzhu; Zhou, Jizhi

    2016-07-01

    Ferrate (VI) is traditionally recognized as a safe oxidant without production of disinfection byproducts (DBPs). However, here we detected probable carcinogenic bromate (BrO3(-)) during ferrate(VI) oxidation of bromide (Br(-))-containing water, and evaluated the effects of pH, ferrate(VI) dose, initial Br(-) concentration, and co-existing anions on the BrO3(-) formation. BrO3(-) was produced at a moderately-weakly acidic pH condition and in the absence of phosphate that was commonly applied as a buffer and stabilizing agent in previous ferrate(VI) studies. At pH 5.0, the produced BrO3(-) was increased from 12.5 to 273.8 μg/L with the increasing initial Br(-) concentration from 200 to 1000 μg/L at 10 mg/L Fe(VI), corresponding to an increase in the molar conversion ([BrO3(-)]/initial [Br(-)]) from 2.3% to 10.3%, in a bicarbonate-buffered solution. As pH increased to 7.0, the BrO3(-) concentration gradually dropped. The BrO3(-) production appeared to be associated with the oxidation by high valence iron species (i.e. Fe(VI), Fe(V) and Fe(IV)). Two key intermediate products (i.e. hypobromous acid/hypobromite (HOBr/OBr(-)) and hydrogen peroxide (H2O2)) relevant to the bromate formation were identified. The production of HOBr, a requisite intermediate for the ensuing bromate formation, was indirectly validated through identification of bromine-containing trihalomethanes and haloacetic acids during ferrate oxidation in a natural water, though these bromo-organic DBPs produced were insignificant. Furthermore, the inhibition effects of various anions on the formation of BrO3(-) followed chloride H2O2 was detected at higher phosphate concentration. It could reduce HOBr to Br(-), thereby inhibiting the bromate formation. PMID:27153235

  12. Phenomenological theory of phase transitions in epitaxial BaxSr1-xTiO3 thin films on (111)-oriented cubic substrates

    Shirokov, V. B.; Shakhovoy, R. A.; Razumnaya, A. G.; Yuzyuk, Yu. I.

    2015-07-01

    A phenomenological thermodynamic theory of BaxSr1-xTiO3 (BST-x) thin films epitaxially grown on (111)-oriented cubic substrates is developed using the Landau-Devonshire approach. The group-theoretical analysis of the low-symmetry phases was performed taking into account two order parameters: the polarization related to ionic shifts in polar zone-center F1u mode and the out-of-phase rotation of TiO6 octahedra corresponding to the R25 zone-boundary mode in the parent cubic phase P m 3 ¯ m . The eight-order thermodynamic potential for BST-x solid solutions was developed and analyzed. We constructed the "concentration-misfit strain" phase diagram for BST-x thin films at room temperature and found that polar rhombohedral R3m phase with the polarization normal to the substrate is stable for x > 0.72 and negative misfit strains, while ferroelectric monoclinic C2 and Cm phases with in-plane polarization are stable for much smaller x and positive or slightly negative misfit strains. We constructed the "temperature-misfit strain" phase diagrams for several concentrations (x = 1, 0.8, 0.6, 0.4, and 0.2). Systematic changes of the phase transition lines between the paraelectric and ferroelectric phases are discussed. The phase diagrams are useful for practical applications in thin-film engineering.

  13. Enhanced ferroelectric and dielectric properties of (111)-oriented highly cation-ordered PbSc{sub 0.5}Ta{sub 0.5}O{sub 3} thin films

    Chopra, Anuj [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Saale) (Germany); Faculty of Science and Technology, MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); Birajdar, Balaji I. [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Saale) (Germany); Special Centre for Nano Sciences, Jawaharlal Nehru University, New Delhi 110067 (India); Kim, Yunseok [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Saale) (Germany); School of Advanced Materials Science and Engineering, Sungkyunkwan University (SKKU), Suwon 440-746 (Korea, Republic of); Alexe, Marin [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Saale) (Germany); Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Hesse, Dietrich [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Saale) (Germany)

    2013-12-14

    Cation-ordered (111)-oriented epitaxial PbSc{sub 0.5}Ta{sub 0.5}O{sub 3} (PST) thin films were deposited by pulsed laser deposition on SrRuO{sub 3}-electroded SrTiO{sub 3} (111) substrates at three different temperatures of 525 °C, 550 °C, and 575 °C. All the films were well crystalline and (111)-oriented at all the three growth temperatures; however, the films deposited at the temperatures other than 550 °C exhibited the presence of a pyrochlore phase. X-ray diffraction analysis and transmission electron microscopy measurements revealed that the films were epitaxial and highly cation-ordered. In comparison to (001)-oriented PST films, (111)-oriented films on SrRuO{sub 3}/SrTiO{sub 3} (111) exhibited enhanced ferroelectric and dielectric properties with a broad size distribution of cation-ordered domains (5–100 nm). At a measurement temperature of 100 K, the remnant polarization of PST (111) films is almost √3 times larger than the remnant polarization observed for (001)-oriented PST films, which is attributed to the (111) orientation of the films, as the spontaneous polarization in PST lies close to the [111] direction. The observed dielectric constant and loss at 1 kHz were around 1145 and 0.11, respectively. The dielectric constant is thus almost three times higher than for previously reported (001)-oriented PST thin films, most probably due to the enhancement in cation-ordering.

  14. Simultaneous achievement of high dielectric constant and low temperature dependence of capacitance in (111-oriented BaTiO3-Bi(Mg0.5Ti0.5O3-BiFeO3 solid solution thin films

    Junichi Kimura

    2016-01-01

    Full Text Available The temperature dependence of the capacitance of (111c-oriented (0.90–xBaTiO3-0.10Bi(Mg0.5Ti0.5O3-xBiFeO3 solid solution films is investigated. These films are prepared on (111cSrRuO3/(111Pt/TiO2/SiO2/(100Si substrates by the chemical solution deposition technique. All the films have perovskite structures and the crystal symmetry at room temperature varies with increasing x ratio, from pseudocubic when x = 0–0.30 to rhombohedral when x = 0.50–0.90. The pseudocubic phase shows a high relative dielectric constant (εr (ranging between 400 and 560 at room temperature and an operating frequency of 100 kHz and a low temperature dependence of capacitance up to 400°C, while maintaining a dielectric loss (tan δ value of less than 0.2 at 100 kHz. In contrast, εr for the rhombohedral phase increases monotonically with increasing temperature up to 250°C, and increasingly high tan δ values are recorded at higher temperatures. These results indicate that pseudocubic (0.90–xBaTiO3-0.10Bi(Mg0.5Ti0.5O3-xBiFeO3 solid solution films with (111 orientation are suitable candidates for high-temperature capacitor applications.

  15. Oxidation of triclosan by ferrate: Reaction kinetics, products identification and toxicity evaluation

    Yang Bin [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Ying Guangguo, E-mail: guang-guo.ying@csiro.au [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Zhao Jianliang; Zhang Lijuan; Fang Yixiang [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Nghiem, Long Duc [School of Civil Mining and Environmental Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia)

    2011-02-15

    Research highlights: {yields} Triclosan reacted rapidly with ferrate. {yields} Oxidation resulted in a decrease in algal toxicity. {yields} No inhibition of algae growth from ferrate. - Abstract: The oxidation of triclosan by commercial grade aqueous ferrate (Fe(VI)) was investigated and the reaction kinetics as a function of pH (7.0-10.0) were experimentally determined. Intermediate products of the oxidation process were characterized using both GC-MS and RRLC-MS/MS techniques. Changes in toxicity during the oxidation process of triclosan using Fe(VI) were investigated using Pseudokirchneriella subcapitata growth inhibition tests. The results show that triclosan reacted rapidly with Fe(VI), with the apparent second-order rate constant, k{sub app}, being 754.7 M{sup -1} s{sup -1} at pH 7. At a stoichiometric ratio of 10:1 (Fe(VI):triclosan), complete removal of triclosan was achieved. Species-specific rate constants, k, were determined for reaction of Fe(VI) with both the protonated and deprotonated triclosan species. The value of k determined for neutral triclosan was 6.7({+-}1.9) x 10{sup 2} M{sup -1} s{sup -1}, while that measured for anionic triclosan was 7.6({+-}0.6) x 10{sup 3} M{sup -1} s{sup -1}. The proposed mechanism for the oxidation of triclosan by the Fe(VI) involves the scission of ether bond and phenoxy radical addition reaction. Coupling reaction may also occur during Fe(VI) degradation of triclosan. Overall, the degradation processes of triclosan resulted in a significant decrease in algal toxicity. The toxicity tests showed that Fe(VI) itself dosed in the reaction did not inhibit green algae growth.

  16. Oxidation of triclosan by ferrate: Reaction kinetics, products identification and toxicity evaluation

    Research highlights: → Triclosan reacted rapidly with ferrate. → Oxidation resulted in a decrease in algal toxicity. → No inhibition of algae growth from ferrate. - Abstract: The oxidation of triclosan by commercial grade aqueous ferrate (Fe(VI)) was investigated and the reaction kinetics as a function of pH (7.0-10.0) were experimentally determined. Intermediate products of the oxidation process were characterized using both GC-MS and RRLC-MS/MS techniques. Changes in toxicity during the oxidation process of triclosan using Fe(VI) were investigated using Pseudokirchneriella subcapitata growth inhibition tests. The results show that triclosan reacted rapidly with Fe(VI), with the apparent second-order rate constant, kapp, being 754.7 M-1 s-1 at pH 7. At a stoichiometric ratio of 10:1 (Fe(VI):triclosan), complete removal of triclosan was achieved. Species-specific rate constants, k, were determined for reaction of Fe(VI) with both the protonated and deprotonated triclosan species. The value of k determined for neutral triclosan was 6.7(±1.9) x 102 M-1 s-1, while that measured for anionic triclosan was 7.6(±0.6) x 103 M-1 s-1. The proposed mechanism for the oxidation of triclosan by the Fe(VI) involves the scission of ether bond and phenoxy radical addition reaction. Coupling reaction may also occur during Fe(VI) degradation of triclosan. Overall, the degradation processes of triclosan resulted in a significant decrease in algal toxicity. The toxicity tests showed that Fe(VI) itself dosed in the reaction did not inhibit green algae growth.

  17. Mobile services in the Rector Gabriel Ferraté Library - Technical University of Catalonia

    Codina Vila, Miquel; Pérez Gálvez, Andrés; Clavero Campos, Javier

    2010-01-01

    Purpose – The purpose of this paper is to compile and explain the mobile services developed by the Rector Gabriel Ferraté Library (BRGF) of the Technical University of Catalonia (UPC), in Barcelona, Spain. From a larger amount of technological features that distinguish the BRGF, only those with a main mobile component are grouped here. Design/methodology/approach – A case study perspective is used to give a detailed picture of the mobile services and features offered by the library in bot...

  18. Hybrid Perovskite/Perovskite Heterojunction Solar Cells.

    Hu, Yinghong; Schlipf, Johannes; Wussler, Michael; Petrus, Michiel L; Jaegermann, Wolfram; Bein, Thomas; Müller-Buschbaum, Peter; Docampo, Pablo

    2016-06-28

    Recently developed organic-inorganic hybrid perovskite solar cells combine low-cost fabrication and high power conversion efficiency. Advances in perovskite film optimization have led to an outstanding power conversion efficiency of more than 20%. Looking forward, shifting the focus toward new device architectures holds great potential to induce the next leap in device performance. Here, we demonstrate a perovskite/perovskite heterojunction solar cell. We developed a facile solution-based cation infiltration process to deposit layered perovskite (LPK) structures onto methylammonium lead iodide (MAPI) films. Grazing-incidence wide-angle X-ray scattering experiments were performed to gain insights into the crystallite orientation and the formation process of the perovskite bilayer. Our results show that the self-assembly of the LPK layer on top of an intact MAPI layer is accompanied by a reorganization of the perovskite interface. This leads to an enhancement of the open-circuit voltage and power conversion efficiency due to reduced recombination losses, as well as improved moisture stability in the resulting photovoltaic devices. PMID:27228558

  19. Oxidation of manganese(II) with ferrate: Stoichiometry, kinetics, products and impact of organic carbon.

    Goodwill, Joseph E; Mai, Xuyen; Jiang, Yanjun; Reckhow, David A; Tobiason, John E

    2016-09-01

    Manganese is a contaminant of concern for many drinking water utilities, and future regulation may be pending. An analysis of soluble manganese (Mn(II)) oxidation by ferrate (Fe(VI)) was executed at the bench-scale, in a laboratory matrix, both with and without the presence of natural organic matter (NOM) and at two different pH values, 6.2 and 7.5. In the matrix without NOM, the oxidation of Mn(II) by Fe(VI) followed a stoichiometry of 2 mol Fe(VI) to 3 mol Mn(II). The presence of NOM did not significantly affect the stoichiometry of the oxidation reaction, indicating relative selectivity of Fe(VI) for Mn(II). The size distribution of resulting particles included significant amounts of nanoparticles. Resulting manganese oxide particles were confirmed to be MnO2 via X-ray photoelectron spectroscopy. The rate of the Mn(II) oxidation reaction was fast relative to typical time scales in drinking water treatment, with an estimated second order rate constant of approximately 1 × 10(4) M(-1) s(-1) at pH 9.2 and > 9 × 10(4) M(-1) s(-1) at pH 6.2. In general, ferrate is a potential option for Mn(II) oxidation in water treatment. PMID:27341149

  20. Investigation of electrochemical synthesis of ferrate, Part I: Electrochemical behavior of iron and its several alloys in concentrated alkaline solutions

    Čekerevac Milan I.

    2009-01-01

    Full Text Available In recent years, considerable attention has been paid to various applications of Fe(VI due to its unique properties such as oxidizing power, selective reactivity, stability of the salt, and non-toxic decomposition by-products of ferric ion. In environmental remediation processes, Fe(VI has been proposed as green oxidant, coagulant, disinfectant, and antifoulant. Therefore, it is considered as a promising multi-purpose water treatment chemical. Fe(VI has also potential applications in electrochemical energy source, as 'green cathode'. The effectiveness of ferrate as a powerful oxidant in the entire pH range, and its use in environmental applications for the removal of wide range of contaminants has been well documented by several researchers. There is scientific evidence that ferrate can effectively remove arsenic, algae, viruses, pharmaceutical waste, and other toxic heavy metals. Although Fe(VI was first discovered in early eighteen century, detailed studies on physical and chemical properties of Fe(VI had to wait until efficient synthetic and analytical methods of Fe(VI were developed by Schreyer et al. in the 1950s. Actually, there have been developed three ways for the preparation of Fe(VI compounds : the wet oxidation of Fe(II and Fe(III compounds, the dry oxidation of the same, and the electrochemistry method, mainly based on the trans passive oxidation of iron. High purity ferrates Fe(VI can be generated when electrode of the pure iron metal or its alloys are anodized in concentrated alkaline solution. It is known that the efficiency of electrochemical process of Fe(VI production depends on many factors such as current density, composition of anode material, types of electrolyte etc. In this paper, the electrochemical synthesis of ferrate(VI solution by the anodic dissolution of iron and its alloys in concentrated water solution of NaOH and KOH is investigated. The process of transpassive dissolution of iron to ferrate(VI was studied by

  1. Calcium ferrite formation from the thermolysis of calcium tris (maleato) ferrate(III)

    B S Randhawa; Kamaljeet Sweety

    2000-08-01

    For preparing calcium ferrite, calcium tris (maleato) ferrate(III) precursor was prepared by mixing aqueous solutions of iron(III) maleate, calcium maleate and maleic acid. Various physico-chemical techniques i.e. TG, DTG, DTA, Mössbauer, XRD, IR etc have been used to study the decomposition behaviour from ambient to 900°C and ferrite formation. Three consecutive decomposition steps leading to the formation of -Fe2O3 and calcium carbonate have been observed at various stages of thermolysis. In the final stage the ferrite, Ca2Fe2O5, is obtained as a result of solid state reaction between -Fe2O3 and calcium carbonate at 788°C, a temperature much lower than for ceramic method. The results have been compared with those of the oxalate precursor.

  2. Potassium ferrate [Fe(VI] does not mediate self-sterilization of a surrogate mars soil

    Paszczynski Andrzej

    2003-03-01

    Full Text Available Abstract Background Martian soil is thought to be enriched with strong oxidants such as peroxides and/or iron in high oxidation states that might destroy biological materials. There is also a high flux of ultraviolet radiation at the surface of Mars. Thus, Mars may be inhospitable to life as we know it on Earth. We examined the hypothesis that if the soil of Mars contains ferrates [Fe(VI], the strongest of the proposed oxidizing species, and also is exposed to high fluxes of UV radiation, it will be self-sterilizing. Results Under ambient conditions (25°C, oxygen and water present K2FeO4 mixed into sand mineralized some reactive organic molecules to CO2, while less reactive compounds were not degraded. Dried endospores of Bacillus subtilis incubated in a Mars surrogate soil comprised of dry silica sand containing 20% by weight K2FeO4 and under conditions similar to those now on Mars (extreme desiccation, cold, and a CO2-dominated atmosphere were resistant to killing by the ferrate-enriched sand. Similar results were observed with permanganate. Spores in oxidant-enriched sand exposed to high fluxes of UV light were protected from the sporocidal activity of the radiation below about 5 mm depths. Conclusion Based on our data and previously published descriptions of ancient but dormant life forms on Earth, we suggest that if entities resembling bacterial endospores were produced at some point by life forms on Mars, they might still be present and viable, given appropriate germination conditions. Endospores delivered to Mars on spacecraft would possibly survive and potentially compromise life detection experiments.

  3. Ferroelectric ultrathin perovskite films

    Rappe, Andrew M; Kolpak, Alexie Michelle

    2013-12-10

    Disclosed herein are perovskite ferroelectric thin-film. Also disclosed are methods of controlling the properties of ferroelectric thin films. These films can be used in a variety materials and devices, such as catalysts and storage media, respectively.

  4. Synthesis and crystal structure of new K and Rb selenido/tellurido ferrate cluster compounds

    In the course of a systematic study of alkali iron chalcogenido salts containing clusters [Fe4Q8] a series of new mixed-valent potassium and rubidium selenido and tellurido ferrates(II/III) was synthesized by carefully heating the pure elements enclosed in sample tubes under an argon atmosphere up to maximum temperatures of 800-900 C. Their crystal structures have been determined by means of single crystal X-ray diffraction. The mixed-valent FeII/III tellurido ferrates A7[Fe4Te8] form three different structure types. All structures contain tetramers of four edge sharing [FeTe4] tetrahedra, which are connected by common edges to form only slightly distorted tetrahedral [Fe4Te8]7- anions ('stella quadrangula') with a [Fe4Te4] cubane core. In all cases, these anions are surrounded by 26 alkali cations, which are located at the eight corners and the midpoints of the six faces and 12 edges of a cube. The three crystal structures can thus be described by three different packings of cuboid moieties: The monoclinic rubidium compound Rb7[Fe4Te8] (space group C2/c, a = 2000.16(7), b = 897.79(3), c = 1768.12(6) pm, β = 117.4995(10) , Z = 4, R1 = 0.0296) is isotypic to the known cesium tellurido and sulfido ferrates Cs7[Fe4(S/Te)8]. Depending on the temperature, K7[Fe4Te8] forms two different but closely related new structure types: The tetragonal r.t. modification (space group P42/nmc, a = 1222.25(14), c = 872.1(2) pm, Z = 2, R1 = 0.0583) crystallizes in a supergroup of the orthorhombic l.t. (100 K) form (space group Pbcn, a = 1715.5, b = 866.76(3), c = 1715.50(7) pm, Z = 4, R1 = 0.0160). In all structures, the cluster centered cubes are stacked to form columns along the short (∼ 870 pm) axis. These columns are themselves densely packed with 4 (both K compounds) and 6 (A = Rb) adjacent face-sharing columns. According to these arrangements of cluster-centered cubes, a relation of the packing of K/Rb cations and cluster anions with the simple cubic packing can be

  5. PEROVSKITE SOLAR CELLS (REVIEW ARTICLE)

    Benli, Deniz Ahmet

    2015-01-01

    A solar cell is a device that converts sunlight into electricity. There are different types of solar cells but this report mainly focuses on a type of new generation solar cell that has the name organo-metal halide perovskite, shortly perovskite solar cells. In this respect, the efficiency of power conversion is taken into account to replace the dominancy of traditional and second generation solar cell fields by perovskite solar cells. Perovskite solar cell is a type of solar cell including a...

  6. Perovskite photonic sources

    Sutherland, Brandon R.; Sargent, Edward H.

    2016-05-01

    The field of solution-processed semiconductors has made great strides; however, it has yet to enable electrically driven lasers. To achieve this goal, improved materials are required that combine efficient (>50% quantum yield) radiative recombination under high injection, large and balanced charge-carrier mobilities in excess of 10 cm2 V-1 s-1, free-carrier densities greater than 1017 cm-3 and gain coefficients exceeding 104 cm-1. Solid-state perovskites are -- in addition to galvanizing the field of solar electricity -- showing great promise in photonic sources, and may be the answer to realizing solution-cast laser diodes. Here, we discuss the properties of perovskites that benefit light emission, review recent progress in perovskite electroluminescent diodes and optically pumped lasers, and examine the remaining challenges in achieving continuous-wave and electrically driven lasing.

  7. Potential side effects of ammonium-ferric-hexacyano-ferrate application: enhanced radiostrontium transfer and free cyanide release

    Vandenhove, Hildegarde E-mail:hvandenh@sckcen.be; Hees, May van; Vandecasteele, Christian

    2000-01-01

    The effect of the application of ammonium-ferric-hexacyano-ferrate (AFCF), effective in reducing soil-to-plant radiocaesium transfer, on radiostrontium transfer was tested for ryegrass grown under greenhouse conditions on sandy soil for 310 days. Identical radiostrontium transfer factors (9.4 kg kg{sup -1}) were obtained with 0 or 10 g AFCF m{sup -2} applied. Amending AFCF to planted or uncovered sandy or loamy soils in quantities of up to 100 g AFCF m{sup -2} did not result in detectable levels of free cyanide. Negative side effects of AFCF application to soil are hence unlikely.

  8. The Handheld Library: Developments at the Rector Gabriel Ferraté Library, UPC

    Beatriz Benítez Juan

    2011-10-01

    Full Text Available The purpose of this paper is to highlight the mobile services developed by the Rector Gabriel Ferraté Library (BRGF of the Universitat Politècnica de Catalunya (UPC-Barcelona Tech in Barcelona, Spain. We hope this paper will be of use to other libraries exploring new technologies for communicating and delivering their services to users at a time when mobile services are an emerging topic in librarianship and information science literature. By setting out the successive steps involved in the as yet unfinished process of building our mobile services portfolio, we aim to offer a detailed picture of the mobile services and features offered by a university library from a case study perspective. The main topics to be discussed include: The BRGF’s mobile website, including the information available, its interactive capabilities and the services it provides to its users. The mobile-friendly version of UP Commons(the UPC Library Service’s institutional repositories. The UPC Library Service’s mobile OPAC. The mobile version of u-win(BRGF’s videogame service. The use of QR codes to deliver information to mobile devices. Text message notifications. Additional topics for discussion include: The library’s organisation and the organisational concepts that underpin and make possible its technological developments (including mobile. BRGF’s concern regarding the reduction of investment in the development of mobile services. The criteria and tools used to guide the library’s decisions regarding the design and orientation of current and future mobile services. How mobile services can help to improve the image of the library as a leading technology site. Selected mobile features that BRGF plans to offer in the near future. Ultimately, this paper aims to delineate the effectiveness and potential of delivering library services by the preferred means of communication of a new generation of students and teachers.

  9. Ferrate(VI) oxidation of tetrabromobisphenol A in comparison with bisphenol A.

    Yang, Bin; Ying, Guang-Guo; Chen, Zhi-Feng; Zhao, Jian-Liang; Peng, Fu-Qiang; Chen, Xiao-Wen

    2014-10-01

    Ferrate(VI) (Fe(VI)) oxidative removal of various organic micropollutants mainly depends on the reactivity of Fe(VI) to target micropollutants and coexisting constituents present in source water. This study evaluated the potential of Fe(VI) oxidation of the brominated flame retardant tetrabromobisphenol A (TBBPA) by using reaction kinetics, products identification and toxicity evaluation, and investigated the influencing effects of humic acid and clay particles on Fe(VI) removal of TBBPA in comparison with bisphenol A (BPA). The obtained apparent second-order rate constants (k(app)) for Fe(VI) reaction with TBBPA ranged from 7.9(±0.3) × 10(3) M(-1) s(-1) to 3.3(±0.1) × 10(1) M(-1) s(-1) with the half-life (t1/2) ranging from 1.7 s to 419.3 s at pH 7.0-10 for an Fe(VI) concentration of 10 mg L(-1). Easier oxidation by Fe(VI) was observed for TBBPA than for BPA. Fe(VI) can destroy and transform the TBBPA molecule through β-scission reaction, yielding the chemical species of low bromine-substituted products. More importantly, the oxidation of TBBPA by Fe(VI) led to the loss of its multiple hormonal activities (androgenic, antiestrogenic and antiandrogenic activities). The organic component humic acid decreased the TBBPA and BPA reactions with Fe(VI), while the inorganic component montmorillonite had no effect on their removal within the tested concentrations. Increasing the Fe(VI) dosage can reduce the effects of soluble organic matter and clay particles present in source waters on the degradation process, leading to the complete removal of target micropollutants. PMID:24956603

  10. Synthesis and crystal structure of new K and Rb selenido/tellurido ferrate cluster compounds

    Stueble, Pirmin; Berroth, Angela; Roehr, Caroline [Freiburg Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie

    2016-08-01

    In the course of a systematic study of alkali iron chalcogenido salts containing clusters [Fe{sub 4}Q{sub 8}] a series of new mixed-valent potassium and rubidium selenido and tellurido ferrates(II/III) was synthesized by carefully heating the pure elements enclosed in sample tubes under an argon atmosphere up to maximum temperatures of 800-900 C. Their crystal structures have been determined by means of single crystal X-ray diffraction. The mixed-valent Fe{sup II/III} tellurido ferrates A{sub 7}[Fe{sub 4}Te{sub 8}] form three different structure types. All structures contain tetramers of four edge sharing [FeTe{sub 4}] tetrahedra, which are connected by common edges to form only slightly distorted tetrahedral [Fe{sub 4}Te{sub 8}]{sup 7-} anions ('stella quadrangula') with a [Fe{sub 4}Te{sub 4}] cubane core. In all cases, these anions are surrounded by 26 alkali cations, which are located at the eight corners and the midpoints of the six faces and 12 edges of a cube. The three crystal structures can thus be described by three different packings of cuboid moieties: The monoclinic rubidium compound Rb{sub 7}[Fe{sub 4}Te{sub 8}] (space group C2/c, a = 2000.16(7), b = 897.79(3), c = 1768.12(6) pm, β = 117.4995(10) , Z = 4, R1 = 0.0296) is isotypic to the known cesium tellurido and sulfido ferrates Cs{sub 7}[Fe{sub 4}(S/Te){sub 8}]. Depending on the temperature, K{sub 7}[Fe{sub 4}Te{sub 8}] forms two different but closely related new structure types: The tetragonal r.t. modification (space group P4{sub 2}/nmc, a = 1222.25(14), c = 872.1(2) pm, Z = 2, R1 = 0.0583) crystallizes in a supergroup of the orthorhombic l.t. (100 K) form (space group Pbcn, a = 1715.5, b = 866.76(3), c = 1715.50(7) pm, Z = 4, R1 = 0.0160). In all structures, the cluster centered cubes are stacked to form columns along the short (∼ 870 pm) axis. These columns are themselves densely packed with 4 (both K compounds) and 6 (A = Rb) adjacent face-sharing columns. According to these

  11. Effects of ferroelectric-poling-induced strain on the electronic transport and magnetic properties of (001)- and (111)-oriented La0.5Ba0.5MnO3 thin films

    We epitaxially grew La0.5Ba0.5MnO3 (LBMO) films on (001)- and (111)-oriented ferroelectric single-crystal substrates and reduced the in-plane tensile strain of LBMO films by poling the ferroelectric substrates along the 〈001〉 or 〈111〉 direction. Upon poling, a large decrease in the resistance and a considerable increase in the magnetization, Curie temperature, and magnetoresistance were observed for the LBMO film, which are driven by interface strain coupling. Such strain effects can be significantly enhanced by the application of a magnetic field. An overall analysis of the findings reveals that the mutual interaction between the strain and the magnetic field is mediated by the electronic phase separation which is sensitive to both strain and magnetic field. Our findings highlight that the electronic phase separation is crucial in understanding the electric-field-manipulated strain effects in manganite film/ferroelectric crystal heterostructures. - Highlights: • La0.5Ba0.5MnO3 films were epitaxially grown on ternary ferroelectric single crystals. • Ferroelectric poling modifies the strain and physical properties of films. • Magnetic field enhances the strain effects of films. • Phase separation is crucial to understand the magnetic-field-tuned strain effect

  12. 3D imaging using X-Ray tomography and SEM combined FIB to study non isothermal creep damage of (111) oriented samples of γ / γ ′ nickel base single crystal superalloy MC2

    Jouiad, Mustapha

    2012-01-01

    An unprecedented investigation consisting of the association of X-Ray tomography and Scanning Electron Microscopy combined with Focus Ion Beam (SEM-FIB) is conducted to perform a 3D reconstruction imaging. These techniques are applied to study the non-isothermal creep behavior of close (111) oriented samples of MC2 nickel base superalloys single crystal. The issue here is to develop a strategy to come out with the 3D rafting of γ\\' particles and its interaction whether with dislocation structures or/and with the preexisting voids. This characterization is uncommonly performed away from the conventional studied orientation [001] in order to feed the viscoplastic modeling leading to its improvement by taking into account the crystal anisotropy. The creep tests were performed at two different conditions: classical isothermal tests at 1050°C under 140 MPa and a non isothermal creep test consisting of one overheating at 1200°C and 30 seconds dwell time during the isothermal creep life. The X-Ray tomography shows a great deformation heterogeneity that is pronounced for the non-isothermal tested samples. This deformation localization seems to be linked to the preexisting voids. Nevertheless, for both tested samples, the voids coalescence is the precursor of the observed damage leading to failure. SEM-FIB investigation by means of slice and view technique gives 3D views of the rafted γ\\' particles and shows that γ corridors evolution seems to be the main creep rate controlling parameter. © 2012 Trans Tech Publications, Switzerland.

  13. Dielectric properties and phase transitions of [001], [110], and [111] oriented Pb(Zn1/3Nb2/3)O3-6%PbTiO3 single crystals

    Amin Hentati, Mouhamed; Dammak, Hichem; Khemakhem, Hamadi; Pham Thi, Mai

    2013-06-01

    Phase transformations of [001], [110], and [111] oriented Pb(Zn1/3Nb2/3)O3-6%PbTiO3 (PZN-6%PT) single crystals have been investigated by means of dielectric permittivity and loss, x-ray diffraction and depolarization current as function of temperature (from 250 to 500 K). The unpoled samples undergo R-T-C phase transition sequence during zero field heating (ZFH), where R, T, and C are rhombohedral, tetragonal, and cubic phases, respectively. Under electric field (0.5 kV/cm), an intermediate orthorhombic (O) phase is induced between the T and R phases in the field cooling (FC) process. This phase reappears during subsequent zero field heating of the poled sample (zero field heating after field cooling: ZFHaFC). The existence range of this O phase depends on both the crystal orientation and the measurement conditions (FC or ZFHaFC). Finally, for the [001] direction, it was found that the piezoelectric activity of the intermediate phase is the highest.

  14. Tunable perovskite microdisk lasers

    Sun, Wenzhao; Wang, Kaiyang; Gu, Zhiyuan; Xiao, Shumin; Song, Qinghai

    2016-04-01

    Perovskite microdisk lasers have been intensively studied recently. But their lasing properties are usually fixed once the devices are synthesized. Here, for the first time, we demonstrated the switchable and tunable perovskite microdisk lasers by surrounding them with 5CB liquid crystals. With the increase of the environmental temperature from 24 °C to 34 °C, the lasing wavelength slightly changed from 552.91 nm to 552.11 nm at the beginning and suddenly shifted to around 552.54 nm at T = 32 °C, where the phase transition of liquid crystals occurs. Our numerical calculation shows that the wavelength shift is caused by the changes of the refractive index of liquid crystals. More than tuning of the wavelength, a more dramatic wavelength transition from ~554 nm to 550 nm has also been observed. This sudden transition is mainly induced by the reduction of scattering rather than the change in the refractive index when the liquid crystals are changed from the nematic phase to the isotropic phase. We believe that our research can shed light on the applications of perovskite optoelectronics.

  15. La Relación entre filosofía y ciencia en la obra de José Ferrater Mora

    Velásquez Giraldo, Carla Isabel; Tafalla, Marta

    2015-01-01

    Esta tesis trata de la relación entre filosofía y ciencia en el pensamiento de José Ferrater Mora. El método empleado para analizar esta relación filosofía-ciencia es de carácter internalista y tiene en cuenta el método integracionista, creado y empleado por el mismo Ferrater. La línea guía del análisis crítico llevado a cabo consiste en buscar las ideas e influencias de la ciencia diseminadas en su obra y aislar tanto como sea posible este aspecto, dándole unidad al tema de la relación filos...

  16. La relación entre filosofía y ciencia en la obra de José Ferrater Mora

    Velásquez Giraldo, Carla Isabel

    2015-01-01

    Esta tesis trata de la relación entre filosofía y ciencia en el pensamiento de José Ferrater Mora. El método empleado para analizar esta relación filosofía-ciencia es de carácter internalista y tiene en cuenta el método integracionista, creado y empleado por el mismo Ferrater. La línea guía del análisis crítico llevado a cabo consiste en buscar las ideas e influencias de la ciencia diseminadas en su obra y aislar tanto como sea posible este aspecto, dándole unidad al tema de la relación filos...

  17. On application of ferrate salts(Ⅵ ) in water treatment%高铁酸盐(Ⅵ)在水处理中的应用

    郭丽

    2012-01-01

    对高铁酸盐这一双功能水处理剂的制备方法及其在水与污水处理中的一些应用作了介绍,指出高铁酸盐在水溶液中同时具有很好的消毒和絮凝作用,由于高铁酸盐制备的困难和比较差的稳定性,目前还没有在工业上规模化应用,为拓展这类化合物在水处理上应用,提出了今后研究应关注的要点。%The paper introduces the application of the ferrate salts in the preparation methods for the double function of water treatment agent and the treatment of water and sewage, points out the ferrate salts has better disinfection and flocculation in aqueous solution, and indicates the tech- nique is not applied in the industrial scale because of difficulties and weak stability for the making of the ferrate salts, so as to extend the appli- cation of the compound in water treatment and points out attentive points for the study in future.

  18. 高铁酸钾氧化处理水中苯酚的研究%Study on treatment of phenol in water using potassium ferrate

    赵胜勇; 刘菲

    2016-01-01

    Potassium ferrate oxidation process was used to treat phenol in water for the purpose of present-ing a high-efficient method for phenol treatment. The influences of mass ratio of potassium ferrate to phenol, so-lution pH value, and reaction time on phenol treatment effect were investigated. The test results showed that, un-der the condition that the initial mass concentration of phenol was 100 mg/L, the mass ratio of potassium ferrate to phenol was 30, the solution pH value was 9, the reaction time was 30 min, the maximum removal rate of phe-nol could reach 96.7%%采用高铁酸钾氧化法处理水中苯酚, 提供了一种高效处理水中苯酚的方法. 考察了高铁酸钾与苯酚质量比、 溶液pH值、 反应时间对水中苯酚处理效果的影响. 试验结果表明, 在苯酚初始质量浓度为100 mg/L、 高铁酸钾与苯酚质量比为30、 溶液pH值为9、 反应时间为30 min的条件下, 苯酚去除率最高可达96.7%.

  19. Methodologies for high efficiency perovskite solar cells

    Park, Nam-Gyu

    2016-06-01

    Since the report on long-term durable solid-state perovskite solar cell in 2012, perovskite solar cells based on lead halide perovskites having organic cations such as methylammonium CH3NH3PbI3 or formamidinium HC(NH2)2PbI3 have received great attention because of superb photovoltaic performance with power conversion efficiency exceeding 22 %. In this review, emergence of perovskite solar cell is briefly introduced. Since understanding fundamentals of light absorbers is directly related to their photovoltaic performance, opto-electronic properties of organo lead halide perovskites are investigated in order to provide insight into design of higher efficiency perovskite solar cells. Since the conversion efficiency of perovskite solar cell is found to depend significantly on perovskite film quality, methodologies for fabricating high quality perovskite films are particularly emphasized, including various solution-processes and vacuum deposition method.

  20. Perovskite solar cells: an emerging photovoltaic technology

    Nam-Gyu Park

    2015-01-01

    Perovskite solar cells based on organometal halides represent an emerging photovoltaic technology. Perovskite solar cells stem from dye-sensitized solar cells. In a liquid-based dye-sensitized solar cell structure, the adsorption of methylammonium lead halide perovskite on a nanocrystalline TiO2 surface produces a photocurrent with a power conversion efficiency (PCE) of around 3–4%, as first discovered in 2009. The PCE was doubled after 2 years by optimizing the perovskite coating conditions....

  1. Inorganic caesium lead iodide perovskite solar cells

    Eperon, GE; Paterno', GM; Sutton, RJ; Zampetti, A.; Haghighirad, A; Cacialli, F.; Snaith, H.

    2015-01-01

    The vast majority of perovskite solar cell research has focused on organic-inorganic lead trihalide perovskites. Herein, we present working inorganic CsPbI3 perovskite solar cells for the first time. CsPbI3 normally resides in a yellow non-perovskite phase at room temperature, but by careful processing control and development of a low-temperature phase transition route we have stabilised the material in the black perovskite phase at room temperature. As such, we have fabricated solar cell dev...

  2. Perovskite solar cells: an emerging photovoltaic technology

    Nam-Gyu Park

    2015-03-01

    Full Text Available Perovskite solar cells based on organometal halides represent an emerging photovoltaic technology. Perovskite solar cells stem from dye-sensitized solar cells. In a liquid-based dye-sensitized solar cell structure, the adsorption of methylammonium lead halide perovskite on a nanocrystalline TiO2 surface produces a photocurrent with a power conversion efficiency (PCE of around 3–4%, as first discovered in 2009. The PCE was doubled after 2 years by optimizing the perovskite coating conditions. However, the liquid-based perovskite solar cell receives little attention because of its stability issues, including instant dissolution of the perovskite in a liquid electrolyte. A long-term, stable, and high efficiency (∼10% perovskite solar cell was developed in 2012 by substituting the solid hole conductor with a liquid electrolyte. Efficiencies have quickly risen to 18% in just 2 years. Since PCE values over 20% are realistically anticipated with the use of cheap organometal halide perovskite materials, perovskite solar cells are a promising photovoltaic technology. In this review, the opto-electronic properties of perovskite materials and recent progresses in perovskite solar cells are described. In addition, comments on the issues to current and future challenges are mentioned.

  3. Stability Issues on Perovskite Solar Cells

    Xing Zhao

    2015-11-01

    Full Text Available Organo lead halide perovskite materials like methylammonium lead iodide (CH3NH3PbI3 and formamidinium lead iodide (HC(NH22PbI3 show superb opto-electronic properties. Based on these perovskite light absorbers, power conversion efficiencies of the perovskite solar cells employing hole transporting layers have increased from 9.7% to 20.1% within just three years. Thus, it is apparent that perovskite solar cell is a promising next generation photovoltaic technology. However, the unstable nature of perovskite was observed when exposing it to continuous illumination, moisture and high temperature, impeding the commercial development in the long run and thus becoming the main issue that needs to be solved urgently. Here, we discuss the factors affecting instability of perovskite and give some perspectives about further enhancement of stability of perovskite solar cell.

  4. Magnetoresistance stories of double perovskites

    Abhishek Nag; Sugata Ray

    2015-06-01

    Tunnelling magnetoresistance (TMR) in polycrystalline double perovskites has been an important research topic for more than a decade now, where the nature of the insulating tunnel barrier is the core issue of debate. Other than the nonmagnetic grain boundaries as conventional tunnel barriers, intragrain magnetic antiphase boundaries (APB) as well as magnetically frustrated grain surfaces have also been proposed to act as tunnel barriers in Sr2FeMoO6. In this review, the present state of the debate has been discussed briefly and how the physical state of the material can affect the magnetoresistance signal of double perovskites in many different ways has been pointed out.

  5. Common features of gallium perovskites

    Aleksiyko, R; Berkowski, M; Byszewski, P; Dabrowski, B; Diduszko, R; Fink-Finowicki, J; Vasylechko, LO

    2001-01-01

    The Czochralski and floating zone methods have been used to grow single crystals of gallium perovskites solid solutions with rare earth elements La, Pr, Nd, Sm and with Sr. The structure of the crystals has been investigated by powder X-ray, synchrotron radiation and neutron diffraction methods over

  6. Perovskite catalysts for oxidative coupling

    Campbell, Kenneth D.

    1991-01-01

    Perovskites of the structure A.sub.2 B.sub.2 C.sub.3 O.sub.10 are useful as catalysts for the oxidative coupling of lower alkane to heavier hydrocarbons. A is alkali metal; B is lanthanide or lanthanum, cerium, neodymium, samarium, praseodymium, gadolinium or dysprosium; and C is titanium.

  7. Relative thermal diffusivities of perovskite and post-perovskite analogues

    Hunt, S. A.; McCormack, R.; Walker, A.; Dobson, D. P.; Li, L.

    2010-12-01

    Using our new X-radiography based variation of the Ångstrom method we have measured the thermal diffusivity of both the perovskite and post-perovskite structure of CaIrO3 at high pressure. The Ångstrom method for measuring thermal diffusivity at high pressure uses a stationary thermal wave which is induced into the sample by sinusoidally varying the power applied to the cylindrical furnace, surrounding the sample. The thermal diffusivity (κ ) is determined from the phase lag, Φ 0 - Φ R, and amplitude difference, θ 0 / θ R, of the thermal wave between points at the axis of the sample and radius, R (e.g. Khedari et al., 1995). Our method differs from previous multi-anvil implementations of the Ångstrom method in that instead of using thermocouples to monitor the temperature variation we use thin strips of metal foil, which are placed at discrete intervals along the sample length and imaged X-radiographically. The metal strips monitor the thermal expansion of a slice across the sample in response to the sinusoidal temperature profile. This represents an improvement over previous methods since (i) the change in temperature is averaged along the sample length, (ii) we measure the phase of the thermal wave at all radii and (iii) since the expansion of the sample is observed as a proxy for the change in temperature there are no problems associated with contact thermal resistance at the thermocouples. Furthermore, this development does away with the need to prepare long cylinders of weakly metastable phases with a thermocouple inserted precisely down the middle; a process which is technically extremely difficult. Using this method we have measured the thermal diffusivity of NaCl, olivine, majorite and a number of other upper-mantle and transition-zone phases and found that our measurements are in agreement with previously published data. In this present study on the CaIrO3 analogue of perovskite and post-perovskite, we find that the thermal diffusivity of the post-perovskite

  8. Strong textural inheritance between perovskite and post-perovskite in the D" layer

    Dobson, David P.; Miyajima, Nobuyosihi; Nestola, Fabrizio; Alvaro, Matteo; Casati, Nicola; Liebske, Christian; Wood, Ian; Andrew M. Walker

    2013-01-01

    The main mineral in the lower mantle, magnesium-silicate perovskite, transforms into a high-pressure, post-perovskite, phase at pressures and temperatures corresponding to the D'' seismic discontinuity approximately 200 km above the core-mantle boundary. The strong elastic anisotropy of post-perovskite has been invoked to explain the observed seismic anisotropy and to infer flow in the D'' region, based on models of textured post-perovskite. Such inferences rely on a knowledge of the mechanis...

  9. Ligand-Stabilized Reduced-Dimensionality Perovskites

    Quan, Li Na

    2016-02-03

    Metal halide perovskites have rapidly advanced thin film photovoltaic performance; as a result, the materials’ observed instabilities urgently require a solution. Using density functional theory (DFT), we show that a low energy of formation, exacerbated in the presence of humidity, explains the propensity of perovskites to decompose back into their precursors. We find, also using DFT, that intercalation of phenylethylammonium between perovskite layers introduces quantitatively appreciable van der Waals interactions; and these drive an increased formation energy and should therefore improve material stability. Here we report the reduced-dimensionality (quasi-2D) perovskite films that exhibit improved stability while retaining the high performance of conventional three-dimensional perovskites. Continuous tuning of the dimensionality, as assessed using photophysical studies, is achieved by the choice of stoichiometry in materials synthesis. We achieved the first certified hysteresis-free solar power conversion in a planar perovskite solar cell, obtaining a 15.3% certified PCE, and observe greatly improved performance longevity.

  10. Stability Issues on Perovskite Solar Cells

    Xing Zhao; Nam-Gyu Park

    2015-01-01

    Organo lead halide perovskite materials like methylammonium lead iodide (CH3NH3PbI3) and formamidinium lead iodide (HC(NH2)2PbI3) show superb opto-electronic properties. Based on these perovskite light absorbers, power conversion efficiencies of the perovskite solar cells employing hole transporting layers have increased from 9.7% to 20.1% within just three years. Thus, it is apparent that perovskite solar cell is a promising next generation photovoltaic technology. However, the unstable natu...

  11. Multiferroic crossover in perovskite oxides

    Weston, L.; Cui, X. Y.; Ringer, S. P.; Stampfl, C.

    2016-04-01

    The coexistence of ferroelectricity and magnetism in A B O3 perovskite oxides is rare, a phenomenon that has become known as the ferroelectric "d0 rule." Recently, the perovskite BiCoO3 has been shown experimentally to be isostructural with PbTiO3, while simultaneously the d6Co3 + ion has a high-spin ground state with C -type antiferromagnetic ordering. It has been suggested that the hybridization of Bi 6 s states with the O 2 p valence band stabilizes the polar phase, however, we have recently demonstrated that Co3 + ions in the perovskite structure can facilitate a ferroelectric distortion via the Co 3 d -O 2 p covalent interaction [L. Weston, et al., Phys. Rev. Lett. 114, 247601 (2015), 10.1103/PhysRevLett.114.247601]. In this paper, using accurate hybrid density functional calculations, we investigate the atomic, electronic, and magnetic structure of BiCoO3 to elucidate the origin of the multiferroic state. To begin with, we perform a more general first-principles investigation of the role of d electrons in affecting the tendency for perovskite materials to exhibit a ferroelectric distortion; this is achieved via a qualitative trend study in artificial cubic and tetragonal La B O3 perovskites. We choose La as the A cation so as to remove the effects of Bi 6 s hybridization. The lattice instability is identified by the softening of phonon modes in the cubic phase, as well as by the energy lowering associated with a ferroelectric distortion. For the La B O3 series, where B is a d0-d8 cation from the 3 d block, the trend study reveals that increasing the d orbital occupation initially removes the tendency for a polar distortion, as expected. However, for high-spin d5-d7 and d8 cations a strong ferroelectric instability is recovered. This effect is explained in terms of increased pseudo-Jahn-Teller (PJT) p -d vibronic coupling. The PJT effect is described by the competition between a stabilizing force (K0) that favors the cubic phase, and a vibronic term that

  12. Perovskites synthesis to SOFC anodes

    Perovskite structure materials containing lanthanum have been widely applied as solid oxide fuel cells (SOFCs) electrodes, due to its electrical properties. Was investigated the obtain of the perovskite structure LaCr0,5Ni0,5O3, by Pechini method, and its suitability as SOFC anode. The choice of this composition was based on the stability provided by chromium and the catalytic properties of nickel. After preparing the resins, the samples were calcined at 300 deg C, 600 deg C, 700 deg C and 850 deg C. The resulting powders were characterized by X-ray diffraction to determine the existing phases. Furthermore, were performed other analysis, like X-ray fluorescence, He pycnometry, specific surface area by BET isotherm and scanning electronic microscopy (author)

  13. Chemical diffusivity of perovskite and post-perovskite from studies of fluoride analogues.

    Dobson, D. P.; Lindsay-Scott, A.; Wood, I. G.; Bailey, E.; Brodholt, J. P.; Vocadlo, L.

    2014-12-01

    The physical properties of post-perovskite are thought to strongly influence the dynamics of the D'' region at the base of the Earth's mantle, however many of these properties are difficult to directly measure on MgSiO3 post-perovskite. Ab initio simulations (1) predicted that chemical diffusivity of Mg and Si in post-perovskite MgSiO3 is significantly anisotropic (with 8 orders of magnitude difference between the fast [001] and slow [010] directions) and with the fast direction some four orders of magnitude faster than diffusion in perovskite. While the simulations reproduced the available experiments on perovskite very well the surprising result for post-perovskite merits testing.Post-perovskite CaIrO3 does not show strong anisotropy in Ir-Pt interdiffusivity by either experiment or simulation (2) but the fluoride analogue systems are predicted by ab initio simulations to show very similar anisotropy to MgSiO3 and the difference between perovskite and post-perovskite are, likewise, similar to the silicate system. Here we present measured and simulated diffusivities for NaXF3 perovskite and post-perovskite (X = Zn, Mn, Co, Ni).References:1) Ammann, M.W., Brodholt, J.P., Wookey, J. and Dobson, D.P. First Principles Constraints on Diffusion in Lower Mantle Minerals and a Weak D'' Layer. Nature, 465, 462-465, 2010.2) McCormack, R. Ph.D thesis University College London, 2012.

  14. Purification Efficiency of Raw Water Containing Microcystis aeruginosa with Composite Ferrate%复合高铁酸盐对含铜绿微囊藻原水的净化效果

    张洁; 邱慧琴; 喻艳菁; 王涌; 丁国际

    2011-01-01

    Composite ferrate was used to treat raw water containing Microcystis aeruginosa. The influencing factors of algae removal, the purification efficiency of raw water, the combined efficiency with PAC and the mechanism of algae removal were investigated. The results show that the pH value of raw water and the oxidation time of composite ferrate have significant effect on removal of Microcystis aeruginosa. The optimal pH value and oxidation time are 5 to 6 and 15 minutes respectively. The removal efficiency of algae can be significantly improved by increasing composite ferrate dosage to some extent. During the preoxidation with composite ferrate, the concentration of TP is decreased while the concentrations of TN and UV254 are increased due to algal cell disruption. The combination of composite ferrate and PAC has a synergistic effect on removal of algae , total nitrogen and UV254. The mechanism of algae removal by composite ferrate is to directly break cell wall of Microcystis aeruginosa to release intracellular components, thus causing algal cell death.%采用复合高铁酸盐处理含铜绿微囊藻原水,考察了其除藻的影响因素和对原水的净化效果,同时考察了其与聚合氯化铝(PAC)的联用效果及除藻机理.结果表明,原水pH值和复合高铁酸盐的氧化时间均对铜绿微囊藻的去除具有明显影响,最佳pH值为5~6、最佳氧化时间为15 min;在一定范围内增加复合高铁酸盐的投量可明显提高除藻效果.另外,复合高铁酸盐预氧化可降低TP浓度,但由于藻细胞的破裂,TN和UV254值会升高.当复合高铁酸盐与PAC联用时,两者对除藻及去除TP和UV254具有协同效果.复合高铁酸盐的除藻机理为直接破坏铜绿微囊藻的细胞壁,使胞内物质流出从而导致藻细胞死亡.

  15. Calculated optical absorption of different perovskite phases

    Castelli, Ivano Eligio; Thygesen, Kristian Sommer; Jacobsen, Karsten Wedel

    2015-01-01

    We present calculations of the optical properties of a set of around 80 oxides, oxynitrides, and organometal halide cubic and layered perovskites (Ruddlesden-Popper and Dion-Jacobson phases) with a bandgap in the visible part of the solar spectrum. The calculations show that for different classes...... are found in the classes of oxynitride and organometal halide perovskites with strong direct transitions....

  16. Achieving High Performance Perovskite Solar Cells

    Yang, Yang

    2015-03-01

    Recently, metal halide perovskite based solar cell with the characteristics of rather low raw materials cost, great potential for simple process and scalable production, and extreme high power conversion efficiency (PCE), have been highlighted as one of the most competitive technologies for next generation thin film photovoltaic (PV). In UCLA, we have realized an efficient pathway to achieve high performance pervoskite solar cells, where the findings are beneficial to this unique materials/devices system. Our recent progress lies in perovskite film formation, defect passivation, transport materials design, interface engineering with respect to high performance solar cell, as well as the exploration of its applications beyond photovoltaics. These achievements include: 1) development of vapor assisted solution process (VASP) and moisture assisted solution process, which produces perovskite film with improved conformity, high crystallinity, reduced recombination rate, and the resulting high performance; 2) examination of the defects property of perovskite materials, and demonstration of a self-induced passivation approach to reduce carrier recombination; 3) interface engineering based on design of the carrier transport materials and the electrodes, in combination with high quality perovskite film, which delivers 15 ~ 20% PCEs; 4) a novel integration of bulk heterojunction to perovskite solar cell to achieve better light harvest; 5) fabrication of inverted solar cell device with high efficiency and flexibility and 6) exploration the application of perovskite materials to photodetector. Further development in film, device architecture, and interfaces will lead to continuous improved perovskite solar cells and other organic-inorganic hybrid optoelectronics.

  17. Flexible Hybrid Organic-Inorganic Perovskite Memory.

    Gu, Chungwan; Lee, Jang-Sik

    2016-05-24

    Active research has been done on hybrid organic-inorganic perovskite materials for application to solar cells with high power conversion efficiency. However, this material often shows hysteresis, which is undesirable, shift in the current-voltage curve. The hysteresis may come from formation of defects and their movement in perovskite materials. Here, we utilize the defects in perovskite materials to be used in memory operations. We demonstrate flexible nonvolatile memory devices based on hybrid organic-inorganic perovskite as the resistive switching layer on a plastic substrate. A uniform perovskite layer is formed on a transparent electrode-coated plastic substrate by solvent engineering. Flexible nonvolatile memory based on the perovskite layer shows reproducible and reliable memory characteristics in terms of program/erase operations, data retention, and endurance properties. The memory devices also show good mechanical flexibility. It is suggested that resistive switching is done by migration of vacancy defects and formation of conducting filaments under the electric field in the perovskite layer. It is believed that organic-inorganic perovskite materials have great potential to be used in high-performance, flexible memory devices. PMID:27093096

  18. Organohalide Lead Perovskites for Photovoltaic Applications.

    Yusoff, Abd Rashid Bin Mohd; Nazeeruddin, Mohammad Khaja

    2016-03-01

    Perovskite solar cells have recently exhibited a significant leap in efficiency due to their broad absorption, high optical absorption coefficient, very low exciton binding energy, long carrier diffusion lengths, efficient charge collection, and very high open-circuit potential, similar to that of III-IV semiconductors. Unlike silicon solar cells, perovskite solar cells can be developed from a variety of low-temperature solutions processed from inexpensive raw materials. When the perovskite absorber film formation is optimized using solvent engineering, a power conversion efficiency of over 21% has been demonstrated, highlighting the unique photovoltaic properties of perovskite materials. Here, we review the current progress in perovskite solar cells and charge transport materials. We highlight crucial challenges and provide a summary and prospects. PMID:26885884

  19. Stability of organometal perovskites with organic overlayers

    Catherine D. T. Tran

    2015-08-01

    Full Text Available The air-stability of vapour-phase-deposited methylammonium lead triiodide (CH3NH3PbI3 perovskite thin films has been studied using X-ray diffraction. It is found that the perovskite structure without organic coating decomposes completely within a short period of time (∼two days upon exposure to ambient environment. The degradation of the perovskite structure is drastically reduced when the perovskite films are capped with thin N,N′-Di(1-naphthyl-N,N′-diphenyl-(1,1′-biphenyl-4,4′-diamine (NPB films. We discovered that the amount of lead iodide (PbI2, a product of the degradation, grows as a function of time in a sigmoidal manner. Further mathematical modeling analysis shows that the perovskite degradation follows the Avrami equation, a kinetics theory developed for quantifying phase transformations in solid-state materials.

  20. Stability of organometal perovskites with organic overlayers

    Tran, Catherine D. T.; Liu, Yi; Thibau, Emmanuel S.; Llanos, Adrian; Lu, Zheng-Hong

    2015-08-01

    The air-stability of vapour-phase-deposited methylammonium lead triiodide (CH3NH3PbI3) perovskite thin films has been studied using X-ray diffraction. It is found that the perovskite structure without organic coating decomposes completely within a short period of time (˜two days) upon exposure to ambient environment. The degradation of the perovskite structure is drastically reduced when the perovskite films are capped with thin N,N'-Di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPB) films. We discovered that the amount of lead iodide (PbI2), a product of the degradation, grows as a function of time in a sigmoidal manner. Further mathematical modeling analysis shows that the perovskite degradation follows the Avrami equation, a kinetics theory developed for quantifying phase transformations in solid-state materials.

  1. Stability of organometal perovskites with organic overlayers

    Tran, Catherine D. T.; Liu, Yi; Thibau, Emmanuel S.; Llanos, Adrian; Lu, Zheng-Hong [Department of Materials Science and Engineering, University of Toronto, Toronto, Canada M5S 3E4 (Canada)

    2015-08-15

    The air-stability of vapour-phase-deposited methylammonium lead triiodide (CH{sub 3}NH{sub 3}PbI{sub 3}) perovskite thin films has been studied using X-ray diffraction. It is found that the perovskite structure without organic coating decomposes completely within a short period of time (∼two days) upon exposure to ambient environment. The degradation of the perovskite structure is drastically reduced when the perovskite films are capped with thin N,N′-Di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) films. We discovered that the amount of lead iodide (PbI{sub 2}), a product of the degradation, grows as a function of time in a sigmoidal manner. Further mathematical modeling analysis shows that the perovskite degradation follows the Avrami equation, a kinetics theory developed for quantifying phase transformations in solid-state materials.

  2. Non-collinear magnetism in multiferroic perovskites.

    Bousquet, Eric; Cano, Andrés

    2016-03-31

    We present an overview of the current interest in non-collinear magnetism in multiferroic perovskite crystals. We first describe the different microscopic mechanisms giving rise to the non-collinearity of spins in this class of materials. We discuss, in particular, the interplay between non-collinear magnetism and ferroelectric and antiferrodistortive distortions of the perovskite structure, and how this can promote magnetoelectric responses. We then provide a literature survey on non-collinear multiferroic perovskites. We discuss numerous examples of spin cantings driving weak ferromagnetism in transition metal perovskites, and of spin-induced ferroelectricity as observed in the rare-earth based perovskites. These examples are chosen to best illustrate the fundamental role of non-collinear magnetism in the design of multiferroicity. PMID:26912212

  3. Efficient Luminescence from Perovskite Quantum Dot Solids

    Kim, Younghoon

    2015-11-18

    © 2015 American Chemical Society. Nanocrystals of CsPbX3 perovskites are promising materials for light-emitting optoelectronics because of their colloidal stability, optically tunable bandgap, bright photoluminescence, and excellent photoluminescence quantum yield. Despite their promise, nanocrystal-only films of CsPbX3 perovskites have not yet been fabricated; instead, highly insulating polymers have been relied upon to compensate for nanocrystals\\' unstable surfaces. We develop solution chemistry that enables single-step casting of perovskite nanocrystal films and overcomes problems in both perovskite quantum dot purification and film fabrication. Centrifugally cast films retain bright photoluminescence and achieve dense and homogeneous morphologies. The new materials offer a platform for optoelectronic applications of perovskite quantum dot solids.

  4. Perovskite Superlattices as Tunable Microwave Devices

    Christen, H. M.; Harshavardhan, K. S.

    2003-01-01

    Experiments have shown that superlattices that comprise alternating epitaxial layers of dissimilar paraelectric perovskites can exhibit large changes in permittivity with the application of electric fields. The superlattices are potentially useful as electrically tunable dielectric components of such microwave devices as filters and phase shifters. The present superlattice approach differs fundamentally from the prior use of homogeneous, isotropic mixtures of base materials and dopants. A superlattice can comprise layers of two or more perovskites in any suitable sequence (e.g., ABAB..., ABCDABCD..., ABACABACA...). Even though a single layer of one of the perovskites by itself is not tunable, the compositions and sequence of the layers can be chosen so that (1) the superlattice exhibits low microwave loss and (2) the interfacial interaction between at least two of the perovskites in the superlattice renders either the entire superlattice or else at least one of the perovskites tunable.

  5. Oxyfluoride Chemistry of Layered Perovskite Compounds

    Yoshihiro Tsujimoto

    2012-03-01

    Full Text Available In this paper, we review recent progress and new challenges in the area of oxyfluoride perovskite, especially layered systems including Ruddlesden-Popper (RP, Dion-Jacobson (DJ and Aurivillius (AV type perovskite families. It is difficult to synthesize oxyfluoride perovskite using a conventional solid-state reaction because of the high chemical stability of the simple fluoride starting materials. Nevertheless, persistent efforts made by solid-state chemists have led to a major breakthrough in stabilizing such a mixed anion system. In particular, it is known that layered perovskite compounds exhibit a rich variety of O/F site occupation according to the synthesis used. We also present the synthetic strategies to further extend RP type perovskite compounds, with particular reference to newly synthesized oxyfluorides, Sr2CoO3F and Sr3Fe2O5+xF2−x (x ~ 0.44.

  6. Stability of organometal perovskites with organic overlayers

    The air-stability of vapour-phase-deposited methylammonium lead triiodide (CH3NH3PbI3) perovskite thin films has been studied using X-ray diffraction. It is found that the perovskite structure without organic coating decomposes completely within a short period of time (∼two days) upon exposure to ambient environment. The degradation of the perovskite structure is drastically reduced when the perovskite films are capped with thin N,N′-Di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) films. We discovered that the amount of lead iodide (PbI2), a product of the degradation, grows as a function of time in a sigmoidal manner. Further mathematical modeling analysis shows that the perovskite degradation follows the Avrami equation, a kinetics theory developed for quantifying phase transformations in solid-state materials

  7. Effects of ammonium-ferric(III)-hexacyano-ferrate(II) and faeces addition on yield and soil-plant transfer of radiocaesium to rye-grass

    Vandenhove, Hildegarde; Van Hees, May; De Brouwer, Simon; Vandecasteele, Christian [SCK-CEN, Mol (Belgium)

    1997-12-31

    AFCF [ammonium-ferric (III)-hexacyano-ferrate (II)] was shown to be an effective countermeasure against radiocaesium uptake by domestic animals. Following the addition of AFCF and faeces to a sandy farm soil, we evaluate here radiocaesium transfer to rye-grass as well as grass yield in a pot experiment under greenhouse conditions. Sheep faeces and/or soil were artificially contaminated with {sup 137}Cs or {sup 134}Cs, respectively. Radiocaesium from both soil and faeces was equally absorbed by rye-grass. AFCF, at concentrations of 1 gm{sup -2} soil, was not deleterious for plant growth. AFCF is, furthermore, an effective countermeasure for radiocaesium soil-plant transfer. The AFCF applications at about 1 g AFCF m{sup -2} on the sandy soil resulted in a fourfold reduction of the radiocaesium transfer to rye-grass. (Author).

  8. Single Crystal Elasticity of Iron Bearing Perovskite and Post Perovskite Analog

    Yoneda, A.; Fukui, H.; Baron, A. Q. R.

    2014-12-01

    We measured single crystal elasticity of (1) pure and iron bearing MgSiO3 perovskite, and (2) Pbnm-CaIrO3 and Cmcm-CaIrO3, a representative analog of MgSiO3 perovskite and post perovskite, respectively, by means of inelastic X ray scattering at BL35XU, SPring-8. The present results for MgSiO3 perovskite demonstrate that elastic anisotropy of magnesium perovskite is highly enhanced by iron incorporation. Furthermore anti-correlation between bulk sound velocity and shear wave velocity was confirmed with iron content, which is against the theoretical prediction. The anti-correlation found in this study is important, because it enables us to interpret the recent seismological observation of the anti-correlation in the deep lower mantle by means of iron content difference in perovskite. On the other hand, we can learn difference of elasticity between perovskite and post perovskite thorough measurement on CaIrO3, as analog of MgSiO3 perovskite and post perovskite. From a characteristics of the single crystal elasticity of CaIrO3 compounds, we interpreted the texture pattern in the D" layer consistent with recent seismic observation.

  9. Comparison of UV/hydrogen peroxide, potassium ferrate(VI), and ozone in oxidizing the organic fraction of oil sands process-affected water (OSPW).

    Wang, Chengjin; Klamerth, Nikolaus; Messele, Selamawit Ashagre; Singh, Arvinder; Belosevic, Miodrag; Gamal El-Din, Mohamed

    2016-09-01

    The efficiency of three different oxidation processes, UV/H2O2 oxidation, ferrate(VI) oxidation, and ozonation with and without hydroxyl radical (OH) scavenger tert-butyl alcohol (TBA) on the removal of organic compounds from oil sands process-affected water (OSPW) was investigated and compared. The removal of aromatics and naphthenic acids (NAs) was explored by synchronous fluorescence spectra (SFS), ion mobility spectra (IMS), proton and carbon nuclear magnetic resonance ((1)H and (13)C NMR), and ultra-performance liquid chromatography coupled with time-of-flight mass spectrometry (UPLC TOF-MS). UV/H2O2 oxidation occurred through radical reaction and photolysis, transforming one-ring, two-ring, and three-ring fluorescing aromatics simultaneously and achieving 42.4% of classical NAs removal at 2.0 mM H2O2 and 950 mJ/cm(2) UV dose provided with medium pressure mercury lamp. Ferrate(VI) oxidation exhibited high selectivity, preferentially removing two-ring and three-ring fluorescing aromatics, sulfur-containing NAs (NAs + S), and NAs with high carbon and high hydrogen deficiency. At 2.0 mM Fe(VI), 46.7% of classical NAs was removed. Ozonation achieved almost complete removal of fluorescing aromatics, NAs + S, and classical NAs (NAs with two oxygen atoms) at the dose of 2.0 mM O3. Both molecular ozone reaction and OH reaction were important pathways in transforming the organics in OSPW as supported by ozonation performance with and without TBA. (1)H NMR analyses further confirmed the removal of aromatics and NAs both qualitatively and quantitatively. All the three oxidation processes reduced the acute toxicity towards Vibrio fischeri and on goldfish primary kidney macrophages (PKMs), with ozonation being the most efficient. PMID:27232992

  10. Stress-induced perovskite to post-perovskite transition in CaIrO3 at room temperature

    Cheng, J.-G.; Zhou, J.-S.; Goodenough, J. B.

    2010-10-01

    Depending on how the compound is synthesized, both perovskite and post-perovskite phases of the CaIrO3 can be obtained easily. However, a transition from the perovskite phase to the post-perovskite phase cannot be achieved under 30 GPa hydrostatic pressure at room temperature. By treating the perovskite sample in different pressure conditions from mostly hydrostatic pressure to uniaxial pressure and examining the residual strain in these samples with x-ray powder diffraction, we have shown that an irreversible transition from the perovskite phase to the post-perovskite phase occurs partially in the sample under a lattice shear stress at room temperature.

  11. Ferroelectricity in Silver Perovskite Oxides

    Fu, Desheng; Itoh, Mitsuru

    2011-01-01

    There are two silver perovskite oxides: AgNbO3 and AgTaO3. AgNbO3 has a noncentrosymmetric group of Pmc21 at room temperature with a ferri-electric ordering of polarization. Such a ferri-electric state with small polarization can be changed into a ferroelectric state with very large polarization by a high electric field or by a chemical modification. The induced ferroelectric phase shows promising electromechanical response for applications in piezoelectric devices. In contrast, AgTaO3 is a q...

  12. Removal of Bacteria and Oil from Oilfield Sewage Using Potassium Ferrate Oxidation-Coagulation%高铁酸盐氧化絮凝去除油田污水中细菌和油

    阚连宝; 王宝辉; 马玲

    2012-01-01

    高铁酸盐是一种新型的水处理药剂.针对高铁酸盐的强氧化性,研究了高铁酸盐氧化絮凝去除油田污水中腐生菌( TGB)、铁细菌(FB)和油,结果表明,30 mg/L Fe (Ⅵ)投加量即可达到显著杀菌效果,而用1.01×10-3 mol/L的Fe(Ⅵ)就可以快速地氧化去除含油污水中的油.%A study was performed to remove saprophytic bacteria (TGB) , iron bacteria (FB) and oil from oilfield sewage using potassium ferrate oxidation-coagulation aiming at the strong oxidizability of potassium ferrate. Results showed that an obvious sterilizing effect could be obtained when the dosage of ferrate was 30 mg/L, and 1.01×l0-3mol/L of Fe (VI) could quickly remove the oil from the oilfield wastewater.

  13. Large Grained Perovskite Solar Cells Derived from Single-Crystal Perovskite Powders with Enhanced Ambient Stability.

    Yen, Hung-Ju; Liang, Po-Wei; Chueh, Chu-Chen; Yang, Zhibin; Jen, Alex K-Y; Wang, Hsing-Lin

    2016-06-15

    In this study, we demonstrate the large grained perovskite solar cells prepared from precursor solution comprising single-crystal perovskite powders for the first time. The resultant large grained perovskite thin film possesses a negligible physical (structural) gap between each large grain and is highly crystalline as evidenced by its fan-shaped birefringence observed under polarized light, which is very different from the thin film prepared from the typical precursor route (MAI + PbI2). PMID:27224963

  14. Strongly correlated perovskite fuel cells

    Zhou, You; Guan, Xiaofei; Zhou, Hua; Ramadoss, Koushik; Adam, Suhare; Liu, Huajun; Lee, Sungsik; Shi, Jian; Tsuchiya, Masaru; Fong, Dillon D.; Ramanathan, Shriram

    2016-06-01

    Fuel cells convert chemical energy directly into electrical energy with high efficiencies and environmental benefits, as compared with traditional heat engines. Yttria-stabilized zirconia is perhaps the material with the most potential as an electrolyte in solid oxide fuel cells (SOFCs), owing to its stability and near-unity ionic transference number. Although there exist materials with superior ionic conductivity, they are often limited by their ability to suppress electronic leakage when exposed to the reducing environment at the fuel interface. Such electronic leakage reduces fuel cell power output and the associated chemo-mechanical stresses can also lead to catastrophic fracture of electrolyte membranes. Here we depart from traditional electrolyte design that relies on cation substitution to sustain ionic conduction. Instead, we use a perovskite nickelate as an electrolyte with high initial ionic and electronic conductivity. Since many such oxides are also correlated electron systems, we can suppress the electronic conduction through a filling-controlled Mott transition induced by spontaneous hydrogen incorporation. Using such a nickelate as the electrolyte in free-standing membrane geometry, we demonstrate a low-temperature micro-fabricated SOFC with high performance. The ionic conductivity of the nickelate perovskite is comparable to the best-performing solid electrolytes in the same temperature range, with a very low activation energy. The results present a design strategy for high-performance materials exhibiting emergent properties arising from strong electron correlations.

  15. Common features of gallium perovskites

    Aleksiyko, R.; Berkowski, M.; Fink-Finowicki, J. [Polska Akademia Nauk, Warsaw (Poland). Inst. Fizyki; Byszewski, P.; Diduszko, R. [Polska Akademia Nauk, Warsaw (Poland). Inst. Fizyki; Inst. of Vacuum Technology, Warsaw (Poland); Dabrowski, B. [Northern Illinois Univ., De Kalb (United States). Dept. of Physics; Vasylechko, L.O. [Semiconductors Electronics Dept., State Univ. ' ' Lviv Politechnic' ' , Lviv (Ukraine)

    2001-07-01

    The Czochralski and floating zone methods have been used to grow single crystals of gallium perovskites solid solutions with rare earth elements La, Pr, Nd, Sm and with Sr. The structure of the crystals has been investigated by powder X-ray, synchrotron radiation and neutron diffraction methods over a wide temperature range. The unit cell volume at room temperature varies from approximately 228 to 236 A{sup 3} in Sm{sub 0.75}Nd{sub 0.25}GaO{sub 3} and La{sub 0.88}Sr{sub 0.12}GaO{sub 3-{delta}}, respectively. Position of atoms in the unit cell and evolution of perovskite lattice deformation induced by continuously varying average rare earth ionic radius is discussed. The unit cell parameters including atoms positions, thermal expansion coefficients, segregation coefficients and phase transition temperature scale with the unit cell volume in all investigated crystals. All these parameters may be represented as a function of average ionic radius of rare elements, however, this value is not well determined in these compounds because of ill determined coordination number. (orig.)

  16. Weakening of CaIrO3 during the perovskite-post perovskite transformation. (Invited)

    Dobson, D.; Hunt, S. A.; Weidner, D.; Walte, N.; Ammann, M. W.; Brodholt, J. P.

    2009-12-01

    The D’’ region at the core-mantle boundary of the Earth is thought to contain iron- and aluminium-bearing magnesium silicate in the calcium iridate structure. This recently discovered post-perovskite phase has been invoked to explain many of the anomalous seismic properties of D’’. Recent studies suggest that the lowermost mantle is rheologicaly distinct from the overlying perovskite-dominated mantle, however no studies of post-perovskite rheology have been reported to date. Here we present results of laboratory studies aimed at measuring the strength of the low-pressure analogue phase calcium iridate as it transforms from perovskite to post-perovskite. Experiments were performed in pure shear geometry using d-DIA presses and real-time X-radiographic imaging of strain; further, quenching, experiments are consistent with the in situ results. The results suggest that perovskite is at least 5 times stronger than post perovskite and there is a further weakening by a factor of two which occurs during the transformation; these are minimum estimates of the weakening. These results are support results from ab initio simulations of chemical diffusivity in MgSiO3 perovskite and post perovskite, which suggest there should be a significant weakening in simple shear and a smaller weakening in pure shear. If, as seems likely, a similar weakening occurs in lower mantle magnesium-silicate compositions this would have significant implications for the base of the lower mantle.

  17. High-performance perovskite light-emitting diodes via morphological control of perovskite films

    Yu, Jae Choul; Kim, Da Bin; Jung, Eui Dae; Lee, Bo Ram; Song, Myoung Hoon

    2016-03-01

    Solution-processable perovskite materials have garnered tremendous attention because of their excellent charge carrier mobility, possibility of a tunable optical bandgap, and high photoluminescence quantum efficiency (PLQE). In particular, the uniform morphology of a perovskite film is the most important factor in realizing perovskite light-emitting diodes (PeLEDs) with high efficiency and full-coverage electroluminescence (EL). In this study, we demonstrate highly efficient PeLEDs that contain a perovskite film with a uniform morphology by introducing HBr into the perovskite precursor. The introduction of HBr into the perovskite precursor results in a perovskite film with a uniform, continuous morphology because the HBr increases the solubility of the inorganic component in the perovskite precursor and reduces the crystallization rate of the perovskite film upon spin-coating. Moreover, PeLEDs fabricated using perovskite films with a uniform, continuous morphology, which were deposited using 6 vol% HBr in a dimethylformamide (DMF)/hydrobromic acid (HBr) cosolvent, exhibited full coverage of the green EL emission. Finally, the optimized PeLEDs fabricated with perovskite films deposited using the DMF/HBr cosolvent exhibited a maximum luminance of 3490 cd m-2 (at 4.3 V) and a luminous efficiency of 0.43 cd A-1 (at 4.3 V).Solution-processable perovskite materials have garnered tremendous attention because of their excellent charge carrier mobility, possibility of a tunable optical bandgap, and high photoluminescence quantum efficiency (PLQE). In particular, the uniform morphology of a perovskite film is the most important factor in realizing perovskite light-emitting diodes (PeLEDs) with high efficiency and full-coverage electroluminescence (EL). In this study, we demonstrate highly efficient PeLEDs that contain a perovskite film with a uniform morphology by introducing HBr into the perovskite precursor. The introduction of HBr into the perovskite precursor results in

  18. Perovskites As Electrocatalysts for Alkaline Water Electrolysis

    Nikiforov, Aleksey Valerievich; De La Osa Puebla, Ana Raquel; Jensen, Jens Oluf;

    2014-01-01

    robust method for synthesis of perovskites with various chemical compositions1. The electrochemical performance of the materials was tested through pellet pressing of the perovskite powders. This involved in some case a time consuming preparation process. Furthermore the technique should show the...... adequate reproducibility.2 In this work we show the development of the method, which was further used to compare the activity of various electrocatalysts (Figures 1,2). The electrocatalytic activity of all prepared perovskites was tested in 1M KOH at 80 °C, using an ink consisting of potassium exchanged...... Nafion®. All tests were performed in the potential window 0-700 mV on a glassy carbon electrode. All the tested perovskites were characterized by their overpotential , measured current at 650 mV, obtained kinetic current and Tafel slopes. It was also shown that this technique do not depend on the initial...

  19. Toxicity of organometal halide perovskite solar cells

    Babayigit, Aslihan; Ethirajan, Anitha; Muller, Marc; Conings, Bert

    2016-03-01

    In the last few years, the advent of metal halide perovskite solar cells has revolutionized the prospects of next-generation photovoltaics. As this technology is maturing at an exceptional rate, research on its environmental impact is becoming increasingly relevant.

  20. Perovskite Thin Films via Atomic Layer Deposition

    Sutherland, Brandon R.

    2014-10-30

    © 2014 Wiley-VCH Verlag GmbH & Co. KGaA. (Graph Presented) A new method to deposit perovskite thin films that benefit from the thickness control and conformality of atomic layer deposition (ALD) is detailed. A seed layer of ALD PbS is place-exchanged with PbI2 and subsequently CH3NH3PbI3 perovskite. These films show promising optical properties, with gain coefficients of 3200 ± 830 cm-1.

  1. Ambipolar solution-processed hybrid perovskite phototransistors

    Li, Feng

    2015-09-08

    Organolead halide perovskites have attracted substantial attention because of their excellent physical properties, which enable them to serve as the active material in emerging hybrid solid-state solar cells. Here we investigate the phototransistors based on hybrid perovskite films and provide direct evidence for their superior carrier transport property with ambipolar characteristics. The field-effect mobilities for triiodide perovskites at room temperature are measured as 0.18 (0.17) cm2 V−1 s−1 for holes (electrons), which increase to 1.24 (1.01) cm2 V−1 s−1 for mixed-halide perovskites. The photoresponsivity of our hybrid perovskite devices reaches 320 A W−1, which is among the largest values reported for phototransistors. Importantly, the phototransistors exhibit an ultrafast photoresponse speed of less than 10 μs. The solution-based process and excellent device performance strongly underscore hybrid perovskites as promising material candidates for photoelectronic applications.

  2. Perovskite Solar Cells: Beyond Methylammonium Lead Iodide.

    Boix, Pablo P; Agarwala, Shweta; Koh, Teck Ming; Mathews, Nripan; Mhaisalkar, Subodh G

    2015-03-01

    Organic-inorganic lead halide based perovskites solar cells are by far the highest efficiency solution-processed solar cells, threatening to challenge thin film and polycrystalline silicon ones. Despite the intense research in this area, concerns surrounding the long-term stability as well as the toxicity of lead in the archetypal perovskite, CH3NH3PbI3, have the potential to derail commercialization. Although the search for Pb-free perovskites have naturally shifted to other transition metal cations and formulations that replace the organic moiety, efficiencies with these substitutions are still substantially lower than those of the Pb-perovskite. The perovskite family offers rich multitudes of crystal structures and substituents with the potential to uncover new and exciting photophysical phenomena that hold the promise of higher solar cell efficiencies. In addressing materials beyond CH3NH3PbI3, this Perspective will discuss a broad palette of elemental substitutions, solid solutions, and multidimensional families that will provide the next fillip toward market viability of the perovskite solar cells. PMID:26262670

  3. High temperature elastic anisotropy of the perovskite and post-perovskite polymorphs of Al2O3

    Stackhouse, S.; Brodholt, J. P.; Price, G. D.

    2005-01-01

    Finite temperature ab initio molecular dynamics calculations were performed to determine the high temperature elastic and seismic properties of the perovskite and post-perovskite phases of pure end-member Al2O3. The post-perovskite phase exhibits very large degrees of shear-wave splitting. The incorporation of a few mole percent of Al2O3 into MgSiO3 is predicted to have little effect on the perovskite to post-perovskite phase transition pressure and seismic properties of the post-perovskite p...

  4. Oxygen permeation modelling of perovskites

    Hassel, van, E Edwin; Kawada, Tatsuya; Sakai, Natsuko; Yokokawa, Harumi; Dokiya, Masayuki; Bouwmeester, Henny J.M.

    1993-01-01

    A point defect model was used to describe the oxygen nonstoichiometry of the perovskites La0.75Sr0.25CrO3, La0.9Sr0.1FeO3, La0.9Sr0.1CoO3 and La0.8Sr0.2MnO3 as a function of the oxygen partial pressure. Form the oxygen vacancy concentration predicte by the point defect model, the ionic conductivity was calculated assuming a vacancy diffusion mechanism. The ionic conductivity was combined with the Wagner model for the oxidation of metals to yield an analytical expression for the oxygen permeat...

  5. Multiferroicity in Perovskite Manganite Superlattice

    Tao, Yong-Mei; Jiang, Xue-Fan; Liu, Jun-Ming

    2016-08-01

    Multiferroic properties of short period perovskite type manganite superlattice ((R1MnO3)n/(R2MnO3)n (n=1,2,3)) are considered within the framework of classical Heisenberg model using Monte Carlo simulation. Our result revealed the interesting behaviors in Mn spins structure in superlattice. Apart from simple plane spin cycloid structure which is shown in all manganites including bulk, film, and superlattice here in low temperature, a non-coplanar spiral spin structure is exhibited in a certain temperature range when n equals 1, 2 or 3. Specific heat, spin-helicity vector, spin correlation function, spin-helicity correlation function, and spin configuration are calculated to confirm this non-coplanar spiral spin structure. These results are associated with the competition among exchange interaction, magnetic anisotropy, and Dzyaloshinskii-Moriya interaction. Supported by the National Natural Science Foundation of China (NSFC) under Grant No. 11447136

  6. Making and Breaking of Lead Halide Perovskites

    Manser, Joseph S.

    2016-02-16

    A new front-runner has emerged in the field of next-generation photovoltaics. A unique class of materials, known as organic metal halide perovskites, bridges the gap between low-cost fabrication and exceptional device performance. These compounds can be processed at low temperature (typically in the range 80–150 °C) and readily self-assemble from the solution phase into high-quality semiconductor thin films. The low energetic barrier for crystal formation has mixed consequences. On one hand, it enables inexpensive processing and both optical and electronic tunability. The caveat, however, is that many as-formed lead halide perovskite thin films lack chemical and structural stability, undergoing rapid degradation in the presence of moisture or heat. To date, improvements in perovskite solar cell efficiency have resulted primarily from better control over thin film morphology, manipulation of the stoichiometry and chemistry of lead halide and alkylammonium halide precursors, and the choice of solvent treatment. Proper characterization and tuning of processing parameters can aid in rational optimization of perovskite devices. Likewise, gaining a comprehensive understanding of the degradation mechanism and identifying components of the perovskite structure that may be particularly susceptible to attack by moisture are vital to mitigate device degradation under operating conditions. This Account provides insight into the lifecycle of organic–inorganic lead halide perovskites, including (i) the nature of the precursor solution, (ii) formation of solid-state perovskite thin films and single crystals, and (iii) transformation of perovskites into hydrated phases upon exposure to moisture. In particular, spectroscopic and structural characterization techniques shed light on the thermally driven evolution of the perovskite structure. By tuning precursor stoichiometry and chemistry, and thus the lead halide charge-transfer complexes present in solution, crystallization

  7. Making and Breaking of Lead Halide Perovskites.

    Manser, Joseph S; Saidaminov, Makhsud I; Christians, Jeffrey A; Bakr, Osman M; Kamat, Prashant V

    2016-02-16

    A new front-runner has emerged in the field of next-generation photovoltaics. A unique class of materials, known as organic metal halide perovskites, bridges the gap between low-cost fabrication and exceptional device performance. These compounds can be processed at low temperature (typically in the range 80-150 °C) and readily self-assemble from the solution phase into high-quality semiconductor thin films. The low energetic barrier for crystal formation has mixed consequences. On one hand, it enables inexpensive processing and both optical and electronic tunability. The caveat, however, is that many as-formed lead halide perovskite thin films lack chemical and structural stability, undergoing rapid degradation in the presence of moisture or heat. To date, improvements in perovskite solar cell efficiency have resulted primarily from better control over thin film morphology, manipulation of the stoichiometry and chemistry of lead halide and alkylammonium halide precursors, and the choice of solvent treatment. Proper characterization and tuning of processing parameters can aid in rational optimization of perovskite devices. Likewise, gaining a comprehensive understanding of the degradation mechanism and identifying components of the perovskite structure that may be particularly susceptible to attack by moisture are vital to mitigate device degradation under operating conditions. This Account provides insight into the lifecycle of organic-inorganic lead halide perovskites, including (i) the nature of the precursor solution, (ii) formation of solid-state perovskite thin films and single crystals, and (iii) transformation of perovskites into hydrated phases upon exposure to moisture. In particular, spectroscopic and structural characterization techniques shed light on the thermally driven evolution of the perovskite structure. By tuning precursor stoichiometry and chemistry, and thus the lead halide charge-transfer complexes present in solution, crystallization

  8. Neutral- and Multi-Colored Semitransparent Perovskite Solar Cells

    Kyu-Tae Lee; L. Jay Guo; Hui Joon Park

    2016-01-01

    In this review, we summarize recent works on perovskite solar cells with neutral- and multi-colored semitransparency for building-integrated photovoltaics and tandem solar cells. The perovskite solar cells exploiting microstructured arrays of perovskite “islands” and transparent electrodes—the latter of which include thin metallic films, metal nanowires, carbon nanotubes, graphenes, and transparent conductive oxides for achieving optical transparency—are investigated. Moreover, the perovskite...

  9. Bismuth centred magnetic perovskite: A projected multiferroic

    In recent time substantial attention has been initiated to understand the physics behind multiferroism and to design new multiferroic materials. BiMnO3 and BiFeO3 are the well-studied Bi-centred multiferroic oxides. BiMnO3 is a ferromagnetic–ferroelectric (metastable) phase and require drastic conditions to synthesize. However, lanthanum substituted BiMnO3 phases stabilized at ambient pressure. It is thus of major importance to increase the number of ferromagnetic perovskites with Bi cations that could be designed under ambient conditions. In this article, we have presented an up to date report of investigations on Bi-centred magnetic perovskites, a prospective material for multiferroic application. Central focus is concentrated on La0.5Bi0.5MnO3 perovskite with various substitutions at different levels. A few of these perovskites are found to be of practical importance e.g. La0.5Bi0.5Mn0.67Co0.33O3 with high dielectric permittivity coupled with ferromagnetism. A comprehensive analysis of different physical functionalities and their interrelation for a wide range of compositions of these Bi-centred perovskites is presented. It has been found that the complex magnetic behaviour originates from mixed valence metal ions. The ferroelectricity is associated with the 6s2 lone pair of Bi3+ cations. The magnetic ground state influences the dielectric properties reflecting the multiferroism in a single material. - Highlights: • Multiferroics have attracted increasing attention due to their possible device applications. • Bismuth centred magnetic perovskite is one kind of such promising multiferroic materials. • Ferromagnetic Bi-perovskites, which are synthesized at ambient conditions, have been discussed

  10. X-ray imaging: Perovskites target X-ray detection

    Heiss, Wolfgang; Brabec, Christoph

    2016-05-01

    Single crystals of perovskites are currently of interest to help fathom fundamental physical parameters limiting the performance of perovskite-based polycrystalline solar cells. Now, such perovskites offer a technology platform for optoelectronic devices, such as cheap and sensitive X-ray detectors.

  11. Enhancing the grain size of organic halide perovskites by sulfonate-carbon nanotube incorporation in high performance perovskite solar cells.

    Zhang, Yong; Tan, Licheng; Fu, Qingxia; Chen, Lie; Ji, Ting; Hu, Xiaotian; Chen, Yiwang

    2016-04-14

    The grain size of perovskites was enhanced and the grain boundary was filled with sulfonate carbon nanotubes (s-CNTs) during the CH3NH3PbI3 perovskite precursor solution spin-coating process with the incorporation of s-CNTs. The performance of s-CNT incorporated perovskite solar cells remarkably increased from 10.3% to 15.1% (best) compared with pristine CNT incorporated perovskite solar cells. PMID:26940646

  12. Rational Strategies for Efficient Perovskite Solar Cells.

    Seo, Jangwon; Noh, Jun Hong; Seok, Sang Il

    2016-03-15

    A long-standing dream in the large scale application of solar energy conversion is the fabrication of solar cells with high-efficiency and long-term stability at low cost. The realization of such practical goals depends on the architecture, process and key materials because solar cells are typically constructed from multilayer heterostructures of light harvesters, with electron and hole transporting layers as a major component. Recently, inorganic-organic hybrid lead halide perovskites have attracted significant attention as light absorbers for the fabrication of low-cost and high-efficiency solar cells via a solution process. This mainly stems from long-range ambipolar charge transport properties, low exciton binding energies, and suitable band gap tuning by managing the chemical composition. In our pioneering work, a new photovoltaic platform for efficient perovskite solar cells (PSCs) was proposed, which yielded a high power conversion efficiency (PCE) of 12%. The platform consisted of a pillared architecture of a three-dimensional nanocomposite of perovskites fully infiltrating mesoporous TiO2, resulting in the formation of continuous phases and perovskite domains overlaid with a polymeric hole conductor. Since then, the PCE of our PSCs has been rapidly increased from 3% to over 20% certified efficiency. The unprecedented increase in the PCE can be attributed to the effective integration of the advantageous attributes of the refined bicontinuous architecture, deposition process, and composition of perovskite materials. Specifically, the bicontinuous architectures used in the high efficiency comprise a layer of perovskite sandwiched between mesoporous metal-oxide layer, which is a very thinner than that of used in conventional dye-sensitized solar cells, and hole-conducting contact materials with a metal back contact. The mesoporous scaffold can affect the hysteresis under different scan direction in measurements of PSCs. The hysteresis also greatly depends on

  13. Quantum-dot-in-perovskite solids

    Ning, Zhijun

    2015-07-15

    © 2015 Macmillan Publishers Limited. All rights reserved. Heteroepitaxy - atomically aligned growth of a crystalline film atop a different crystalline substrate - is the basis of electrically driven lasers, multijunction solar cells, and blue-light-emitting diodes. Crystalline coherence is preserved even when atomic identity is modulated, a fact that is the critical enabler of quantum wells, wires, and dots. The interfacial quality achieved as a result of heteroepitaxial growth allows new combinations of materials with complementary properties, which enables the design and realization of functionalities that are not available in the single-phase constituents. Here we show that organohalide perovskites and preformed colloidal quantum dots, combined in the solution phase, produce epitaxially aligned \\'dots-in-a-matrix\\' crystals. Using transmission electron microscopy and electron diffraction, we reveal heterocrystals as large as about 60 nanometres and containing at least 20 mutually aligned dots that inherit the crystalline orientation of the perovskite matrix. The heterocrystals exhibit remarkable optoelectronic properties that are traceable to their atom-scale crystalline coherence: photoelectrons and holes generated in the larger-bandgap perovskites are transferred with 80% efficiency to become excitons in the quantum dot nanocrystals, which exploit the excellent photocarrier diffusion of perovskites to produce bright-light emission from infrared-bandgap quantum-tuned materials. By combining the electrical transport properties of the perovskite matrix with the high radiative efficiency of the quantum dots, we engineer a new platform to advance solution-processed infrared optoelectronics.

  14. Removal of selected endocrine disrupting chemicals (EDCs) and pharmaceuticals and personal care products (PPCPs) during ferrate(VI) treatment of secondary wastewater effluents.

    Yang, Bin; Ying, Guang-Guo; Zhao, Jian-Liang; Liu, Shan; Zhou, Li-Jun; Chen, Feng

    2012-05-01

    We investigated the removal efficiencies of 68 selected endocrine disrupting chemicals (EDCs) and pharmaceuticals and personal care products (PPCPs) spiked in a wastewater matrix by ferrate (Fe(VI)) and further evaluated the degradation of these micropollutants present in secondary effluents of two wastewater treatment plants (WWTPs) by applying Fe(VI) treatment technology. Fe(VI)treatment resulted in selective oxidation of electron-rich organic moieties of these target compounds, such as phenol, olefin, amine and aniline moieties. But Fe(VI) failed to react with triclocarban, 3 androgens, 7 acidic pharmaceuticals, 2 neutral pharmaceuticals and erythromycin-H(2)O.Thirty-one target EDCs and PPCPs were detected in the effluents of the two WWTPs with concentrations ranging from 0.2 ± 0.1 ng L(-1) to 1156 ± 182 ng L(-1).Fe(VI) treatment resulted in further elimination of the detected EDCs and PPCPs during Fe(VI) treatment of the secondary wastewater effluents. The results from this study clearly demonstrated the effectiveness of Fe(VI) treatment as a tertiary treatment technology for a broad spectrum of micropollutants in wastewater. PMID:22342241

  15. Nanophotonic front electrodes for perovskite solar cells

    Paetzold, Ulrich Wilhelm; Qiu, Weiming; Finger, Friedhelm; Poortmans, Jef; Cheyns, David

    2015-04-01

    In less than 3 years' time, a vast progress in power conversion efficiencies of organometal halide perovskite solar cells has been achieved by optimization of the device architecture, charge transport layers, and interfaces. A further increase in these efficiencies is expected from an improvement in the optical properties via anti-reflection coatings and nanophotonic light management concepts. In this contribution, we report on the development and implementation of a nanophotonic front electrode for perovskite solar cells. The nanostructures were replicated via the versatile and large-area compatible UV-nanoimprint lithography. The shallow design of the used transparent and conductive nanostructures enabled easy integration into our solution-based baseline process. Prototype methylammonium lead iodide perovskite solar cells show an improvement of 5% in short-circuit current density and an improvement from 9.6% to 9.9% in power conversion efficiency compared to the flat reference device.

  16. Metal halide perovskites for energy applications

    Zhang, Wei; Eperon, Giles E.; Snaith, Henry J.

    2016-06-01

    Exploring prospective materials for energy production and storage is one of the biggest challenges of this century. Solar energy is one of the most important renewable energy resources, due to its wide availability and low environmental impact. Metal halide perovskites have emerged as a class of semiconductor materials with unique properties, including tunable bandgap, high absorption coefficient, broad absorption spectrum, high charge carrier mobility and long charge diffusion lengths, which enable a broad range of photovoltaic and optoelectronic applications. Since the first embodiment of perovskite solar cells showing a power conversion efficiency of 3.8%, the device performance has been boosted up to a certified 22.1% within a few years. In this Perspective, we discuss differing forms of perovskite materials produced via various deposition procedures. We focus on their energy-related applications and discuss current challenges and possible solutions, with the aim of stimulating potential new applications.

  17. Autothermal reforming catalyst having perovskite structure

    Krumpel, Michael; Liu, Di-Jia

    2009-03-24

    The invention addressed two critical issues in fuel processing for fuel cell application, i.e. catalyst cost and operating stability. The existing state-of-the-art fuel reforming catalyst uses Rh and platinum supported over refractory oxide which add significant cost to the fuel cell system. Supported metals agglomerate under elevated temperature during reforming and decrease the catalyst activity. The catalyst is a perovskite oxide or a Ruddlesden-Popper type oxide containing rare-earth elements, catalytically active firs row transition metal elements, and stabilizing elements, such that the catalyst is a single phase in high temperature oxidizing conditions and maintains a primarily perovskite or Ruddlesden-Popper structure under high temperature reducing conditions. The catalyst can also contain alkaline earth dopants, which enhance the catalytic activity of the catalyst, but do not compromise the stability of the perovskite structure.

  18. 二沉池出水中双酚A的高铁酸钾氧化降解行为%Potassium ferrate (Ⅵ) degradation of bisphenol A in the secondary sedimentation tank effluent

    丁博; 尹平河; 赵玲; 王丹

    2011-01-01

    考察了pH、温度、反应时间、浓度、光照、腐殖酸、干扰离子等因素对高铁酸钾降解双酚A的影响,并探讨了高铁酸钾降解双酚A的动力学机理以及对二沉池出水中双酚A的降解作用.研究表明:在pH=9.0,室温条件下,反应10min后双酚A的降解率达最大值;光照对双酚A降解基本没有影响;腐殖酸对双酚A的降解有一定促进作用;干扰离子对双酚A降解影响较为复杂,既有促进作用又有抑制作用.以二沉池出水为基体,当m(高铁酸钾):m(双酚A)=5:1,双酚A初始质量浓度为5.0 mg/L时,反应4min后,双酚A的降解率达99%.实验结果表明高铁酸钾对双酚A具有良好的降解效果.%The effects of pH, te mperature,time, concentration, illumination, humic acid, interference ions, etc. on potassium ferrate ( Ⅵ ) degradation of bisphenol A have been investigated. The kinetics mechanisms of potassium ferrate (Ⅵ) degradation of bisphenol A and the degradation effect on the secondary sedimentation tank effluent are discussed. The research shows that the degradation rate of bisphenol A reaches the maximum value ,when pH is 9.0,at room temperature and reaction time is 10 min. Illumination has no effect on the degradation of bisphenol A, humic acid has stimulative effect on the degradation of bisphenol A to a certain extent, and the effect of interference ions on the degradation of bisphenol A is rather complicated, having both stimulative effect and inhibition effect. The secondary sedimentation tank effluent is used as substrate, and the degradation rate of bisphenol A reaches 99%,when m[potassium ferrate ( Ⅵ )] :m(bisphenol A)=5:l ,the initial mass concentration of bisphenol A is 5.0 mg/L and reaction time is 4 min. The results show that potassium ferrate (Ⅵ) has quite good degradation effect on bisphenol A.

  19. Ordered perovskites with cationic vacancies. 4

    Compounds of the composition Ba6B(III)2vacantTe(VI)3O18 equivalent to Ba2Ba(III)sub(2/3)vacantsub(1/3)Te(VI)O6, with B(III) = Pr, Nd, Sm-Lu, Y crystallize with a cubic perovskite lattice. The cell parameters diminish as the size of B(III) falls (B(III) = Pr: a = 8.52 A; Lu: a = 8.33 A). In contrast to the corresponding perovskites with U(VI) and W(VI) no polymorphism is observed. (author)

  20. Synthesis of solid solutions of perovskites

    Dambekalne, M.Y.; Antonova, M.K.; Perro, I.T.; Plaude, A.V.

    1986-03-01

    The authors carry out thermographic studies, using a derivatograph, in order to understand the nature of the processes taking place during the synthesis of solid solutions of perovskites. Based on the detailed studies on the phase transformations occurring in the charges of the PSN-PMN solid solutions and on the selection of the optimum conditions for carrying out their synthesis, the authors obtained a powder containing a minimum quantity of the undesirable pyrochlore phase and by sintering it using the hot pressing method, they produced single phase ceramic specimens containing the perovskite phase alone with a density close to the theoretical value and showing zero apparent porosity and water absorption.

  1. Partial oxidation of 2-propanol on perovskites

    Sumathi, R.; Viswanathan, B.; Varadarajan, T.K. [Indian Inst. of Tech., Madras (India). Dept. of Chemistry

    1998-12-31

    Partial oxidation of 2-propanol was carried out on AB{sub 1-x}B`{sub x}O{sub 3} (A=Ba, B=Pb, Ce, Ti; B`=Bi, Sb and Cu) type perovskite oxides. Acetone was the major product observed on all the catalysts. All the catalysts underwent partial reduction during the reaction depending on the composition of the reactant, nature of the B site cation and the extent of substitution at B site. The catalytic activity has been correlated with the reducibility of the perovskite oxides determined from Temperature Programmed Reduction (TPR) studies. (orig.)

  2. Elastic anisotropy of FeSiO3 end-members of the perovskite and post-perovskite phases

    Stackhouse, S.; Brodholt, J. P.; Price, G. D.

    2006-01-01

    The athermal elastic constants of the perovskite and post-perovskite polymorphs of pure end-member FeSiO3 were calculated from ab initio calculations. We predict that incorporating ten mole percent FeSiO3 together with four mole percent Al2O3 into MgSiO3 reduces the perovskite to post-perovskite phase transition pressure by 5 GPa. Small changes in the seismic properties of the post-perovskite phase due to the incorporation of iron and alumina are compatible with observations for the lower man...

  3. Prediction of post-post-perovskite transitions

    Umemoto, K.

    2008-12-01

    In the Earth, the post-perovskite structure is the final form of MgSiO3. However, in the solar giants and exoplanets in which pressure is much higher than the Earth, we can expect further phase transitions beyond the post-perovskite phase, i.e., post-post-perovskite transitions. Here we propose by first principles two candidates of crystalline post-post-perovskite phases of NaMgF3, which is a low-pressure analog of MgSiO3: U2S3-type and P63/mmc phases. Then we demonstrate that Al2O3 should undergo a transition to the U2S3-type phase at ~3.7 Mbar. This transformation should be important for the analysis of shock data in this pressure range, since alumina is used as window material. Our calculated compression curves agree with shock data excellently, suggesting the presence of two phase transitions (corundum-to-Rh2O3(II)-type and Rh2O3(II)-type-to-CaIrO3-type) in shock data. Our prediction also suggests that the multi-Mbar crystal chemistry of planet-forming minerals might be related to that of the rare-earth sulfides. Computations were performed at the Minnesota Supercomputing Institute. Research was supported by NSF grants EAR-0135533, EAR-0230319, and ITR-0428774 (VLab).

  4. High performance magnetocaloric perovskites for magnetic refrigeration

    Bahl, Christian R. H.; Velazquez, David; Nielsen, Kaspar K.;

    2012-01-01

    We have applied mixed valance manganite perovskites as magnetocaloric materials in a magnetic refrigeration device. Relying on exact control of the composition and a technique to process the materials into single adjoined pieces, we have observed temperature spans above 9 K with two materials...

  5. Electrochemical Preparation of Sodium Ferrate(Ⅵ) Using Silicon Iron as Anode in Non-Diaphragm Electrobath%硅铁阳极溶出非隔膜电解制备高铁酸钠

    刘永春; 谢家理

    2004-01-01

    Using silicon iron as anode to preparation sodium ferrate(Ⅵ) in non-diaphragm electrobath. The maximum current yield was reached to 43.0% (concentration of ferrate (Ⅵ) is electrolysis duration is 180mins. It proved that silicon iron anode is better than other reported anode, such as carbon iron or zinc white ironanode ect..%作者报道了用硅铁作为阳极,在非隔膜电解槽中电解制备了新型高效水处理剂高铁酸钠,并探索了最佳反应条件.当槽电压为3~7V,电流密度为40 mA·cm-2,用含1%硅酸钠的40%的氢氧化钠为电解液,反应体系温度控制在35~40℃,电解180min,电流效率可达43.0%,可得到浓度为0.078mol·L-1的高铁酸钠.实验表明,用硅铁作阳极材料,比碳钢、镀锌铁皮、铸铁等阳极材料的电流效率以及电解产率都高得多.

  6. Implications of post-perovskite transport properties for core-mantle dynamics

    ČÍŽKOVÁ, Hana; Čadek, Ondřej; Matyska, Ctirad; Yuen, David A.

    2010-01-01

    Abstract Recent evidence on perovskite to post-perovskite phase change in the lowermost mantle suggests that post-perovskite piles or lens should be present in the relatively cold downwelling areas, while the roots of the hot upwelling plumes consist of perovskite. Post-perovskite is often believed to be deformed predominantly by the dislocation creep and there are some hints that the activation parameters of the dislocation creep in post-perovskite induce lower viscosity than that...

  7. Band gap engineering strategy via polarization rotation in perovskite ferroelectrics

    We propose a strategy to engineer the band gaps of perovskite oxide ferroelectrics, supported by first principles calculations. We find that the band gaps of perovskites can be substantially reduced by as much as 1.2 eV through local rhombohedral-to-tetragonal structural transition. Furthermore, the strong polarization of the rhombohedral perovskite is largely preserved by its tetragonal counterpart. The B-cation off-center displacements and the resulting enhancement of the antibonding character in the conduction band give rise to the wider band gaps of the rhombohedral perovskites. The correlation between the structure, polarization orientation, and electronic structure lays a good foundation for understanding the physics of more complex perovskite solid solutions and provides a route for the design of photovoltaic perovskite ferroelectrics

  8. Perovskite type nanopowders and thin films obtained by chemical methods

    Viktor Fruth

    2010-09-01

    Full Text Available The review presents the contribution of the authors, to the preparation of two types of perovskites, namely BiFeO3 and LaCoO3, by innovative methods. The studied perovskites were obtained as powders, films and sintered bodies. Their complex structural and morphological characterization is also presented. The obtained results have underlined the important influence of the method of preparation on the properties of the synthesized perovskites.

  9. A Review on Visible Light Active Perovskite-Based Photocatalysts

    Pushkar Kanhere; Zhong Chen

    2014-01-01

    Perovskite-based photocatalysts are of significant interest in the field of photocatalysis. To date, several perovskite material systems have been developed and their applications in visible light photocatalysis studied. This article provides a review of the visible light (λ > 400 nm) active perovskite-based photocatalyst systems. The materials systems are classified by the B site cations and their crystal structure, optical properties, electronic structure, and photocatalytic performance ...

  10. A Physics-based Analytical Model for Perovskite Solar Cells

    Sun, Xingshu; Asadpour, Reza; Nie, Wanyi; Mohite, Aditya D.; Alam, Muhammad A.

    2015-01-01

    Perovskites are promising next-generation absorber materials for low-cost and high-efficiency solar cells. Although perovskite cells are configured similar to the classical solar cells, their operation is unique and requires development of a new physical model for characterization, optimization of the cells, and prediction of the panel performance. In this paper, we develop such a physics-based analytical model to describe the operation of different types of perovskite solar cells, explicitly...

  11. Plasmonic Nanostructures and Film Crystallization in Perovskite Solar Cells

    Saliba, Michael; SNAITH, Henry

    2014-01-01

    The aim of this thesis is to develop a deeper understanding and the technology in the nascent field of solid-state organic-inorganic perovskite solar cells. In recent years, perovskite materials have emerged as a low-cost, thin-film technology with efficiencies exceeding 16% challenging the quasi-paradigm that high efficiency photovoltaics must come at high costs. This thesis investigates perovskite solar cells in more detail with a focus on incorporating plasmonic nanostructures and p...

  12. Predominant Intermediate-Spin Ferrous Iron in Lowermost Mantle Post-Perovskite and Perovskite

    Lin, J.; Watson, H. C.; Vanko, G.; Alp, E. E.; Prakapenka, V.; Dera, P.; Struzhkin, V. V.; Kubo, A.; Zhao, J.; McCammon, C.; Evans, W. J.

    2008-12-01

    Silicate post-perovskite and perovskite are believed to be the dominant minerals of the lowermost mantle and the lower mantle, respectively, and their properties, which can be strongly influenced by the electronic state of iron in these phases, affect our understanding of the nature of the deep Earth. To date, in these minerals the electronic spin state of iron remains unknown under lowermost-mantle pressure-temperature conditions, although recent studies have showed an electronic spin crossover from high-spin to low-spin in ferropericlase over an extended pressure-temperature range of the lower mantle (i.e., Lin et al., Science, 2007) and from high-spin to intermediate-spin in silicate perovskite near the top of the lower mantle (McCammon et al., Nature Geoscience, 2008). Here we report the spin and valence states of iron in post-perovskite and perovskite at pressure-temperature conditions relevant to the lowermost mantle using in situ X-ray emission, X-ray diffraction, and synchrotron Mossbauer spectroscopies in a laser-heated diamond cell. Perovskite and post-perovskite display extremely high quadrupole splitting (QS) of approximately 4 mm/s and relatively high center shift in the synchrotron Mossbauer spectra at 110 GPa and 134 GPa, respectively. Our results show that Fe2+ exists predominantly in the intermediate-spin state with a total spin number of one in both phases (Lin et al., Nature Geoscience, 2008). Together with recent results on the effects of the spin transition in the lower-mantle ferropericlase (see a recent review by Lin and Tsuchiya, PEPI, 2008), here we will address how the electronic spin states in lower-mantle phases and their associated effects affect our understanding on the composition, geophysics, and dynamics of the lower mantle.. References: 1. Lin, J. F., H. C. Watson, G. Vanko, E. E. Alp, V. B. Prakapenka, P. Dera, V. V. Struzhkin, A. Kubo, J. Zhao, C. McCammon, W. J. Evans, Intermediate-spin ferrous iron in lowermost mantle post-perovskite

  13. Organohalide Perovskites for Solar Energy Conversion.

    Lin, Qianqian; Armin, Ardalan; Burn, Paul L; Meredith, Paul

    2016-03-15

    Lead-based organohalide perovskites have recently emerged as arguably the most promising of all next generation thin film solar cell technologies. Power conversion efficiencies have reached 20% in less than 5 years, and their application to other optoelectronic device platforms such as photodetectors and light emitting diodes is being increasingly reported. Organohalide perovskites can be solution processed or evaporated at low temperatures to form simple thin film photojunctions, thus delivering the potential for the holy grail of high efficiency, low embedded energy, and low cost photovoltaics. The initial device-driven "perovskite fever" has more recently given way to efforts to better understand how these materials work in solar cells, and deeper elucidation of their structure-property relationships. In this Account, we focus on this element of organohalide perovskite chemistry and physics in particular examining critical electro-optical, morphological, and architectural phenomena. We first examine basic crystal and chemical structure, and how this impacts important solar-cell related properties such as the optical gap. We then turn to deeper electronic phenomena such as carrier mobilities, trap densities, and recombination dynamics, as well as examining ionic and dielectric properties and how these two types of physics impact each other. The issue of whether organohalide perovskites are predominantly nonexcitonic at room temperature is currently a matter of some debate, and we summarize the evidence for what appears to be the emerging field consensus: an exciton binding energy of order 10 meV. Having discussed the important basic chemistry and physics we turn to more device-related considerations including processing, morphology, architecture, thin film electro-optics and interfacial energetics. These phenomena directly impact solar cell performance parameters such as open circuit voltage, short circuit current density, internal and external quantum efficiency

  14. Elastic anisotropy of experimental analogues of perovskite and post-perovskite help to interpret D'' diversity.

    Yoneda, Akira; Fukui, Hiroshi; Xu, Fang; Nakatsuka, Akihiko; Yoshiasa, Akira; Seto, Yusuke; Ono, Kenya; Tsutsui, Satoshi; Uchiyama, Hiroshi; Baron, Alfred Q R

    2014-01-01

    Recent studies show that the D'' layer, just above the Earth's core-mantle boundary, is composed of MgSiO3 post-perovskite and has significant lateral inhomogeneity. Here we consider the D'' diversity as related to the single-crystal elasticity of the post-perovskite phase. We measure the single-crystal elasticity of the perovskite Pbnm-CaIrO3 and post-perovskite Cmcm-CaIrO3 using inelastic X-ray scattering. These materials are structural analogues to same phases of MgSiO3. Our results show that Cmcm-CaIrO3 is much more elastically anisotropic than Pbnm-CaIrO3, which offers an explanation for the enigmatic seismic wave velocity jump at the D'' discontinuity. Considering the relation between lattice preferred orientation and seismic anisotropy in the D'' layer, we suggest that the c axis of post-perovskite MgSiO3 aligns vertically beneath the Circum-Pacific rim, and the b axis vertically beneath the Central Pacific. PMID:24670790

  15. Molecular dynamics of MgSiO3 perovskite melting

    Liu Zi-Jiang; Cheng Xin-Lu; Yang Xiang-Dong; Zhang Hong; Cai Ling-Cang

    2006-01-01

    The melting curve of MgSiO3 perovskite is simulated using molecular dynamics simulations method at high pressure. It is shown that the simulated equation of state of MgSiO3 perovskite is very successful in reproducing accurately the experimental data. The pressure dependence of the simulated melting temperature of MgSiO3 perovskite reproduces the stability of the orthorhombic perovskite phase up to high pressure of 13OGPa at ambient temperature, consistent with the theoretical data of the other calculations. It is shown that its transformation to the cubic phase and melting at high pressure and high temperature are in agreement with recent experiments.

  16. Multiferroic Compounds with Double-Perovskite Structures

    Noriya Ichikawa

    2011-01-01

    Full Text Available New multiferroic compounds with double-perovskite structures were synthesized. Bi2NiMnO6 was synthesized in bulk form by high-pressure synthesis and also in a thin-film form by epitaxial growth. The material showed both ferromagnetic and ferroelectric properties, i.e., the multiferroic property at low temperature. Bi2FeCrO6 was also fabricated in a (1 1 1 oriented BiFeO3/BiCrO3 artificial superlattice, with a 1/1 stacking period. The superlattice film showed ferromagnetic behavior and polarization switching at room temperature. In the compounds, Bi3+ ion, located at the A site in the perovskite structure, caused ferroelectric structural distortion, and the B-site ordering of the Ni2+ and Mn4+ ions (Fe3+ and Cr3+ ions in a rock-salt configuration led to ferromagnetism according to the Kanamori-Goodenough rule.

  17. Machine learning bandgaps of double perovskites

    Pilania, G.; Mannodi-Kanakkithodi, A.; Uberuaga, B. P.; Ramprasad, R.; Gubernatis, J. E.; Lookman, T.

    2016-01-01

    The ability to make rapid and accurate predictions on bandgaps of double perovskites is of much practical interest for a range of applications. While quantum mechanical computations for high-fidelity bandgaps are enormously computation-time intensive and thus impractical in high throughput studies, informatics-based statistical learning approaches can be a promising alternative. Here we demonstrate a systematic feature-engineering approach and a robust learning framework for efficient and accurate predictions of electronic bandgaps of double perovskites. After evaluating a set of more than 1.2 million features, we identify lowest occupied Kohn-Sham levels and elemental electronegativities of the constituent atomic species as the most crucial and relevant predictors. The developed models are validated and tested using the best practices of data science and further analyzed to rationalize their prediction performance.

  18. Post-perovskite transitions in CaB4+O3 at high pressure

    Akaogi, M.; Shirako, Y.; Kojitani, H.; Takamori, S.; Yamaura, K.; Takayama-Muromachi, E.

    2010-03-01

    High-pressure phase transitions in CaRhO3 were examined using a multianvil apparatus up to 27 GPa and 1930 oC. CaRhO3 perovskite transforms to post-perovskite via a monoclinic intermediate phase with increasing pressure. Volume changes for the transitions of perovskite - intermediate phase and of intermediate phase - post-perovskite are -1.1 and -0.7 %, respectively. CaRhO3 post-perovskite is the fourth quenchable post-perovskite oxide found so far. By high-temperature calorimetric experiments, enthalpy of the perovskite - post-perovskite transition in CaRuO3 was measured as 15.2±3.3 kJ/mol. Combining the datum with those of CaIrO3, it is shown that CaIrO3 perovskite is energetically less stable than CaRuO3 perovskite. This is consistent with the fact that orthorhombic distortion of CaIrO3 perovskite is larger than CaRuO3, as indicated with the tilt-angle of octahedral framework of perovskite structure. The transition pressure from perovskite to post-perovskite in CaBO3 (B = Ru, Rh, Ir) increases almost linearly with decreasing the tilt-angle, suggesting that the perovskite - post-perovskite transition may result from instability of the perovskite structure with pressure.

  19. Elastic anisotropy of experimental analogues of perovskite and post-perovskite help to interpret D′′ diversity

    Yoneda, Akira; Fukui, Hiroshi; Xu, Fang; Nakatsuka, Akihiko; Yoshiasa, Akira; Seto, Yusuke; Ono, Kenya; Tsutsui, Satoshi; Uchiyama, Hiroshi; Baron, Alfred Q. R.

    2014-01-01

    Recent studies show that the D′′ layer, just above the Earth's core–mantle boundary, is composed of MgSiO3 post-perovskite and has significant lateral inhomogeneity. Here we consider the D′′ diversity as related to the single-crystal elasticity of the post-perovskite phase. We measure the single-crystal elasticity of the perovskite Pbnm-CaIrO3 and post-perovskite Cmcm-CaIrO3 using inelastic X-ray scattering. These materials are structural analogues to same phases of MgSiO3. Our results show t...

  20. Theoretical determination of the Raman spectra of MgSiO3 perovskite and post-perovskite at high pressure

    Caracas, Razvan; Cohen, Ronald E.

    2006-01-01

    We use the density functional perturbation theory to determine for the first time the pressure evolution of the Raman intensities for a mineral, the two high-pressure structures of MgSiO3 perovskite and post-perovskite. At high pressures, the Raman powder spectra reveals three main peaks for the perovskite structure and one main peak for the post-perovskite structure. Due to the large differences in the spectra of the two phases Raman spectroscopy can be used as a good experimental indication...

  1. Wet etching methods for perovskite substrates

    Leca, Victor; Rijnders, Guus; Koster, Gertjan; Blank, Dave H.A.; Rogalla, Horst

    2000-01-01

    In oxide electronics substrates with atomically flat terraces are a request for growing high-quality epitaxial thin films. In this paper results on chemical etching of some substrates with perovskite, ABO3, structure (e.g., SrTiO3, LSAT - the (LaAlO3)0.3(Sr2AlTaO6)0.35 solid solution, and NdGaO3) ar

  2. Nanophotonic front electrodes for perovskite solar cells

    Paetzold, Ulrich Wilhelm; Qiu, Weiming; Finger, Friedhelm; POORTMANS, Jef; Cheyns, David

    2015-01-01

    In less than 3 years' time, a vast progress in power conversion efficiencies of organometal halide perovskite solar cells has been achieved by optimization of the device architecture, charge transport layers, and interfaces. A further increase in these efficiencies is expected from an improvement in the optical properties via anti-reflection coatings and nanophotonic light management concepts. In this contribution, we report on the development and implementation of a nanophotonic front electr...

  3. Incoherent Charge Dynamics in Perovskite Manganese Oxides

    NAKANO, HIROKI; Motome, Yukitoshi; Imada, Masatoshi

    2000-01-01

    A minimal model is proposed for the perovskite manganese oxides showing the strongly incoherent charge dynamics with a suppressed Drude weight in the ferromagnetic and metallic phase near the insulator. We investigate a generalized double-exchange model including three elements; the orbital degeneracy of $e_g$ conduction bands, the Coulomb interaction and fluctuating Jahn-Teller distortions. We demonstrate that Lancz$\\ddot{\\rm o}$s diagonalization calculations combined with Monte Carlo sampli...

  4. High performance magnetocaloric perovskites for magnetic refrigeration

    VelÁzquez, David

    2012-01-01

    We have applied mixed valance manganite perovskites as magnetocaloric materials in a magnetic refrigeration device. Relying on exact control of the composition and a technique to process the materials into single adjoined pieces, we have observed temperature spans above 9 K with two materials. Reasonable correspondence is found between experiments and a 2D numerical model, using the measured magnetocaloric properties of the two materials as input. © 2012 American Institute of Physics.

  5. Topological Oxide Insulator in Cubic Perovskite Structure

    Hosub Jin; Rhim, Sonny H.; Jino Im; Freeman, Arthur J.

    2013-01-01

    The emergence of topologically protected conducting states with the chiral spin texture is the most prominent feature at the surface of topological insulators. On the application side, large band gap and high resistivity to distinguish surface from bulk degrees of freedom should be guaranteed for the full usage of the surface states. Here, we suggest that the oxide cubic perovskite YBiO3, more than just an oxide, defines itself as a new three-dimensional topological insulator exhibiting both ...

  6. Transformational Weakening During the Perovskite-Post Perovskite Phase Transition in CaIrO3

    Hunt, S. A.; Dobson, D. P.; Weidner, D. J.; Li, L.; Vaughan, M. T.; Walte, N.; Brodholt, J. P.

    2007-12-01

    The D" layer plays a fundamental role in core - mantle interactions. The recent discovery of a CaIrO3 structured phase of MgSiO3, the so called post-perovskite (ppv) phase, significantly altered our understanding of the seismic and dynamic properties of the D". Here we report results of a study of the rheology during transformation from pv to pvv. The experiments were performed using the D-DIA on the X17B2 beamline at NSLS. A sample of presintered perovskite structured CaIrO3 was deformed, along with a MgO stress calibrant, during heating at 3 GPa and up to 1000°C in a 8mm D-DIA assembly. The stress was measured by X-ray diffraction from the MgO sample and a proxy for the phase proportions was the relative strengths of unique perovskite and post-perovskite diffraction peaks from the CaIrO3 sample. The strain was measured by X-radiography, from the position of Platinum foils placed above, between and below the two samples. From this data the viscosity of the CaIrO3 sample can be calculated as well as the progress of the reaction. During the transformation to post-perovskite we observed a two fold weakening of the pv and ppv mixture; followed by an increase in the strength of the mixture to greater than that of that starting perovskite-structured material. If MgSiO3 behaves in the same way during pv - ppv transformation it will cause a viscous decoupling between the lower mantle and the D". This in turn has major implications for the topography that can be supported at the top of the D" layer.

  7. Resistance switching memory in perovskite oxides

    The resistance switching behavior has recently attracted great attentions for its application as resistive random access memories (RRAMs) due to a variety of advantages such as simple structure, high-density, high-speed and low-power. As a leading storage media, the transition metal perovskite oxide owns the strong correlation of electrons and the stable crystal structure, which brings out multifunctionality such as ferroelectric, multiferroic, superconductor, and colossal magnetoresistance/electroresistance effect, etc. The existence of rich electronic phases, metal–insulator transition and the nonstoichiometric oxygen in perovskite oxide provides good platforms to insight into the resistive switching mechanisms. In this review, we first introduce the general characteristics of the resistance switching effects, the operation methods and the storage media. Then, the experimental evidences of conductive filaments, the transport and switching mechanisms, and the memory performances and enhancing methods of perovskite oxide based filamentary RRAM cells have been summarized and discussed. Subsequently, the switching mechanisms and the performances of the uniform RRAM cells associating with the carrier trapping/detrapping and the ferroelectric polarization switching have been discussed. Finally, the advices and outlook for further investigating the resistance switching and enhancing the memory performances are given

  8. Light-trapping in perovskite solar cells

    Qing Guo Du

    2016-06-01

    Full Text Available We numerically demonstrate enhanced light harvesting efficiency in both CH3NH3PbI3 and CH(NH22PbI3-based perovskite solar cells using inverted vertical-cone photonic-crystal nanostructures. For CH3NH3PbI3 perovskite solar cells, the maximum achievable photocurrent density (MAPD reaches 25.1 mA/cm2, corresponding to 92% of the total available photocurrent in the absorption range of 300 nm to 800 nm. Our cell shows 6% absorption enhancement compared to the Lambertian limit (23.7 mA/cm2 and has a projected power conversion efficiency of 12.9%. Excellent solar absorption is numerically demonstrated over a broad angular range from 0 to 60 degree for both S- and P- polarizations. For the corresponding CH(NH22PbI3 based perovskite solar cell, with absorption range of 300 nm to 850 nm, we find a MAPD of 29.1 mA/cm2, corresponding to 95.4% of the total available photocurrent. The projected power conversion efficiency of the CH(NH22PbI3 based photonic crystal solar cell is 23.4%, well above the current world record efficiency of 20.1%.

  9. A Heteroepitaxial Perovskite Metal-Base Transistor

    Yajima, T.; Hikita, Y.; /Tokyo U.; Hwang, H.Y.; /Tokyo U. /JST, PRESTO /SLAC

    2011-08-11

    'More than Moore' captures a concept for overcoming limitations in silicon electronics by incorporating new functionalities in the constituent materials. Perovskite oxides are candidates because of their vast array of physical properties in a common structure. They also enable new electronic devices based on strongly-correlated electrons. The field effect transistor and its derivatives have been the principal oxide devices investigated thus far, but another option is available in a different geometry: if the current is perpendicular to the interface, the strong internal electric fields generated at back-to-back heterojunctions can be used for oxide electronics, analogous to bipolar transistors. Here we demonstrate a perovskite heteroepitaxial metal-base transistor operating at room temperature, enabled by interface dipole engineering. Analysis of many devices quantifies the evolution from hot-electron to permeable-base behaviour. This device provides a platform for incorporating the exotic ground states of perovskite oxides, as well as novel electronic phases at their interfaces.

  10. Defect Tolerance in Methylammonium Lead Triiodide Perovskite

    Steirer, K. Xerxes; Schulz, Philip; Teeter, Glenn; Stevanovic, Vladan; Yang, Mengjin; Zhu, Kai; Berry, Joseph J.

    2016-08-12

    Photovoltaic applications of perovskite semiconductor material systems have generated considerable interest in part because of predictions that primary defect energy levels reside outside the bandgap. We present experimental evidence that this enabling material property is present in the halide-lead perovskite, CH3NH3PbI3 (MAPbI3), consistent with theoretical predictions. By performing X-ray photoemission spectroscopy, we induce and track dynamic chemical and electronic transformations in the perovskite. These data show compositional changes that begin immediately with exposure to X-ray irradiation, whereas the predominant electronic structure of the thin film on compact TiO2 appears tolerant to the formation of compensating defect pairs of VI and VMA and for a large range of I/Pb ratios. Changing film composition is correlated with a shift of the valence-band maximum only as the halide-lead ratio drops below 2.5. This delay is attributed to the invariance of MAPbI3 electronic structure to distributed defects that can significantly transform the electronic density of states only when in high concentrations.

  11. Light-trapping in perovskite solar cells

    Du, Qing Guo; Shen, Guansheng; John, Sajeev

    2016-06-01

    We numerically demonstrate enhanced light harvesting efficiency in both CH3NH3PbI3 and CH(NH2)2PbI3-based perovskite solar cells using inverted vertical-cone photonic-crystal nanostructures. For CH3NH3PbI3 perovskite solar cells, the maximum achievable photocurrent density (MAPD) reaches 25.1 mA/cm2, corresponding to 92% of the total available photocurrent in the absorption range of 300 nm to 800 nm. Our cell shows 6% absorption enhancement compared to the Lambertian limit (23.7 mA/cm2) and has a projected power conversion efficiency of 12.9%. Excellent solar absorption is numerically demonstrated over a broad angular range from 0 to 60 degree for both S- and P- polarizations. For the corresponding CH(NH2)2PbI3 based perovskite solar cell, with absorption range of 300 nm to 850 nm, we find a MAPD of 29.1 mA/cm2, corresponding to 95.4% of the total available photocurrent. The projected power conversion efficiency of the CH(NH2)2PbI3 based photonic crystal solar cell is 23.4%, well above the current world record efficiency of 20.1%.

  12. Oxidação de microcistinas-LR em águas pelo íon ferrato(VI Aqueous oxidation of microcystin-LR by ferrate(VI

    Sérgio João de Luca

    2010-03-01

    Full Text Available Toxinas de cianobactérias têm se tornado um grave problema na produção segura de água para consumo humano e animal. Técnicas convencionais de tratamento falham em atingir padrões de potabilidade. O ferrato(VI de potássio, um composto oxidante e coagulante, mostra potencialidade no tratamento de águas contaminadas. Neste trabalho, são apresentados resultados da oxidação pelo ferrato(VI de uma toxina gerada por cianobactérias, a microcistina-LR. Ensaios de cinética de oxidação e de teste de jarros mostram um valor médio de 0,012 min-1 para a constante de taxa de reação de pseudoprimeira ordem, para concentrações de MC-LR de 100 a 200 µg.L-1 na água bruta. Dosagens de 1,6 a 5,0 mg.L-1 de ferrato(VI sugerem o atendimento ao padrão de potabilidade para microcistinas, mostrando que o oxidante poderá ser empregado como coadjuvante no tratamento de água.Algae toxins are becoming a severe problem in the water treatment industry, especially for human and animal consumption. Traditional treatment processes have failed in complying with water supply standards. Potassium ferrate(VI is a powerful oxidant, disinfectant and, also, a coagulant. In this paper, the results of microcystin-LR oxidation by ferrate(VI ion are presented. Kinetic and jar tests showed a average value of 0,012 min-1 for the pseudo first order reaction rate constant, for 100 and 200 µg.L-1 concentration of MC-LR. Ferrate(VI dosages between 1.6 and 5.0 mg.L-1 suggest that water supply standards for MC-LR can be reached, which means that the oxidant may be employed as coadjuvant in water treatment.

  13. Bandgap calculations and trends of organometal halide perovskites

    Castelli, Ivano Eligio; García Lastra, Juan Maria; Thygesen, Kristian Sommer;

    2014-01-01

    Energy production from the Sun requires a stable efficient light absorber. Promising candidates in this respect are organometal perovskites (ABX3), which have been intensely investigated during the last years. Here, we have performed electronic structure calculations of 240 perovskites composed o...

  14. Formability, synthesis and properties of perovskite-type oxynitrides

    Li, Wenjie

    2015-01-01

    Metal perovskite oxynitrides are a highly interesting class of materials due to their tunable physical and chemical properties by varying the cationic and anionic stoichiometry. In this thesis, the formability of novel perovskite oxynitrides, synthesis and functionalities of metal oxynitrides have been investigated concerning their solid state structure, processing, microstructure, structure evolution and thermodynamic stability.

  15. Two Dimensional Organometal Halide Perovskite Nanorods with Tunable Optical Properties.

    Aharon, Sigalit; Etgar, Lioz

    2016-05-11

    Organo-metal halide perovskite is an efficient light harvester in photovoltaic solar cells. Organometal halide perovskite is used mainly in its "bulk" form in the solar cell. Confined perovskite nanostructures could be a promising candidate for efficient optoelectronic devices, taking advantage of the superior bulk properties of organo-metal halide perovskite, as well as the nanoscale properties. In this paper, we present facile low-temperature synthesis of two-dimensional (2D) lead halide perovskite nanorods (NRs). These NRs show a shift to higher energies in the absorbance and in the photoluminescence compared to the bulk material, which supports their 2D structure. X-ray diffraction (XRD) analysis of the NRs demonstrates their 2D nature combined with the tetragonal 3D perovskite structure. In addition, by alternating the halide composition, we were able to tune the optical properties of the NRs. Fast Fourier transform, and electron diffraction show the tetragonal structure of these NRs. By varying the ligands ratio (e.g., octylammonium to oleic acid) in the synthesis, we were able to provide the formation mechanism of these novel 2D perovskite NRs. The 2D perovskite NRs are promising candidates for a variety of optoelectronic applications, such as light-emitting diodes, lasing, solar cells, and sensors. PMID:27089497

  16. Self-Assembled PbSe Nanowire:Perovskite Hybrids

    Yang, Zhenyu

    2015-12-02

    © 2015 American Chemical Society. Inorganic semiconductor nanowires are of interest in nano- and microscale photonic and electronic applications. Here we report the formation of PbSe nanowires based on directional quantum dot alignment and fusion regulated by hybrid organic-inorganic perovskite surface ligands. All material synthesis is carried out at mild temperatures. Passivation of PbSe quantum dots was achieved via a new perovskite ligand exchange. Subsequent in situ ammonium/amine substitution by butylamine enables quantum dots to be capped by butylammonium lead iodide, and this further drives the formation of a PbSe nanowire superlattice in a two-dimensional (2D) perovskite matrix. The average spacing between two adjacent nanowires agrees well with the thickness of single atomic layer of 2D perovskite, consistent with the formation of a new self-assembled semiconductor nanowire:perovskite heterocrystal hybrid.

  17. Highly efficient light management for perovskite solar cells

    Wang, Dong-Lin; Hou, Guo-Jiao; Zhu, Zhen-Gang; Yan, Qing-Bo; Su, Gang

    2015-01-01

    Organic-inorganic halide perovskite solar cells have enormous potential to impact the existing photovoltaic industry. As realizing a higher conversion efficiency of the solar cell is still the most crucial task, a great number of schemes were proposed to minimize the carrier loss by optimizing the electrical properties of the perovskite solar cells. Here, we focus on another significant aspect that is to minimize the light loss by optimizing the light management to gain a high efficiency for perovskite solar cells. In our scheme, the slotted and inverted prism structured SiO2 layers are adopted to trap more light into the solar cells, and a better transparent conducting oxide layer is employed to reduce the parasitic absorption. For such an implementation, the efficiency and the serviceable angle of the perovskite solar cell can be promoted impressively. This proposal would shed new light on developing the high-performance perovskite solar cells.

  18. Planar-integrated single-crystalline perovskite photodetectors

    Saidaminov, Makhsud I.

    2015-11-09

    Hybrid perovskites are promising semiconductors for optoelectronic applications. However, they suffer from morphological disorder that limits their optoelectronic properties and, ultimately, device performance. Recently, perovskite single crystals have been shown to overcome this problem and exhibit impressive improvements: low trap density, low intrinsic carrier concentration, high mobility, and long diffusion length that outperform perovskite-based thin films. These characteristics make the material ideal for realizing photodetection that is simultaneously fast and sensitive; unfortunately, these macroscopic single crystals cannot be grown on a planar substrate, curtailing their potential for optoelectronic integration. Here we produce large-area planar-integrated films made up of large perovskite single crystals. These crystalline films exhibit mobility and diffusion length comparable with those of single crystals. Using this technique, we produced a high-performance light detector showing high gain (above 104 electrons per photon) and high gain-bandwidth product (above 108 Hz) relative to other perovskite-based optical sensors.

  19. Random lasing actions in self-assembled perovskite nanoparticles

    Liu, Shuai; Li, Jiankai; Gu, Zhiyuan; Wang, Kaiyang; Xiao, Shumin; Song, Qinghai

    2015-01-01

    Solution-based perovskite nanoparticles have been intensively studied in past few years due to their applications in both photovoltaic and optoelectronic devices. Here, based on the common ground between the solution-based perovskite and random lasers, we have studied the mirrorless lasing actions in self-assembled perovskite nanoparticles. After the synthesis from solution, discrete lasing peaks have been observed from the optically pumped perovskites without any well-defined cavity boundaries. The obtained quality (Q) factors and thresholds of random lasers are around 500 and 60 uJ/cm2, respectively. Both values are comparable to the conventional perovskite microdisk lasers with polygon shaped cavity boundaries. From the corresponding studies on laser spectra and fluorescence microscope images, the lasing actions are considered as random lasers that are generated by strong multiple scattering in random gain media. In additional to conventional single-photon excitation, due to the strong nonlinear effects of...

  20. Nano-structured electron transporting materials for perovskite solar cells

    Liu, Hefei; Huang, Ziru; Wei, Shiyuan; Zheng, Lingling; Xiao, Lixin; Gong, Qihuang

    2016-03-01

    Organic-inorganic hybrid perovskite solar cells have been developing rapidly in the past several years, and their power conversion efficiency has reached over 20%, nearing that of polycrystalline silicon solar cells. Because the diffusion length of the hole in perovskites is longer than that of the electron, the performance of the device can be improved by using an electron transporting layer, e.g., TiO2, ZnO and TiO2/Al2O3. Nano-structured electron transporting materials facilitate not only electron collection but also morphology control of the perovskites. The properties, morphology and preparation methods of perovskites are reviewed in the present article. A comprehensive understanding of the relationship between the structure and property will benefit the precise control of the electron transporting process and thus further improve the performance of perovskite solar cells.

  1. Perovskite Catalysts—A Special Issue on Versatile Oxide Catalysts

    Yu-Chuan Lin

    2014-08-01

    Full Text Available Perovskite-type catalysts have been prominent oxide catalysts for many years due to attributes such as flexibility in choosing cations, significant thermal stability, and the unique nature of lattice oxygen. Nearly 90% metallic elements of the Periodic Table can be stabilized in perovskite’s crystalline framework [1]. Moreover, by following the Goldschmidt rule [2], the A- and/or B-site elements can be partially substituted, making perovskites extremely flexible in catalyst design. One successful example is the commercialization of noble metal-incorporated perovskites (e.g., LaFe0.57Co0.38Pd0.05O3 for automotive emission control used by Daihatsu Motor Co. Ltd. [3]. Thus, growing interest in, and application of perovskites in the fields of material sciences, heterogeneous catalysis, and energy storage have prompted this Special Issue on perovskite catalysts. [...

  2. Highly efficient light management for perovskite solar cells

    Wang, Dong-Lin; Cui, Hui-Juan; Hou, Guo-Jiao; Zhu, Zhen-Gang; Yan, Qing-Bo; Su, Gang

    2016-01-01

    Organic-inorganic halide perovskite solar cells have enormous potential to impact the existing photovoltaic industry. As realizing a higher conversion efficiency of the solar cell is still the most crucial task, a great number of schemes were proposed to minimize the carrier loss by optimizing the electrical properties of the perovskite solar cells. Here, we focus on another significant aspect that is to minimize the light loss by optimizing the light management to gain a high efficiency for perovskite solar cells. In our scheme, the slotted and inverted prism structured SiO2 layers are adopted to trap more light into the solar cells, and a better transparent conducting oxide layer is employed to reduce the parasitic absorption. For such an implementation, the efficiency and the serviceable angle of the perovskite solar cell can be promoted impressively. This proposal would shed new light on developing the high-performance perovskite solar cells.

  3. Perovskite-fullerene hybrid materials suppress hysteresis in planar diodes.

    Xu, Jixian

    2015-05-08

    Solution-processed planar perovskite devices are highly desirable in a wide variety of optoelectronic applications; however, they are prone to hysteresis and current instabilities. Here we report the first perovskite-PCBM hybrid solid with significantly reduced hysteresis and recombination loss achieved in a single step. This new material displays an efficient electrically coupled microstructure: PCBM is homogeneously distributed throughout the film at perovskite grain boundaries. The PCBM passivates the key PbI3(-) antisite defects during the perovskite self-assembly, as revealed by theory and experiment. Photoluminescence transient spectroscopy proves that the PCBM phase promotes electron extraction. We showcase this mixed material in planar solar cells that feature low hysteresis and enhanced photovoltage. Using conductive AFM studies, we reveal the memristive properties of perovskite films. We close by positing that PCBM, by tying up both halide-rich antisites and unincorporated halides, reduces electric field-induced anion migration that may give rise to hysteresis and unstable diode behaviour.

  4. Two-photon pumped lead halide perovskite nanowire lasers

    Gu, Zhiyuan; Sun, Wenzhao; Li, Jinakai; Liu, Shuai; Song, Qinghai; Xiao, Shumin

    2015-01-01

    Solution-processed lead halide perovskites have shown very bright future in both solar cells and microlasers. Very recently, the nonlinearity of perovskites started to attract considerable research attention. Second harmonic generation and two-photon absorption have been successfully demonstrated. However, the nonlinearity based perovskite devices such as micro- & nano- lasers are still absent. Here we demonstrate the two-photon pumped nanolasers from perovskite nanowires. The CH3NH3PbBr3 perovskite nanowires were synthesized with one-step solution self-assembly method and dispersed on glass substrate. Under the optical excitation at 800 nm, two-photon pumped lasing actions with periodic peaks have been successfully observed at around 546 nm. The obtained quality (Q) factors of two-photon pumped nanolasers are around 960, and the corresponding thresholds are about 674?J=cm2. Both the Q factors and thresholds are comparable to conventional whispering gallery modes in two-dimensional polygon microplates. Ou...

  5. On the increase in thermal diffusivity caused by the perovskite to post-perovskite phase transition and its implications for mantle dynamics

    Hunt, S. A.; Davies, D. R.; WALKER, A.M.; McCormack, R. J.; Wills, A. S.; D. P. Dobson; Li, L.

    2012-01-01

    The thermal diffusivity (κ) of perovskite and post-perovskite CaIrO3 has been measured, at elevated pressure and temperatures up to 600 °C, using the X-radiographic Ångström method. At high temperatures we find that the thermal diffusivity of post-perovskite is slightly below twice that of isochemical perovskite over the temperature range investigated. Assuming a similar effect occurs in MgSiO3 post-perovskite, the effect of the contrasting thermal transport properties between perovskite and ...

  6. Size-Dependent Photon Emission from Organometal Halide Perovskite Nanocrystals Embedded in an Organic Matrix

    Di, Dawei; Musselman, Kevin P.; Li, Guangru; Sadhanala, Aditya; Ievskaya, Yulia; Song, Qilei; Tan, Zhi-Kuang; Lai, May Ling; MacManus-Driscoll, Judith L; Greenham, Neil C.; Friend, Richard H

    2015-01-01

    In recent years, organometal halide perovskite materials have attracted significant research interest in the field of optoelectronics. Here, we introduce a simple and low-temperature route for the formation of self-assembled perovskite nanocrystals in a solid organic matrix. We demonstrate that the size and photoluminescence peak of the perovskite nanocrystals can be tuned by varying the concentration of perovskite in the matrix material. The physical origin of the blue shift of the perovskit...

  7. Potassium ferrate/O3 removal of organophosphorus pesticides and application prospects of comparative effectiveness%高铁酸钾与O3对有机磷农药的去除效力对比及应用前景

    龚可雅; 李娜

    2012-01-01

    The physical describes the ozone/potassium ferrate Degradation of organophosphorus pesticides and chemical mechanism of the basic research status at home and abroad,compared from the five aspects of ozone and ferrate removal of the pros and cons of organic phosphorus pesticides,Analysis of the degradation of organophosphorus pesticides in future research.%本文介绍了臭氧/高铁酸钾技术降解有机磷农药的基本化学机理以及在国内外的研究现状,从五个方面对比了臭氧和高铁酸钾去除有机磷农药的的优劣性,分析了今后有机磷农药降解的研究方向。

  8. The Photophysics of Perovskite Solar Cells

    Sum, Tze-Chien

    2015-03-01

    Solution processed organic-inorganic lead halide perovskite solar cells, with power conversion efficiencies approaching 20%, are presently the forerunner amongst the next generation photovoltaic technologies. These remarkable performances can be attributed to their large absorption coefficients, long charge carrier diffusion lengths and low non-radiative recombination rates. In addition, these materials also possess excellent light emission and optical gain properties. In this talk, I will review the developmental milestones in this field and distil the recent findings on the photophysical mechanisms of this remarkable material. I will also highlight some of our latest charge dynamics studies and other investigations on the novel properties of this amazing material system.

  9. Axial electron-channelling analysis of perovskite

    The orientation dependence of characteristic X-ray emission (the Borrmann effect) under near-zone-axis diffraction conditions has been used to identify the site preferences of strontium, zirconium and uranium impurities within a CaTiO3 (perovskite) host structure. As characteristic emission lines from these impurities occur at both higher and lower energies than the calcium or titanium K-shell excitations, effects of delocalization are clearly measureable, and are used as a tool in axial electron channeling or ALCHEMI analysis. It is found that strontium and uranium strongly partition into calcium sites, whereas zirconium occupies titanium sites. (author)

  10. Electronic doping of transition metal oxide perovskites

    Cammarata, Antonio; Rondinelli, James M.

    2016-05-01

    CaFeO3 is a prototypical negative charge transfer oxide that undergoes electronic metal-insulator transition concomitant with a dilation and contraction of nearly rigid octahedra. Altering the charge neutrality of the bulk system destroys the electronic transition, while the structure is significantly modified at high charge content. Using density functional theory simulations, we predict an alternative avenue to modulate the structure and the electronic transition in CaFeO3. Charge distribution can be modulated using strain-rotation coupling and thin film engineering strategies, proposing themselves as a promising avenue for fine tuning electronic features in transition metal-oxide perovskites.

  11. Properties of perovskites and other oxides

    Müller, K Alex

    2010-01-01

    In this book some 50 papers published by K A Muller as author or co-author over several decades, amplified by more recent work mainly by T W Kool with collaborators, are reproduced. The main subject is Electron Paramagnetic Resonance (EPR) applied to the study of perovskites and other oxides with related subjects. This wealth of papers is organized into eleven chapters, each with an introductory text written in the light of current understanding. The contributions of the first author on structural phase transitions have been immense, and because K A Muller and J C Fayet have published a review

  12. A Review on Visible Light Active Perovskite-Based Photocatalysts

    Pushkar Kanhere

    2014-12-01

    Full Text Available Perovskite-based photocatalysts are of significant interest in the field of photocatalysis. To date, several perovskite material systems have been developed and their applications in visible light photocatalysis studied. This article provides a review of the visible light (λ > 400 nm active perovskite-based photocatalyst systems. The materials systems are classified by the B site cations and their crystal structure, optical properties, electronic structure, and photocatalytic performance are reviewed in detail. Titanates, tantalates, niobates, vanadates, and ferrites form important photocatalysts which show promise in visible light-driven photoreactions. Along with simple perovskite (ABO3 structures, development of double/complex perovskites that are active under visible light is also reviewed. Various strategies employed for enhancing the photocatalytic performance have been discussed, emphasizing the specific advantages and challenges offered by perovskite-based photocatalysts. This review provides a broad overview of the perovskite photocatalysts, summarizing the current state of the work and offering useful insights for their future development.

  13. Modeling of optical losses in perovskite solar cells

    Taghavi, M. Javad; Houshmand, Mohammad; Zandi, M. Hossein; Gorji, Nima E.

    2016-09-01

    The optical losses within the structure of hybrid perovskite solar cells are investigated using only the optical properties of each layer e.g. refractive index and extinction coefficient. This model allows calculating the transmission/reflection rates at the interfaces and absorption loss within any layer. Then, the short circuit current density and loss percentage are calculated versus the perovskite and TiO2 thicknesses from 50 nm to 150 nm. To make our calculations closer to reality, we extracted the optical properties of each device component from the literature reports on glass/TCO/TiO2/perovskite/metal. The simulations were fitted with the experimental results of some relevant references. Our simulations show that ITO transmits the light better than SnO2 as the TCO front electrode, and the light reflection at both sides of the perovskite layer, e.g. at TiO2/perovskite and perovskite/Spiro-OMeTAD, is lower than 25%. The light interference and multiple reflections have been accounted in our calculations and finally we showed that a thicker TiO2 and perovskite cause more optical loss in current density due to stronger absorption.

  14. Deciphering Halogen Competition in Organometallic Halide Perovskite Growth.

    Yang, Bin; Keum, Jong; Ovchinnikova, Olga S; Belianinov, Alex; Chen, Shiyou; Du, Mao-Hua; Ivanov, Ilia N; Rouleau, Christopher M; Geohegan, David B; Xiao, Kai

    2016-04-20

    Organometallic halide perovskites (OHPs) hold great promise for next-generation, low-cost optoelectronic devices. During the chemical synthesis and crystallization of OHP thin films, a major unresolved question is the competition between multiple halide species (e.g., I(-), Cl(-), Br(-)) in the formation of the mixed-halide perovskite crystals. Whether Cl(-) ions are successfully incorporated into the perovskite crystal structure or, alternatively, where they are located is not yet fully understood. Here, in situ X-ray diffraction measurements of crystallization dynamics are combined with ex situ TOF-SIMS chemical analysis to reveal that Br(-) or Cl(-) ions can promote crystal growth, yet reactive I(-) ions prevent them from incorporating into the lattice of the final perovskite crystal structure. The Cl(-) ions are located in the grain boundaries of the perovskite films. These findings significantly advance our understanding of the role of halogens during synthesis of hybrid perovskites and provide an insightful guidance to the engineering of high-quality perovskite films, essential for exploring superior-performing and cost-effective optoelectronic devices. PMID:26931634

  15. On the increase in thermal diffusivity caused by the perovskite to post-perovskite phase transition and its implications for mantle dynamics

    Hunt, Simon A.; Davies, D. Rhodri; Walker, Andrew M.; McCormack, Richard J.; Wills, Andrew S.; Dobson, David P.; Li, Li

    2012-02-01

    The thermal diffusivity (κ) of perovskite and post-perovskite CaIrO3 has been measured, at elevated pressure and temperatures up to 600 °C, using the X-radiographic Ångström method. At high temperatures we find that the thermal diffusivity of post-perovskite is slightly below twice that of isochemical perovskite over the temperature range investigated. Assuming a similar effect occurs in MgSiO3 post-perovskite, the effect of the contrasting thermal transport properties between perovskite and post-perovskite on mantle dynamics has been investigated using simple two-dimensional convection models. These show a reduction in extent and increase in depth of post-perovskite lenses, as well as increased core-mantle-boundary heat-flux, broader upwellings and more vigorous downwellings when compared to the reference, constant a, case.

  16. Halide-Dependent Electronic Structure of Organolead Perovskite Materials

    Buin, Andrei

    2015-06-23

    © 2015 American Chemical Society. Organometal halide perovskites have recently attracted tremendous attention both at the experimental and theoretical levels. These materials, in particular methylammonium triiodide, are still limited by poor chemical and structural stability under ambient conditions. Today this represents one of the major challenges for polycrystalline perovskite-based photovoltaic technology. In addition to this, the performance of perovskite-based devices is degraded by deep localized states, or traps. To achieve better-performing devices, it is necessary to understand the nature of these states and the mechanisms that lead to their formation. Here we show that the major sources of deep traps in the different halide systems have different origin and character. Halide vacancies are shallow donors in I-based perovskites, whereas they evolve into a major source of traps in Cl-based perovskites. Lead interstitials, which can form lead dimers, are the dominant source of defects in Br-based perovskites, in line with recent experimental data. As a result, the optimal growth conditions are also different for the distinct halide perovskites: growth should be halide-rich for Br and Cl, and halide-poor for I-based perovskites. We discuss stability in relation to the reaction enthalpies of mixtures of bulk precursors with respect to final perovskite product. Methylammonium lead triiodide is characterized by the lowest reaction enthalpy, explaining its low stability. At the opposite end, the highest stability was found for the methylammonium lead trichloride, also consistent with our experimental findings which show no observable structural variations over an extended period of time.

  17. The thermoelastic properties of post-perovskite analogue phases

    Lindsay-Scott, A.

    2011-01-01

    Post-perovskite MgSiO3 is a major component of the D'' zone at the base of the lower mantle, so knowledge of its physical properties is essential to understanding mantle dynamics. Unfortunately, MgSiO3 post-perovskite is stable only at Mbar pressures. This difficulty can be addressed by combining computer simulations with experiments on analogue post-perovskite ABX3 phases, stable at ambient pressure and temperature. In this project, the properties of MgSiO3 and other oxide and...

  18. Spontaneous polarization behaviors in hybrid halide perovskite film

    Spontaneous polarization behaviors of hybrid perovskite CH3NH3PbI3 film were confirmed by in situ PFM and spectroscopic ellipsometry. The film exhibits uniform spontaneous polarization and ferroelectric domain inversion performance. The fitted dielectric constants spectra agree well with the calculated ones. We attribute the spontaneous polarization behaviors of hybrid perovskite to lone pair electrons, and its outstanding photovoltaic performance partially originates from spontaneous polarization and plasma resonance. This report will facilitate understanding of the instinct physical essence of hybrid perovskite solar cells

  19. Generalized trends in the formation energies of perovskite oxides

    Zeng, Zhenhua; Calle-Vallejo, Federico; Mogensen, Mogens Bjerg;

    2013-01-01

    usually have quite different but ordered formation energies. On the other hand, for a given A-site cation, (III) the formation energies of perovskites vary linearly with respect to the atomic number of the elements at the B site within the same period of the periodic table, and the slopes depend...... systematically on the oxidation state of the A-site cation; and (IV) the trends in formation energies of perovskites with elements from different periods at the B site depend on the oxidation state of A-site cations. Since the energetics of perovskites is shown to be the superposition of the individual...

  20. NREL Studies Carrier Separation and Transport in Perovskite Solar Cells

    2016-01-01

    NREL scientists studied charge separation and transport in perovskite solar cells by determining the junction structure across the solar device using the nanoelectrical characterization technique of Kelvin probe force microscopy. The distribution of electrical potential across both planar and porous devices demonstrates a p-n junction structure at the interface between titanium dioxide and perovskite. In addition, minority-carrier transport within the devices operates under diffusion/drift. Clarifying the fundamental junction structure provides significant guidance for future research and development. This NREL study points to the fact that improving carrier mobility is a critical factor for continued efficiency gains in perovskite solar cells.

  1. Finding New Perovskite Halides via Machine learning

    Ghanshyam ePilania

    2016-04-01

    Full Text Available Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach towards rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning via building a support vector machine (SVM based classifier that uses elemental features (or descriptors to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br or I anion in the perovskite crystal structure. The classification model is built by learning from a dataset of 181 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. The trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.

  2. Finding New Perovskite Halides via Machine learning

    Pilania, Ghanshyam; Balachandran, Prasanna V.; Kim, Chiho; Lookman, Turab

    2016-04-01

    Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach towards rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning) via building a support vector machine (SVM) based classifier that uses elemental features (or descriptors) to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br or I anion) in the perovskite crystal structure. The classification model is built by learning from a dataset of 181 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. The trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.

  3. Emergent phenomena in perovskite-type manganites

    Taguchi, Y., E-mail: y-taguchi@riken.jp [Cross-Correlated Materials Research Group (CMRG) and Correlated Electron Research Group (CERG), RIKEN Advanced Science Institute, Wako 351-0198 (Japan); Sakai, H.; Okuyama, D. [Cross-Correlated Materials Research Group (CMRG) and Correlated Electron Research Group (CERG), RIKEN Advanced Science Institute, Wako 351-0198 (Japan); Ishiwata, S. [Cross-Correlated Materials Research Group (CMRG) and Correlated Electron Research Group (CERG), RIKEN Advanced Science Institute, Wako 351-0198 (Japan); Department of Applied Physics, University of Tokyo, Tokyo 113-8656 (Japan); Fujioka, J. [Department of Applied Physics, University of Tokyo, Tokyo 113-8656 (Japan); Multiferroics Project, ERATO, JST, c/o University of Tokyo, Tokyo 113-8656 (Japan); Fukuda, T. [Synchrotron Radiation Research Unit, SPring-8/JAEA, Hyogo 679-5148 (Japan); Materials Dynamics Laboratory, RIKEN SPring-8 Center, Hyogo 679-5148 (Japan); Hashizume, D. [Advanced Technology Support Division, RIKEN, Wako 351-0198 (Japan); Kagawa, F. [Department of Applied Physics, University of Tokyo, Tokyo 113-8656 (Japan); Takahashi, Y. [Multiferroics Project, ERATO, JST, c/o University of Tokyo, Tokyo 113-8656 (Japan); Shimano, R. [Multiferroics Project, ERATO, JST, c/o University of Tokyo, Tokyo 113-8656 (Japan); Dept. of Physics, Univ. of Tokyo, 113-8656 (Japan); Tokunaga, Y. [Cross-Correlated Materials Research Group (CMRG) and Correlated Electron Research Group (CERG), RIKEN Advanced Science Inst., Wako 351-0198 (Japan); Multiferroics Project, ERATO, JST, c/o Univ. of Tokyo, Tokyo 113-8656 (Japan); Kaneko, Y. [Multiferroics Project, ERATO, JST, c/o Univ. of Tokyo, Tokyo 113-8656 (Japan); Nakao, A.; Nakao, H.; Murakami, Y. [Condensed Matter Research Center and Photon Factory, Inst. of Materials Structure Science, KEK, Tuskuba 305-0801 (Japan); Sugimoto, K. [JASRI SPring-8, Hyogo 679-5198 (Japan); Takata, M. [RIKEN SPring-8 Center, Hyogo 679-5148 (Japan)

    2012-06-01

    Perovskite-type manganites exhibit various interesting phenomena arising from complex interplay among spin, charge, orbital, and lattice degrees of freedom. One such example is the keen competition between phases with different spin/charge/orbital orders. Keen competition between antiferromagnetic metal and orbital-ordered insulator is found in the slightly electron-doped regime near Mn{sup 4+} state which is stabilized by the high oxygen-pressure condition. Another one is the emergence of ferroelectricity either induced by the magnetic ordering or independently of the magnetic ordering. As the respective examples, perovskite-type YMnO{sub 3} and Sr{sub 1-x}Ba{sub x}MnO{sub 3} are discussed. In the YMnO{sub 3}, the ferroelectric lattice distortion associated with the E-type spin order is observed for the first time. Displacement-type ferroelectricity with off-center magnetic ions is discovered for Sr{sub 0.5}Ba{sub 0.5}MnO{sub 3}, which shows both large polarization value and strong coupling between ferroelectricity and magnetism.

  4. Electrically Anisotropic Layered Perovskite Single Crystal

    Li, Ting-You

    2016-04-01

    Organic-inorganic hybrid perovskites (OIHPs), which are promising materials for electronic and optoelectronic applications (1-10), have made into layered organic-inorganic hybrid perovskites (LOIHPs). These LOIHPs have been applied to thin-film transistors, solar cells and tunable wavelength phosphors (11-18). It is known that devices fabricated with single crystal exhibit the superior performance, which makes the growth of large-sized single crystals critical for future device applications (19-23). However, the difficulty in growing large-sized LOIHPs single crystal with superior electrical properties limits their practical applications. Here, we report a method to grow the centimeter-scaled LOIHP single crystal of [(HOC2H4NH3)2PbI4], demonstrating the potentials in mass production. After that, we reveal anisotropic electrical and optoelectronic properties which proved the carrier propagating along inorganic framework. The carrier mobility of in-inorganic-plane (in-plane) devices shows the average value of 45 cm2 V–1 s–1 which is about 100 times greater than the record of LOIHP devices (15), showing the importance of single crystal in device application. Moreover, the LOIHP single crystals show its ultra-short carrier lifetime of 42.7 ps and photoluminescence quantum efficiency (PLQE) of 25.4 %. We expect this report to be a start of LOIHPs for advanced applications in which the anisotropic properties are needed (24-25), and meets the demand of high-speed applications and fast-response applications.

  5. Neutral Color Semitransparent Microstructured Perovskite Solar Cells

    Eperon, Giles E.

    2014-01-28

    Neutral-colored semitransparent solar cells are commercially desired to integrate solar cells into the windows and cladding of buildings and automotive applications. Here, we report the use of morphological control of perovskite thin films to form semitransparent planar heterojunction solar cells with neutral color and comparatively high efficiencies. We take advantage of spontaneous dewetting to create microstructured arrays of perovskite "islands", on a length-scale small enough to appear continuous to the eye yet large enough to enable unattenuated transmission of light between the islands. The islands are thick enough to absorb most visible light, and the combination of completely absorbing and completely transparent regions results in neutral transmission of light. Using these films, we fabricate thin-film solar cells with respectable power conversion efficiencies. Remarkably, we find that such discontinuous films still have good rectification behavior and relatively high open-circuit voltages due to the inherent rectification between the n- and p-type charge collection layers. Furthermore, we demonstrate the ease of "color-tinting" such microstructured perovksite solar cells with no reduction in performance, by incorporation of a dye within the hole transport medium. © 2013 American Chemical Society.

  6. Perovskite oxides: Oxygen electrocatalysis and bulk structure

    Carbonio, R. E.; Fierro, C.; Tryk, D.; Scherson, D.; Yeager, Ernest

    1987-01-01

    Perovskite type oxides were considered for use as oxygen reduction and generation electrocatalysts in alkaline electrolytes. Perovskite stability and electrocatalytic activity are studied along with possible relationships of the latter with the bulk solid state properties. A series of compounds of the type LaFe(x)Ni1(-x)O3 was used as a model system to gain information on the possible relationships between surface catalytic activity and bulk structure. Hydrogen peroxide decomposition rate constants were measured for these compounds. Ex situ Mossbauer effect spectroscopy (MES), and magnetic susceptibility measurements were used to study the solid state properties. X ray photoelectron spectroscopy (XPS) was used to examine the surface. MES has indicated the presence of a paramagnetic to magnetically ordered phase transition for values of x between 0.4 and 0.5. A correlation was found between the values of the MES isomer shift and the catalytic activity for peroxide decomposition. Thus, the catalytic activity can be correlated to the d-electron density for the transition metal cations.

  7. Lattice preferred orientation in CaIrO3 perovskite and post-perovskite formed by plastic deformation under pressure

    Niwa, Ken; Yagi, Takehiko; Ohgushi, Kenya; Merkel, Sébastien; Miyajima, Nobuyoshi; Kikegawa, Takumi

    2007-11-01

    Lattice preferred orientations (LPO) developed in perovskite and post-perovskite structured CaIrO3 were studied using the radial X-ray diffraction technique combined with a diamond anvil cell. Starting materials of each phase were deformed from 0.1 MPa to 6 GPa at room temperature. Only weak LPO was formed in the perovskite phase, whereas strong LPO was formed in the post-perovskite phase with an alignment of the (010) plane perpendicular to the compression axis. The present result suggests that the (010) is a dominant slip plane in the post-perovskite phase and it is in good agreement with the crystallographic prediction, dislocation observations via transmission electron microscopy, and a recent result of simple shear deformation experiment at 1 GPa 1,173 K. However, the present result contrasts markedly from the results on MgGeO3 and (Mg,Fe)SiO3, which suggested that the (100) or (110) is a dominant slip plane with respect to the post-perovskite structure. Therefore it is difficult to discuss the behavior of the post-perovskite phase in the Earth’s deep interior based on existing data of MgGeO3, (Mg,Fe)SiO3 and CaIrO3. The possible sources of the differences between MgGeO3, (Mg,Fe)SiO3 and CaIrO3 are discussed.

  8. Perovskite Solar Cells: High Efficiency Pb-In Binary Metal Perovskite Solar Cells (Adv. Mater. 31/2016).

    Wang, Zhao-Kui; Li, Meng; Yang, Ying-Guo; Hu, Yun; Ma, Heng; Gao, Xing-Yu; Liao, Liang-Sheng

    2016-08-01

    On page 6695, X. Y. Gao, L.-S. Liao, and co-workers describe the fabrication of mixed Pb-In perovskite solar cells, using indium (III) chloride and lead (II) chloride with methylammonium iodide. A maximum power conversion efficiency as high as 17.55% is achieved owing to the high quality of the perovskites with multiple ordered crystal orientations. This work demonstrates the possibility of substituting the Pb (II) by using In (III), which opens a broad route to fabricating alloy perovskite solar cells with mitigated ecological impact. PMID:27511533

  9. Geophysically Consistent Values of the Perovskite to Post-Perovskite Transition Clapeyron Slope

    Hernlund, John,; Labrosse, Stéphane

    2007-01-01

    The double‐crossing hypothesis posits that post‐perovskite bearing rock in Earth's D″ layer exists as a layer above the core‐mantle boundary bounded above and below by intersections between a curved thermal boundary layer geotherm and a relatively steep phase boundary. Increasing seismic evidence for the existence of pairs of discontinuities predicted to occur at the top and bottom of this layer motivates an examination of the consistency of this model with mineral physics constraints for the...

  10. The Coulombic Lattice Potential of Ionic Compounds: The Cubic Perovskites.

    Francisco, E.; And Others

    1988-01-01

    Presents coulombic models representing the particles of a system by point charges interacting through Coulomb's law to explain coulombic lattice potential. Uses rubidium manganese trifluoride as an example of cubic perovskite structure. Discusses the effects on cluster properties. (CW)

  11. Two-Dimensional Organic-Inorganic Hybrid Perovskite Photonic Films.

    Meng, Ke; Gao, Shanshan; Wu, Longlong; Wang, Geng; Liu, Xin; Chen, Gang; Liu, Zhou; Chen, Gang

    2016-07-13

    Organic-inorganic hybrid perovskites have created enormous expectations for low-cost and high-performance optoelectronic devices. In prospect, future advancements may derive from reaping novel electrical and optical properties beyond pristine perovskites through microscopic structure design and engineering. Herein, we report the successful preparation of two-dimensional inverse-opal perovskite (IOP) photonic films, featuring unique nanostructures and vivid colors. Further compositional and structural managements promise optical property and energy level tunability of the IOP films. They are further functionalized in solar cells, resulting in colorful devices with respectable power conversion efficiency. Such concept has not been previously applied for perovskite-based solar cells, which could open a route for more versatile optoelectronic devices. PMID:27267266

  12. High-pressure phase behaviors of ZnTiO3: ilmenite-perovskite transition, decomposition of perovskite into constituent oxides, and perovskite-lithium niobate transition

    Akaogi, M.; Abe, K.; Yusa, H.; Kojitani, H.; Mori, D.; Inaguma, Y.

    2015-06-01

    High-pressure high-temperature phase transitions of ZnTiO3 ilmenite were examined using multianvil apparatus up to 25.5 GPa and 1,500 °C and diamond anvil cell to 26.5 GPa and about 2,000 °C. Combined results of the multianvil quench experiments and in situ diamond anvil cell experiments indicated that at about 10 GPa and 1,200 °C ZnTiO3 ilmenite transforms to orthorhombic perovskite which is converted to lithium niobate phase on release of pressure. The boundary of the ilmenite-provskite transition is expressed by P(GPa) = 15.9 - 0.005 T (°C). The high-pressure experiments also indicated that at 20-24 GPa and 1,000-1,400 °C ZnTiO3 orthorhombic perovskite dissociates into rocksalt-type ZnO + baddeleyite-type TiO2 which are recovered, respectively, as wurtzite-type ZnO and α-PbO2-type TiO2 at 1 atm. The boundary of the perovskite dissociation is expressed by P(GPa) = 8.7 + 0.011 T (°C). Molar volume changes of ZnTiO3 at ambient conditions were estimated as -4.7 % for the ilmenite-perovskite transition and -3.5 % for the perovskite decomposition into the oxides. The absence of CaIrO3-type postperovskite in ZnTiO3 is consistent with that dissociation of ZnTiO3 perovskite into the oxides has the larger molar volume change than -1 to -2 % of the perovskite-postperovskite transition in various ABO3 compounds and with previous data that ABO3 perovskites with relatively ionic B-O bonds do not transform to the postperovskite. The transition behaviors of ZnTiO3 are similar to those of MnTiO3 and FeTiO3, but ZnTiO3 perovskite dissociates into the constituent oxides.

  13. Lead iodide perovskite light-emitting field-effect transistor

    Chin, Xin Yu; Cortecchia, Daniele; Yin, Jun; Bruno, Annalisa; Soci, Cesare

    2015-01-01

    Despite the widespread use of solution-processable hybrid organic–inorganic perovskites in photovoltaic and light-emitting applications, determination of their intrinsic charge transport parameters has been elusive due to the variability of film preparation and history-dependent device performance. Here we show that screening effects associated to ionic transport can be effectively eliminated by lowering the operating temperature of methylammonium lead iodide perovskite (CH3NH3PbI3) field-eff...

  14. Planar organic-inorganic hybrid perovskite solar cell by electrospray

    Chen, Wenjun

    2015-01-01

    Recently, the organic-inorganic perovskite solar cell has attracted great attention due to the easy processing and rapid developed power conversion efficiency. The tri-halide perovskite CH3NH3PbI3-xClx possessing excellent optical and electronic properties, such as absorption hands span the visible region, long charge carrier diffusion lengths, and appropriate direct band gap, makes them ideal active layer material for photovoltaic devices. In this thesis, electrohydrodynamic spraying is used...

  15. Highly Efficient Perovskite Solar Cells with Tunable Structural Color

    Zhang, Wei; Anaya, Miguel; Lozano, Gabriel; Calvo, Mauricio E.; Johnston, Michael B; Míguez, Hernán; Snaith, Henry J.

    2015-01-01

    The performance of perovskite solar cells has been progressing over the past few years and efficiency is likely to continue to increase. However, a negative aspect for the integration of perovskite solar cells in the built environment is that the color gamut available in these materials is very limited and does not cover the green-to-blue region of the visible spectrum, which has been a big selling point for organic photovoltaics. Here, we integrate a porous photonic crystal (PC) scaffold wit...

  16. Radiative efficiency of lead iodide based perovskite solar cells

    Kristofer Tvingstedt; Olga Malinkiewicz; Andreas Baumann; Carsten Deibel; Snaith, Henry J.; Vladimir Dyakonov; Bolink, Henk J.

    2015-01-01

    The maximum efficiency of any solar cell can be evaluated in terms of its corresponding ability to emit light. We herein determine the important figure of merit of radiative efficiency for Methylammonium Lead Iodide perovskite solar cells and, to put in context, relate it to an organic photovoltaic (OPV) model device. We evaluate the reciprocity relation between electroluminescence and photovoltaic quantum efficiency and conclude that the emission from the perovskite devices is dominated by a...

  17. Highly efficient light management for perovskite solar cells

    Dong-Lin Wang; Hui-Juan Cui; Guo-Jiao Hou; Zhen-Gang Zhu; Qing-Bo Yan; Gang Su

    2016-01-01

    Organic-inorganic halide perovskite solar cells have enormous potential to impact the existing photovoltaic industry. As realizing a higher conversion efficiency of the solar cell is still the most crucial task, a great number of schemes were proposed to minimize the carrier loss by optimizing the electrical properties of the perovskite solar cells. Here, we focus on another significant aspect that is to minimize the light loss by optimizing the light management to gain a high efficiency for ...

  18. Enhancement of perovskite solar cells by plasmonic nanoparticles

    Omelyanovich, Mikhail; Makarov, Sergey; Milichko, Valentin; Simovski, Constantin

    2016-01-01

    Synthetic perovskites with photovoltaic properties open a new era in solar photovoltaics. Due to high optical absorption perovskite-based thin-film solar cells are usually considered as fully absorbing solar radiation on condition of ideal blooming. However, is it really so? The analysis of the literature data has shown that the absorbance of all photovoltaic pervoskites has the spectral hole at infrared frequencies where the solar radiation spectrum has a small local peak. This absorption di...

  19. Double perovskite heterostructures: Magnetism, Chern bands, and Chern insulators

    Cook, A M; Paramekanti, A.

    2014-01-01

    Experiments demonstrating the controlled growth of oxide heterostructures have raised the prospect of realizing topologically nontrivial states of correlated electrons in low dimensions. Here, we study heterostructures consisting of {111}-bilayers of double perovskites separated by inert band insulators. In bulk, these double perovskites have well-defined local moments interacting with itinerant electrons leading to high temperature ferromagnetism. Incorporating spin-orbit coupling in the two...

  20. Tracking the formation of methylammonium lead triiodide perovskite

    The formation mechanism of perovskite methylammonium lead triiodide (CH3NH3PbI3) was studied with in situ X-ray photoelectron spectroscopy (XPS) on successive depositions of thermally evaporated methylammonium iodide (CH3NH3I) on a lead iodide (PbI2) film. This deposition method mimics the “two-step” synthesis method commonly used in device fabrication. We find that several competing processes occur during the formation of perovskite CH3NH3PbI3. Our most important finding is that during vapour deposition of CH3NH3I onto PbI2, at least two carbon species are present in the resulting material, while only one nitrogen species is present. This suggests that CH3NH3I can dissociate during the transition to a perovskite phase, and some of the resulting molecules can be incorporated into the perovskite. The effect of partial CH3NH3 substitution with CH3 was evaluated, and electronic structure calculations show that CH3 defects would impact the photovoltaic performance in perovskite solar cells. The possibility that not all A sites in the APbI3 perovskite are occupied by CH3NH3 is therefore an important consideration when evaluating the performance of organometallic trihalide solar cells synthesized using typical approaches

  1. Quantum Size Effect in Organometal Halide Perovskite Nanoplatelets.

    Sichert, Jasmina A; Tong, Yu; Mutz, Niklas; Vollmer, Mathias; Fischer, Stefan; Milowska, Karolina Z; García Cortadella, Ramon; Nickel, Bert; Cardenas-Daw, Carlos; Stolarczyk, Jacek K; Urban, Alexander S; Feldmann, Jochen

    2015-10-14

    Organometal halide perovskites have recently emerged displaying a huge potential for not only photovoltaic, but also light emitting applications. Exploiting the optical properties of specifically tailored perovskite nanocrystals could greatly enhance the efficiency and functionality of applications based on this material. In this study, we investigate the quantum size effect in colloidal organometal halide perovskite nanoplatelets. By tuning the ratio of the organic cations used, we can control the thickness and consequently the photoluminescence emission of the platelets. Quantum mechanical calculations match well with the experimental values. We find that not only do the properties of the perovskite, but also those of the organic ligands play an important role. Stacking of nanoplatelets leads to the formation of minibands, further shifting the bandgap energies. In addition, we find a large exciton binding energy of up to several hundreds of meV for nanoplatelets thinner than three unit cells, partially counteracting the blueshift induced by quantum confinement. Understanding of the quantum size effects in perovskite nanoplatelets and the ability to tune them provide an additional method with which to manipulate the optical properties of organometal halide perovskites. PMID:26327242

  2. Two-Photon Absorption in Organometallic Bromide Perovskites.

    Walters, Grant; Sutherland, Brandon R; Hoogland, Sjoerd; Shi, Dong; Comin, Riccardo; Sellan, Daniel P; Bakr, Osman M; Sargent, Edward H

    2015-09-22

    Organometallic trihalide perovskites are solution-processed semiconductors that have made great strides in third-generation thin film light-harvesting and light-emitting optoelectronic devices. Recently, it has been demonstrated that large, high-purity single crystals of these perovskites can be synthesized from the solution phase. These crystals' large dimensions, clean bandgap, and solid-state order have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW(-1) at 800 nm, comparable to epitaxial single-crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics. PMID:26196162

  3. Two-Photon Absorption in Organometallic Bromide Perovskites

    Walters, Grant

    2015-07-21

    Organometallic trihalide perovskites are solution processed semiconductors that have made great strides in third generation thin film light harvesting and light emitting optoelectronic devices. Recently it has been demonstrated that large, high purity single crystals of these perovskites can be synthesized from the solution phase. These crystals’ large dimensions, clean bandgap, and solid-state order, have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW-1 at 800 nm, comparable to epitaxial single crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.

  4. Study of transport properties of bodies with a perovskite structure: application to the MgSiO3 perovskite

    After some recalls on transport in ionic solids (Nernst-Einstein relationship, variation of ionic conductivity, hybrid conduction, fast ionic conduction), this research thesis presents the physical properties of perovskites and more particularly the structure and stability of the MgSiO3 perovskite: structure and elastic properties, electric conductivity and transport properties in compounds with a perovskite structure. Then, the author reports the experimental study of the KZnF3 perovskite (a structural analogous of MgSiO3): measurements of electric conductivity under pressure, measurements under atmospheric pressure, result discussion. The next part addresses the numerical simulation of MgSiO3: simulation techniques (generalities on molecular dynamics, model description), investigation of structural, elastic and thermodynamic properties, diffusion properties in quadratic phase

  5. Properties and applications of perovskite proton conductors

    A brief overview is given of the main types and principles of solid-state proton conductors with perovskite structure. Their properties are summarized in terms of the defect chemistry, proton transport and chemical stability. A good understanding of these subjects allows the manufacturing of compounds with the desired electrical properties, for application in renewable and sustainable energy devices. A few trends and highlights of the scientific advances are given for some classes of protonic conductors. Recent results and future prospect about these compounds are also evaluated. The high proton conductivity of barium cerate and zirconate based electrolytes lately reported in the literature has taken these compounds to a highlight position among the most studied conductor ceramic materials. (author)

  6. Properties and applications of perovskite proton conductors

    Souza, Eduardo Caetano Camilo de; Muccillo, Reginaldo, E-mail: ecsouza@ipen.b [Energy and Nuclear Research Institute (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Center of Science and Technology of Materials

    2010-07-01

    A brief overview is given of the main types and principles of solid-state proton conductors with perovskite structure. Their properties are summarized in terms of the defect chemistry, proton transport and chemical stability. A good understanding of these subjects allows the manufacturing of compounds with the desired electrical properties, for application in renewable and sustainable energy devices. A few trends and highlights of the scientific advances are given for some classes of protonic conductors. Recent results and future prospect about these compounds are also evaluated. The high proton conductivity of barium cerate and zirconate based electrolytes lately reported in the literature has taken these compounds to a highlight position among the most studied conductor ceramic materials. (author)

  7. Ferroelastic Fingerprints in Methylammonium Lead Iodide Perovskite

    Hermes, Ilka M.

    2016-02-12

    Methylammonium lead iodide (MAPbI3) perovskite materials show an outstanding performance in photovoltaic devices. However, certain material properties, especially the possible ferroic behavior, remain unclear. We observed distinct nanoscale periodic domains in the piezoresponse of MAPbI3(Cl) grains. The structure and the orientation of these striped domains indicate ferroelasticity as their origin. By correlating vertical and lateral piezoresponse force microscopy experiments performed at different sample orientations with x-ray diffraction, the preferred domain orientation was suggested to be the a1-a2-phase. The observation of these ferroelastic fingerprints appears to strongly depend on the film texture and thus the preparation route. The formation of the ferroelastic twin domains could be induced by internal strain during the cubic-tetragonal phase transition.

  8. Properties and applications of perovskite proton conductors

    Eduardo Caetano Camilo de Souza

    2010-09-01

    Full Text Available A brief overview is given of the main types and principles of solid-state proton conductors with perovskite structure. Their properties are summarized in terms of the defect chemistry, proton transport and chemical stability. A good understanding of these subjects allows the manufacturing of compounds with the desired electrical properties, for application in renewable and sustainable energy devices. A few trends and highlights of the scientific advances are given for some classes of protonic conductors. Recent results and future prospect about these compounds are also evaluated. The high proton conductivity of barium cerate and zirconate based electrolytes lately reported in the literature has taken these compounds to a highlight position among the most studied conductor ceramic materials.

  9. The perovskite to post-perovskite transition in CaIrO3

    Tronnes, R. G.; Frost, D. J.; Boffa-Ballaran, T.; Stolen, S.

    2006-12-01

    The phase transition of MgSiO3-dominated perovskite to a post-perovskite phase with CaIrO3-type structure in the deep mantle has important implications for the core-mantle boundary heat flux and Earth's dynamics. The Clapeyron slope of the phase boundary is a critical parameter in geodynamical models but cannot be determined accurately in laser-heated diamond anvil experiments. Experiments using suitable analogue compositions where the perovskite to post-perovskite transition (PvPPpvT) can be studied within the pressure ranges of the piston cylinder or multianvil apparatus may therefore be useful. Hirose and Fujita [1] investigated the PvPPvT in CaIrO3 at 1-3 GPa and 1350-1550 ºC, and found a dp/dT-slope of 14-20 MPa/K. We investigated the transition, using narrower brackets and a few reversal experiments and located the transition at the somewhat higher temperatures of 1458-1513 at 1-2.5 GPa, with dp/dT-slope of 26-29 MPa/K. In addition to the reversal experiments, using Pv and PPv, we also investigated the potential effect of different starting materials including CaO + IrO2 oxide mixes and oxide mixes reacted at 850-900 C. The starting material issue is especially important for CaIrO3, because CaO is hygroscopic and because minor amounts of reduced Ir starts to form even in air at temperatures above about 800 C. Special care was taken to minimize these effects. The Clapeyron slopes determined for the PvPPvT in the CaIrO3-system are considerably larger that those estimated for MgSiO3 from first principles and ab-initio models and from modelling of the topography of the upper and lower D"-discontinuities, assuming that these discontinuities are caused by the PvPPvT. Clapeyron slopes ranging from 6 to 10 MPa/K have been used in such geodynamic modelling. In order to characterize the PvPPvT in CaIrO3 further, we will derive crystallographic, elastic and thermodynamic parameters for the perovskite and post-perovskite phases by single-crystal XRD, combined with

  10. The interaction between hybrid organic-inorganic halide perovskite and selective contacts in perovskite solar cells: an infrared spectroscopy study.

    Idígoras, J; Todinova, A; Sánchez-Valencia, J R; Barranco, A; Borrás, A; Anta, J A

    2016-05-11

    The interaction of hybrid organic-inorganic halide perovskite and selective contacts is crucial to get efficient, stable and hysteresis-free perovskite-based solar cells. In this report, we analyze the vibrational properties of methylammonium lead halide perovskites deposited on different substrates by infrared absorption (IR) measurements (4000-500 cm(-1)). The materials employed as substrates are not only characterized by different chemical natures (TiO2, ZnO and Al2O3), but also by different morphologies. For all of them, we have investigated the influence of these substrate properties on perovskite formation and its degradation by humidity. The effect of selective-hole contact (Spiro-OmeTad and P3HT) layers on the degradation rate by moisture has also been studied. Our IR results reveal the existence of a strong interaction between perovskite and all ZnO materials considered, evidenced by a shift of the peaks related to the N-H vibrational modes. The interaction even induces a morphological change in ZnO nanoparticles after perovskite deposition, pointing to an acid-base reaction that takes place through the NH3(+) groups of the methylammonium cation. Our IR and X-ray diffraction results also indicate that this specific interaction favors perovskite decomposition and PbI2 formation for ZnO/perovskite films subjected to humid conditions. Although no interaction is observed for TiO2, Al2O3, and the hole selective contact, the morphology and chemical nature of both contacts appear to play an important role in the rate of degradation upon exposure to moisture. PMID:27138224

  11. Fine control of perovskite-layered morphology and composition via sequential deposition crystallization process towards improved perovskite solar cells

    Luo, Yi; Meng, Fanli; Zhao, Erfei; Zheng, Yan-Zhen; Zhou, Yali; Tao, Xia

    2016-04-01

    The ability to prepare high coverage and compact perovskite films via solution-based crystallization manipulation processes still represents a vital issue towards improving the ultimate photoelectric conversion efficiency of devices. In this work, we prepare the active perovskite layer by means of sequential deposition crystallization process i.e. dipping PbI2-infiltrated TiO2 film within CH3NH3I solution from 20s to 60s. The morphology and thickness of the as-prepared perovskite layer, and its overall performance superiority are investigated. X-ray diffraction (XRD) reveals that a maximum conversion of PbI2 to perovskite is completed upon applying a sequential deposition crystallization process of 40s. Field emission scanning electron microscope (FESEM) demonstrates that the coverage of the perovskite capping layer exhibits a trend from rise to decline in the whole dipping time from 20s to 60s. By fine control of the dipping time, a 620 nm-thickness compact perovskite active layer is obtained at the optimized dipping time of 40s and is verified to possess strong light absorption and high electron extraction efficiency, leading to a higher photocurrent. By further optimizing the mesoporous TiO2 film thickness, a high photocurrent of 23.98 mA cm-2 and an efficiency of 13.47% are achieved.

  12. Selective dissolution of halide perovskites as a step towards recycling solar cells

    Kim, Byeong Jo; Kim, Dong Hoe; Kwon, Seung Lee; Park, So Yeon; Li, Zhen; Zhu, Kai; Jung, Hyun Suk

    2016-05-01

    Most research on perovskite solar cells has focused on improving power-conversion efficiency and stability. However, if one could refurbish perovskite solar cells, their stability might not be a critical issue. From the perspective of cost effectiveness, if failed, perovskite solar cells could be collected and recycled; reuse of their gold electrodes and transparent conducting glasses could reduce the price per watt of perovskite photovoltaic modules. Herein, we present a simple and effective method for removing the perovskite layer and reusing the mesoporous TiO2-coated transparent conducting glass substrate via selective dissolution. We find that the perovskite layer can be easily decomposed in polar aprotic solvents because of the reaction between polar aprotic solvents and Pb2+ cations. After 10 cycles of recycling, a mesoporous TiO2-coated transparent conducting glass substrate-based perovskite solar cell still shows a constant power-conversion efficiency, thereby demonstrating the possibility of recycling perovskite solar cells.

  13. Selective Dissolution of Halide Perovskites as a Step Towards Recycling Solar Cells

    Kim, Byeong Jo; Kim, Dong Hoe; Kwon, Seung Lee; Park, So Yeon; Li, Zhen; Zhu, Kai; Jung, Hyun Suk

    2016-05-23

    Most research on perovskite solar cells has focused on improving power-conversion efficiency and stability. However, if one could refurbish perovskite solar cells, their stability might not be a critical issue. From the perspective of cost effectiveness, if failed, perovskite solar cells could be collected and recycled; reuse of their gold electrodes and transparent conducting glasses could reduce the price per watt of perovskite photovoltaic modules. Herein, we present a simple and effective method for removing the perovskite layer and reusing the mesoporous TiO2-coated transparent conducting glass substrate via selective dissolution. We find that the perovskite layer can be easily decomposed in polar aprotic solvents because of the reaction between polar aprotic solvents and Pb2+ cations. After 10 cycles of recycling, a mesoporous TiO2-coated transparent conducting glass substrate-based perovskite solar cell still shows a constant power-conversion efficiency, thereby demonstrating the possibility of recycling perovskite solar cells.

  14. Selective dissolution of halide perovskites as a step towards recycling solar cells.

    Kim, Byeong Jo; Kim, Dong Hoe; Kwon, Seung Lee; Park, So Yeon; Li, Zhen; Zhu, Kai; Jung, Hyun Suk

    2016-01-01

    Most research on perovskite solar cells has focused on improving power-conversion efficiency and stability. However, if one could refurbish perovskite solar cells, their stability might not be a critical issue. From the perspective of cost effectiveness, if failed, perovskite solar cells could be collected and recycled; reuse of their gold electrodes and transparent conducting glasses could reduce the price per watt of perovskite photovoltaic modules. Herein, we present a simple and effective method for removing the perovskite layer and reusing the mesoporous TiO2-coated transparent conducting glass substrate via selective dissolution. We find that the perovskite layer can be easily decomposed in polar aprotic solvents because of the reaction between polar aprotic solvents and Pb(2+) cations. After 10 cycles of recycling, a mesoporous TiO2-coated transparent conducting glass substrate-based perovskite solar cell still shows a constant power-conversion efficiency, thereby demonstrating the possibility of recycling perovskite solar cells. PMID:27211006

  15. Selective dissolution of halide perovskites as a step towards recycling solar cells

    Kim, Byeong Jo; Kim, Dong Hoe; Kwon, Seung Lee; Park, So Yeon; Li, Zhen; Zhu, Kai; Jung, Hyun Suk

    2016-01-01

    Most research on perovskite solar cells has focused on improving power-conversion efficiency and stability. However, if one could refurbish perovskite solar cells, their stability might not be a critical issue. From the perspective of cost effectiveness, if failed, perovskite solar cells could be collected and recycled; reuse of their gold electrodes and transparent conducting glasses could reduce the price per watt of perovskite photovoltaic modules. Herein, we present a simple and effective method for removing the perovskite layer and reusing the mesoporous TiO2-coated transparent conducting glass substrate via selective dissolution. We find that the perovskite layer can be easily decomposed in polar aprotic solvents because of the reaction between polar aprotic solvents and Pb2+ cations. After 10 cycles of recycling, a mesoporous TiO2-coated transparent conducting glass substrate-based perovskite solar cell still shows a constant power-conversion efficiency, thereby demonstrating the possibility of recycling perovskite solar cells. PMID:27211006

  16. Photoinduced Coherent Spin Fluctuation in Primary Dynamics of Insulator to Metal Transition in Perovskite Cobalt Oxide

    Arima T.; Iwai S.; Itoh H; Yamada K; Ishikawa T; Yamada S; Sasaki T.

    2013-01-01

    Coherent spin fluctuation was detected in the photoinduced Mott insulator-metal transition in perovskite cobalt oxide by using 3 optical-cycle infrared pulse. Such coherent spin fluctuation is driven by the perovskite distortion changing orbital gap.

  17. Selective dissolution of halide perovskites as a step towards recycling solar cells

    Kim, Byeong Jo; Kim, Dong Hoe; Kwon, Seung Lee; Park, So Yeon; LI, ZHEN; ZHU, KAI; Jung, Hyun Suk

    2016-01-01

    Most research on perovskite solar cells has focused on improving power-conversion efficiency and stability. However, if one could refurbish perovskite solar cells, their stability might not be a critical issue. From the perspective of cost effectiveness, if failed, perovskite solar cells could be collected and recycled; reuse of their gold electrodes and transparent conducting glasses could reduce the price per watt of perovskite photovoltaic modules. Herein, we present a simple and effective...

  18. Controlling the Cavity Structures of Two-Photon-Pumped Perovskite Microlasers.

    Zhang, Wei; Peng, Lan; Liu, Jie; Tang, Aiwei; Hu, Jin-Song; Yao, Jiannian; Zhao, Yong Sheng

    2016-06-01

    Low-threshold two-photon-pumped (TPP) perovskite microcavity lasers are achieved in crystal perovskite 1D or 2D microstructures fabricated through a liquid-phase self-assembly method assisted by two distinct surfactant soft templates. The lasing actions from the perovskite materials exhibit a shape-dependent microcavity effect, which is subsequently utilized for the modulation of the lasing modes and for the achievement of two-photon-pumped single-mode perovskite microlasers. PMID:27007487

  19. Influence of void-free perovskite capping layer on the charge recombination process in high performance CH3NH3PbI3 perovskite solar cells

    Fu, Kunwu; Nelson, Christopher T.; Scott, Mary Cooper; Minor, Andrew; Mathews, Nripan; Wong, Lydia Helena

    2016-02-01

    The stunning rise of methylammonium lead iodide perovskite material as a light harvesting material in recent years has drawn much attention in the photovoltaic community. Here, we investigated in detail the uniform and void-free perovskite capping layer in the mesoscopic perovskite devices and found it to play a critical role in determining device performance and charge recombination process. Compared to the rough surface with voids of the perovskite layer, surface of the perovskite capping layer obtained from sequential deposition process is much more uniform with less void formation and distribution within the TiO2 mesoscopic scaffold is more homogeneous, leading to much improved photovoltaic parameters of the devices. The impact of void free perovskite capping layer surface on the charge recombination processes within the mesoscopic perovskite solar cells is further scrutinized via charge extraction measurement. Modulation of precursor solution concentrations in order to further improve the perovskite layer surface morphology leads to higher efficiency and lower charge recombination rates. Inhibited charge recombination in these solar cells also matches with the higher charge density and slower photovoltage decay profiles measured.The stunning rise of methylammonium lead iodide perovskite material as a light harvesting material in recent years has drawn much attention in the photovoltaic community. Here, we investigated in detail the uniform and void-free perovskite capping layer in the mesoscopic perovskite devices and found it to play a critical role in determining device performance and charge recombination process. Compared to the rough surface with voids of the perovskite layer, surface of the perovskite capping layer obtained from sequential deposition process is much more uniform with less void formation and distribution within the TiO2 mesoscopic scaffold is more homogeneous, leading to much improved photovoltaic parameters of the devices. The impact of

  20. Recent Advances in Interface Engineering for Planar Heterojunction Perovskite Solar Cells

    Wei Yin

    2016-06-01

    Full Text Available Organic-inorganic hybrid perovskite solar cells are considered as one of the most promising next-generation solar cells due to their advantages of low-cost precursors, high power conversion efficiency (PCE and easy of processing. In the past few years, the PCEs have climbed from a few to over 20% for perovskite solar cells. Recent developments demonstrate that perovskite exhibits ambipolar semiconducting characteristics, which allows for the construction of planar heterojunction (PHJ perovskite solar cells. PHJ perovskite solar cells can avoid the use of high-temperature sintered mesoporous metal oxides, enabling simple processing and the fabrication of flexible and tandem perovskite solar cells. In planar heterojunction materials, hole/electron transport layers are introduced between a perovskite film and the anode/cathode. The hole and electron transporting layers are expected to enhance exciton separation, charge transportation and collection. Further, the supporting layer for the perovskite film not only plays an important role in energy-level alignment, but also affects perovskite film morphology, which have a great effect on device performance. In addition, interfacial layers also affect device stability. In this review, recent progress in interfacial engineering for PHJ perovskite solar cells will be reviewed, especially with the molecular interfacial materials. The supporting interfacial layers for the optimization of perovskite films will be systematically reviewed. Finally, the challenges remaining in perovskite solar cells research will be discussed.

  1. Recent Advances in Interface Engineering for Planar Heterojunction Perovskite Solar Cells.

    Yin, Wei; Pan, Lijia; Yang, Tingbin; Liang, Yongye

    2016-01-01

    Organic-inorganic hybrid perovskite solar cells are considered as one of the most promising next-generation solar cells due to their advantages of low-cost precursors, high power conversion efficiency (PCE) and easy of processing. In the past few years, the PCEs have climbed from a few to over 20% for perovskite solar cells. Recent developments demonstrate that perovskite exhibits ambipolar semiconducting characteristics, which allows for the construction of planar heterojunction (PHJ) perovskite solar cells. PHJ perovskite solar cells can avoid the use of high-temperature sintered mesoporous metal oxides, enabling simple processing and the fabrication of flexible and tandem perovskite solar cells. In planar heterojunction materials, hole/electron transport layers are introduced between a perovskite film and the anode/cathode. The hole and electron transporting layers are expected to enhance exciton separation, charge transportation and collection. Further, the supporting layer for the perovskite film not only plays an important role in energy-level alignment, but also affects perovskite film morphology, which have a great effect on device performance. In addition, interfacial layers also affect device stability. In this review, recent progress in interfacial engineering for PHJ perovskite solar cells will be reviewed, especially with the molecular interfacial materials. The supporting interfacial layers for the optimization of perovskite films will be systematically reviewed. Finally, the challenges remaining in perovskite solar cells research will be discussed. PMID:27347923

  2. Dielectric properties of hybrid perovskites and drift-diffusion modeling of perovskite cells

    Pedesseau, Laurent; Kepenekian, M; Sapori, Daniel; Y. HUANG; Rolland, Alain; Beck, Alexandre; Cornet, C.; Durand, Olivier; Wang, Shijian; Katan, Claudine; Even, Jacky

    2016-01-01

    A method based on DFT is used to obtained dielectric profiles. The high frequency ε∞(z) and the static εs(z) dielectric profiles are compared for 3D, 2D-3D and 2D Hybrid Organic Perovskites (HOP). A dielectric confinement is observed for the 2D materials between the high dielectric constant of the inorganic part and the low dielectric constant of the organic part. The effect of the ionic contribution on the dielectric constant is also shown. The quantum and dielectric confinements of 3D HOP n...

  3. A Long-Term View on Perovskite Optoelectronics.

    Docampo, Pablo; Bein, Thomas

    2016-02-16

    Recently, metal halide perovskite materials have become an exciting topic of research for scientists of a wide variety of backgrounds. Perovskites have found application in many fields, starting from photovoltaics and now also making an impact in light-emitting applications. This new class of materials has proven so interesting since it can be easily solution processed while exhibiting materials properties approaching the best inorganic optoelectronic materials such as GaAs and Si. In photovoltaics, in only 3 years, efficiencies have rapidly increased from an initial value of 3.8% to over 20% in recent reports for the commonly employed methylammonium lead iodide (MAPI) perovskite. The first light emitting diodes and light-emitting electrochemical cells have been developed already exhibiting internal quantum efficiencies exceeding 15% for the former and tunable light emission spectra. Despite their processing advantages, perovskite optoelectronic materials suffer from several drawbacks that need to be overcome before the technology becomes industrially relevant and hence achieve long-term application. Chief among these are the sensitivity of the structure toward moisture and crystal phase transitions in the device operation regime, unreliable device performance dictated by the operation history of the device, that is, hysteresis, the inherent toxicity of the structure, and the high cost of the employed charge selective contacts. In this Account, we highlight recent advances toward the long-term viability of perovskite photovoltaics. We identify material decomposition routes and suggest strategies to prevent damage to the structure. In particular, we focus on the effect of moisture upon the structure and stabilization of the material to avoid phase transitions in the solar cell operating range. Furthermore, we show strategies to achieve low-cost chemistries for the development of hole transporters for perovskite solar cells, necessary to be able to compete with other

  4. Various perovskite-type oxide phosphors

    This report reviews various perovskite-type oxide phosphors. Photoluminescence properties of Pr-doped (Ba, Sr, Ca)TiO3 were studied by emission, excitation, and diffuse reflectance spectra. The intensities of red luminescence at 610 nm due to Pr3+ ions increase in the order of Pr-doped cubic SrTiO3, tetragonal BaTiO3, and orthorhombic CaTiO3. Luminescence efficiency of SrTiO3:Pr3+ was intensified up to significantly by addition of Al ions. Extensive studies for photoluminescence have been performed for alkaline-earth stannates (Ba, Sr, Ca)SnO3 doped with various ions. CaSnO3 was found to show intense white luminescence by Pr doping and green luminescence by Tb-Mg co-doping. Pr doped CaSnO3 showed not only a red emission line, which was observed in Pr doped CaTiO3 or SrTiO3, but also an intense blue-green line. Because of the mixture of the red and blue-green luminescence, the Pr doped CaSnO3 was seen in white under UV excitation. Tb-Mg co-doping effectively enhanced the green luminescence of Tb3+ ions due to the local lattice distortion around Tb ions induced by the small Mg ions at Ca sites. Sr2SnO4:Ti4+ shows blue luminescence originated from Ti4+ of TiO6 complex, and Eu3+-Ti4+ co-doped Sr2SnO4 emits red luminescence due to energy transfer between two luminescence centers. Titanate octahedral, replaced stannate octahedral, containing a short Ti-O distance showed efficient luminescence if these octahedral were isolated from each other. The small tolerance factor of CaZrO3 indicated a promising material for phosphors. Blue violet or green luminescence and red luminescence were observed in CaZrO3 by doping Tb3+-Mg2+ and Eu3+-Mg2+, respectively. In order to develop multifunctional photoelectronic devices, the epitaxial films of calcium and strontium stannates phosphors with perovskite-type structure were fabricated by the pulsed-laser deposition method. The films showed intense luminescence of several colors under UV excitation. Post-annealing treatment markedly

  5. Electron–phonon coupling in hybrid lead halide perovskites

    Wright, Adam D.; Verdi, Carla; Milot, Rebecca L.; Eperon, Giles E.; Pérez-Osorio, Miguel A.; Snaith, Henry J.; Giustino, Feliciano; Johnston, Michael B.; Herz, Laura M.

    2016-01-01

    Phonon scattering limits charge-carrier mobilities and governs emission line broadening in hybrid metal halide perovskites. Establishing how charge carriers interact with phonons in these materials is therefore essential for the development of high-efficiency perovskite photovoltaics and low-cost lasers. Here we investigate the temperature dependence of emission line broadening in the four commonly studied formamidinium and methylammonium perovskites, HC(NH2)2PbI3, HC(NH2)2PbBr3, CH3NH3PbI3 and CH3NH3PbBr3, and discover that scattering from longitudinal optical phonons via the Fröhlich interaction is the dominant source of electron–phonon coupling near room temperature, with scattering off acoustic phonons negligible. We determine energies for the interacting longitudinal optical phonon modes to be 11.5 and 15.3 meV, and Fröhlich coupling constants of ∼40 and 60 meV for the lead iodide and bromide perovskites, respectively. Our findings correlate well with first-principles calculations based on many-body perturbation theory, which underlines the suitability of an electronic band-structure picture for describing charge carriers in hybrid perovskites. PMID:27225329

  6. Effect of Perovskite Film Preparation on Performance of Solar Cells

    Yaxian Pei

    2016-01-01

    Full Text Available For the perovskite solar cells (PSCs, the performance of the PSCs has become the focus of the research by improving the crystallization and morphology of the perovskite absorption layer. In this thesis, based on the structure of mesoporous perovskite solar cells (MPSCs, we designed the experiments to improve the photovoltaic performance of the PSCs by improved processing technique, which mainly includes the following two aspects. Before spin-coating PbI2 solution, we control the substrate temperature to modify the crystal quality and morphology of perovskite films. On the other hand, before annealing, we keep PbI2 films for the different drying time at room temperature to optimize films morphology. In our trials, it was found that the substrate temperature is more important in determining the photovoltaic performance than drying time. These results indicate that the crystallization and morphology of perovskite films affect the absorption intensity and obviously influence the short circuit current density of MPSCs. Utilizing films prepared by mentioning two methods, MPSCs with maximum power conversion efficiency of over 4% were fabricated for the active area of 0.5 × 0.5 cm2.

  7. Halide Perovskites: Poor Man's High-Performance Semiconductors.

    Stoumpos, Constantinos C; Kanatzidis, Mercouri G

    2016-07-01

    Halide perovskites are a rapidly developing class of medium-bandgap semiconductors which, to date, have been popularized on account of their remarkable success in solid-state heterojunction solar cells raising the photovoltaic efficiency to 20% within the last 5 years. As the physical properties of the materials are being explored, it is becoming apparent that the photovoltaic performance of the halide perovskites is just but one aspect of the wealth of opportunities that these compounds offer as high-performance semiconductors. From unique optical and electrical properties stemming from their characteristic electronic structure to highly efficient real-life technological applications, halide perovskites constitute a brand new class of materials with exotic properties awaiting discovery. The nature of halide perovskites from the materials' viewpoint is discussed here, enlisting the most important classes of the compounds and describing their most exciting properties. The topics covered focus on the optical and electrical properties highlighting some of the milestone achievements reported to date but also addressing controversies in the vastly expanding halide perovskite literature. PMID:27174223

  8. Magnetoresistance and magnetic properties of the double perovskites

    The magnetic double perovskite materials of composition A2BB'O6 with A an alkaline earth ion and B and B' a magnetic and non-magnetic transition metal or lanthanide ions, respectively, have attracted considerable attention due to their interesting magnetic properties ranging from antiferromagnetism to geometrically frustrated spin systems and ferromagnetism. With respect to application in spin electronics, the ferromagnetic double perovskites with BB' = CrW, CrRe, FeMo or FeRe and A = Ca, Ba, Sr are highly interesting due to their in most cases high Curie temperatures well above room temperature and their half-magnetic behaviour. Here, we summarize the structural, magnetotransport, magnetic and optical properties of the ferromagnetic double perovskites and discuss the underlying physics. In particular, we discuss the impact of the steric effects resulting in a distorted perovskite structure, doping effects obtained by a partial replacing of the divalent alkaline earth ions on the A site by a trivalent lanthanide as well as B/B' cationic disorder on the Curie temperature TC, the saturation magnetization and the magnetotransport properties. Our results support the presence of a kinetic energy driven mechanism in the ferromagnetic double perovskites, where ferromagnetism is stabilised by a hybridization of states of the non-magnetic B'- site positioned in between the high spin B-sites. (author)

  9. Degradation of organometallic perovskite solar cells induced by trap states

    Song, Dandan; Ji, Jun; Li, Yaoyao; Li, Guanying; Li, Meicheng; Wang, Tianyue; Wei, Dong; Cui, Peng; He, Yue; Mbengue, Joseph Michel

    2016-02-01

    The degradation of organometallic perovskite solar cells (PSCs) is the key bottleneck hampering their development, which is typically ascribed to the decomposition of perovskite (CH3NH3PbI3). In this work, the degradation of PSCs is observed to be significant, with the decrease in efficiency from 18.2% to 11.5% in ambient air for 7 days. However, no obvious decomposition or structural evolution of the perovskite was observed, except the notable degradation phenomenon of the device. The degradation of PSCs derives from deteriorated photocurrent and fill factor, which are proven to be induced by increased trap states for enlarged carrier recombination in degraded PSCs. The increased trap states in PSCs over storage time are probably induced by the increased defects at the surface of perovskite. The trap states induced degradation provides a physical insight into the degradation mechanisms of PSCs. Moreover, as the investigations were performed on real PSCs instead of individual perovskite films, the findings here present one of their actual degradation mechanisms.

  10. LSFM perovskites as cathodes for the electrochemical reduction of NO

    Kammer Hansen, K.; Skou, E.M.

    Six La0.6Sr0.4Fe1-xMnO3-delta (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0) perovskite compounds have been synthesised by the citric-acid route. The perovskites have been characterised by powder XRD and are shown to belong to the hexagonal crystal system. The perovskites are also evaluated by TG-measurements in...... degrees C on a ceria based electrolyte. Only La0.6Sr0.4Fe0.8Mn0.2O3-delta (LSFM020) and La0.6Sr0.4FeO3-delta (LSFM000) show significant activity for the reduction of NO. This can probably be related to the high redox capacity of these compounds. The activity of the perovskites for the reduction of oxygen...... increases systematically with increasing iron content. The selectivity of the perovskites towards the reduction of NO with regard to the reduction of O-2 is highest at the lowest temperatures. (c) 2004 Published by Elsevier B.V....

  11. Electron-phonon coupling in hybrid lead halide perovskites.

    Wright, Adam D; Verdi, Carla; Milot, Rebecca L; Eperon, Giles E; Pérez-Osorio, Miguel A; Snaith, Henry J; Giustino, Feliciano; Johnston, Michael B; Herz, Laura M

    2016-01-01

    Phonon scattering limits charge-carrier mobilities and governs emission line broadening in hybrid metal halide perovskites. Establishing how charge carriers interact with phonons in these materials is therefore essential for the development of high-efficiency perovskite photovoltaics and low-cost lasers. Here we investigate the temperature dependence of emission line broadening in the four commonly studied formamidinium and methylammonium perovskites, HC(NH2)2PbI3, HC(NH2)2PbBr3, CH3NH3PbI3 and CH3NH3PbBr3, and discover that scattering from longitudinal optical phonons via the Fröhlich interaction is the dominant source of electron-phonon coupling near room temperature, with scattering off acoustic phonons negligible. We determine energies for the interacting longitudinal optical phonon modes to be 11.5 and 15.3 meV, and Fröhlich coupling constants of ∼40 and 60 meV for the lead iodide and bromide perovskites, respectively. Our findings correlate well with first-principles calculations based on many-body perturbation theory, which underlines the suitability of an electronic band-structure picture for describing charge carriers in hybrid perovskites. PMID:27225329

  12. Novel materials for stable perovskite solar cells (Presentation Recording)

    Abate, Antonio

    2015-09-01

    Organic-inorganic perovskites are quickly overrunning research activities in new materials for cost-effective and high-efficiency photovoltaic technologies. Since the first demonstration from Kojima and co-workers in 2009, several perovskite-based solar cells have been reported and certified with rapidly improving power conversion efficiency. Recent reports demonstrate that perovskites can compete with the most efficient inorganic materials, while they still allow processing from solution as potential advantage to deliver a cost-effective solar technology. Compare to the impressive progress in power conversion efficiency, stability studies are rather poor and often controversial. An intrinsic complication comes from the fact that the stability of perovskite solar cells is strongly affected by any small difference in the device architecture, preparation procedure, materials composition and testing procedure. In the present talk we will focus on the stability of perovskite solar cells in working condition. We will discuss a measuring protocol to extract reliable and reproducible ageing data. We will present new materials and preparation procedures which improve the device lifetime without giving up on high power conversion efficiency.

  13. Employing Lead Thiocyanate Additive to Reduce the Hysteresis and Boost the Fill Factor of Planar Perovskite Solar Cells

    Ke, Weijun [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo OH 43606 USA; Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072 China; National Renewable Energy Laboratory, 15013 Denver West Parkway Golden CO 80401 USA; Xiao, Chuanxiao [National Renewable Energy Laboratory, 15013 Denver West Parkway Golden CO 80401 USA; Wang, Changlei [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo OH 43606 USA; Saparov, Bayrammurad [Department of Mechanical Engineering and Materials Science, Duke University, Durham NC 27708 USA; Department of Chemistry, Duke University, Durham NC 27708 USA; Duan, Hsin-Sheng [Department of Mechanical Engineering and Materials Science, Duke University, Durham NC 27708 USA; Zhao, Dewei [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo OH 43606 USA; National Renewable Energy Laboratory, 15013 Denver West Parkway Golden CO 80401 USA; Xiao, Zewen [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo OH 43606 USA; Schulz, Philip [National Renewable Energy Laboratory, 15013 Denver West Parkway Golden CO 80401 USA; Harvey, Steven P. [National Renewable Energy Laboratory, 15013 Denver West Parkway Golden CO 80401 USA; Liao, Weiqiang [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo OH 43606 USA; Meng, Weiwei [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo OH 43606 USA; Yu, Yue [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo OH 43606 USA; Cimaroli, Alexander J. [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo OH 43606 USA; Jiang, Chun-Sheng [National Renewable Energy Laboratory, 15013 Denver West Parkway Golden CO 80401 USA; Zhu, Kai [National Renewable Energy Laboratory, 15013 Denver West Parkway Golden CO 80401 USA; Al-Jassim, Mowafak [National Renewable Energy Laboratory, 15013 Denver West Parkway Golden CO 80401 USA; Fang, Guojia [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072 China; Mitzi, David B. [Department of Mechanical Engineering and Materials Science, Duke University, Durham NC 27708 USA; Department of Chemistry, Duke University, Durham NC 27708 USA; Yan, Yanfa [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo OH 43606 USA

    2016-05-04

    Lead thiocyanate in the perovskite precursor can increase the grain size of a perovskite thin film and reduce the conductivity of the grain boundaries, leading to perovskite solar cells with reduced hysteresis and enhanced fill factor. A planar perovskite solar cell with grain boundary and interface passivation achieves a steady-state efficiency of 18.42%.

  14. Employing Lead Thiocyanate Additive to Reduce the Hysteresis and Boost the Fill Factor of Planar Perovskite Solar Cells.

    Ke, Weijun; Xiao, Chuanxiao; Wang, Changlei; Saparov, Bayrammurad; Duan, Hsin-Sheng; Zhao, Dewei; Xiao, Zewen; Schulz, Philip; Harvey, Steven P; Liao, Weiqiang; Meng, Weiwei; Yu, Yue; Cimaroli, Alexander J; Jiang, Chun-Sheng; Zhu, Kai; Al-Jassim, Mowafak; Fang, Guojia; Mitzi, David B; Yan, Yanfa

    2016-07-01

    Lead thiocyanate in the perovskite precursor can increase the grain size of a perovskite thin film and reduce the conductivity of the grain boundaries, leading to perovskite solar cells with reduced hysteresis and enhanced fill factor. A planar perovskite solar cell with grain boundary and interface passivation achieves a steady-state efficiency of 18.42%. PMID:27145346

  15. A novel rapid synthesis of Fe2O3/graphene nanocomposite using ferrate(VI) and its application as a new kind of nanocomposite modified electrode as electrochemical sensor

    Highlights: • A novel rapid synthesis of rGO–Fe2O3 nanocomposite was developed using Fe(VI). • Fe(VI) as an environmentally friendly oxidant was introduced for GO synthesis. • Synthesized rGO–Fe2O3 nanocomposite was applied as electrochemical sensor. • A non-enzymatic sensor was developed for H2O2. - Abstract: In this study, a novel, simple and sensitive non-enzymatic hydrogen peroxide electrochemical sensor was developed using reduced graphene oxide/Fe2O3 nanocomposite modified glassy carbon electrode. This nanocomposite was synthesized by reaction of sodium ferrate with graphene in alkaline media. This reaction completed in 5 min and the products were stable and its deposition on the surface of electrode is investigated. It has been found the apparent charge transfer rate constant (ks) is 0.52 and transfer coefficient (α) is 0.61 for electron transfer between the modifier and glassy carbon electrode. Electrochemical behavior of this electrode and its ability to catalyze the electro-reduction of H2O2 has been studied by cyclic voltammetry and chronoamperometry at different experimental conditions. The analytical parameters showed the good ability of electrode as a sensor for H2O2 amperometric reduction

  16. A novel rapid synthesis of Fe{sub 2}O{sub 3}/graphene nanocomposite using ferrate(VI) and its application as a new kind of nanocomposite modified electrode as electrochemical sensor

    Karimi, Mohammad Ali, E-mail: ma_karimi43@yahoo.com [Department of Chemistry, Payame Noor University, 19395-4697 Tehran (Iran, Islamic Republic of); Department of Chemistry & Nanoscience and Nanotechnology Research Laboratory (NNRL), Payame Noor University, Sirjan (Iran, Islamic Republic of); Banifatemeh, Fatemeh [Department of Chemistry, Payame Noor University, 19395-4697 Tehran (Iran, Islamic Republic of); Department of Chemistry, Payame Noor University, Mashhad (Iran, Islamic Republic of); Hatefi-Mehrjardi, Abdolhamid [Department of Chemistry, Payame Noor University, 19395-4697 Tehran (Iran, Islamic Republic of); Department of Chemistry & Nanoscience and Nanotechnology Research Laboratory (NNRL), Payame Noor University, Sirjan (Iran, Islamic Republic of); Tavallali, Hossein [Department of Chemistry, Payame Noor University, 19395-4697 Tehran (Iran, Islamic Republic of); Department of Chemistry, Payame Noor University, Shiraz (Iran, Islamic Republic of); Eshaghia, Zarrin [Department of Chemistry, Payame Noor University, Mashhad (Iran, Islamic Republic of); Deilamy-Rad, Gohar [Department of Chemistry, Payame Noor University, Shiraz (Iran, Islamic Republic of)

    2015-10-15

    Highlights: • A novel rapid synthesis of rGO–Fe{sub 2}O{sub 3} nanocomposite was developed using Fe(VI). • Fe(VI) as an environmentally friendly oxidant was introduced for GO synthesis. • Synthesized rGO–Fe{sub 2}O{sub 3} nanocomposite was applied as electrochemical sensor. • A non-enzymatic sensor was developed for H{sub 2}O{sub 2}. - Abstract: In this study, a novel, simple and sensitive non-enzymatic hydrogen peroxide electrochemical sensor was developed using reduced graphene oxide/Fe{sub 2}O{sub 3} nanocomposite modified glassy carbon electrode. This nanocomposite was synthesized by reaction of sodium ferrate with graphene in alkaline media. This reaction completed in 5 min and the products were stable and its deposition on the surface of electrode is investigated. It has been found the apparent charge transfer rate constant (ks) is 0.52 and transfer coefficient (α) is 0.61 for electron transfer between the modifier and glassy carbon electrode. Electrochemical behavior of this electrode and its ability to catalyze the electro-reduction of H{sub 2}O{sub 2} has been studied by cyclic voltammetry and chronoamperometry at different experimental conditions. The analytical parameters showed the good ability of electrode as a sensor for H{sub 2}O{sub 2} amperometric reduction.

  17. Elasticity of CaIrO3 with perovskite and post-perovskite structure

    Niwa, Ken; Yagi, Takehiko; Ohgushi, Kenya

    2011-01-01

    Compression behaviors of CaIrO3 with perovskite (Pv) and post-perovskite (pPv) structures have been investigated up to 31.0(1.0) and 35.3(1) GPa at room temperature, respectively, in a diamond-anvil cell with hydrostatic pressure media. CaIrO3 Pv and pPv phases were compressed with the axial compressibility of β a > β c > β b and β b > β a > β c, respectively and no phase transition was observed in both phases up to the highest pressure in the present study. The order of axial compressibility for pPv phase is consistent with the crystallographic consideration for layer structured materials and previous experimental results. On the other hand, Pv phase shows anomalous compression behavior in b axis, which exhibit constant or slightly expanded above 13 GPa, although the applied pressure remained hydrostatic. Volume difference between Pv and pPv phases was gradually decreased with increasing pressure and this is consistent with the results of theoretical study based on the ab initio calculation. Present results, combined with theoretical study, suggest that these complicate compression behaviors in CaIrO3 under high pressure might be caused by the partially filled electron of Ir4+. Special attention must be paid in case of using CaIrO3 as analog materials to MgSiO3, although CaIrO3 exhibits interesting physical properties under high pressure.

  18. CH3 NH3 PbBr3 -CH3 NH3 PbI3 Perovskite-Perovskite Tandem Solar Cells with Exceeding 2.2 V Open Circuit Voltage.

    Heo, Jin Hyuck; Im, Sang Hyuk

    2016-07-01

    Perovskite-perovskite tandem solar cells with open-circuit voltages of over 2.2 V are reported. These cost-effective, solution-processible perovskite hybrid tandem solar cells with high open-circuit voltages are fabricated by the simple lamination of a front planar MAPbBr3 perovskite cell and a back MAPbI3 planar perovskite solar cell. PMID:26505740

  19. Interfacial segregation in perovskites. Part 1

    Based on thermodynamic principles a theory for equilibrium interfacial segregation is proposed for perovskite materials, and this theory is applied to BaTiO3. An approach developed by Frenkel and refined by Kliewer and Koehler is extended to undoped ternary oxide materials such as BaTiO3. The approach uses regular solution approximations and considers space charge effects as the major driving force for segregation. The analysis based on this model indicates the presence of a negative space charge potential (-0.1 V at 800 degrees C) at the surface of pure BaTiO3. The model also predicts cation enrichment at the interface. The thickness of the space charge layer decreases with increasing temperature, and calculated values agree well with experimental results. Since both elastic and electrostatic driving forces are important for dopant/impurity segregation, an approach where the grain boundary is considered to be a two-dimensional phase, in equilibrium with the three-dimensional phase of the grain, proves useful. Solving for the impurity/dopant segregation ratio is case specific and requires knowledge of the charge neutrality conditions as well as the strain energy contribution

  20. Topological Oxide Insulator in Cubic Perovskite Structure

    Jin, Hosub; Rhim, Sonny H.; Im, Jino; Freeman, Arthur J.

    2013-04-01

    The emergence of topologically protected conducting states with the chiral spin texture is the most prominent feature at the surface of topological insulators. On the application side, large band gap and high resistivity to distinguish surface from bulk degrees of freedom should be guaranteed for the full usage of the surface states. Here, we suggest that the oxide cubic perovskite YBiO3, more than just an oxide, defines itself as a new three-dimensional topological insulator exhibiting both a large bulk band gap and a high resistivity. Based on first-principles calculations varying the spin-orbit coupling strength, the non-trivial band topology of YBiO3 is investigated, where the spin-orbit coupling of the Bi 6p orbital plays a crucial role. Taking the exquisite synthesis techniques in oxide electronics into account, YBiO3 can also be used to provide various interface configurations hosting exotic topological phenomena combined with other quantum phases.

  1. Elastic anisotropy of experimental analogues of perovskite and post-perovskite help to interpret D′′ diversity

    Yoneda, Akira; Fukui, Hiroshi; Xu, Fang; Nakatsuka, Akihiko; Yoshiasa, Akira; Seto, Yusuke; Ono, Kenya; Tsutsui, Satoshi; Uchiyama, Hiroshi; Baron, Alfred Q. R.

    2014-01-01

    Recent studies show that the D′′ layer, just above the Earth's core–mantle boundary, is composed of MgSiO3 post-perovskite and has significant lateral inhomogeneity. Here we consider the D′′ diversity as related to the single-crystal elasticity of the post-perovskite phase. We measure the single-crystal elasticity of the perovskite Pbnm-CaIrO3 and post-perovskite Cmcm-CaIrO3 using inelastic X-ray scattering. These materials are structural analogues to same phases of MgSiO3. Our results show that Cmcm-CaIrO3 is much more elastically anisotropic than Pbnm-CaIrO3, which offers an explanation for the enigmatic seismic wave velocity jump at the D′′ discontinuity. Considering the relation between lattice preferred orientation and seismic anisotropy in the D′′ layer, we suggest that the c axis of post-perovskite MgSiO3 aligns vertically beneath the Circum-Pacific rim, and the b axis vertically beneath the Central Pacific. PMID:24670790

  2. Elastic anisotropy of experimental analogues of perovskite and post-perovskite help to interpret D‧‧ diversity

    Yoneda, Akira; Fukui, Hiroshi; Xu, Fang; Nakatsuka, Akihiko; Yoshiasa, Akira; Seto, Yusuke; Ono, Kenya; Tsutsui, Satoshi; Uchiyama, Hiroshi; Baron, Alfred Q. R.

    2014-03-01

    Recent studies show that the D‧‧ layer, just above the Earth's core-mantle boundary, is composed of MgSiO3 post-perovskite and has significant lateral inhomogeneity. Here we consider the D‧‧ diversity as related to the single-crystal elasticity of the post-perovskite phase. We measure the single-crystal elasticity of the perovskite Pbnm-CaIrO3 and post-perovskite Cmcm-CaIrO3 using inelastic X-ray scattering. These materials are structural analogues to same phases of MgSiO3. Our results show that Cmcm-CaIrO3 is much more elastically anisotropic than Pbnm-CaIrO3, which offers an explanation for the enigmatic seismic wave velocity jump at the D‧‧ discontinuity. Considering the relation between lattice preferred orientation and seismic anisotropy in the D‧‧ layer, we suggest that the c axis of post-perovskite MgSiO3 aligns vertically beneath the Circum-Pacific rim, and the b axis vertically beneath the Central Pacific.

  3. Perovskite oxide SrTiO3 as an efficient electron transporter for hybrid perovskite solar cells

    Bera, Ashok

    2014-12-11

    In this work, we explored perovskite oxide SrTiO3 (STO) for the first time as the electron-transporting layer in organolead trihalide perovskite solar cells. The steady-state photoluminescence (PL) quenching and transient absorption experiments revealed efficient photoelectron transfer from CH3NH3PbI3-xClx to STO. Perovskite solar cells with meso-STO exhibit an open circuit voltage of 1.01 V, which is 25% higher than the value of 0.81 V achieved in the control device with the conventional meso-TiO2. In addition, an increase of 17% in the fill factor was achieved by tailoring the thickness of the meso-STO layer. We found that the application of STO leads to uniform perovskite layers with large grains and complete surface coverage, leading to a high shunt resistance and improved performance. These findings suggest STO as a competitive candidate as electron transport material in organometal perovskite solar cells.

  4. Organic-inorganic hybrid perovskites as light absorbing/hole conducting material in solar cells

    Ghanavi, Saman

    2013-01-01

    Solar cells involving two different perovskites were manufactured and analyzed. The perovskites were (CH3NH3)PbI3 and (CH3NH3)SnI3. Both perovskites have a shared methyl ammonium group (MA) and are used as both light absorbing material and hole conducting material (HTM) in this project. The preparation procedures for the complete device were according to previous attempts to make stable organic-inorganic hybrid perovskites and involved different layers and procedures. Both perovskites were ma...

  5. A polymer scaffold for self-healing perovskite solar cells

    Zhao, Yicheng; Wei, Jing; Li, Heng; Yan, Yin; Zhou, Wenke; Yu, Dapeng; Zhao, Qing

    2016-01-01

    Advancing of the lead halide perovskite solar cells towards photovoltaic market demands large-scale devices of high-power conversion efficiency, high reproducibility and stability via low-cost fabrication technology, and in particular resistance to humid environment for long-time operation. Here we achieve uniform perovskite film based on a novel polymer-scaffold architecture via a mild-temperature process. These solar cells exhibit efficiency of up to ~16% with small variation. The unencapsulated devices retain high output for up to 300 h in highly humid environment (70% relative humidity). Moreover, they show strong humidity resistant and self-healing behaviour, recovering rapidly after removing from water vapour. Not only the film can self-heal in this case, but the corresponding devices can present power conversion efficiency recovery after the water vapour is removed. Our work demonstrates the value of cheap, long chain and hygroscopic polymer scaffold in perovskite solar cells towards commercialization.

  6. Theoretical insights into multibandgap hybrid perovskites for photovoltaic applications

    Even, Jacky; Sapori, Daniel; Pedesseau, Laurent; Rolland, Alain; Kepenekian, Mikael; Robles, Roberto; Wang, Shijian; Huang, Yong; Beck, Alexandre; Durand, Olivier; Katan, C.

    2015-09-01

    This paper reviews some of the recent theoretical investigations on the Rashba Dresselhaus spin effects and dielectric properties of CH3NH3PbI3 hybrid perovskites and CsPbI3 all-inorganic perovskites using Density functional theory. The spin vectors rotate in the non-centrosymmetric P4mm tetragonal phase, respectively clockwise and counterclockwise, in a manner that is characteristic of a pure Rashba effect. The high frequency dielectric constants ɛ∞ of MAPbI3 and CsPbI3 are similar as anticipated, since large differences are only expected at very low frequency where additional contributions from molecular reorientations show off for the hybrid compounds. A first simulation of a perovskite on silicon tandem cell, including a tunnel junction, is also investigated. Effect of halogen substitution (I/Br) is inspected, revealing limitations for short-circuit current and open-circuit voltage electrical characteristics.

  7. A Review of ABO3 Perovskite Photocatalysts for Water Splitting

    Zhang Hongjie; Chen Gang; Li Zhonghua; Liu Jiangwen

    2007-01-01

    Photocatalysts with perovskites for hydrogen production from aqueous solution were reviewed. Among the most of metal oxide photocatalysts, the family of ABO3 Perovskite-type oxide shows higher photocatalytie activity, especially alkaline earth titanate and alkali tantalate. Therein, sodium tantalate showed the highest activity for water splitting. The reasons for the high photocatalytic activity of ABO3 perovskties are considered to the diverse and flexible crystal structure. The photocatalytic activity of ABO3 perovskties can be improved by doping other element at A site, B site or O site and loading CO-catalysts such as NiO and Pt. In this paper, the mechanism of photocatalytic water splitting, the structure of ABO3 perovsktie, and Perovskite-type photocatalysts were reviewed.

  8. Conformal Organohalide Perovskites Enable Lasing on Spherical Resonators

    Sutherland, Brandon R.

    2014-10-28

    © 2014 American Chemical Society. Conformal integration of semiconductor gain media is broadly important in on-chip optical communication technology. Here we deploy atomic layer deposition to create conformally deposited organohalide perovskites-an attractive semiconducting gain medium-with the goal of achieving coherent light emission on spherical optical cavities. We demonstrate the high quality of perovskite gain media fabricated with this method, achieving optical gain in the nanosecond pulse regime with a threshold for amplified spontaneous emission of 65 ± 8 μJ cm-2. Through variable stripe length measurements, we report a net modal gain of 125 ± 22 cm-1 and a gain bandwidth of 50 ± 14 meV. Leveraging the high quality of the gain medium, we conformally coat silica microspheres with perovskite to form whispering gallery mode optical cavities and achieve lasing.

  9. Photon recycling in lead iodide perovskite solar cells

    Pazos-Outón, Luis M.; Szumilo, Monika; Lamboll, Robin; Richter, Johannes M.; Crespo-Quesada, Micaela; Abdi-Jalebi, Mojtaba; Beeson, Harry J.; Vrućinić, Milan; Alsari, Mejd; Snaith, Henry J.; Ehrler, Bruno; Friend, Richard H.; Deschler, Felix

    2016-03-01

    Lead-halide perovskites have emerged as high-performance photovoltaic materials. We mapped the propagation of photogenerated luminescence and charges from a local photoexcitation spot in thin films of lead tri-iodide perovskites. We observed light emission at distances of ≥50 micrometers and found that the peak of the internal photon spectrum red-shifts from 765 to ≥800 nanometers. We used a lateral-contact solar cell with selective electron- and hole-collecting contacts and observed that charge extraction for photoexcitation >50 micrometers away from the contacts arose from repeated recycling between photons and electron-hole pairs. Thus, energy transport is not limited by diffusive charge transport but can occur over long distances through multiple absorption-diffusion-emission events. This process creates high excitation densities within the perovskite layer and allows high open-circuit voltages.

  10. Exciton localization in solution-processed organolead trihalide perovskites

    He, Haiping; Yu, Qianqian; Li, Hui; Li, Jing; Si, Junjie; Jin, Yizheng; Wang, Nana; Wang, Jianpu; He, Jingwen; Wang, Xinke; Zhang, Yan; Ye, Zhizhen

    2016-03-01

    Organolead trihalide perovskites have attracted great attention due to the stunning advances in both photovoltaic and light-emitting devices. However, the photophysical properties, especially the recombination dynamics of photogenerated carriers, of this class of materials are controversial. Here we report that under an excitation level close to the working regime of solar cells, the recombination of photogenerated carriers in solution-processed methylammonium-lead-halide films is dominated by excitons weakly localized in band tail states. This scenario is evidenced by experiments of spectral-dependent luminescence decay, excitation density-dependent luminescence and frequency-dependent terahertz photoconductivity. The exciton localization effect is found to be general for several solution-processed hybrid perovskite films prepared by different methods. Our results provide insights into the charge transport and recombination mechanism in perovskite films and help to unravel their potential for high-performance optoelectronic devices.

  11. Spatially resolved optoelectronic characterization of perovskite lead iodide nanostructures

    Xiao, Rui; Peng, Xingyu; Hou, Yasen; Yu, Dong

    The high power conversion efficiency of organo-lead halide perovskite-based solar cells has attracted world-wide attention over the past few years. The high efficiency was believed to originate from the unusual properties including long carrier lifetimes and consequent long carrier diffusion lengths in these materials. Ion drift, ferroelectricity, and charge traps have been proposed to account for the efficient charge separation and photocurrent hysteresis. However, it remains unclear which mechanism is dominating. We fabricate field effect transistors (FETs) incorporating single nanoplates/nanowires of organic perovskite and perform scanning photocurrent microscopic (SPCM) measurements to extract carrier diffusion lengths as a function of gate voltage, source-drain bias. Spatially resolved optoelectronic investigations of single crystalline perovskite nanostructures provide valuable information and key evidence on distinguishing the dominating charge transport/separation mechanism.

  12. Specific features of nonvalent interactions in orthorhombic perovskites

    Serezhkin, V. N.; Pushkin, D. V.; Serezhkina, L. B.

    2014-07-01

    It is established that isostructural orthorhombic perovskites ABO3 (sp. gr. Pnma in different systems, no. 62, Z = 4), depending on the specificity of nonvalent interactions (which determine the combinatorial-topological type of the Voronoi-Dirichlet polyhedra (VDPs) of four basis atoms), are divided into ten different stereotypes. It is shown by the example of 259 perovskites belonging to the DyCrO3 stereotype that VDP characteristics can be used to quantitatively estimate the distortion of BO6 octahedra, including that caused by the Jahn-Teller effect. It is found that one of the causes of the distortion of the coordination polyhedra of atoms in the structure of orthorhombic perovskites is heteroatomic metal-metal interactions, for which the interatomic distances are much shorter than the sum of the Slater radii of A and B atoms.

  13. High-performance photovoltaic perovskite layers fabricated through intramolecular exchange

    Yang, Woon Seok; Noh, Jun Hong; Jeon, Nam Joong; Kim, Young Chan; Ryu, Seungchan; Seo, Jangwon; Seok, Sang Il

    2015-06-01

    The band gap of formamidinium lead iodide (FAPbI3) perovskites allows broader absorption of the solar spectrum relative to conventional methylammonium lead iodide (MAPbI3). Because the optoelectronic properties of perovskite films are closely related to film quality, deposition of dense and uniform films is crucial for fabricating high-performance perovskite solar cells (PSCs). We report an approach for depositing high-quality FAPbI3 films, involving FAPbI3 crystallization by the direct intramolecular exchange of dimethylsulfoxide (DMSO) molecules intercalated in PbI2 with formamidinium iodide. This process produces FAPbI3 films with (111)-preferred crystallographic orientation, large-grained dense microstructures, and flat surfaces without residual PbI2. Using films prepared by this technique, we fabricated FAPbI3-based PSCs with maximum power conversion efficiency greater than 20%.

  14. Exciton localization in solution-processed organolead trihalide perovskites

    He, Haiping; Yu, Qianqian; Li, Hui; Li, Jing; Si, Junjie; Jin, Yizheng; Wang, Nana; Wang, Jianpu; He, Jingwen; Wang, Xinke; Zhang, Yan; Ye, Zhizhen

    2016-01-01

    Organolead trihalide perovskites have attracted great attention due to the stunning advances in both photovoltaic and light-emitting devices. However, the photophysical properties, especially the recombination dynamics of photogenerated carriers, of this class of materials are controversial. Here we report that under an excitation level close to the working regime of solar cells, the recombination of photogenerated carriers in solution-processed methylammonium–lead–halide films is dominated by excitons weakly localized in band tail states. This scenario is evidenced by experiments of spectral-dependent luminescence decay, excitation density-dependent luminescence and frequency-dependent terahertz photoconductivity. The exciton localization effect is found to be general for several solution-processed hybrid perovskite films prepared by different methods. Our results provide insights into the charge transport and recombination mechanism in perovskite films and help to unravel their potential for high-performance optoelectronic devices. PMID:26996605

  15. Multifunctional Fullerene Derivative for Interface Engineering in Perovskite Solar Cells.

    Li, Yaowen; Zhao, Yue; Chen, Qi; Yang, Yang Michael; Liu, Yongsheng; Hong, Ziruo; Liu, Zonghao; Hsieh, Yao-Tsung; Meng, Lei; Li, Yongfang; Yang, Yang

    2015-12-16

    In perovskite based planar heterojunction solar cells, the interface between the TiO2 compact layer and the perovskite film is critical for high photovoltaic performance. The deep trap states on the TiO2 surface induce several challenging issues, such as charge recombination loss and poor stability etc. To solve the problems, we synthesized a triblock fullerene derivative (PCBB-2CN-2C8) via rational molecular design for interface engineering in the perovskite solar cells. Modifying the TiO2 surface with the compound significantly improves charge extraction from the perovskite layer. Together with its uplifted surface work function, open circuit voltage and fill factor are dramatically increased from 0.99 to 1.06 V, and from 72.2% to 79.1%, respectively, resulting in 20.7% improvement in power conversion efficiency for the best performing devices. Scrutinizing the electrical properties of this modified interfacial layer strongly suggests that PCBB-2CN-2C8 passivates the TiO2 surface and thus reduces charge recombination loss caused by the deep trap states of TiO2. The passivation effect is further proven by stability testing of the perovskite solar cells with shelf lifetime under ambient conditions improved by a factor of more than 4, from ∼40 h to ∼200 h, using PCBB-2CN-2C8 as the TiO2 modification layer. This work offers not only a promising material for cathode interface engineering, but also provides a viable approach to address the challenges of deep trap states on TiO2 surface in planar perovskite solar cells. PMID:26592525

  16. Tracking the formation of methylammonium lead triiodide perovskite

    Liu, Lijia, E-mail: ljliu@suda.edu.cn, E-mail: jmcleod@suda.edu.cn; McLeod, John A., E-mail: ljliu@suda.edu.cn, E-mail: jmcleod@suda.edu.cn; Wang, Rongbin; Shen, Pengfei; Duhm, Steffen [Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, 199 Ren' ai Road, Suzhou, Jiangsu 215123 (China)

    2015-08-10

    The formation mechanism of perovskite methylammonium lead triiodide (CH{sub 3}NH{sub 3}PbI{sub 3}) was studied with in situ X-ray photoelectron spectroscopy (XPS) on successive depositions of thermally evaporated methylammonium iodide (CH{sub 3}NH{sub 3}I) on a lead iodide (PbI{sub 2}) film. This deposition method mimics the “two-step” synthesis method commonly used in device fabrication. We find that several competing processes occur during the formation of perovskite CH{sub 3}NH{sub 3}PbI{sub 3}. Our most important finding is that during vapour deposition of CH{sub 3}NH{sub 3}I onto PbI{sub 2}, at least two carbon species are present in the resulting material, while only one nitrogen species is present. This suggests that CH{sub 3}NH{sub 3}I can dissociate during the transition to a perovskite phase, and some of the resulting molecules can be incorporated into the perovskite. The effect of partial CH{sub 3}NH{sub 3} substitution with CH{sub 3} was evaluated, and electronic structure calculations show that CH{sub 3} defects would impact the photovoltaic performance in perovskite solar cells. The possibility that not all A sites in the APbI{sub 3} perovskite are occupied by CH{sub 3}NH{sub 3} is therefore an important consideration when evaluating the performance of organometallic trihalide solar cells synthesized using typical approaches.

  17. Alpha-decay damage of Cm-doped perovskite

    Curium-doped perovskite slurry, which had the nominal composition of Ca0.98919(CM,Pu)0.01081Al0.01081Ti0.98919O3, was calcined at 750 C for 2 h and then hot-pressed at 1,250 C and 29MPa for 2 h. The hot-pressed cylinder samples had the specific 244Cm activity of 22.3 GBq/g on 31 March 1993. Their average density was 4.083 g/cm3 after the samples got a cumulative dose of 0.7 x 1017 α decays/g. The rate of density change was slightly larger in the present perovskite material than in Cm-doped Synroc reported previously. Half-disk perovskite specimens, which had accumulated doses of 1.6 x 1017 and 4.0 x 1017 α decays/g, were MCC-1 leach tested in pH ∼2 solution at 90 C and 2.3 g/m2/day, respectively. These high leach rates caused a significant increase in pH in the later stage of the leaching runs. As-leached surfaces of Cm-doped perovskite showed the formation of anatase (TiO2). For the first 28 days, the Ca and Cm leach rates at the two different doses increased with leach time. More damaged specimens tended to give higher leach rates. In the final 28-day leaching run, both leach rates at the two different doses converged on each lower value although the Cm leach rate was lower than the Ca leach rate by a factor of >20. Nonradioactive perovskite material showed similar changes in Ca leach rate and pH to the Cm-doped one although the as-leached surfaces of the former material showed much higher degree of alteration of perovskite to anatase

  18. Removing Oscillatoria and Humic Acid from Mixed Water by Potassium Ferrate(Ⅵ) Pre-oxidation and Co-coagulation%K2FeO4预氧化复合絮凝处理颤藻和腐殖酸混合水

    赵春禄; 刘琰

    2011-01-01

    采用K2FeO4预氧化复合高岭土和聚合氯化铝(PAC)混凝处理了含颤藻和腐殖酸的混合水,并探讨了对处理后水中残留铝含量及其形态分布的影响.结果表明:投加4.0 mg·L-1K2FeO4预氧化就能使混合水样的浊度、腐殖酸和藻类的去除率分别达到94.05%、91.67%和90.78%,明显优于相同条件下单纯的PAC处理效果;水样的pH值对K2FeO4预氧化有显著的影响,在pH=6.5时效果最好;K2FeO4预氧化影响处理后水中残留铝的含量和形态,在最佳条件下总铝浓度降低了51.8%,特别是对人体毒害作用最大的溶解态铝降低了43.9%.%The mixed water containing Oscillatoria and humic acid was disposed by using potassium ferrate(Ⅵ) as the pre-oxidation agent, poly-aluminum chloride(PAC) and Kaolin as the co-coagulation agents. The residual aluminum morphology was also studied.The consequence was that the ferrate concentration with 4.0 mg· L-1 could improve the removal rate of turbidity, HA and algae, whose value was 94.05%, 91.67% and 90. 78% respectively, and the effect was much better than PAC singly. The pH value affected the efficiency of ferrate pre-oxidation processing mixed water. In acidic condition (pH = 6. 5) the effect was best. Potassium ferrate(Ⅵ) pre-oxidation affected the content and form of residual aluminum. Under the best condition the total aluminum concentration reduced by 51.8%, and especially the dissolved aluminum which poisoned human body decreased by 43.9%.

  19. Studies of Fe-Co based perovskite cathodes with different A-site cations

    Kammer Hansen, K.

    Iron-cobalt based perovskite cathodes with different A-site cations ((Ln(0.6)Sr(0.4))(0.99)Fe0.8Co0.2O3-delta, where Ln is La, Pr, Sm or Gd) have been synthesised, characterised by a powder XRD, dilatometry, 4-point DC conductivity measurements, and electrochemical impedance spectroscopy (EIS) on...... cone shaped electrodes. In addition to this scanning electron microscopy (SEM) was used to characterise the bars. XRD revealed that only the La-containing perovskite was hexagonal. The Pr and Sm perovskites were orthorhombic. The gadolinium-based perovskite was a two phase system consisting of an...... orthorhombic and a cubic perovskite phase. The thermal expansion coefficient (TEC) increased systematically with a decrease in the size of the A-site cation until the gadoliniurn-containing perovskite where the TEC decreases abruptly. The total electric conductivity was the highest for the La-based perovskite...

  20. NaIrO3 - A pentavalent post-perovskite

    Bremholm, M.; Dutton, S. E.; Stephens, P.W.; Cava, R. J.

    2010-01-01

    Sodium iridium(V) oxide, NaIrO3, was synthesized by a high pressure solid state method and recovered to ambient conditions. It is found to be isostructural with CaIrO3, the much-studied structural analogue of the high-pressure post-perovskite phase of MgSiO3. Among the oxide post-perovskites, NaIrO3 is the first example with a pentavalent cation. The structure consists of layers of corner- and edge-sharing IrO6 octahedra separated by layers of NaO8 bicapped trigonal prisms. NaIrO3 shows no ma...

  1. Ultrafast time-resolved spectroscopy of lead halide perovskite films

    Idowu, Mopelola A.; Yau, Sung H.; Varnavski, Oleg; Goodson, Theodore

    2015-09-01

    Recently, lead halide perovskites which are organic-inorganic hybrid structures, have been discovered to be highly efficient as light absorbers. Herein, we show the investigation of the excited state dynamics and emission properties of non-stoichiometric precursor formed lead halide perovskites grown by interdiffusion method using steady-state and time-resolved spectroscopic measurements. The influence of the different ratios of the non-stoichiometric precursor solution was examined. The observed photoluminescence properties were correlated with the femtosecond transient absorption measurements.

  2. Spin State Control of the Perovskite Rh/Co Oxides

    Wataru Kobayashi; Shin Yoshida; Soichiro Shibasaki; Ichiro Terasaki

    2010-01-01

    We show why and how the spin state of transition-metal ions affects the thermoelectric properties of transition-metal oxides by investigating two perovskite-related oxides. In the A-site ordered cobalt oxide Sr3YCo4O10.5, partial substitution of Ca for Sr acts as chemical pressure, which compresses the unit cell volume to drive the spin state crossover, and concomitantly changes the magnetization and thermopower. In the perovskite rhodium oxide LaRhO3, partial substitution of Sr for La acts a...

  3. Hydrothermal synthesis of perovskite and pyrochlore powders of potassium tantalate

    Goh, Gregory K. L.; Haile, Sossina M.; Levi, Carlos G.; Lange, Fred F.

    2002-01-01

    Potassium tantalate powders were hydrothermally synthesized at 100 to 200 °C in 4 to 15 M aqueous KOH solutions. A defect pyrochlore, Kta_(2)O_(5)(OH). nH2O (n ≈ 1.4), was obtained at 4 M KOH, but at 7–12 M KOH, this pyrochlore was gradually replaced by a defect perovskite as the stable phase. At 15 M KOH, there was no intermediate pyrochlore, only a defect perovskite, K_(0.85)Ta_(0.92)O_(2.43)(OH)_(0.57) 0.15H_(2)O. Synthesis at higher KOH concentrations led to greater incorporation of prot...

  4. Plasmonic-enhanced perovskite-graphene hybrid photodetectors

    Sun, Zhenhua; Aigouy, Lionel; Chen, Zhuoying

    2016-03-01

    The surface plasmonic effect of metal nanostructures is a promising method to boost the performance of optoelectronic devices such as solar cells and photodetectors. In this report, gold nanoparticles with surface plasmon resonance localized at about 530 nm were synthesized and integrated into graphene/methylammonium lead iodide perovskite (CH3NH3PbI3) hybrid photodetectors. Compared with pristine graphene-CH3NH3PbI3 devices, a device with gold nanoparticles embedded has a doubly higher photo-responsivity as well as a faster photoresponse speed. The present devices adopt a unique configuration with gold nanoparticles physically separated from the light harvesting component, i.e., the perovskite layer by graphene. Advantages are revealed through a series of characterization techniques and analyses. First, thanks to the tiny thickness of graphene, the plasmonic effect of gold nanoparticles can effectively enhance the near-field of perovskite and thus facilitate light-harvesting. Second, the enhanced light-harvesting in perovskite happens very close to this interface where photo-induced carriers have relatively short paths to diffuse toward graphene, favoring a fast photo-response. This work demonstrates a feasible and inspiring strategy to improve the performance of photodetectors through the surface plasmonic effect of metallic nanostructures.The surface plasmonic effect of metal nanostructures is a promising method to boost the performance of optoelectronic devices such as solar cells and photodetectors. In this report, gold nanoparticles with surface plasmon resonance localized at about 530 nm were synthesized and integrated into graphene/methylammonium lead iodide perovskite (CH3NH3PbI3) hybrid photodetectors. Compared with pristine graphene-CH3NH3PbI3 devices, a device with gold nanoparticles embedded has a doubly higher photo-responsivity as well as a faster photoresponse speed. The present devices adopt a unique configuration with gold nanoparticles physically

  5. Elasticity of AlFeO(3) and FeAlO(3) perovskite and post-perovskite from first-principles calculations

    Caracas, Razvan

    2010-01-01

    We use state-of-the-art ab initio calculations based on the generalized gradient approximation of the density functional theory in the planar augmented wavefunction formalism to determine the elastic constants tensor of perovskite and post-perovskite with formulas AlFeO(3) and FeAlO(3) in which Fe or Al respectively occupy only octahedral sites, for the stable magnetic configurations. The phase transition between perovskite and post-perovskite is associated with a site exchange, during which ...

  6. Comprehensive design of omnidirectional high-performance perovskite solar cells

    Zhang, Yutao; Xuan, Yimin

    2016-01-01

    The comprehensive design approach is established with coupled optical-electrical simulation for perovskite-based solar cell, which emerged as one of the most promising competitors to silicon solar cell for its low-cost fabrication and high PCE. The selection of structured surface, effect of geometry parameters, incident angle-dependence and polarization-sensitivity are considered in the simulation. The optical modeling is performed via the finite-difference time-domain method whilst the electrical properties are obtained by solving the coupled nonlinear equations of Poisson, continuity, and drift-diffusion equations. The optical and electrical performances of five different structured surfaces are compared to select a best structured surface for perovskite solar cell. The effects of the geometry parameters on the optical and electrical properties of the perovskite cell are analyzed. The results indicate that the light harvesting is obviously enhanced by the structured surface. The electrical performance can be remarkably improved due to the enhanced light harvesting of the designed best structured surface. The angle-dependence for s- and p-polarizations is investigated. The structured surface exhibits omnidirectional behavior and favorable polarization-insensitive feature within a wide incident angle range. Such a comprehensive design approach can highlight the potential of perovskite cell for power conversion in the full daylight. PMID:27405419

  7. Structural Polymorphism in Al-bearing Magnesiumsilicate Post-perovskite

    Tschauner, O.; Kiefer, B.; Liu, H.; Somayazulu, M.; Luo, S. N.

    2006-12-01

    We show formation of a post-perovskite phase of Al-bearing magnesiummetasilicate which does not assume the CaIrO3 structure [1]. X-ray diffraction data and first principle calculations indicate that the present material assumes a structure composed of kinked SiO2- and MgO layers similar but not identical to topologies of novel post-perovskite phases recently proposed [2]. Minor element chemistry and actual stress regime are plausible reasons of the differences between the present and the previously reported post- perovskite phase. The presence of minor elements could stabilize this "kinked" post-perovskite structure and hence effect elasticity and the interpretations of seismic observations in cold areas of D". Acknowledgements: Supported through the NNSA Cooperative Agreement DE-FC88-01NV14049. Use of the HPCAT facility was supported by DOE-BES, DOE-NNSA, NSF, DOD -TACOM, and the W.M. Keck Foundation. APS is supported by DOE-BES under Contract No. W-31-109-Eng-38. [1] O. Tschauner, B. Kiefer, H.Z. Liu, M. Somayazulu, S.N. Luo, submitted [2] A.R.Oganov, R. Martonak, A. Laio, P. Raiteri, M. Parinello Nature 438, 1142-1144 (2005)

  8. Materials Processing Routes to Trap-Free Halide Perovskites

    Buin, Andrei

    2014-11-12

    © 2014 American Chemical Society. Photovoltaic devices based on lead iodide perovskite films have seen rapid advancements, recently achieving an impressive 17.9% certified solar power conversion efficiency. Reports have consistently emphasized that the specific choice of growth conditions and chemical precursors is central to achieving superior performance from these materials; yet the roles and mechanisms underlying the selection of materials processing route is poorly understood. Here we show that films grown under iodine-rich conditions are prone to a high density of deep electronic traps (recombination centers), while the use of a chloride precursor avoids the formation of key defects (Pb atom substituted by I) responsible for short diffusion lengths and poor photovoltaic performance. Furthermore, the lowest-energy surfaces of perovskite crystals are found to be entirely trap-free, preserving both electron and hole delocalization to a remarkable degree, helping to account for explaining the success of polycrystalline perovskite films. We construct perovskite films from I-poor conditions using a lead acetate precursor, and our measurement of a long (600 ± 40 nm) diffusion length confirms this new picture of the importance of growth conditions.

  9. Lithium intercalation in perovskite and hexagonal tungsten bronze derivatives

    Lithium has been intercalated chemically and electrochemically in LnNb3O9 (Ln = La,Nd) perovskite-type phases and LiW3O9F which can be considered as a hexagonal tungsten bronze derivative. The crystallographic formula of the LnNb3O9 starting material is described

  10. Comprehensive design of omnidirectional high-performance perovskite solar cells

    Zhang, Yutao; Xuan, Yimin

    2016-07-01

    The comprehensive design approach is established with coupled optical-electrical simulation for perovskite-based solar cell, which emerged as one of the most promising competitors to silicon solar cell for its low-cost fabrication and high PCE. The selection of structured surface, effect of geometry parameters, incident angle-dependence and polarization-sensitivity are considered in the simulation. The optical modeling is performed via the finite-difference time-domain method whilst the electrical properties are obtained by solving the coupled nonlinear equations of Poisson, continuity, and drift-diffusion equations. The optical and electrical performances of five different structured surfaces are compared to select a best structured surface for perovskite solar cell. The effects of the geometry parameters on the optical and electrical properties of the perovskite cell are analyzed. The results indicate that the light harvesting is obviously enhanced by the structured surface. The electrical performance can be remarkably improved due to the enhanced light harvesting of the designed best structured surface. The angle-dependence for s- and p-polarizations is investigated. The structured surface exhibits omnidirectional behavior and favorable polarization-insensitive feature within a wide incident angle range. Such a comprehensive design approach can highlight the potential of perovskite cell for power conversion in the full daylight.

  11. Oxide perovskite crystals for HTSC film substrates microwave applications

    Bhalla, A. S.; Guo, Ruyan

    1995-01-01

    The research focused upon generating new substrate materials for the deposition of superconducting yttrium barium cuprate (YBCO) has yielded several new hosts in complex perovskites, modified perovskites, and other structure families. New substrate candidates such as Sr(Al(1/2)Ta(1/2))O3 and Sr(Al(1/2)Nb(1/2))O3, Ba(Mg(1/3)Ta(2/3))O3 in complex oxide perovskite structure family and their solid solutions with ternary perovskite LaAlO3 and NdGaO3 are reported. Conventional ceramic processing techniques were used to fabricate dense ceramic samples. A laser heated molten zone growth system was utilized for the test-growth of these candidate materials in single crystal fiber form to determine crystallographic structure, melting point, thermal, and dielectric properties as well as to make positive identification of twin free systems. Some of those candidate materials present an excellent combination of properties suitable for microwave HTSC substrate applications.

  12. Hysteresis, Stability, and Ion Migration in Lead Halide Perovskite Photovoltaics.

    Miyano, Kenjiro; Yanagida, Masatoshi; Tripathi, Neeti; Shirai, Yasuhiro

    2016-06-16

    Ion migration has been suspected as the origin of various irreproducible and unstable properties, most notably the hysteresis, of lead halide perovskite photovoltaic (PV) cells since the early stage of the research. Although many evidence of ionic movement have been presented both numerically and experimentally, a coherent and quantitative picture that accounts for the observed irreproducible phenomena is still lacking. At the same time, however, it has been noticed that in certain types of PV cells, the hysteresis is absent or at least within the measurement reproducibility. We have previously shown that the electronic properties of hysteresis-free cells are well represented in terms of the conventional inorganic semiconductors. The reproducibility of these measurements was confirmed typically within tens of minutes under the biasing field of -1 V to +1.5 V. In order to probe the effect of ionic motion in the hysteresis-free cells, we extended the time scale and the biasing rage in the electronic measurements, from which we conclude the following: (1) From various evidence, it appears that ion migration is inevitable. However, it does not cause detrimental effects to the PV operation. (2) We propose, based on the quantitative characterization, that the degradation is more likely due to the chemical change at the interfaces between the carrier selective layers and perovskite rather than the compositional change of the lead iodide perovskite bulk. Together, they give much hope in the use of the lead iodide perovskite in the use of actual application. PMID:27227427

  13. Comprehensive design of omnidirectional high-performance perovskite solar cells.

    Zhang, Yutao; Xuan, Yimin

    2016-01-01

    The comprehensive design approach is established with coupled optical-electrical simulation for perovskite-based solar cell, which emerged as one of the most promising competitors to silicon solar cell for its low-cost fabrication and high PCE. The selection of structured surface, effect of geometry parameters, incident angle-dependence and polarization-sensitivity are considered in the simulation. The optical modeling is performed via the finite-difference time-domain method whilst the electrical properties are obtained by solving the coupled nonlinear equations of Poisson, continuity, and drift-diffusion equations. The optical and electrical performances of five different structured surfaces are compared to select a best structured surface for perovskite solar cell. The effects of the geometry parameters on the optical and electrical properties of the perovskite cell are analyzed. The results indicate that the light harvesting is obviously enhanced by the structured surface. The electrical performance can be remarkably improved due to the enhanced light harvesting of the designed best structured surface. The angle-dependence for s- and p-polarizations is investigated. The structured surface exhibits omnidirectional behavior and favorable polarization-insensitive feature within a wide incident angle range. Such a comprehensive design approach can highlight the potential of perovskite cell for power conversion in the full daylight. PMID:27405419

  14. Degradation mechanism for planar heterojunction perovskite solar cells

    Yamamoto, Kouhei; Furumoto, Yoshikazu; Shahiduzzaman, M.; Kuwabara, Takayuki; Takahashi, Kohshin; Taima, Tetsuya

    2016-04-01

    Organic-inorganic hybrid perovskite materials have recently emerged as a promising cost- and energy-efficient light absorber material for photovoltaic applications. Unfortunately, perovskite solar cells have a problem with decreasing power conversion efficiency owing to their degradation in air. To clarify the cause of the degradation of perovskite solar cells, we exposed deposited CH3NH3PbI3 and HC(NH2)2PbI3 films to an O2 or (H2O+N2) atmosphere condition. Analysis of these films revealed that a large energy band gap was observed as a result of the influence of the H2O molecule in CH3NH3PbI3 and HC(NH2)2PbI3. Under the (H2O+N2) atmosphere condition, the existence of CH3NH3I and HC(NH2)2I molecules was found to affect the morphology and as well as the crystalline diffraction peak. The resultant perovskite crystalline structure was degraded by H2O molecules under the air exposure condition.

  15. Two-Dimensional Halide Perovskites: Tuning Electronic Activities of Defects.

    Liu, Yuanyue; Xiao, Hai; Goddard, William A

    2016-05-11

    Two-dimensional (2D) halide perovskites are emerging as promising candidates for nanoelectronics and optoelectronics. To realize their full potential, it is important to understand the role of those defects that can strongly impact material properties. In contrast to other popular 2D semiconductors (e.g., transition metal dichalcogenides MX2) for which defects typically induce harmful traps, we show that the electronic activities of defects in 2D perovskites are significantly tunable. For example, even with a fixed lattice orientation one can change the synthesis conditions to convert a line defect (edge or grain boundary) from electron acceptor to inactive site without deep gap states. We show that this difference originates from the enhanced ionic bonding in these perovskites compared with MX2. The donors tend to have high formation energies and the harmful defects are difficult to form at a low halide chemical potential. Thus, we unveil unique properties of defects in 2D perovskites and suggest practical routes to improve them. PMID:27100910

  16. Size of oxide vacancies in fluorite and perovskite structured oxides

    Chatzichristodoulou, Christodoulos; Norby, Poul; Hendriksen, Peter Vang;

    2015-01-01

    An analysis of the effective radii of vacancies and the stoichiometric expansion coefficient is performed on metal oxides with fluorite and perovskite structures. Using the hard sphere model with Shannon ion radii we find that the effective radius of the oxide vacancy in fluorites increases with...

  17. Preparation of manganese perovskite magnetic nanoparticles and their mechanical treatment

    Dědourková, T.; Veverka, Miroslav; Veverka, Pavel; Zelenka, J.; Svoboda, L.

    Dresden: Technische Universität, 2014. s. 69-69. [International Conference on the Scientific and Clinical Applications of Magnetic Carriers /10./. 10.06.2014-14.06.2014, Dresden] R&D Projects: GA MPO FR-TI3/521 Institutional support: RVO:68378271 Keywords : manganese perovskite * magnetic nanoparticles * mechanical treatment Subject RIV: BM - Solid Matter Physics ; Magnetism

  18. Krypton irradiation damage in Nd-doped zirconolite and perovskite

    Davoisne, C.; Stennett, M. C.; Hyatt, N. C.; Peng, N.; Jeynes, C.; Lee, W. E.

    2011-08-01

    Understanding the effect of radiation damage and noble gas accommodation in potential ceramic hosts for plutonium disposition is necessary to evaluate their long-term behaviour during geological disposal. Polycrystalline samples of Nd-doped zirconolite and Nd-doped perovskite were irradiated ex situ with 2 MeV Kr + at a dose of 5 × 10 15 ions cm -2 to simulate recoil of Pu nuclei during alpha decay. The feasibility of thin section preparation of both pristine and irradiated samples by Focused Ion Beam sectioning was demonstrated. After irradiation, the Nd-doped zirconolite revealed a well defined amorphous region separated from the pristine material by a thin (40-60 nm) damaged interface. The zirconolite lattice was lost in the damaged interface, but the fluorite sublattice was retained. The Nd-doped perovskite contained a defined irradiated layer composed of an amorphous region surrounded by damaged but still crystalline layers. The structural evolution of the damaged regions is consistent with a change from orthorhombic to cubic symmetry. In addition in Nd-doped perovskite, the amorphisation dose depended on crystallographic orientation and possibly sample configuration (thin section or bulk). Electron Energy Loss Spectroscopy revealed Ti remained in the 4+ oxidation state but there was a change in Ti coordination in both Nd-doped perovskite and Nd-doped zirconolite associated with the crystalline to amorphous transition.

  19. On the possibility of excitonic magnetism in Ir double perovskites

    Pajskr, K.; Novák, Pavel; Pokorný, Vladislav; Kolorenč, Jindřich; Arita, R.; Kuneš, Jan

    2016-01-01

    Roč. 93, č. 3 (2016), "035129-1"-"035129-6". ISSN 1098-0121 R&D Projects: GA ČR GA13-25251S Institutional support: RVO:68378271 Keywords : spin-orbit coupling * double perovskite * excitonic magnetism Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  20. Emission Enhancement and Intermittency in Polycrystalline Organolead Halide Perovskite Films

    Cheng Li

    2016-08-01

    Full Text Available Inorganic-organic halide organometal perovskites have demonstrated very promising performance for opto-electronic applications, such as solar cells, light-emitting diodes, lasers, single-photon sources, etc. However, the little knowledge on the underlying photophysics, especially on a microscopic scale, hampers the further improvement of devices based on this material. In this communication, correlated conventional photoluminescence (PL characterization and wide-field PL imaging as a function of time are employed to investigate the spatially- and temporally-resolved PL in CH3NH3PbI3−xClx perovskite films. Along with a continuous increase of the PL intensity during light soaking, we also observe PL blinking or PL intermittency behavior in individual grains of these films. Combined with significant suppression of PL blinking in perovskite films coated with a phenyl-C61-butyric acid methyl ester (PCBM layer, it suggests that this PL intermittency is attributed to Auger recombination induced by photoionized defects/traps or mobile ions within grains. These defects/traps are detrimental for light conversion and can be effectively passivated by the PCBM layer. This finding paves the way to provide a guideline on the further improvement of perovskite opto-electronic devices.

  1. Controlling Octahedral Rotations in a Perovskite via Strain Doping.

    Herklotz, A; Wong, A T; Meyer, T; Biegalski, M D; Lee, H N; Ward, T Z

    2016-01-01

    The perovskite unit cell is the fundamental building block of many functional materials. The manipulation of this crystal structure is known to be of central importance to controlling many technologically promising phenomena related to superconductivity, multiferroicity, mangetoresistivity, and photovoltaics. The broad range of properties that this structure can exhibit is in part due to the centrally coordinated octahedra bond flexibility, which allows for a multitude of distortions from the ideal highly symmetric structure. However, continuous and fine manipulation of these distortions has never been possible. Here, we show that controlled insertion of He atoms into an epitaxial perovskite film can be used to finely tune the lattice symmetry by modifying the local distortions, i.e., octahedral bonding angle and length. Orthorhombic SrRuO3 films coherently grown on SrTiO3 substrates are used as a model system. Implanted He atoms are confirmed to induce out-of-plane strain, which provides the ability to controllably shift the bulk-like orthorhombically distorted phase to a tetragonal structure by shifting the oxygen octahedra rotation pattern. These results demonstrate that He implantation offers an entirely new pathway to strain engineering of perovskite-based complex oxide thin films, useful for creating new functionalities or properties in perovskite materials. PMID:27215804

  2. d.sup.0./sup. ferromagnetic interface between nonmagnetic perovskites

    Oja, R.; Tyunina, Marina; Yao, L.; Pinomaa, T.; Kocourek, Tomáš; Dejneka, Alexandr; Stupakov, Oleksandr; Jelínek, Miroslav; Trepakov, Vladimír; van Dijken, S.; Nieminen, R.M.

    2012-01-01

    Roč. 109, č. 12 (2012), "127207-1"-"127207-5". ISSN 0031-9007 Institutional research plan: CEZ:AV0Z10100522 Keywords : d 0 ferromagnetic interface * perovskite films Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.943, year: 2012

  3. A Monolithic Perovskite Structure for Use as a Magnetic Regenerator

    Pryds, Nini; Clemens, Frank; Menon, Mohan; Nielsen, Pernille Hedemark; Brodersen, Karen; Bjørk, Rasmus; Bahl, Christian Robert Haffenden; Engelbrecht, Kurt; Nielsen, Kaspar Kirstein; Smith, Anders

    2011-01-01

    A La0.67Ca0.26Sr0.07Mn1.05O3 (LCSM) perovskite was prepared for the first time as a ceramic monolithic regenerator used in a regenerative magnetic refrigeration device. The parameters influencing the extrusion process and the performance of the regenerator, such as the nature of the monolith paste...

  4. Magnetism of perovskite cobaltites with Kramers rare-earth ions

    Jirák, Zdeněk; Hejtmánek, Jiří; Knížek, Karel; Novák, Pavel; Šantavá, Eva; Fujishiro, H.

    2014-01-01

    Roč. 115, č. 17 (2014), "17E118-1"-"17E118-3". ISSN 0021-8979 R&D Projects: GA ČR(CZ) GAP204/11/0713 Institutional support: RVO:68378271 Keywords : perovskite cobaltites * RE * AFM * Schottky anomaly * Zeeman splitting Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.183, year: 2014

  5. Enhancement of Exciton Emission in Lead Halide-Based Layered Perovskites by Cation Mixing.

    Era, Masanao; Komatsu, Yumeko; Sakamoto, Naotaka

    2016-04-01

    Spin-coated films of a lead halide, PbX: X = I and Br, layered perovskites having cyclohexenylethyl ammonium molecule as an organic layer, which were mixed with other metal halide-based layered perovskites consisting of various divalent metal halides (for example, Ca2, Cdl2, FeI2, SnBr2 and so on), were prepared. The results of X-ray diffraction measurements exhibited that solid solution formation between PbX-based layered perovskite and other divalent metal halide-based layered perovskites was observed up to very high molar concentration of 50 molar% in the mixed film samples when divalent cations having ionic radius close to that of Pb2+ were employed. In the solid solution films, the exciton emission was much enhanced at room temperature. Exciton emission intensity of Pbl-based layered perovskite mixed with Cal-based layered perovskite (20 molar%) is about 5 times large that of the pristine Pbl-based layered perovskite, and that of PbBr-based layered perovskite mixed with SnBr-based layered perovskite (20 molar%) was also about 5 times large that of the pristine PbBr-based layered perovskite at room temperature. PMID:27451628

  6. The Post-Perovskite Transition in NaMgF3 Measured Under an Ar Medium

    Hustoft, J. W.; Catalli, K.; Shim, S.; Kubo, A.; Prakapenka, V. B.; Caldwell, W. A.; Kunz, M.

    2007-12-01

    Neighborite, NaMgF3, is isostructural to MgSiO3 perovskite and has been shown to transform to the CaIrO3 type (post-perovskite) at much lower pressure and room temperature. We have conducted X-ray diffraction of the post-perovskite transition in NaMgF3 using argon as a pressure medium at the GSECARS sector of APS and beamline 12.2.2 of ALS. We observe the first appearance of post-perovskite occurring between 37 and 42 GPa during compression at room temperature and a mixed phase of perovskite and post-perovskite was observed up to 49 GPa at room temperature, whereas a complete transition to post-perovskite was documented by previous studies at 19-30 GPa and room temperature with a Si-oil, NaCl, or MgO pressure medium. This difference in pressure may indicate that deviatoric stresses are an important factor in explaining the different observations. In situ double-sided laser heating at GSECARS demonstrated that perovskite transforms completely to pure post-perovskite at ~2000 K and ~47 GPa. We did not observe a new high-temperature phase, N-phase, proposed by Martin (2005) at 37 GPa after heating to 2000 K. We also found that the volume decreases by 2±1% across the post-perovskite transition in NaMgF3.

  7. Interfacial Degradation of Planar Lead Halide Perovskite Solar Cells.

    Guerrero, Antonio; You, Jingbi; Aranda, Clara; Kang, Yong Soo; Garcia-Belmonte, Germà; Zhou, Huanping; Bisquert, Juan; Yang, Yang

    2016-01-26

    The stability of perovskite solar cells is one of the major challenges for this technology to reach commercialization, with water believed to be the major degradation source. In this work, a range of devices containing different cathode metal contacts in the configuration ITO/PEDOT:PSS/MAPbI3/PCBM/Metal are fully electrically characterized before and after degradation caused by steady illumination during 4 h that induces a dramatic reduction in power conversion efficiency from values of 12 to 1.8%. We show that a decrease in performance and generation of the S-shape is associated with chemical degradation of the metal contact. Alternatively, use of Cr2O3/Cr as the contact enhances the stability, but modification of the energetic profile during steady illumination takes place, significantly reducing the performance. Several techniques including capacitance-voltage, X-ray diffraction, and optical absorption results suggest that the properties of the bulk perovskite layer are little affected in the device degradation process. Capacitance-voltage and impedance spectroscopy results show that the electrical properties of the cathode contact are being modified by generation of a dipole at the cathode that causes a large shift of the flat-band potential that modifies the interfacial energy barrier and impedes efficient extraction of electrons. Ionic movement in the perovskite layer changes the energy profile close to the contacts, modifying the energy level stabilization at the cathode. These results provide insights into the degradation mechanisms of perovskite solar cells and highlight the importance to further study the use of protecting layers to avoid the chemical reactivity of the perovskite with the external contacts. PMID:26679510

  8. Temperature-independent sensors based on perovskite-type oxides

    The need of energy security and environment sustainability drives toward the development of energy technology in order to enhance the performance of internal combustion engines. Gas sensors play a key role for controlling the fuel oxygen ratio and monitoring the pollution emissions. The perovskite-type oxides can be synthesized for an extremely wide variety of combinations of chemical elements, allowing to design materials with suitable properties for sensing application. Lanthanum strontium ferrites, such as La0.7Sr0.3FeO3, are suitable oxygen sensing materials with temperature-independence conductivity, but they have low chemical stability under reducing conditions. The addition of aluminum into the perovskite structure improves the material properties in order to develop suitable oxygen sensing probes for lean burn engine control systems. Perovskite-type oxides with formula (La0.7Sr0.3)(AlxFe1−x)O3 was synthesized by the citrate-nitrate combustion synthesis method. XRD analyses, show that it was synthesized a phase-pure powder belonging to the perovskite structure. Aluminum affects both the unit cell parameters, by shrinking the unit cell, and the powder morphology, by promoting the synthesis of particles with small crystallite size and large specific surface area. The partial substitution of iron with aluminum improves the chemical stability under reducing gas conditions and modulates the oxygen sensitivity by affecting the relative amount of Fe4+ and Fe3+, as confirmed from TPR profiles. In the same time, the addition of aluminum does not affects the temperature-independent properties of lanthanum strontium ferrites. Indeed, the electrical measurements show that (La0.7Sr0.3)(AlxFe1−x)O3 perovskites have temperature-independence conductivity from 900 K

  9. Modeling organohalide perovskites for photovoltaic applications: From materials to interfaces

    de Angelis, Filippo

    2015-03-01

    The field of hybrid/organic photovoltaics has been revolutionized in 2012 by the first reports of solid-state solar cells based on organohalide perovskites, now topping at 20% efficiency. First-principles modeling has been widely applied to the dye-sensitized solar cells field, and more recently to perovskite-based solar cells. The computational design and screening of new materials has played a major role in advancing the DSCs field. Suitable modeling strategies may also offer a view of the crucial heterointerfaces ruling the device operational mechanism. I will illustrate how simulation tools can be employed in the emerging field of perovskite solar cells. The performance of the proposed simulation toolbox along with the fundamental modeling strategies are presented using selected examples of relevant materials and interfaces. The main issue with hybrid perovskite modeling is to be able to accurately describe their structural, electronic and optical features. These materials show a degree of short range disorder, due to the presence of mobile organic cations embedded within the inorganic matrix, requiring to average their properties over a molecular dynamics trajectory. Due to the presence of heavy atoms (e.g. Sn and Pb) their electronic structure must take into account spin-orbit coupling (SOC) in an effective way, possibly including GW corrections. The proposed SOC-GW method constitutes the basis for tuning the materials electronic and optical properties, rationalizing experimental trends. Modeling charge generation in perovskite-sensitized TiO2 interfaces is then approached based on a SOC-DFT scheme, describing alignment of energy levels in a qualitatively correct fashion. The role of interfacial chemistry on the device performance is finally discussed. The research leading to these results has received funding from the European Union Seventh Framework Programme [FP7/2007 2013] under Grant Agreement No. 604032 of the MESO project.

  10. A two-step route to planar perovskite cells exhibiting reduced hysteresis

    A simple two-step method was used to produce efficient planar organolead halide perovskite solar cells. Films produced using solely iodine containing precursors resulted in poor morphology and failed devices, whereas addition of chlorine to the process greatly improved morphology and resulted in dense, uniform perovskite films. This process was used to produce perovskite solar cells with a fullerene-based passivation layer. The hysteresis effect, to which planar perovskite devices are otherwise prone, was greatly suppressed through the use of this interface modifier. The combined techniques resulted in perovskite solar cells having a stable efficiency exceeding 11%. This straightforward fabrication procedure holds promise in development of various optoelectronic applications of planar perovskite films

  11. A two-step route to planar perovskite cells exhibiting reduced hysteresis

    Ip, Alexander H.; Adachi, Michael M.; McDowell, Jeffrey J.; Xu, Jixian; Sargent, Edward H., E-mail: ted.sargent@utoronto.ca [Department of Electrical and Computer Engineering, University of Toronto, 10 King' s College Road, Toronto, Ontario M5S 3G4 (Canada); Quan, Li Na; Kim, Dong Ha [Department of Chemistry and Nano Science, Ewha Womans University, 52, Ewhayeodae-gil, Seodaemun-gu, Seoul 120-750 (Korea, Republic of)

    2015-04-06

    A simple two-step method was used to produce efficient planar organolead halide perovskite solar cells. Films produced using solely iodine containing precursors resulted in poor morphology and failed devices, whereas addition of chlorine to the process greatly improved morphology and resulted in dense, uniform perovskite films. This process was used to produce perovskite solar cells with a fullerene-based passivation layer. The hysteresis effect, to which planar perovskite devices are otherwise prone, was greatly suppressed through the use of this interface modifier. The combined techniques resulted in perovskite solar cells having a stable efficiency exceeding 11%. This straightforward fabrication procedure holds promise in development of various optoelectronic applications of planar perovskite films.

  12. Material Exchange Property of Organo Lead Halide Perovskite with Hole-Transporting Materials

    Seigo Ito

    2015-10-01

    Full Text Available Using X-ray diffraction (XRD, it was confirmed that the deposition of hole-transporting materials (HTM on a CH3NH3PbI3 perovskite layer changed the CH3NH3PbI3 perovskite crystal, which was due to the material exchanging phenomena between the CH3NH3PbI3 perovskite and HTM layers. The solvent for HTM also changed the perovskite crystal. In order to suppress the crystal change, doping by chloride ion, bromide ion and 5-aminovaleric acid was attempted. However, the doping was unable to stabilize the perovskite crystal against HTM deposition. It can be concluded that the CH3NH3PbI3 perovskite crystal is too soft and flexible to stabilize against HTM deposition.

  13. Formation of Single-mode Laser in Perovskite Nanowire via Nano-manipulation

    Wang, Kaiyang; Liu, Shuai; Li, Jiankai; Xiao, Shumin; Song, Qinghai

    2015-01-01

    Perovskite based micro- and nano- lasers have attracted considerable research attention in past two years. However, the properties of perovskite devices are mostly fixed once they are synthesized. Here we demonstrate the tailoring of lasing properties of perovskite nanowire lasers via nano-manipulation. By utilizing a tungsten probe, one nanowire has been lifted from the wafer and re-positioned its two ends on two nearby perovskite blocks. Consequently, the conventional Fabry-Perot lasers are completely suppressed and a single laser peak has been observed. The corresponding numerical model reveals that the single-mode lasing operation is formed by the whispering gallery mode in the transverse plane of perovskite nanowire. Our research provides a simple way to tailor the properties of nanowire and it will be essential for the applications of perovskite optoelectronics.

  14. Some Aspects of the Crystal Chemistry of Perovskites under High Pressures

    Wang, Di

    2012-01-01

    This thesis makes contributions to the methodology of quantitative description of the tilting systems of perovskite structures and theoretical analysis of high-pressure phase transitions of representative perovskites. Chapter 1 and 2 introduce the perovskite structures, tilting classification and descriptions. The structures in each of the 15 tilt systems have been decomposed in to the amplitudes of symmetry-adapted modes in order to provide a clear and unambiguous definition of the tilt ...

  15. Tailored surfaces of perovskite oxide substrates for conducted growth of thin films

    Sanchez, Florencio; Ocal, Carmen; Fontcuberta, Josep

    2014-01-01

    Oxide electronics relies on the availability of epitaxial oxide thin films. The extreme flexibility of the chemical composition of ABO3 perovskites and the broad spectrum of properties they cover, inspire the creativity of scientists and place perovskites in the lead of functional materials for advanced technologies. Moreover, emerging properties are being discovered at interfaces between distinct perovskites that could not be anticipated on the basis of those of the adjacent epitaxial layers...

  16. Humidity versus photo-stability of metal halide perovskite films in a polymer matrix.

    Manshor, Nurul Ain; Wali, Qamar; Wong, Ka Kan; Muzakir, Saifful Kamaluddin; Fakharuddin, Azhar; Schmidt-Mende, Lukas; Jose, Rajan

    2016-08-21

    Despite the high efficiency of over 21% reported for emerging thin film perovskite solar cells, one of the key issues prior to their commercial deployment is to attain their long term stability under ambient and outdoor conditions. The instability in perovskite is widely conceived to be humidity induced due to the water solubility of its initial precursors, which leads to decomposition of the perovskite crystal structure; however, we note that humidity alone is not the major degradation factor and it is rather the photon dose in combination with humidity exposure that triggers the instability. In our experiment, which is designed to decouple the effect of humidity and light on perovskite degradation, we investigate the shelf-lifetime of CH3NH3PbI3 films in the dark and under illumination under high humidity conditions (Rel. H. > 70%). We note minor degradation in perovskite films stored in a humid dark environment whereas upon exposure to light, the films undergo drastic degradation, primarily owing to the reactive TiO2/perovskite interface and also the surface defects of TiO2. To enhance its air-stability, we incorporate CH3NH3PbI3 perovskite in a polymer (poly-vinylpyrrolidone, PVP) matrix which retained its optical and structural characteristics in the dark for ∼2000 h and ∼800 h in room light soaking, significantly higher than a pristine perovskite film, which degraded completely in 600 h in the dark and in less than 100 h when exposed to light. We attribute the superior stability of PVP incorporated perovskite films to the improved structural stability of CH3NH3PbI3 and also to the improved TiO2/perovskite interface upon incorporating a polymer matrix. Charge injection from the polymer embedded perovskite films has also been confirmed by fabricating solar cells using them, thereby providing a promising future research pathway for stable and efficient perovskite solar cells. PMID:27432518

  17. Efficient methylammonium lead iodide perovskite solar cells with active layers from 300 to 900 nm

    Momblona, C.; O. Malinkiewicz; Roldán-Carmona, C.; Soriano, A; L. Gil-Escrig; Bandiello, E.; Scheepers, M.; Edri, E.; Bolink, H. J.

    2014-01-01

    Efficient methylammonium lead iodide perovskite-based solar cells have been prepared in which the perovskite layer is sandwiched in between two organic charge transporting layers that block holes and electrons, respectively. This configuration leads to stable and reproducible devices that do not suffer from strong hysteresis effects and when optimized lead to efficiencies close to 15%. The perovskite layer is formed by using a dual-source thermal evaporation method, whereas the organic layers...

  18. The Efficiency Limit of CH3NH3PbI3 Perovskite Solar Cells

    Sha, Wei; Ren, X.; Chen, L.; Choy, WCH

    2015-01-01

    With the consideration of photon recycling effect, the efficiency limit of methylammonium lead iodide (CH3NH3PbI3) perovskite solar cells is predicted by a detailed balance model. To obtain convincing predictions, both AM 1.5 spectrum of Sun and experimentally measured complex refractive index of perovskite material are employed in the detailed balance model. The roles of light trapping and angular restriction in improving the maximal output power of thin-film perovskite solar cells are also ...

  19. Research Update: Physical and electrical characteristics of lead halide perovskites for solar cell applications

    Bretschneider, Simon A.; Jonas Weickert; James A. Dorman; Lukas Schmidt-Mende

    2014-01-01

    The field of thin-film photovoltaics has been recently enriched by the introduction of lead halide perovskites as absorber materials, which allow low-cost synthesis of solar cells with efficiencies exceeding 16%. The exact impact of the perovskite crystal structure and composition on the optoelectronic properties of the material are not fully understood. Our progress report highlights the knowledge gained about lead halide perovskites with a focus on physical and optoelectronic properties. We...

  20. Formamidinium lead trihalide: a broadly tunable perovskite for efficient planar heterojunction solar cells

    Eperon, GE; Stranks, SD; Menelaou, C.; Johnston, MB; Herz, LM; Snaith, HJ

    2014-01-01

    Perovskite-based solar cells have attracted significant recent interest, with power conversion efficiencies in excess of 15% already superceding a number of established thin-film solar cell technologies. Most work has focused on a methylammonium lead trihalide perovskites, with a bandgaps of ∼1.55 eV and greater. Here, we explore the effect of replacing the methylammonium cation in this perovskite, and show that with the slightly larger formamidinium cation, we can synthesise formamidinium le...

  1. Can Ferroelectric Polarization Explain the High Performance of Hybrid Halide Perovskite Solar Cells?

    Sherkar, Tejas; Koster, L Jan Anton

    2016-01-01

    The power conversion efficiency of photovoltaic cells based on the use of hybrid halide perovskites, CH3NH3PbX3 (X = Cl, Br, I), now exceeds 20%. Recently, it was suggested that this high performance originates from the presence of ferroelectricity in the perovskite, which is hypothesized to lower charge recombination in the device. Here, we investigate and quantify the influence of mesoscale ferroelectric polarization on the device performance of perovskite solar cells. We implement a 3D dri...

  2. Magnetic properties of rare earth oxides with perovskite structure

    A perovskite composite oxide is represented by the general formula of ABO3. Cations at the B site characterize magnetic properties of the oxide. Many studies have been accumulated for transition metal elements at the B sites. In this report the studies of rare earth elements at the B sites are reviewed. In rare elements, tetravalent ions such as Ce4+, Pr4+ and Tb4+ can occupy the B sites with Ba and Sr ions at the A sites. Both the SrTbO3 and BaTbO3 have an orthorhombic structure and show the antiferromagnetic transition at about 33 K, which is originated from terbium ions coupled antiferromagnetically with the six neighboring terbium ions. A tetravalent praseodymium perovskite SrPrO3 shows no existence of the magnetic ordering down to 2.0 K. This is in contrast to the result of isomorphous BaPrO3, which shows an antiferromagnetic transition at 11.5 K. A double perovskite structure is represented by the formula A2LnMO6 (A=Ba, Sr, Ca; M=Ru, Ir). In a double perovskite compound Ba2PrRuO6, the Pr3+ and Ru5+ ions are arranged with regularity over the six-coordinate B sites. This compound transforms to an antiferromagnetic state below 117 K. Antiferromagnetic transition temperatures TN for isomorphous Sr and Ca show a clear tendency, TN(A=Ba)>TN(Sr)>TN(Ca), in the compounds with the same rare earth elements (Ln). The 6H-perovskite structure Ba3LnRu2O9 consists of linkages between LnO6 octahedra and Ru2O9 dimers made from face-shared RuO6 octahedra. The 6H-perovskite structure Ba3MRu2O9 (M=Sc, Y, La, Nd-Gd, Dy-Lu) have the valence state of Ba3M3+Ru24.5+O9. The magnetic susceptibilities show a broad maximum at 135-370 K. This magnetic behavior is ascribed to the antiferromagnetic coupling between two Ru ions in a Ru2O9 dimer and to the magnetic interaction between the Ru2O9 dimers. (author)

  3. Research Update: Physical and electrical characteristics of lead halide perovskites for solar cell applications

    Simon A. Bretschneider

    2014-04-01

    Full Text Available The field of thin-film photovoltaics has been recently enriched by the introduction of lead halide perovskites as absorber materials, which allow low-cost synthesis of solar cells with efficiencies exceeding 16%. The exact impact of the perovskite crystal structure and composition on the optoelectronic properties of the material are not fully understood. Our progress report highlights the knowledge gained about lead halide perovskites with a focus on physical and optoelectronic properties. We discuss the crystal and band structure of perovskite materials currently implemented in solar cells and the impact of the crystal properties on ferroelectricity, ambipolarity, and the properties of excitons.

  4. In-situ measurement of texture development rate in CaIrO₃ post-perovskite

    Hunt, SA; Walker, AM; Mariani, E

    2016-01-01

    The rate of crystallographic preferred orientation (CPO) development during deformation of post-perovskite is crucial in interpreting seismic anisotropy in the lowermost mantle but the stability field of MgSiO3 post-perovskite prevents high-strain deformation experiments being performed on it. Therefore, to constrain the rate of CPO development in post-perovskite, we deformed CaIrO3, a low-pressure analogue of MgSiO3 post-perovskite, in simple shear at 3.2GPa and 400○C to a shear strain (γ) o...

  5. Investigating the Effect of Pyridine Vapor Treatment on Perovskite Solar Cells

    Ong, Alison [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-08-20

    Perovskite photovoltaics have recently come to prominence as a viable alternative to crystalline silicon based solar cells. In an effort to create consistent and high-quality films, we studied the effect of various annealing conditions as well as the effect of pyridine vapor treatment on mixed halide methylammonium lead perovskite films. Of six conditions tested, we found that annealing at 100°C for 90 minutes followed by 120°C for 15 minutes resulted in the purest perovskite. Perovskite films made using that condition were treated with pyridine for various amounts of time, and the effects on perovskite microstructure were studied using x-ray diffraction, UV-Vis spectroscopy, and time-resolved photoluminescence lifetime analysis (TRPL). A previous study found that pyridine vapor caused perovskite films to have higher photoluminescence intensity and become more homogenous. In this study we found that the effects of pyridine are more complex: while films appeared to become more homogenous, a decrease in bulk photoluminescence lifetime was observed. In addition, the perovskite bandgap appeared to decrease with increased pyridine treatment time. Finally, X-ray diffraction showed that pyridine vapor treatment increased the perovskite (110) peak intensity but also often gave rise to new unidentified peaks, suggesting the formation of a foreign species. It was observed that the intensity of this unknown species had an inverse correlation with the increase in perovskite peak intensity, and also seemed to be correlated with the decrease in TRPL lifetime.

  6. Life Cycle Assessment of Titania Perovskite Solar Cell Technology for Sustainable Design and Manufacturing.

    Zhang, Jingyi; Gao, Xianfeng; Deng, Yelin; Li, Bingbing; Yuan, Chris

    2015-11-01

    Perovskite solar cells have attracted enormous attention in recent years due to their low cost and superior technical performance. However, the use of toxic metals, such as lead, in the perovskite dye and toxic chemicals in perovskite solar cell manufacturing causes grave concerns for its environmental performance. To understand and facilitate the sustainable development of perovskite solar cell technology from its design to manufacturing, a comprehensive environmental impact assessment has been conducted on titanium dioxide nanotube based perovskite solar cells by using an attributional life cycle assessment approach, from cradle to gate, with manufacturing data from our laboratory-scale experiments and upstream data collected from professional databases and the literature. The results indicate that the perovskite dye is the primary source of environmental impact, associated with 64.77% total embodied energy and 31.38% embodied materials consumption, contributing to more than 50% of the life cycle impact in almost all impact categories, although lead used in the perovskite dye only contributes to about 1.14% of the human toxicity potential. A comparison of perovskite solar cells with commercial silicon and cadmium-tellurium solar cells reveals that perovskite solar cells could be a promising alternative technology for future large-scale industrial applications. PMID:26489525

  7. APPLICATION OF DOPANT-FREE HOLE TRANSPORT MATERIALS FOR PEROVSKITE SOLAR CELLS

    Franckevičius, Marius; Mishra, Amaresh; Steck, Christopher

    2015-01-01

    In this work we present the synthesis, characterization and application of a series of additive and dopant free hole transport materials (HTM) for solid-state perovskite-based solar cells. Newly synthesized HTMs showed strong absorption in the visible spectral range and suitable HOMO-LUMO energy levels for the application for methylammonium lead(II) iodide (CH3NH3PbI3) perovskite. Dopant-free perovskite solar cells have been fabricated using CH3NH3PbI3 perovskite and the newly synthesized HTM...

  8. Material Exchange Property of Organo Lead Halide Perovskite with Hole-Transporting Materials

    Seigo Ito; Shusaku Kanaya; Hitoshi Nishino; Tomokazu Umeyama; Hiroshi Imahori

    2015-01-01

    Using X-ray diffraction (XRD), it was confirmed that the deposition of hole-transporting materials (HTM) on a CH3NH3PbI3 perovskite layer changed the CH3NH3PbI3 perovskite crystal, which was due to the material exchanging phenomena between the CH3NH3PbI3 perovskite and HTM layers. The solvent for HTM also changed the perovskite crystal. In order to suppress the crystal change, doping by chloride ion, bromide ion and 5-aminovaleric acid was attempted. However, the doping was unable to stabili...

  9. Additive to regulate the perovskite crystal film growth in planar heterojunction solar cells

    We reported a planar heterojunction perovskite solar cell fabricated from MAPbI3−xClx perovskite precursor solution containing 1-chloronaphthalene (CN) additive. The MAPbI3−xClx perovskite films have been characterized by UV-vis, SEM, XRD, and steady-state photoluminescence (PL). UV-vis absorption spectra measurement shows that the absorbance of the film with CN additive is significantly higher than the pristine film and the absorption peak is red shift by 30 nm, indicating the perovskite film with additive possessing better crystal structures. In-situ XRD study of the perovskite films with additive demonstrated intense diffraction peaks from MAPbI3−xClx perovskite crystal planes of (110), (220), and (330). SEM images of the films with additive indicated the films were more smooth and homogenous with fewer pin-holes and voids and better surface coverage than the pristine films. These results implied that the additive CN is beneficial to regulate the crystallization transformation kinetics of perovskite to form high quality crystal films. The steady-state PL measurement suggested that the films with additive contained less charge traps and defects. The planar heterojunction perovskite solar cells fabricated from perovskite precursor solution containing CN additive demonstrated 30% enhancement in performance compared to the devices with pristine films. The improvement in device efficiency is mainly attributed to the good crystal structures, more homogenous film morphology, and also fewer trap centers and defects in the films with the additive

  10. Efficient methylammonium lead iodide perovskite solar cells with active layers from 300 to 900 nm

    Efficient methylammonium lead iodide perovskite-based solar cells have been prepared in which the perovskite layer is sandwiched in between two organic charge transporting layers that block holes and electrons, respectively. This configuration leads to stable and reproducible devices that do not suffer from strong hysteresis effects and when optimized lead to efficiencies close to 15%. The perovskite layer is formed by using a dual-source thermal evaporation method, whereas the organic layers are processed from solution. The dual-source thermal evaporation method leads to smooth films and allows for high precision thickness variations. Devices were prepared with perovskite layer thicknesses ranging from 160 to 900 nm. The short-circuit current observed for these devices increased with increasing perovskite layer thickness. The main parameter that decreases with increasing perovskite layer thickness is the fill factor and as a result optimum device performance is obtained for perovskite layer thickness around 300 nm. However, here we demonstrate that with a slightly oxidized electron blocking layer the fill factor for the solar cells with a perovskite layer thickness of 900 nm increases to the same values as for the devices with thin perovskite layers. As a result the power conversion efficiencies for the cells with 300 and 900 nm are very similar, 12.7% and 12%, respectively

  11. Investigating the Effect of Pyridine Vapor Treatment on Perovskite Solar Cells - Oral Presentation

    Ong, Alison J. [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-08-25

    Perovskite photovoltaics have recently come to prominence as a viable alternative to crystalline silicon based solar cells. In an effort to create consistent and high-quality films, we studied the effect of various annealing conditions as well as the effect of pyridine vapor treatment on mixed halide methylammonium lead perovskite films. Of six conditions tested, we found that annealing at 100 degree Celsius for 90 minutes followed by 120 degree Celsius for 15 minutes resulted in the purest perovskite. Perovskite films made using that condition were treated with pyridine for various amounts of time, and the effects on perovskite microstructure were studied using x-ray diffraction, UV-Vis spectroscopy, and time-resolved photoluminescence lifetime analysis (TRPL). A previous study found that pyridine vapor caused perovskite films to have higher photoluminescence intensity and become more homogenous. In this study we found that the effects of pyridine are more complex: while films appeared to become more homogenous, a decrease in bulkphotoluminescence lifetime was observed. In addition, the perovskite bandgap appeared to decrease with increased pyridine treatment time. Finally, X-ray diffraction showed that pyridine vapor treatment increased the perovskite (110) peak intensity but also often gave rise to new unidentified peaks, suggesting the formation of a foreign species. It was observed that the intensity of this unknown species had an inverse correlation with the increase in perovskite peak intensity, and also seemed to be correlated with the decrease in TRPL lifetime.

  12. High-Efficiency Flexible Solar Cells Based on Organometal Halide Perovskites.

    Wang, Yuming; Bai, Sai; Cheng, Lu; Wang, Nana; Wang, Jianpu; Gao, Feng; Huang, Wei

    2016-06-01

    Flexible and light-weight solar cells are important because they not only supply power to wearable and portable devices, but also reduce the transportation and installation cost of solar panels. High-efficiency organometal halide perovskite solar cells can be fabricated by a low-temperature solution process, and hence are promising for flexible-solar-cell applications. Here, the development of perovskite solar cells is briefly discussed, followed by the merits of organometal halide perovskites as promising candidates as high-efficiency, flexible, and light-weight photovoltaic materials. Afterward, recent developments of flexible solar cells based on perovskites are reviewed. PMID:26669326

  13. The melting behavior of lutetium aluminum perovskite LuAlO3

    Klimm, Detlef

    2009-01-01

    DTA measurements with mixtures of aluminum oxide and lutetium oxide around the 1:1 perovskite composition were performed up to 1970 deg. C. A peak with onset 1901 deg C was due to the melting of the eutectic Lu4Al2O9 (monoclinic phase) and LuAlO3 (perovskite). Neither peritectic melting of the perovskite nor its decomposition in the solid phase could be resolved experimentally. The maximum of the eutectic peak size is near x=0.44, on the Lu-rich side of the perovskite, which is consistent wit...

  14. Efficient and stable perovskite solar cells prepared in ambient air irrespective of the humidity

    Tai, Qidong; You, Peng; Sang, Hongqian; Liu, Zhike; Hu, Chenglong; Chan, Helen L. W.; Yan, Feng

    2016-01-01

    Poor stability of organic–inorganic halide perovskite materials in humid condition has hindered the success of perovskite solar cells in real applications since controlled atmosphere is required for device fabrication and operation, and there is a lack of effective solutions to this problem until now. Here we report the use of lead (II) thiocyanate (Pb(SCN)2) precursor in preparing perovskite solar cells in ambient air. High-quality CH3NH3PbI3−x (SCN) x perovskite films can be readily prepare...

  15. Synthesis and characterization of perovskite-type SrxY1−xFeO3−δ (0.63≤x0.75Y0.25Fe1−yMyO3−δ (M=Cr, Mn, Ni), (y=0.2, 0.33, 0.5)

    Oxygen-deficient ferrates with the cubic perovskite structure SrxY1−xFeO3−δ were prepared in air (0.71≤x≤0.91) as well as in N2 (x=0.75 and 0.79) at 1573 K. The oxygen content of the compounds prepared in air increases with increasing strontium content from 3−δ=2.79(2) for x=0.75 to 3−δ=2.83(2) for x=0.91. Refinement of the crystal structure of Sr0.75Y0.25FeO2.79 using TOF neutron powder diffraction (NPD) data shows high anisotropic atomic displacement parameter (ADP) for the oxygen atom resulting from a substantial cation and anion disorder. Electron diffraction (ED) and high-resolution electron microscopy (HREM) studies of Sr0.75Y0.25FeO2.79 reveal a modulation along 〈1 0 0〉p with G± ∼0.4〈1 0 0〉p indicating a local ordering of oxygen vacancies. Magnetic susceptibility measurements at 5–390 K show spin-glass behaviour with dominating antiferromagnetic coupling between the magnetic moments of Fe cations. Among the studied compositions, Sr0.75Y0.25FeO2.79 shows the lowest thermal expansion coefficient (TEC) of 10.5 ppm/K in air at 298–673 K. At 773–1173 K TEC increases up to 17.2 ppm/K due to substantial reduction of oxygen content. The latter also results in a dramatic decrease of the electrical conductivity in air above 673 K. Partial substitution of Fe by Cr, Mn and Ni according to the formula Sr0.75Y0.25Fe1−yMyO3−δ (y=0.2, 0.33, 0.5) leads to cubic perovskites for all substituents with y=0.2. Their TECs are higher in comparison with un-doped Sr0.75Y0.25FeO2.79. Only M=Ni has increased electrical conductivity compared to un-doped Sr0.75Y0.25FeO2.79. - Graphical abstract: Oxygen-deficient ferrates with the cubic perovskite structure SrxY1−xFeO3−δ were prepared both in air (0.71≤x≤0.91) and N2 (x=0.75 and 0.79) at 1573 K. Refinement of the crystal structure of Sr0.75Y0.25FeO2.79 using TOF neutron powder diffraction (NPD) data (S.G. Pm-3m, a=3.86455(3) Å; χ2=6.71, Rp=0.03; Rwp=0.04) confirmed the cubic perovskite

  16. A novel synthesis of perovskite bismuth ferrite nanoparticles

    Alexandre Z. Simões

    2011-09-01

    Full Text Available Microwave assisted hydrothermal (MAH method was used to synthesize crystalline bismuth ferrite (BiFeO3 nanoparticles (BFO at temperature of 180°C with times ranging from 5 min to 1 h. For comparison, BFO powders were also crystallized by the soft chemistry route in a conventional furnace at a temperature of 850°C for 4 h. X-ray diffraction (XRD results verified the formation of perovskite BFO crystallites while infrared data showed no traces of carbonate. Field emission scanning microcopy (FE/SEM revealed a homogeneous size distribution of nanometric BFO powders. MAH method produced nanoparticles of 96% pure perovskite, with a size of 130 nm. These results are in agreement with Raman scattering values which show that the MAH synthesis route is rapid and cost effective. This method could be used as an alternative to other chemical methods in order to obtain BFO nanoparticles.

  17. Origin of J-V Hysteresis in Perovskite Solar Cells.

    Chen, Bo; Yang, Mengjin; Priya, Shashank; Zhu, Kai

    2016-03-01

    High-performance perovskite solar cells (PSCs) based on organometal halide perovskite have emerged in the past five years as excellent devices for harvesting solar energy. Some remaining challenges should be resolved to continue the momentum in their development. The photocurrent density-voltage (J-V) responses of the PSCs demonstrate anomalous dependence on the voltage scan direction/rate/range, voltage conditioning history, and device configuration. The hysteretic J-V behavior presents a challenge for determining the accurate power conversion efficiency of the PSCs. Here, we review the recent progress on the investigation of the origin(s) of J-V hysteresis behavior in PSCs. We discuss the impact of slow transient capacitive current, trapping and detrapping process, ion migrations, and ferroelectric polarization on the hysteresis behavior. The remaining issues and future research required toward the understanding of J-V hysteresis in PSCs will also be discussed. PMID:26886052

  18. Perovskite Oxide Thin Film Growth, Characterization, and Stability

    Izumi, Andrew

    Studies into a class of materials known as complex oxides have evoked a great deal of interest due to their unique magnetic, ferroelectric, and superconducting properties. In particular, materials with the ABO3 perovskite structure have highly tunable properties because of the high stability of the structure, which allows for large scale doping and strain. This also allows for a large selection of A and B cations and valences, which can further modify the material's electronic structure. Additionally, deposition of these materials as thin films and superlattices through techniques such as pulsed laser deposition (PLD) results in novel properties due to the reduced dimensionality of the material. The novel properties of perovskite oxide heterostructures can be traced to a several sources, including chemical intermixing, strain and defect formation, and electronic reconstruction. The correlations between microstructure and physical properties must be investigated by examining the physical and electronic structure of perovskites in order to understand this class of materials. Some perovskites can undergo phase changes due to temperature, electrical fields, and magnetic fields. In this work we investigated Nd0.5Sr 0.5MnO3 (NSMO), which undergoes a first order magnetic and electronic transition at T=158K in bulk form. Above this temperature NSMO is a ferromagnetic metal, but transitions into an antiferromagnetic insulator as the temperature is decreased. This rapid transition has interesting potential in memory devices. However, when NSMO is deposited on (001)-oriented SrTiO 3 (STO) or (001)-oriented (LaAlO3)0.3-(Sr 2AlTaO6)0.7 (LSAT) substrates, this transition is lost. It has been reported in the literature that depositing NSMO on (110)-oriented STO allows for the transition to reemerge due to the partial epitaxial growth, where the NSMO film is strained along the [001] surface axis and partially relaxed along the [11¯0] surface axis. This allows the NSMO film enough

  19. Enhancement of perovskite solar cells by plasmonic nanoparticles

    Omelyanovich, Mikhail; Milichko, Valentin; Simovski, Constantin

    2016-01-01

    Synthetic perovskites with photovoltaic properties open a new era in solar photovoltaics. Due to high optical absorption perovskite-based thin-film solar cells are usually considered as fully absorbing solar radiation on condition of ideal blooming. However, is it really so? The analysis of the literature data has shown that the absorbance of all photovoltaic pervoskites has the spectral hole at infrared frequencies where the solar radiation spectrum has a small local peak. This absorption dip results in the decrease of the optical efficiency of thin-film pervoskite solar cells by nearly 3% and close the ways of utilise them at this range for any other applications. In our work we show that to cure this shortage is possible complementing the basic structure by an inexpensive plasmonic array.

  20. Spin State Control of the Perovskite Rh/Co Oxides

    Wataru Kobayashi

    2010-01-01

    Full Text Available We show why and how the spin state of transition-metal ions affects the thermoelectric properties of transition-metal oxides by investigating two perovskite-related oxides. In the A-site ordered cobalt oxide Sr3YCo4O10.5, partial substitution of Ca for Sr acts as chemical pressure, which compresses the unit cell volume to drive the spin state crossover, and concomitantly changes the magnetization and thermopower. In the perovskite rhodium oxide LaRhO3, partial substitution of Sr for La acts as hole-doping, and the resistivity and thermopower decrease systematically with the Sr concentration. The thermopower remains large values at high temperatures (>150 μV/K at 800 K, which makes a remarkable contrast to La1-xSrxCoO3. We associate this with the stability of the low spin state of the Rh3+ ions.

  1. Growing perovskite into polymers for easy-processable optoelectronic devices.

    Masi, Sofia; Colella, Silvia; Listorti, Andrea; Roiati, Vittoria; Liscio, Andrea; Palermo, Vincenzo; Rizzo, Aurora; Gigli, Giuseppe

    2015-01-01

    Here we conceive an innovative nanocomposite to endow hybrid perovskites with the easy processability of polymers, providing a tool to control film quality and material crystallinity. We verify that the employed semiconducting polymer, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), controls the self-assembly of CH₃NH₃PbI₃ (MAPbI₃) crystalline domains and favors the deposition of a very smooth and homogenous layer in one straightforward step. This idea offers a new paradigm for the implementation of polymer/perovskite nanocomposites towards versatile optoelectronic devices combined with the feasibility of mass production. As a proof-of-concept we propose the application of such nanocomposite in polymer solar cell architecture, demonstrating a power conversion efficiency up to 3%, to date the highest reported for MEH-PPV. On-purpose designed polymers are expected to suit the nanocomposite properties for the integration in diverse optoelectronic devices via facile processing condition. PMID:25579988

  2. Method for fabricating high aspect ratio structures in perovskite material

    Karapetrov, Goran T.; Kwok, Wai-Kwong; Crabtree, George W.; Iavarone, Maria

    2003-10-28

    A method of fabricating high aspect ratio ceramic structures in which a selected portion of perovskite or perovskite-like crystalline material is exposed to a high energy ion beam for a time sufficient to cause the crystalline material contacted by the ion beam to have substantially parallel columnar defects. Then selected portions of the material having substantially parallel columnar defects are etched leaving material with and without substantially parallel columnar defects in a predetermined shape having high aspect ratios of not less than 2 to 1. Etching is accomplished by optical or PMMA lithography. There is also disclosed a structure of a ceramic which is superconducting at a temperature in the range of from about 10.degree. K. to about 90.degree. K. with substantially parallel columnar defects in which the smallest lateral dimension of the structure is less than about 5 microns, and the thickness of the structure is greater than 2 times the smallest lateral dimension of the structure.

  3. Molecular Dynamics Simulation of MgSiO3 Perovskite

    Lin-xiang, Zhou; L, Zhou X.; J, Hardy R.; Xin, Xu; X, Xu

    1998-06-01

    Using molecular dynamics to simulate MgSiO3 perovskite is performed to investigate its phase transitions and superionicity. These simulations has used parameter-free Gordon-Kim potentials and a novel technique to monitor the motion of ions which clearly demonstrates the sublattice melting of ions O2- and the rotations of SiO6 octahedra. MgSiO3 has to undergo a few of phase transitions, then enter into the cubic phase. In particular, there is a transitional phase between orthorhombic phase and cubic phase. There are a superionic phase and the cubic phase in magnesium-rich silicate perovskite. This superionic phase occurs after the onset of cubic phase before the melting point. The onset temparature Tc for superionicity is about 200-700 K below the melting point Tm, Tc / Tm similar 0.92.

  4. Photoinduced surface voltage mapping study for large perovskite single crystals

    Liu, Xiaojing; Liu, Yucheng; Gao, Fei; Yang, Zhou; Liu, Shengzhong Frank

    2016-05-01

    Using a series of illumination sources, including white light (tungsten-halogen lamp), 445-nm, 532-nm, 635-nm, and 730-nm lasers, the surface photovoltage (SPV) images were mapped for centimeter-sized CH3NH3PbX3 (X = Cl, Br, I) perovskite single crystals using Kelvin probe force microscopy. The significant SPV signals were observed to be wavelength-dependent. We attribute the appreciable SPV to the built-in electric field in the space charge region. This study shines light into the understanding of photoinduced charge generation and separation processes at nanoscale to help advance the development of perovskite solar cells, optoelectronics, laser, photodetector, and light-emitting diode (LED).

  5. Charge segregation in RNiO3 perovskites

    Complete text of publication follows. RNiO3 perovskites are one of the few families of undoped oxides showing a metal-insulator transition as a function of temperature. The origin this first-order transition has been one of the long-standing questions associated with these compounds. Neutron and synchrotron diffraction data of small-rare-earth members of the series provide the first observation of changes in the crystal symmetry at the metal-insulator (MI) transition in RNiO3 perovskites. At high temperatures, RNiO3 are orthorhombic and metallic and below TMI they change to a monoclinic insulator. The structural reorganization at TMI gives rise to two crystallographically independent Ni positions and the insulating phase consist of alternating expanded (Ni1O6) and contracted (Ni2O6) octahedra along the three directions of the crystal cell. This finding indicates a Ni charge segregation. (author)

  6. Partial Oxidation of Methane Over the Perovskite Oxides

    2001-01-01

    Ba0.sSr0.5Co0.8Fe0.2O3-δ and Ba0.5Sr0.5Co0.8Ti0.2O3-δ oxides were synthesized by a combined EDTA-citrate complexing method. The catalytic behavior of these two oxides with the perovskite structure was studied during the reaction of methane oxidation. The pre-treatment with methane has different effect on the catalytic activities of both the oxides. The methane pre-treatment has not resulted in the change of the catalytic activity of BSCFO owing to its excellent reversibility of the perovskite structure resulting from the excellent synergistic interaction between Co and Fe in the oxide. However, the substitution with Ti on Fe-site in the lattice makes the methane pre-treatment have an obvious influence on the activity of the formed BSCTO oxide.

  7. Random lasing in organo-lead halide perovskite microcrystal networks

    We report optically pumped random lasing in planar methylammonium lead iodide perovskite microcrystal networks that form spontaneously from spin coating. Low thresholds (<200 μJ/cm2) and narrow linewidths (Δλ < 0.5 nm) reflect lasing from closed quasi-modes that result from ballistic waveguiding in linear network segments linked by scattering at the junctions. Spatio-spectral imaging indicates that these quasi-modes extend over lateral length scales >100 μm and spatially overlap with one another, resulting in chaotic pulse-to-pulse intensity fluctuations due to gain competition. These results demonstrate this class of hybrid organic-inorganic perovskite as a platform to study random lasing with well-defined, low-level disorder, and support the potential of these materials for use in semiconductor laser applications.

  8. Perovskite solid electrolytes: Structure, transport properties and fuel cell applications

    Bonanos, N.; Knight, K.S.; Ellis, B.

    1995-01-01

    addition to performance data, have provided an unexpected insight into the transport processes operating in these materials. In the temperature range of 600-1000 degrees C, the dominant transport process varies from protonic to oxide-ion dominated. This transition has been confirmed by measurement of water...... vapour transfer in a cell in which the perovskite is exposed to wet hydrogen on both sides. The evolution of transport properties with temperature is discussed in relation to structure. Neutron diffraction studies of doped and undoped barium cerate are reported, revealing a series of phase transitions......Doped barium cerate perovskites, first investigated by Iwahara and co-workers, have ionic conductivities of the order of 20 mS/cm at 800 degrees C making them attractive as fuel cell electrolytes for this temperature region. They have been used to construct laboratory scale fuel cells, which, in...

  9. Simple characterization of electronic processes in perovskite photovoltaic cells

    Miyano, Kenjiro, E-mail: MIYANO.Kenjiro@nims.go.jp; Yanagida, Masatoshi; Tripathi, Neeti; Shirai, Yasuhiro [Global Research Center for Environment and Energy Based on Nanomaterials Science (GREEN), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

    2015-03-02

    Electronic properties of perovskite lead-halide photovoltaic cells have been studied. The dc current/voltage characteristics were found to be well fitted by a standard diode equation under optical excitation and in the dark, while the impedance spectroscopy revealed a pronounced slow process under light illumination, which is absent in the dark. A simple model is proposed, which can explain all aspects of the observed behavior quantitatively and consistently.

  10. Chemical compatibility of rare earth cobaltite perovskites with YSZ

    Rare earth cobaltite perovskites are interesting cathode materials for the reduced temperature SOFC because of their high catalytic activity for oxygen reduction. The chemical compatibility of perovskites in Ln1-xSrxCoO3-δ(Ln=Sm, Dy), Ln0.4Sr0.6Co0.8Fe0.2O3-δ (Ln=La, Pr, Nd, Sm, Gd), Gd0.8Ca0.2Co1-xMnxO3-δ with 8 mol% yttria stabilized zirconia(8YSZ) has been investigated. Powder mixtures of these perovskites and 8YSZ have been annealed at different temperatures for 96 h in air. As the main reaction product, SrZrO3 has been found in 8YSZ/Ln, 1-xSrxCoO3-δ(Ln=Sm,Dy) with high Sr content and 8YSZ/Ln0.4Sr0.6Co0.8Fe0.2O3-δ (Ln=La,Pr,Nd,Sm,Gd) at 900 deg C. No reaction product has been detected in 8YSZ/Gd0.8Ca0.2Co1-6MnxO3-δ by XRD. However, significant diffusion of Co into 8YSZ has been found by EDX at the interface of 8YSZ/ Gd0.8Ca0.2Co0.6Mn0.4O3-δ after annealing at 1200 deg C for 24h. The bond-valence model has been used to discuss the chemical compatibility of the different perovskites with 8YSZ. Copyright (1999) Australasian Ceramic Society

  11. Dynamic electrical behavior of halide perovskite based solar cells

    Nemnes, George Alexandru; Besleaga, Cristina; Tomulescu, Andrei Gabriel; Pintilie, Ioana; Pintilie, Lucian; Torfason, Kristinn; Manolescu, Andrei

    2016-01-01

    A dynamic electrical model is introduced to investigate the hysteretic effects in the I-V characteristics of perovskite based solar cells. By making a simple ansatz for the polarization relaxation, our model is able to reproduce qualitatively and quantitatively detailed features of measured I-V characteristics. Pre-poling effects are discussed, pointing out the differences between initially over- and under-polarized samples. In particular, the presence of the current over-shoot observed in th...

  12. Characterization and application of Pb-based organometal halide perovskite

    Feipeng CHEN

    2015-01-01

    In the foreseeable future, the global energy consumption is expected to increase significantly. Solar energy, as an alternative form of energy, has gained popularity as a way to solve the greenhouse gas emission and sustainability problem of fossil fuels. This thesis mainly concerns a novel materials system, namely organometal trihalide perovskite, that is currently receiving considerable attention as light absorber in solar cells, due to the promise to obtain significant impro...

  13. What is moving in hybrid halide perovskite solar cells?

    Frost, Jarvist M.; Walsh, Aron

    2016-01-01

    Conspectus Organic–inorganic semiconductors, which adopt the perovskite crystal structure, have perturbed the landscape of contemporary photovoltaics research. High-efficiency solar cells can be produced with solution-processed active layers. The materials are earth abundant, and the simple processing required suggests that high-throughput and low-cost manufacture at scale should be possible. While these materials bear considerable similarity to traditional inorganic semiconductors, there are...

  14. Device architecture and characterization of organic and hybrid perovskite photovoltaic

    Yang, Yang

    2015-01-01

    Photovoltaic (PV), which converts sunlight into electricity, is a promising solution to the energy and environmental crisis we are facing right now. In this dissertation, we are focusing on next generation semiconductors as the photoactive materials, i.e. organic and orgainic/inorganic hybrid perovskite semiconductors, to achieve cost effective and energy efficient solar cell technology. Organic semiconductor always shows narrow absorption compared with the conventional inorganic semiconducto...

  15. Ionic transport in hybrid lead iodide perovskite solar cells

    Eames, Christopher; Frost, Jarvist Moore; Piers R. F. Barnes; O'Regan, Brian C.; Walsh, Aron; Islam, M. Saiful

    2015-01-01

    Solar cells based on organic–inorganic halide perovskites have recently shown rapidly rising power conversion efficiencies, but exhibit unusual behaviour such as current–voltage hysteresis and a low-frequency giant dielectric response. Ionic transport has been suggested to be an important factor contributing to these effects; however, the chemical origin of this transport and the mobile species are unclear. Here, the activation energies for ionic migration in methylammonium lead iodide (CH3NH...

  16. Polymer/Perovskite Amplifying Waveguides for Active Hybrid Silicon Photonics.

    Suárez, Isaac; Juárez-Pérez, Emilio J; Bisquert, Juan; Mora-Seró, Iván; Martínez-Pastor, Juan P

    2015-10-28

    The emission properties of hybrid halide perovskites are exploited to implement a stable and very low power operation waveguide optical amplifier integrated in a silicon platform. By optimizing its design with a poly(methyl methacrylate) (PMMA) encapsulation, this novel photonic device presents a net gain of around 10 dB cm(-1) and 3-4 nm linewidth with an energy threshold as low as 2 nJ pulse(-1) and exhibiting no degradation after one year. PMID:26331838

  17. Raman spectroscopy of organic-inorganic halide perovskites

    Ledinský, Martin; Löper, P.; Niesen, B.; Holovský, Jakub; Moon, S.J.; Yum, J. H.; De Wolf, S.; Fejfar, Antonín; Ballif, C.

    2015-01-01

    Roč. 6, č. 3 (2015), 401-406. ISSN 1948-7185 R&D Projects: GA ČR GA14-15357S; GA MŠk(CZ) LM2011026 Institutional support: RVO:68378271 Keywords : mixed iodide and bromide lead perovskites * micro-Raman mapping * local chemical sensitivity * moisture-induced degradation * lead iodide * photoluminesce Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.458, year: 2014

  18. Luminescence of lead-containing tungstates with perovskite structure

    Bleijenberg, K.C.; Blasse, G.

    1975-01-01

    The luminescence of perovskites with formula Sr1-xPbxLaLiWO6 and Ba2-xPbxMgWO6 is reported. The lower-energy emission in the lead-containing compounds is ascribed to a transition within a centre consisting of a tungstate octahedron with lead-ion neighbours. The presence of Bi3+ is SrLaLiWO6 causes a

  19. Electrostatic engineering of strained ferroelectric perovskites from first-principles

    Cazorla, Claudio; Stengel, Massimiliano

    2015-01-01

    Design of novel artificial materials based on ferroelectric perovskites relies on the basic principles of electrostatic coupling and in-plane lattice matching. These rules state that the out-of-plane component of the electric displacement field and the in-plane components of the strain are preserved across a layered superlattice, provided that certain growth conditions are respected. Intense research is currently directed at optimizing materials functionalities based on these guidelines, ofte...

  20. Perovskite electrodes and method of making the same

    Seabaugh, Matthew M.; Swartz, Scott L.

    2005-09-20

    The invention relates to perovskite oxide electrode materials in which one or more of the elements Mg, Ni, Cu, and Zn are present as minority components that enhance electrochemical performance, as well as electrode products with these compositions and methods of making the electrode materials. Such electrodes are useful in electrochemical system applications such as solid oxide fuel cells, ceramic oxygen generation systems, gas sensors, ceramic membrane reactors, and ceramic electrochemical gas separation systems.

  1. Perovskite to postperovskite transition in NaFeF3.

    Bernal, Fabian L; Yusenko, Kirill V; Sottmann, Jonas; Drathen, Christina; Guignard, Jérémy; Løvvik, Ole Martin; Crichton, Wilson A; Margadonna, Serena

    2014-11-17

    The GdFeO3-type perovskite NaFeF3 transforms to CaIrO3-type postperovskite at pressures as low as 9 GPa at room temperature. The details of such a transition were investigated by in situ synchrotron powder diffraction in a multianvil press. Fit of the p-V data showed that the perovskite phase is more compressible than related chemistries with a strongly anisotropic response of the lattice metrics to increasing pressure. The reduction in volume is accommodated by a rapid increase of the octahedral tilting angle, which reaches a critical value of 26° at the transition boundary. The postperovskite form, which is fully recoverable at ambient conditions, shows a regular geometry of the edge-sharing octahedra and its structural properties are comparable to those found in CaIrO3-type MgSiO3 at high pressure and temperature. Theoretical studies using density functional theory at the GGA + U level were also performed and describe a scenario where both perovskite and postperovskite phases can be considered Mott-Hubbard insulators with collinear magnetic G- and C-type antiferromagnetic structures, respectively. Magnetic measurements are in line with the theoretical predictions with both forms showing the typical behavior of canted antiferromagnets. PMID:25351883

  2. Recycling Perovskite Solar Cells To Avoid Lead Waste.

    Binek, Andreas; Petrus, Michiel L; Huber, Niklas; Bristow, Helen; Hu, Yinghong; Bein, Thomas; Docampo, Pablo

    2016-05-25

    Methylammonium lead iodide (MAPbI3) perovskite based solar cells have recently emerged as a serious competitor for large scale and low-cost photovoltaic technologies. However, since these solar cells contain toxic lead, a sustainable procedure for handling the cells after their operational lifetime is required to prevent exposure of the environment to lead and to comply with international electronic waste disposal regulations. Herein, we report a procedure to remove every layer of the solar cells separately, which gives the possibility to selectively isolate the different materials. Besides isolating the toxic lead iodide in high yield, we show that the PbI2 can be reused for the preparation of new solar cells with comparable performance and in this way avoid lead waste. Furthermore, we show that the most expensive part of the solar cell, the conductive glass (FTO), can be reused several times without any reduction in the performance of the devices. With our simple recycling procedure, we address both the risk of contamination and the waste disposal of perovskite based solar cells while further reducing the cost of the system. This brings perovskite solar cells one step closer to their introduction into commercial systems. PMID:27149009

  3. Sensitive, Fast, and Stable Perovskite Photodetectors Exploiting Interface Engineering

    Sutherland, Brandon R.

    2015-08-19

    © 2015 American Chemical Society. Organometallic halide perovskites are a class of solution-processed semiconductors exhibiting remarkable optoelectronic properties. They have seen rapid strides toward enabling efficient third-generation solar cell technologies. Here, we report the first material-tailoring of TiO2/perovskite/spiro-OMeTAD junction-based photodiodes toward applications in photodetection, a field in need of fast, sensitive, low-cost, spectrally tunable materials that offer facile integration across a broad range of substrates. We report photodetection that exhibits 1 μs temporal response, and we showcase stable operation in the detection of over 7 billion transient light pulses through a continuous pulsed-illumination period. The perovskite diode photodetector has a peak responsivity approaching 0.4 A W-1 at 600 nm wavelength, which is superior to red light detection in crystalline silicon photodiodes used in commercial image sensors. Only by developing a composite Al2O3/PCBM front contact interface layer were we able to stabilize device operation in air, reduce dark current, and enhance the responsivity in the low-bias regime to achieve an experimentally measured specific detectivity of 1012 Jones.

  4. Modelling of defects and surfaces in perovskite ferroelectrics

    The results of electronic structure calculations for different terminations of SrTiO3 (100) and (110) perovskite thin films are discussed. These calculations are based on the ab initio Hartree-Fock (HF) method and Density Functional Theory (DFT). Results are compared with previous ab initio plane-wave LDA and classical Shell Model (SM) calculations. Calculated considerable increase of the Ti-O chemical bond covalency nearby the surface is confirmed by experimental data. Our quantum chemical calculations performed by means of the intermediate neglect of differential overlap (INDO) method confirm the existence of self-trapped electrons in KNbO3, KTaO3 and BaTiO3 crystals. The relevant lattice relaxation energies are 0.21 eV, 0.27 eV and 0.24 eV, and the optical absorption energies 0.78 eV, 0.75 eV and 0.69 eV, respectively. We suggest a theoretical interpretation of the so-called green luminescence (2.2-2.3 eV) in ABO3 perovskite crystals as a result of the recombination of electrons and holes forming the Charge-Transfer-Vibronic-Exciton (CTVE). The calculated luminescence energies for SrTiO3, BaTiO3, KNbO3 and KTaO3 perovskite crystals are in a good agreement with the experimentally observed energies. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  5. Tunable Near-Infrared Luminescence in Tin Halide Perovskite Devices.

    Lai, May L; Tay, Timothy Y S; Sadhanala, Aditya; Dutton, Siân E; Li, Guangru; Friend, Richard H; Tan, Zhi-Kuang

    2016-07-21

    Infrared emitters are reasonably rare in solution-processed materials. Recently, research into hybrid organo-lead halide perovskite, originally popular in photovoltaics,1-3 has gained traction in light-emitting diodes (LED) due to their low-cost solution processing and good performance.4-9 The lead-based electroluminescent materials show strong colorful emission in the visible region, but lack emissive variants further in the infrared. The concerns with the toxicity of lead may, additionally, limit their wide-scale applications. Here, we demonstrate tunable near-infrared electroluminescence from a lead-free organo-tin halide perovskite, using an ITO/PEDOT:PSS/CH3NH3Sn(Br1-xIx)3/F8/Ca/Ag device architecture. In our tin iodide (CH3NH3SnI3) LEDs, we achieved a 945 nm near-infrared emission with a radiance of 3.4 W sr(-1) m(-2) and a maximum external quantum efficiency of 0.72%, comparable with earlier lead-based devices. Increasing the bromide content in these tin perovskite devices widens the semiconductor bandgap and leads to shorter wavelength emissions, tunable down to 667 nm. These near-infrared LEDs could find useful applications in a range of optical communication, sensing and medical device applications. PMID:27336412

  6. Control of Perovskite Crystal Growth by Methylammonium Lead Chloride Templating.

    Binek, Andreas; Grill, Irene; Huber, Niklas; Peters, Kristina; Hufnagel, Alexander G; Handloser, Matthias; Docampo, Pablo; Hartschuh, Achim; Bein, Thomas

    2016-04-20

    State-of-the-art solar cells based on methylammonium lead iodide (MAPbI3 ) now reach efficiencies over 20 %. This fast improvement was possible with intensive research in perovskite processing. In particular, chloride-based precursors are known to have a positive influence on the crystallization of the perovskite. Here, we used a combination of in-situ X-ray diffraction and charge-transport measurements to understand the influence of chloride during perovskite crystallization in planar heterojunction solar cells. We show that MAPbCl3 crystallizes directly after the deposition of the starting solution and acts as a template for the formation of MAPbI3 . Additionally, we show that the charge-carrier mobility doubles by extending the time for the template formation. Our results give a deeper understanding of the influence of chloride in the synthesis of MAPbI3 and illustrate the importance of carefully controlling crystallization for reproducible, high-efficiency solar cells. PMID:26928877

  7. Perovskite thin films grown by direct liquid injection MOCVD

    The continuous scaling down of devices dimensions, in silicon technology, imposes to replace silicon dioxide. Among the potential candidates for new capacitors, some perovskite structure materials (such as titanate or zirconate) show interesting characteristics. The first way to develop perovskite films is to use a mixture of two β-diketonates by varying the solution's cationic ratio. However, our previous results on SrZrO3 showed that a wide parametric study had to be carried on. Another way is to design novel heterometallic precursors that contain both cations on the same molecule. The ligands could be chosen so that peculiar evaporation and decomposition temperatures could be obtained. Thus, perovskite films (SrZrO3) were deposited on plane Si(1 0 0) substrates by direct liquid injection MOCVD from two original heterometallic precursors Sr2Zr2(OnPr)8(thd)4(nPrOH)2 and Sr2Zr2(thd)4(OiPr)8. The oxide films were deposited at substrate temperature ranging from 550 to 900 deg. C. At the lowest temperatures (550 and 600 deg. C) the as-deposited films were amorphous. After a postannealing at 700 deg. C for 1 h under N2/O2, the films deposited at 550 deg. C were crystallized in the SrZrO3 orthorhombic phase. Crystallographic and chemical structures were controlled applying grazing X-ray diffraction and infrared spectroscopy measurements. Results are discussed with respect to experimental synthesis conditions

  8. Laser cooling of organic-inorganic lead halide perovskites

    Ha, Son-Tung; Shen, Chao; Zhang, Jun; Xiong, Qihua

    2016-02-01

    Optical irradiation with suitable energy can cool solids, a phenomenon known as optical refrigeration, first proposed in 1929 and experimentally achieved in ytterbium-doped glasses in 1995. Since then, considerable progress has been made in various rare earth element-doped materials, with a recent record of cooling to 91 K directly from ambient temperatures. For practical use and to suit future applications of optical refrigeration, the discovery of materials with facile and scalable synthesis and high cooling power density will be required. Herein we present the realization of a net cooling of 23.0 K in micrometre-thick 3D CH3NH3PbI3 (MAPbI3) and 58.7 K in exfoliated 2D (C6H5C2H4NH3)2PbI4 (PhEPbI4) perovskite crystals directly from room temperature. We found that the perovskite crystals exhibit strong photoluminescence upconversion and near unity external quantum efficiency, properties that are responsible for the realization of net laser cooling. Our findings indicate that solution-processed perovskite thin films may be a highly suitable candidate for constructing integrated optical cooler devices.

  9. Coloring Semitransparent Perovskite Solar Cells via Dielectric Mirrors.

    Ramírez Quiroz, César Omar; Bronnbauer, Carina; Levchuk, Ievgen; Hou, Yi; Brabec, Christoph J; Forberich, Karen

    2016-05-24

    While perovskite-based semitransparent solar cells for window applications show competitive levels of transparency and efficiency compared to organic photovoltaics, the color perception of the perovskite films is highly restricted because band gap engineering results in losses in power conversion efficiencies. To overcome the limitation in visual aesthetics, we combined semitransparent perovskite solar cells with dielectric mirrors. This approach enables one to tailor the device appearance to almost any desired color and simultaneously offers additional light harvesting for the solar cell. In the present work, opto-electrical effects are investigated through quantum efficiency and UV-to-visible spectroscopic measurements. Likewise, a detailed chromaticity analysis, featuring the transmissive and reflective color perception of the device including the mirror, from both sides and in different illumination conditions, is presented and analyzed. Photocurrent density enhancement of up to 21% along with overall device transparency values of up to 31% (4.2% efficiency) is demonstrated for cells showing a colored aesthetic appeal. Finally, a series of simulations emulating the device chromaticity, transparency, and increased photocurrent density as a function of the photoactive layer thickness and the design wavelength of the dielectric mirror are presented. Our simulations and their experimental validation enabled us to establish the design rules that consider the color efficiency/transparency interplay for real applications. PMID:27070738

  10. Persistent photovoltage in methylammonium lead iodide perovskite solar cells

    A. Baumann

    2014-08-01

    Full Text Available We herein perform open circuit voltage decay (OCVD measurements on methylammonium lead iodide (CH3NH3PbI3 perovskite solar cells to increase the understanding of the charge carrier recombination dynamics in this emerging technology. Optically pulsed OCVD measurements are conducted on CH3NH3PbI3 solar cells and compared to results from another type of thin-film photovoltaics, namely, the two reference polymer–fullerene bulk heterojunction solar cell devices based on P3HT:PC60BM and PTB7:PC70BM blends. We observe two very different time domains of the voltage transient in the perovskite solar cell with a first drop on a short time scale that is similar to the decay in the studied organic solar cells. However, 65%–70% of the maximum photovoltage persists on much longer timescales in the perovskite solar cell than in the organic devices. In addition, we find that the recombination dynamics in all time regimes are dependent on the starting illumination intensity, which is also not observed in the organic devices. We then discuss the potential origins of these unique behaviors.

  11. Output Coupling of Perovskite Lasers from Embedded Nanoscale Plasmonic Waveguides.

    Li, Yong Jun; Lv, Yuanchao; Zou, Chang-Ling; Zhang, Wei; Yao, Jiannian; Zhao, Yong Sheng

    2016-02-24

    Nanoscale lasers are ideal light-signal sources for integrated photonic devices. Most of the present lasers made of dielectric materials are restricted to being larger than half the wavelength of the optical field. Plasmon lasers made from metallic nanostructures can help to break the diffraction limit, yet they suffer from low optical pump efficiencies and low quality factors. Integrating dielectric lasers with plasmonic waveguides to construct hybrid material systems may circumvent these problems and combine the advantages of the two components. Here we demonstrate the nanoscale output of dielectric lasers via photon-plasmon coupling in rationally designed perovskite/silver heterostructures. The perovskite crystals offer the gain and high-Q cavity for low-threshold laser generation, while the embedded silver nanowires (AgNWs) help to output the lasing modes efficiently in the form of surface plasmons. The output coupling can be modulated by controlling the resonant modes of the two-dimensional perovskite microcavities. The results would pave an alternative avenue to ultrasmall light sources as well as fundamental studies of light-matter interactions. PMID:26849536

  12. Perovskite phase thin films and method of making

    Boyle, Timothy J.; Rodriguez, Mark A.

    2000-01-01

    The present invention comprises perovskite-phase thin films, of the general formula A.sub.x B.sub.y O.sub.3 on a substrate, wherein A is selected from beryllium, magnesium, calcium, strontium, and barium or a combination thereof; B is selected from niobium and tantalum or a combination thereof; and x and y are mole fractions between approximately 0.8 and 1.2. More particularly, A is strontium or barium or a combination thereof and B is niobium or tantalum or a combination thereof. Also provided is a method of making a perovskite-phase thin film, comprising combining at least one element-A-containing compound, wherein A is selected from beryllium, magnesium, calcium, strontium or barium, with at least one element-B-containing compound, wherein B niobium or tantalum, to form a solution; adding a solvent to said solution to form another solution; spin-coating the solution onto a substrate to form a thin film; and heating the film to form the perovskite-phase thin film.

  13. Iron-based perovskite cathodes for solid oxide fuel cells

    Ralph, James M.; Rossignol, Cecile C.R.; Vaughey, John T.

    2007-01-02

    An A and/or A' site deficient perovskite of general formula of (A.sub.1-xA'.sub.x).sub.1-yFeO.sub.3-.delta. or of general formula A.sub.1-x-yA'.sub.xFeO.sub.3-67, wherein A is La alone or with one or more of the rare earth metals or a rare earth metal other than Ce alone or a combination of rare earth metals and X is in the range of from 0 to about 1; A' is Sr or Ca or mixtures thereof and Y is in the range of from about 0.01 to about 0.3; .delta. represents the amount of compensating oxygen loss. If either A or A' is zero the remaining A or A' is deficient. A fuel cell incorporating the inventive perovskite as a cathode is disclosed as well as an oxygen separation membrane. The inventive perovskite is preferably single phase.

  14. Magnetic domain wall induced ferroelectricity in double perovskites

    Zhou, Hai Yang; Zhao, Hong Jian, E-mail: dielectric-hjzhao@126.com, E-mail: xmchen59@zju.edu.cn; Chen, Xiang Ming, E-mail: dielectric-hjzhao@126.com, E-mail: xmchen59@zju.edu.cn [Laboratory of Dielectric Materials, Department of Materials Science and Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027 (China); Zhang, Wen Qing [Department of Physics, Shanghai University, 99 Shangda Road, Shanghai 200444 (China)

    2015-04-13

    Recently, a magnetically induced ferroelectricity occurring at magnetic domain wall of double perovskite Lu{sub 2}CoMnO{sub 6} has been reported experimentally. However, there exists a conflict whether the electric polarization is along b or c direction. Here, by first-principles calculations, we show that the magnetic domain wall (with ↑↑↓↓ spin configuration) can lead to the ferroelectric displacements of R{sup 3+}, Ni{sup 2+}, Mn{sup 4+}, and O{sup 2−} ions in double perovskites R{sub 2}NiMnO{sub 6} (R = rare earth ion) via exchange striction. The resulted electric polarization is along b direction with the P2{sub 1} symmetry. We further reveal the origin of the ferroelectric displacements as that: (1) on a structural point of view, such displacements make the two out-of-plane Ni-O-Mn bond angles as well as Ni-Mn distance unequal, and (2) on an energy point of view, such displacements weaken the out-of-plane Ni-Mn super-exchange interaction obviously. Finally, our calculations show that such a kind of ferroelectric order is general in ferromagnetic double perovskites.

  15. Parameters influencing the deposition of methylammonium lead halide iodide in hole conductor free perovskite-based solar cells

    Bat-El Cohen; Shany Gamliel; Lioz Etgar

    2014-01-01

    Perovskite is a promising light harvester for use in photovoltaic solar cells. In recent years, the power conversion efficiency of perovskite solar cells has been dramatically increased, making them a competitive source of renewable energy. An important parameter when designing high efficiency perovskite-based solar cells is the perovskite deposition, which must be performed to create complete coverage and optimal film thickness. This paper describes an in-depth study on two-step deposition, ...

  16. Selective Precipitation and Concentrating of Perovskite Crystals from Titanium-Bearing Slag Melt in Supergravity Field

    Gao, Jintao; Zhong, Yiwei; Guo, Zhancheng

    2016-08-01

    Selective precipitation and concentrating of perovskite crystals from titanium-bearing slag melt in the supergravity field was investigated in this study. Since perovskite was the first precipitated phase from the slag melt during the cooling process, and a greater precipitation quantity and larger crystal sizes of perovskite were obtained at 1593 K to 1563 K (1320 °C to 1290 °C), concentrating of perovskite crystals from the slag melt was carried out at this temperature range in the supergravity field, at which the perovskite transforms into solid particles while the other minerals remain in the liquid melt. The layered structures appeared significantly in the sample obtained by supergravity treatment, and all the perovskite crystals moved along the supergravity direction and concentrated as the perovskite-rich phase in the bottom area, whereas the molten slag concentrated in the upper area along the opposite direction, in which it was impossible to find any perovskite crystals. With the gravity coefficient of G = 750, the mass fraction of TiO2 in the perovskite-rich phase was up to 34.65 wt pct, whereas that of the slag phase was decreased to 12.23 wt pct, and the recovery ratio of Ti in the perovskite-rich phase was up to 75.28 pct. On this basis, an amplification experimental centrifugal apparatus was exploited and the continuous experiment with larger scale was further carried out, the results confirming that selective precipitation and concentrating of perovskite crystals from the titanium-bearing slag melt by supergravity was a feasible method.

  17. Thermal conductivity of MgO, MgSiO3 perovskite and post-perovskite in the Earth's deep mantle

    Volker Haigis; Salanne, M; Sandro Jahn

    2012-01-01

    We report lattice thermal conductivities of MgO and MgSiO3 in the perovskite and post-perovskite structures at conditions of the Earth's lower mantle, obtained from equilibrium molecular dynamics simulations. Using an advanced ionic interaction potential, the full conductivity tensor was calculated by means of the Green-Kubo method, and the conductivity of MgSiO3 post-perovskite was found to be significantly anisotropic. The thermal conductivities of all three phases were parameterized as a f...

  18. Upscaling of Perovskite Solar Cells: Fully Ambient Roll Processing of Flexible Perovskite Solar Cells with Printed Back Electrodes

    Schmidt, Thomas Mikael; Larsen-Olsen, Thue Trofod; Carlé, Jon Eggert;

    2015-01-01

    morphology falls in the range of 5–45 min depending on the perovskite precursor, where the former timescale is compatible with mass production and the latter is best suited for laboratory work. A signifi cant loss in solar cell performance of around 50% is found when progressing to using a fully scalable...... device type and active area realized using slot-die coating on fl exible ITO-polyethyleneterphthalate (PET) with a printed back electrode gives a PCE of 4.9%....

  19. Photophysics of Hybrid Lead Halide Perovskites: The Role of Microstructure.

    Srimath Kandada, Ajay Ram; Petrozza, Annamaria

    2016-03-15

    Since the first reports on high efficiency, solution processed solar cells based on hybrid lead halide perovskites, there has been an explosion of activities on these materials. Researchers with interests spanning the full range from conventional inorganic to emerging organic and hybrid optoelectronic technologies have been contributing to the prolific research output. This has led to solar cell power conversion efficiencies now exceeding 20% and the demonstration of proofs of concept for electroluminescent and lasing devices. Hybrid perovskites can be self-assembled by a simple chemical deposition of the constituent units, with the possibility of integrating the useful properties of organic and inorganic compounds at the molecular scale within a single crystalline material, thus enabling a fine-tuning of the electronic properties. Tellingly, the fundamental properties of these materials may make us think of a new, solution processable, GaAs-like semiconductor. While this can be true to a first approximation, hybrid perovskites are intrinsically complex materials, where the presence of various types of interactions and structural disorder may strongly affect their properties. In particular, a clear understanding and control of the relative interactions between the organic and inorganic moieties is of paramount importance to properly disentangle their innate physics. In this Account we review our recent studies which aim to clarify the relationship between structural and electronic properties from a molecular to mesoscopic level. First we identify the markers for local disorder at the molecular level by using Raman spectroscopy as a probe. Then, we exploit such a tool to explore the role of microstructure on the absorption and luminescence properties of the semiconductor. Finally we address the controversy surrounding electron-hole interactions and excitonic effects. We show that in hybrid lead-halide perovskites dielectric screening also depends on the local

  20. Artificial Synapses: Organometal Halide Perovskite Artificial Synapses (Adv. Mater. 28/2016).

    Xu, Wentao; Cho, Himchan; Kim, Young-Hoon; Kim, Young-Tae; Wolf, Christoph; Park, Chan-Gyung; Lee, Tae-Woo

    2016-07-01

    A synapse-emulating electronic device based on organometal halide perovskite thin films is described by T.-W. Lee and co-workers on page 5916. The device successfully emulates important characteristics of a biological synapse. This work extends the application of organometal halide perovskites to bioinspired electronic devices, and contributes to the development of neuromorphic electronics. PMID:27442971

  1. Formability of ABX3 (X = F, Cl, Br, I) halide perovskites.

    Li, Chonghea; Lu, Xionggang; Ding, Weizhong; Feng, Liming; Gao, Yonghui; Guo, Ziming

    2008-12-01

    In this study a total of 186 complex halide systems were collected; the formabilities of ABX3 (X = F, Cl, Br and I) halide perovskites were investigated using the empirical structure map, which was constructed by Goldschmidt's tolerance factor and the octahedral factor. A model for halide perovskite formability was built up. In this model obtained, for all 186 complex halides systems, only one system (CsF-MnF2) without perovskite structure and six systems (RbF-PbF2, CsF-BeF2, KCl-FeCl2, TlI-MnI2, RbI-SnI2, TlI-PbI2) with perovskite structure were wrongly classified, so its predicting accuracy reaches 96%. It is also indicated that both the tolerance factor and the octahedral factor are a necessary but not sufficient condition for ABX3 halide perovskite formability, and a lowest limit of the octahedral factor exists for halide perovskite formation. This result is consistent with our previous report for ABO3 oxide perovskite, and may be helpful to design novel halide materials with the perovskite structure. PMID:19029699

  2. Influence of the orientation of methylammonium lead iodide perovskite crystals on solar cell performance

    Pablo Docampo; Hanusch, Fabian C.; Nadja Giesbrecht; Philipp Angloher; Alesja Ivanova; Thomas Bein

    2014-01-01

    Perovskite solar cells are emerging as serious candidates for thin film photovoltaics with power conversion efficiencies already exceeding 16%. Devices based on a planar heterojunction architecture, where the MAPbI3 perovskite film is simply sandwiched between two charge selective extraction contacts, can be processed at low temperatures (

  3. Robust and Air-Stable Sandwiched Organo-Lead Halide Perovskites for Photodetector Applications

    Mohammed, Omar F.

    2016-02-25

    We report the simplest possible method to date for fabricating robust, air-stable, sandwiched perovskite photodetectors. Our proposed sandwiched structure is devoid of electron or hole transporting layers and also the expensive electrodes. These simpler architectures may have application in the perovskite-only class of solar cells scaling up towards commercialization.

  4. Degradation of Methylammonium Lead Iodide Perovskite Structures through Light and Electron Beam Driven Ion Migration.

    Yuan, Haifeng; Debroye, Elke; Janssen, Kris; Naiki, Hiroyuki; Steuwe, Christian; Lu, Gang; Moris, Michèle; Orgiu, Emanuele; Uji-I, Hiroshi; De Schryver, Frans; Samorì, Paolo; Hofkens, Johan; Roeffaers, Maarten

    2016-02-01

    Organometal halide perovskites show promising features for cost-effective application in photovoltaics. The material instability remains a major obstacle to broad application because of the poorly understood degradation pathways. Here, we apply simultaneous luminescence and electron microscopy on perovskites for the first time, allowing us to monitor in situ morphology evolution and optical properties upon perovskite degradation. Interestingly, morphology, photoluminescence (PL), and cathodoluminescence of perovskite samples evolve differently upon degradation driven by electron beam (e-beam) or by light. A transversal electric current generated by a scanning electron beam leads to dramatic changes in PL and tunes the energy band gaps continuously alongside film thinning. In contrast, light-induced degradation results in material decomposition to scattered particles and shows little PL spectral shifts. The differences in degradation can be ascribed to different electric currents that drive ion migration. Moreover, solution-processed perovskite cuboids show heterogeneity in stability which is likely related to crystallinity and morphology. Our results reveal the essential role of ion migration in perovskite degradation and provide potential avenues to rationally enhance the stability of perovskite materials by reducing ion migration while improving morphology and crystallinity. It is worth noting that even moderate e-beam currents (86 pA) and acceleration voltages (10 kV) readily induce significant perovskite degradation and alter their optical properties. Therefore, attention has to be paid while characterizing such materials using scanning electron microscopy or transmission electron microscopy techniques. PMID:26804213

  5. Fiber-Shaped Perovskite Solar Cells with High Power Conversion Efficiency.

    Qiu, Longbin; He, Sisi; Yang, Jiahua; Deng, Jue; Peng, Huisheng

    2016-05-01

    A perovskite solar cell fiber is created with a high power conversion efficiency of 7.1% through a controllable deposition method. A combination of aligned TiO2 nanotubes, a uniform perovskite layer, and transparent aligned carbon nanotube sheet contributes to the high photovoltaic performance. It is flexible and stable, and can be woven into smart clothes for wearable applications. PMID:27002590

  6. Vacancy ordering and superstructure formation in dry and hydrated strontium tantalate perovskites: A TEM perspective

    Ashok, Anuradha M.; Haavik, Camilla; Norby, Poul; Norby, Truls; Olsen, Arne

    2014-01-01

    corresponding unit cells of all the perovskites based on the ordering of oxygen vacancies is deduced. Crystal unit cells based on the observations are proposed with ideal atomic coordinates. Finally an attempt is made to explain the water uptake behaviour of these perovskites based on the proposed crystal...

  7. Polarized emission from CsPbX3 perovskite quantum dots

    Wang, Dan; Wu, Dan; Dong, Di; Chen, Wei; Hao, Junjie; Qin, Jing; Xu, Bing; Wang, Kai; Sun, Xiaowei

    2016-06-01

    Compared to organic/inorganic hybrid perovskites, full inorganic perovskite quantum dots (QDs) exhibit higher stability. In this study, full inorganic CsPbX3 (X = Br, I and mixed halide systems Br/I) perovskite QDs have been synthesized and interestingly, these QDs showed highly polarized photoluminescence which is systematically studied for the first time. Furthermore, the polarization of CsPbI3 was as high as 0.36 in hexane and 0.40 as a film. The CsPbX3 perovskite QDs with high polarization properties indicate that they possess great potential for application in new generation displays with wide colour gamut and low power consumption.Compared to organic/inorganic hybrid perovskites, full inorganic perovskite quantum dots (QDs) exhibit higher stability. In this study, full inorganic CsPbX3 (X = Br, I and mixed halide systems Br/I) perovskite QDs have been synthesized and interestingly, these QDs showed highly polarized photoluminescence which is systematically studied for the first time. Furthermore, the polarization of CsPbI3 was as high as 0.36 in hexane and 0.40 as a film. The CsPbX3 perovskite QDs with high polarization properties indicate that they possess great potential for application in new generation displays with wide colour gamut and low power consumption. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01915c

  8. Photoinduced Coherent Spin Fluctuation in Primary Dynamics of Insulator to Metal Transition in Perovskite Cobalt Oxide

    Arima T.

    2013-03-01

    Full Text Available Coherent spin fluctuation was detected in the photoinduced Mott insulator-metal transition in perovskite cobalt oxide by using 3 optical-cycle infrared pulse. Such coherent spin fluctuation is driven by the perovskite distortion changing orbital gap.

  9. Fabrication of organic-inorganic perovskite thin films for planar solar cells via pulsed laser deposition

    Liang, Yangang; Zhang, Xiaohang; Gong, Yunhui; Shin, Jongmoon; Wachsman, Eric D.; Takeuchi, Ichiro, E-mail: takeuchi@umd.edu [Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20740 (United States); Yao, Yangyi; Hsu, Wei-Lun; Dagenais, Mario [Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20740 (United States)

    2016-01-15

    We report on fabrication of organic-inorganic perovskite thin films using a hybrid method consisting of pulsed laser deposition (PLD) of lead iodide and spin-coating of methylammonium iodide. Smooth and highly crystalline CH{sub 3}NH{sub 3}PbI{sub 3} thin films have been fabricated on silicon and glass coated substrates with fluorine doped tin oxide using this PLD-based hybrid method. Planar perovskite solar cells with an inverted structure have been successfully fabricated using the perovskite films. Because of its versatility, the PLD-based hybrid fabrication method not only provides an easy and precise control of the thickness of the perovskite thin films, but also offers a straightforward platform for studying the potential feasibility in using other metal halides and organic salts for formation of the organic-inorganic perovskite structure.

  10. Fabrication of organic-inorganic perovskite thin films for planar solar cells via pulsed laser deposition

    We report on fabrication of organic-inorganic perovskite thin films using a hybrid method consisting of pulsed laser deposition (PLD) of lead iodide and spin-coating of methylammonium iodide. Smooth and highly crystalline CH3NH3PbI3 thin films have been fabricated on silicon and glass coated substrates with fluorine doped tin oxide using this PLD-based hybrid method. Planar perovskite solar cells with an inverted structure have been successfully fabricated using the perovskite films. Because of its versatility, the PLD-based hybrid fabrication method not only provides an easy and precise control of the thickness of the perovskite thin films, but also offers a straightforward platform for studying the potential feasibility in using other metal halides and organic salts for formation of the organic-inorganic perovskite structure

  11. Approaching Bulk Carrier Dynamics in Organo-Halide Perovskite Nanocrystalline Films by Surface Passivation.

    Stewart, Robert J; Grieco, Christopher; Larsen, Alec V; Maier, Joshua J; Asbury, John B

    2016-04-01

    The electronic properties of organo-halide perovskite absorbers described in the literature have been closely associated with their morphologies and processing conditions. However, the underlying origins of this dependence remain unclear. A combination of inorganic synthesis, surface chemistry, and time-resolved photoluminescence spectroscopy was used to show that charge recombination centers in organo-halide perovskites are almost exclusively localized on the surfaces of the crystals rather than in the bulk. Passivation of these surface defects causes average charge carrier lifetimes in nanocrystalline thin films to approach the bulk limit reported for single-crystal organo-halide perovskites. These findings indicate that the charge carrier lifetimes of perovskites are correlated with their thin-film processing conditions and morphologies through the influence these have on the surface chemistry of the nanocrystals. Therefore, surface passivation may provide a means to decouple the electronic properties of organo-halide perovskites from their thin-film processing conditions and corresponding morphologies. PMID:26966792

  12. Integrated Photoelectrolysis of Water Implemented On Organic Metal Halide Perovskite Photoelectrode.

    Hoang, Minh Tam; Pham, Ngoc Duy; Han, Ji Hun; Gardner, James M; Oh, Ilwhan

    2016-05-18

    Herein we report on integrated photoelectrolysis of water employing organic metal halide (OMH) perovskite material. Generic OMH perovskite material and device architecture are highly susceptible to degradation by moisture and water. We found that decomposition of perovskite devices proceeds by water ingress through pinholes in upper layers and is strongly affected by applied bias/light and electrolyte pH. It was also found that a pinhole-free hole transport layer (HTL) could significantly enhance the stability of the perovskite photoelectrode, thereby extending the photoelectrode lifetime to several tens of minutes, which is an unprecedented record-long operation. Furthermore, a carbon nanotube (CNT)/polymer composite layer was developed that can effectively protect the underlying perovskite layer from electrolyte molecules. PMID:27120406

  13. Toward Revealing the Critical Role of Perovskite Coverage in Highly Efficient Electron-Transport Layer-Free Perovskite Solar Cells: An Energy Band and Equivalent Circuit Model Perspective.

    Huang, Like; Xu, Jie; Sun, Xiaoxiang; Du, Yangyang; Cai, Hongkun; Ni, Jian; Li, Juan; Hu, Ziyang; Zhang, Jianjun

    2016-04-20

    Currently, most efficient perovskite solar cells (PVKSCs) with a p-i-n structure require simultaneously electron transport layers (ETLs) and hole transport layers (HTLs) to help collecting photogenerated electrons and holes for obtaining high performance. ETL free planar PVKSC is a relatively new and simple structured solar cell that gets rid of the complex and high temperature required ETL (such as compact and mesoporous TiO2). Here, we demonstrate the critical role of high coverage of perovskite in efficient ETL free PVKSCs from an energy band and equivalent circuit model perspective. From an electrical point of view, we confirmed that the low coverage of perovskite does cause localized short circuit of the device. With coverage optimization, a planar p-i-n(++) device with a power conversion efficiency of over 11% was achieved, implying that the ETL layer may not be necessary for an efficient device as long as the perovskite coverage is approaching 100%. PMID:27020395

  14. Equations of state and stability of MgSiO$_3$ perovskite and post-perovskite phases from quantum Monte Carlo simulations

    Y. Lin; Cohen, R E; Stackhouse, S.; Driver, K. P.; Militzer, B.; Shulenburger, L.; J. Kim

    2014-01-01

    We have performed quantum Monte Carlo (QMC) simulations and density functional theory calculations to study the equations of state of MgSiO3 perovskite (Pv, bridgmanite) and post-perovskite (PPv) up to the pressure and temperature conditions of the base of Earth's lower mantle. The ground-state energies were derived using QMC simulations and the temperature-dependent Helmholtz free energies were calculated within the quasiharmonic approximation and density functional perturbation theory. The ...

  15. Antiferroelectric Nature of CH3NH3PbI3‑xClx Perovskite and Its Implication for Charge Separation in Perovskite Solar Cells

    Sewvandi, Galhenage A.; Kodera, Kei; Ma, Hao; Nakanishi, Shunsuke; Feng, Qi

    2016-07-01

    Perovskite solar cells (PSCs) have been attracted scientific interest due to high performance. Some researchers have suggested anomalous behavior of PSCs to the polarizations due to the ion migration or ferroelectric behavior. Experimental results and theoretical calculations have suggested the possibility of ferroelectricity in organic-inorganic perovskite. However, still no studies have been concretely discarded the ferroelectric nature of perovskite absorbers in PSCs. Hysteresis of P-E (polarization-electric field) loops is an important evidence to confirm the ferroelectricity. In this study, P-E loop measurements, in-depth structural study, analyses of dielectric behavior and the phase transitions of CH3NH3PbI3‑xClx perovskite were carried out and investigated. The results suggest that CH3NH3PbI3‑xClx perovskite is in an antiferroelectric phase at room temperature. The antiferroelectric phase can be switched to ferroelectric phase by the poling treatment and exhibits ferroelectric-like hysteresis P-E loops and dielectric behavior around room temperature; namely, the perovskite can generate a ferroelectric polarization under PSCs operating conditions. Furthermore, we also discuss the implications of ferroelectric polarization on PSCs charge separation.

  16. Antiferroelectric Nature of CH3NH3PbI3-xClx Perovskite and Its Implication for Charge Separation in Perovskite Solar Cells.

    Sewvandi, Galhenage A; Kodera, Kei; Ma, Hao; Nakanishi, Shunsuke; Feng, Qi

    2016-01-01

    Perovskite solar cells (PSCs) have been attracted scientific interest due to high performance. Some researchers have suggested anomalous behavior of PSCs to the polarizations due to the ion migration or ferroelectric behavior. Experimental results and theoretical calculations have suggested the possibility of ferroelectricity in organic-inorganic perovskite. However, still no studies have been concretely discarded the ferroelectric nature of perovskite absorbers in PSCs. Hysteresis of P-E (polarization-electric field) loops is an important evidence to confirm the ferroelectricity. In this study, P-E loop measurements, in-depth structural study, analyses of dielectric behavior and the phase transitions of CH3NH3PbI3-xClx perovskite were carried out and investigated. The results suggest that CH3NH3PbI3-xClx perovskite is in an antiferroelectric phase at room temperature. The antiferroelectric phase can be switched to ferroelectric phase by the poling treatment and exhibits ferroelectric-like hysteresis P-E loops and dielectric behavior around room temperature; namely, the perovskite can generate a ferroelectric polarization under PSCs operating conditions. Furthermore, we also discuss the implications of ferroelectric polarization on PSCs charge separation. PMID:27468802

  17. Lattice constant prediction of defective rare earth titanate perovskites

    Engineering defective structures in an attempt to modify properties is an established technique in materials chemistry, yet, no models exist which can predict the structure of perovskite compounds containing extrinsic point defects such as vacancies. An empirically derived predictive model, based solely on chemical composition and published ionic radii has been developed. Effective vacancy sizes were derived both empirically from an existing model for pseudocubic lattice-constants, as well as experimentally, from average bond lengths calculated from neutron diffraction data. Compounds of lanthanum-doped barium titanate and strontium-doped magnesium titanate were synthesized with vacancies engineered on the A and B sites. Effective vacancy sizes were then used in empirical models to predict changes in lattice constants. Experimentally refined bond lengths used in the derivation of an effective vacancy size seemed to overestimate the effect of the point defects. Conversely, using calculated vacancy sizes, derived from a previously reported predictive model, showed significant improvements in the prediction of the pseudocubic perovskite lattice. - Graphical abstract: Atomistic model of Sr0.3Nd0.7Mg0.35Ti0.65O3 and Rietveld refinement of neutron diffraction data. - Highlights: • Defective perovskites were synthesized using the organic steric entrapment method. • Oxygen tilt systems were solved through X-ray, electron, and neutron diffraction. • An effective vacancy size for the cations was calculated from experimental bond lengths. • Discrepancies between Shannon radii and experimental measurements are explored. • An empirical model for predicting apc, with an absolute error of 0.20%, was developed

  18. Competing interactions in ferromagnetic/antiferromagnetic perovskite superlattices

    Takamura, Y.; Biegalski, M.B.; Christen, H.M.

    2009-10-22

    Soft x-ray magnetic dichroism, magnetization, and magnetotransport measurements demonstrate that the competition between different magnetic interactions (exchange coupling, electronic reconstruction, and long-range interactions) in La{sub 0.7}Sr{sub 0.3}FeO{sub 3}(LSFO)/La{sub 0.7}Sr{sub 0.3}MnO{sub 3}(LSMO) perovskite oxide superlattices leads to unexpected functional properties. The antiferromagnetic order parameter in LSFO and ferromagnetic order parameter in LSMO show a dissimilar dependence on sublayer thickness and temperature, illustrating the high degree of tunability in these artificially layered materials.

  19. Crystal chemistry of the perovskite based superconducting oxides

    The crystal chemistry of K2NiF4 and Ba2YCu3O7 type compounds is discussed. The composition dependence of the lattice parameters for the Ba2-xLaxYCu3O7+δ solid solution and of the oxygen stoichiometry in Ba2-xLaxYCu3O7+δ annealed in O2 at 500 C, as well as a tentative partial phase equilibria diagram for ABO3-x perovskites in the (Ba, La, Y) CuO3-x chemical system are given. 19 refs, 4 figs

  20. Chemistry of bismuth and lead based superconducting perovskites

    At the present time, there are three known members of the Bi and Pb based family of perovskite superconductors, Ba(Pb,Bi)O3, (Ba,K)BiO3, and Ba(Pb,Sb)O3. This paper describes the crystal chemistry of these materials and also of the nonsuperconducting end members BaPbO3 and BaBiO3. In particular, it is a basic introduction to the chemical characteristics which make them an intriguing family of materials

  1. Simulation of perovskite solar cells with inorganic hole transporting materials

    Wang, Yan; Xia, Zhonggao; Liu, Yiming;

    2015-01-01

    improvement in power conversion efficiency (PCE). Here, we investigated the effect of band offset between inorganic HTM/absorber layers. The solar cell simulation program adopted in this work is named wxAMPS, an updated version of the AMPS tool (Analysis of Microelectronic and Photonic Structure).......Device modeling organolead halide perovskite solar cells with planar architecture based on inorganic hole transporting materials (HTMs) were performed. A thorough understanding of the role of the inorganic HTMs and the effect of band offset between HTM/absorber layers is indispensable for further...

  2. Heterogeneous catalysis of mixed oxides perovskite and heteropoly catalysts

    Misono, M

    2014-01-01

    Mixed oxides are the most widely used catalyst materials for industrial catalytic processes. The principal objective of this book is to describe systematically the mixed oxide catalysts, from their fundamentals through their practical applications.  After describing concisely general items concerning mixed oxide and mixed oxide catalysts, two important mixed oxide catalyst materials, namely, heteropolyacids and perovskites, are taken as typical examples and discussed in detail. These two materials have several advantages: 1. They are, respectively, typical examples of salts of oxoacids an

  3. Growing perovskite into polymers for easy-processable optoelectronic devices

    Sofia Masi; Silvia Colella; Andrea Listorti; Vittoria Roiati; Andrea Liscio; Vincenzo Palermo; Aurora Rizzo; Giuseppe Gigli

    2015-01-01

    Here we conceive an innovative nanocomposite to endow hybrid perovskites with the easy processability of polymers, providing a tool to control film quality and material crystallinity. We verify that the employed semiconducting polymer, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), controls the self-assembly of CH3NH3PbI3 (MAPbI3) crystalline domains and favors the deposition of a very smooth and homogenous layer in one straightforward step. This idea offers a new paradi...

  4. What Is Moving in Hybrid Halide Perovskite Solar Cells?

    2016-01-01

    Conspectus Organic–inorganic semiconductors, which adopt the perovskite crystal structure, have perturbed the landscape of contemporary photovoltaics research. High-efficiency solar cells can be produced with solution-processed active layers. The materials are earth abundant, and the simple processing required suggests that high-throughput and low-cost manufacture at scale should be possible. While these materials bear considerable similarity to traditional inorganic semiconductors, there are notable differences in their optoelectronic behavior. A key distinction of these materials is that they are physically soft, leading to considerable thermally activated motion. In this Account, we discuss the internal motion of methylammonium lead iodide (CH3NH3PbI3) and formamidinium lead iodide ([CH(NH2)2]PbI3), covering: (i) molecular rotation-libration in the cuboctahedral cavity; (ii) drift and diffusion of large electron and hole polarons; (iii) transport of charged ionic defects. These processes give rise to a range of properties that are unconventional for photovoltaic materials, including frequency-dependent permittivity, low electron–hole recombination rates, and current–voltage hysteresis. Multiscale simulations, drawing from electronic structure, ab initio molecular dynamic and Monte Carlo computational techniques, have been combined with neutron diffraction measurements, quasi-elastic neutron scattering, and ultrafast vibrational spectroscopy to qualify the nature and time scales of the motions. Electron and hole motion occurs on a femtosecond time scale. Molecular libration is a sub-picosecond process. Molecular rotations occur with a time constant of several picoseconds depending on the cation. Recent experimental evidence and theoretical models for simultaneous electron and ion transport in these materials has been presented, suggesting they are mixed-mode conductors with similarities to fast-ion conducting metal oxide perovskites developed for battery

  5. Persistent photovoltage in methylammonium lead iodide perovskite solar cells

    Baumann, A.; Tvingstedt, K.; Heiber, M. C.; Väth, S.; C. Momblona; H. J. Bolink; Dyakonov, V.

    2014-01-01

    We herein perform open circuit voltage decay (OCVD) measurements on methylammonium lead iodide (CH3NH3PbI3) perovskite solar cells to increase the understanding of the charge carrier recombination dynamics in this emerging technology. Optically pulsed OCVD measurements are conducted on CH3NH3PbI3 solar cells and compared to results from another type of thin-film photovoltaics, namely, the two reference polymer–fullerene bulk heterojunction solar cell devices based on P3HT:PC60BM and PTB7:PC70...

  6. Modeling mechanisms of hysteresis in perovskite solar cells

    Zhou, Yecheng; Huang, Fuzhi; Cheng, Yi-Bing; Gray-Weale, Angus

    2016-01-01

    Previously, we proposed that the polarization and capacitive charge inCH3NH3PbI3 screens the external electric field that hinders charge transport. We argue here that this screening effect is in significant part responsible for the power conversion characteristics and hysteresis in CH3NH3PbI3 photovoltaic cells. In this paper, we implement capacitive charge and polarization charge into the numerical model that we have developed for perovskite solar cells. Fields induced by these two charges s...

  7. Magnetic coupling at perovskite and rock-salt structured interfaces

    We study magnetic coupling between hole-doped manganite layers separated by either a perovskite or a rock-salt barrier of variable thickness. Both the type and the quality of the interface have a strong impact on the minimum critical barrier thickness where the manganite layers become magnetically decoupled. A rock-salt barrier layer only 1 unit cell (0.5 nm) thick remains insulating and is able to magnetically de-couple the electrode layers. The technique can therefore be used for developing high-performance planar oxide electronic devices such as magnetic tunnel junctions and quantum well structures that depend on magnetically and electronically sharp heterointerfaces

  8. Perovskite solid electrolytes: Structure, transport properties and fuel cell applications

    Bonanos, N.; Knight, K.S.; Ellis, B.

    1995-01-01

    Doped barium cerate perovskites, first investigated by Iwahara and co-workers, have ionic conductivities of the order of 20 mS/cm at 800 degrees C making them attractive as fuel cell electrolytes for this temperature region. They have been used to construct laboratory scale fuel cells, which, in...... addition to performance data, have provided an unexpected insight into the transport processes operating in these materials. In the temperature range of 600-1000 degrees C, the dominant transport process varies from protonic to oxide-ion dominated. This transition has been confirmed by measurement of water...

  9. Oxygen evolution studies on perovskite films in alkaline media

    Hermann, V.; Comninellis, Ch. [Swiss Federal Inst. of Technology, Lausanne (Switzerland); Mueller, S. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    Thin films of La{sub 0.6}Ca{sub 0.4}CoO{sub 3} perovskite were deposited on nickel plates by thermal decomposition of the metal nitrates. The electrochemical activity of the films for oxygen evolution in KOH solutions (0.1-1 M) was investigated. The reaction order with respect to OH{sup -} ion was found to be around 0.7. The results correlate fairly well with a mechanism in which breaking of the intermediate metal-peroxide bond at the Co ion is the rate-determining step. (author) 4 figs., 4 refs.

  10. Defect luminescence of ordered perovskites A2BWO6

    Bode, J.H.G.; Oosterhout, A.B. van

    1975-01-01

    This paper describes luminescence spectra of ordered perovskites of the type A2BWO6. The compounds A2MgWO6 show two different emission bands. From the Raman spectra of Ba2MgWO6 and Ba2CaWO6 and from luminescence experiments on Ba2Na0.8W1.2O6 and Ba2Ca0.95Na0.04W1.01 it is concluded that there is a s

  11. Optical Properties of Photovoltaic Organic-Inorganic Lead Halide Perovskites.

    Green, Martin A; Jiang, Yajie; Soufiani, Arman Mahboubi; Ho-Baillie, Anita

    2015-12-01

    Over the last several years, organic-inorganic lead halide perovskites have rapidly emerged as a new photovoltaic contender. Although energy conversion efficiency above 20% has now been certified, improved understanding of the material properties contributing to these high performance levels may allow the progression to even higher efficiency, stable cells. The optical properties of these new materials are important not only to device design but also because of the insight they provide into less directly accessible properties, including energy-band structures, binding energies, and likely impact of excitons, as well as into absorption and inverse radiative recombination processes. PMID:26560862

  12. Magnetic coupling at perovskite and rock-salt structured interfaces

    Matvejeff, M., E-mail: mikko.matvejeff@picosun.com [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, 277-8581 Chiba (Japan); Department of Chemistry, Aalto University, Kemistintie 1, 02150 Espoo (Finland); Ahvenniemi, E. [Department of Chemistry, Aalto University, Kemistintie 1, 02150 Espoo (Finland); Takahashi, R.; Lippmaa, M. [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, 277-8581 Chiba (Japan)

    2015-10-05

    We study magnetic coupling between hole-doped manganite layers separated by either a perovskite or a rock-salt barrier of variable thickness. Both the type and the quality of the interface have a strong impact on the minimum critical barrier thickness where the manganite layers become magnetically decoupled. A rock-salt barrier layer only 1 unit cell (0.5 nm) thick remains insulating and is able to magnetically de-couple the electrode layers. The technique can therefore be used for developing high-performance planar oxide electronic devices such as magnetic tunnel junctions and quantum well structures that depend on magnetically and electronically sharp heterointerfaces.

  13. Growth Model for Pulsed-Laser Deposited Perovskite Oxide Films

    WANG Xu; FEI Yi-Yan; ZHU Xiang-Dong; Lu Hui-Bin; YANG Guo-Zhen

    2008-01-01

    We present a multi-level growth model that yields some of the key features of perovskite oxide film growth as observed in the reflection high energy electron diffraction(RHEED)and ellipsometry studies.The model describes the effect of deposition,temperature,intra-layer transport,interlayer transport and Ostwald ripening on the morphology of a growth surface in terms of the distribution of terraces and step edges during and after deposition.The numerical results of the model coincide well with the experimental observation.

  14. Organic-inorganic hybrid lead halide perovskites for optoelectronic and electronic applications.

    Zhao, Yixin; Zhu, Kai

    2016-02-01

    Organic and inorganic hybrid perovskites (e.g., CH(3)NH(3)PbI(3)), with advantages of facile processing, tunable bandgaps, and superior charge-transfer properties, have emerged as a new class of revolutionary optoelectronic semiconductors promising for various applications. Perovskite solar cells constructed with a variety of configurations have demonstrated unprecedented progress in efficiency, reaching about 20% from multiple groups after only several years of active research. A key to this success is the development of various solution-synthesis and film-deposition techniques for controlling the morphology and composition of hybrid perovskites. The rapid progress in material synthesis and device fabrication has also promoted the development of other optoelectronic applications including light-emitting diodes, photodetectors, and transistors. Both experimental and theoretical investigations on organic-inorganic hybrid perovskites have enabled some critical fundamental understandings of this material system. Recent studies have also demonstrated progress in addressing the potential stability issue, which has been identified as a main challenge for future research on halide perovskites. Here, we review recent progress on hybrid perovskites including basic chemical and crystal structures, chemical synthesis of bulk/nanocrystals and thin films with their chemical and physical properties, device configurations, operation principles for various optoelectronic applications (with a focus on solar cells), and photophysics of charge-carrier dynamics. We also discuss the importance of further understanding of the fundamental properties of hybrid perovskites, especially those related to chemical and structural stabilities. PMID:26645733

  15. Additive to regulate the perovskite crystal film growth in planar heterojunction solar cells

    Song, Xin; Sun, Po; Chen, Zhi-Kuan, E-mail: wlma@suda.edu.cn, E-mail: iamzkchen@njtech.edu.cn [Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), National Jiangsu Synergistic Innovation Center for Advanced Materials, Nanjing Tech University, 30 South Puzhu Road, Nanjing 211816 (China); Wang, Weiwei; Ma, Wanli, E-mail: wlma@suda.edu.cn, E-mail: iamzkchen@njtech.edu.cn [Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM) and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, 199 Ren' ai Road, Suzhou 215123 (China)

    2015-01-19

    We reported a planar heterojunction perovskite solar cell fabricated from MAPbI{sub 3−x}Cl{sub x} perovskite precursor solution containing 1-chloronaphthalene (CN) additive. The MAPbI{sub 3−x}Cl{sub x} perovskite films have been characterized by UV-vis, SEM, XRD, and steady-state photoluminescence (PL). UV-vis absorption spectra measurement shows that the absorbance of the film with CN additive is significantly higher than the pristine film and the absorption peak is red shift by 30 nm, indicating the perovskite film with additive possessing better crystal structures. In-situ XRD study of the perovskite films with additive demonstrated intense diffraction peaks from MAPbI{sub 3−x}Cl{sub x} perovskite crystal planes of (110), (220), and (330). SEM images of the films with additive indicated the films were more smooth and homogenous with fewer pin-holes and voids and better surface coverage than the pristine films. These results implied that the additive CN is beneficial to regulate the crystallization transformation kinetics of perovskite to form high quality crystal films. The steady-state PL measurement suggested that the films with additive contained less charge traps and defects. The planar heterojunction perovskite solar cells fabricated from perovskite precursor solution containing CN additive demonstrated 30% enhancement in performance compared to the devices with pristine films. The improvement in device efficiency is mainly attributed to the good crystal structures, more homogenous film morphology, and also fewer trap centers and defects in the films with the additive.

  16. The electronic structure of metal oxide/organo metal halide perovskite junctions in perovskite based solar cells

    Alex Dymshits; Alex Henning; Gideon Segev; Yossi Rosenwaks; Lioz Etgar

    2015-01-01

    Cross-sections of a hole-conductor-free CH3NH3PbI3 perovskite solar cell were characterized with Kelvin probe force microscopy. A depletion region width of about 45 nm was determined from the measured potential profiles at the interface between CH3NH3PbI3 and nanocrystalline TiO2, whereas a negligible depletion was measured at the CH3NH3PbI3/Al2O3 interface. A complete solar cell can be realized with the CH3NH3PbI3 that functions both as light harvester and hole conductor in combination with ...

  17. Solvent and Intermediate Phase as Boosters for the Perovskite Transformation and Solar Cell Performance

    Jinhyun Kim; Taehyun Hwang; Sangheon Lee; Byungho Lee; Jaewon Kim; Gil Su Jang; Seunghoon Nam; Byungwoo Park

    2016-01-01

    High power conversion efficiency and device stabilization are two major challenges for CH3NH3PbI3 (MAPbI3) perovskite solar cells to be commercialized. Herein, we demonstrate a diffusion-engineered perovskite synthesis method using MAI/ethanol dipping, and compared it to the conventional synthesis method from MAI/iso-propanol. Diffusion of MAI/C2H5OH into the PbCl2 film was observed to be more favorable than that of MAI/C3H7OH. Facile perovskite conversion from ethanol and highly-crystalline ...

  18. The Isothermal Equation of State of CaPtO Post-perovskite to 40 GPa

    Lindsay-Scott, Alex; Wood, Ian G.; Dobson, David P; Vočadlo, Lidunka; Brodholt, John P.; Crichton, Wilson; Hanfland, Michael; Taniguchi, Takashi

    2010-01-01

    Abstract ABX3 post-perovskite phases that are stable (or strongly metastable) at room-pressure are of importance as analogues of post-perovskite MgSiO3, a deep-Earth phase stable only at very high pressure. Commonly, CaIrO3 has been used for this purpose, but it has been suggested that CaPtO3 might provide a better analogue. We have measured the isothermal incompressibility, at ambient temperature, of orthorhombic post-perovskite structured CaPtO3 to 40GPa by X-ray powder diffracti...

  19. Efficient luminescent solar cells based on tailored mixed-cation perovskites

    Bi, Dongqin; Tress, Wolfgang; Dar, M. Ibrahim; Gao, Peng; Luo, Jingshan; Renevier, Clémentine; Schenk, Kurt; Abate, Antonio; Giordano, Fabrizio; Correa Baena, Juan-Pablo; Decoppet, Jean-David; Zakeeruddin, Shaik Mohammed; Nazeeruddin, Mohammad Khaja; Grätzel, Michael; Hagfeldt, Anders

    2016-01-01

    We report on a new metal halide perovskite photovoltaic cell that exhibits both very high solar-to-electric power-conversion efficiency and intense electroluminescence. We produce the perovskite films in a single step from a solution containing a mixture of FAI, PbI2, MABr, and PbBr2 (where FA stands for formamidinium cations and MA stands for methylammonium cations). Using mesoporous TiO2 and Spiro-OMeTAD as electron- and hole-specific contacts, respectively, we fabricate perovskite solar ce...

  20. Computational design of high performance hybrid perovskite on silicon tandem solar cells

    Rolland, Alain; Pedesseau, L.; Beck, Alexandre; Kepenekian, M; Katan, Claudine; Yong HUANG; Wang, Shijian; Cornet, C.; Durand, Olivier; Even, J.

    2016-01-01

    In this study, the optoelectronic properties of a monolithically integrated series-connected tandem solar cell are simulated. Following the large success of hybrid organic-inorganic perovskites, which have recently demonstrated large efficiencies with low production costs, we examine the possibility of using the same perovskites as absorbers in a tandem solar cell. The cell consists in a methylammonium mixed bromide-iodide lead perovskite, CH3NH3PbI3(1-x)Br3x (0 \\textless x \\textless 1), top ...

  1. Fabrication and Properties of High-Efficiency Perovskite/PCBM Organic Solar Cells

    Chen, Lung-Chien; Chen, Jhih-Chyi; Chen, Cheng-Chiang; Wu, Chun-Guey

    2015-01-01

    This work presents a CH3NH3PbI3/PCBM organic solar cell. Organic PCBM film and CH3NH3PbI3 perovskite film are deposited on the PEDOT:PSS/ITO glass substrate by the spin coating method. The performance of the organic solar cells was observed by changing the thickness of CH3NH3PbI3 perovskite. The thickness of a perovskite film can affect the carrier diffusion length in a device that strongly absorbs light in the red spectral region. The short-circuit current density and the power conversion ef...

  2. Highly Efficient Reproducible Perovskite Solar Cells Prepared by Low-Temperature Processing

    Hao Hu

    2016-04-01

    Full Text Available In this work, we describe the role of the different layers in perovskite solar cells to achieve reproducible, ~16% efficient perovskite solar cells. We used a planar device architecture with PEDOT:PSS on the bottom, followed by the perovskite layer and an evaporated C60 layer before deposition of the top electrode. No high temperature annealing step is needed, which also allows processing on flexible plastic substrates. Only the optimization of all of these layers leads to highly efficient and reproducible results. In this work, we describe the effects of different processing conditions, especially the influence of the C60 top layer on the device performance.

  3. Molecular Origin of Properties of Organic-Inorganic Hybrid Perovskites: The Big Picture from Small Clusters.

    Fang, Hong; Jena, Puru

    2016-04-21

    We show that the electronic properties, including the band gap, the gap deformation potential, and the exciton binding energy as well as the chemical stability of organic-inorganic hybrid perovskites can be traced back to their corresponding molecular motifs. This understanding allows one to quickly estimate the properties of the bulk semiconductors from their corresponding molecular building blocks. New hybrid perovskite admixtures are proposed by replacing halogens with superhalogens having compatible ionic radii. The mechanism of the boron-hydride based hybrid perovskite reacting with water is investigated by using a cluster model. PMID:27064550

  4. Single-component routes to perovskite phase mixed metal oxides

    This paper reports that crystalline perovskite phase mixed metal oxides have been prepared at low temperatures from single-component mixed metal-organic precursors specifically designed for this purpose. Pyridine solutions of divalent metal α-hydroxycarboxylates of general empirical formula A(O2CMe2OH)2 where A = Pb, Ca, Sr, Ba: Me = methyl, react with metal alkoxide compounds such as B(OR')4, where B = Ti, Zr, Sn with the elimination of two equivalents of alcohol to form species with a fixed A:B stoichiometry of 1:1 according to the equation below. A(O2C(CMe2OH)2 + B(OR')4 > A(O2CCMe2O)2B(OR')2 + 2HOR'. Hydrolysis of these solutions with an excess of water results in homogeneous clear solutions from which white or pale yellow solids can be isolated, by evaporation of the volatile components in vacuo. Thermolysis at 350 degrees C in O2 resulted in formation of crystalline perovskite phase products for the representative examples PbTiO3, PbZrO3, BaTiO3 CaTiO3 and BaSnO3

  5. Ultrafast transient reflectance of epitaxial semiconducting perovskite thin films

    Smolin, S. Y.; Guglietta, G. W.; Baxter, J. B., E-mail: jbaxter@drexel.edu, E-mail: smay@coe.drexel.edu [Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Scafetta, M. D.; May, S. J., E-mail: jbaxter@drexel.edu, E-mail: smay@coe.drexel.edu [Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States)

    2014-07-14

    Ultrafast pump-probe transient reflectance (TR) spectroscopy was used to study carrier dynamics in an epitaxial perovskite oxide thin film of LaFeO{sub 3} (LFO) with a thickness of 40 unit cells (16 nm) grown by molecular beam epitaxy on (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.7} (LSAT). TR spectroscopy shows two negative transients in reflectance with local maxima at ∼2.5 eV and ∼3.5 eV which correspond to two optical transitions in LFO as determined by ellipsometry. The kinetics at these transients were best fit with an exponential decay model with fast (5–40 ps), medium (∼200 ps), and slow (∼ 3 ns) components that we attribute mainly to recombination of photoexcited carriers. Moreover, these reflectance transients did not completely decay within the observable time window, indicating that ∼10% of photoexcited carriers exist for at least 3 ns. This work illustrates that TR spectroscopy can be performed on thin (<20 nm) epitaxial oxide films to provide a quantitative understanding of recombination lifetimes, which are important parameters for the potential utilization of perovskite films in photovoltaic and photocatalytic applications.

  6. Ultrafast transient reflectance of epitaxial semiconducting perovskite thin films

    Smolin, S. Y.; Scafetta, M. D.; Guglietta, G. W.; Baxter, J. B.; May, S. J.

    2014-07-01

    Ultrafast pump-probe transient reflectance (TR) spectroscopy was used to study carrier dynamics in an epitaxial perovskite oxide thin film of LaFeO3 (LFO) with a thickness of 40 unit cells (16 nm) grown by molecular beam epitaxy on (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT). TR spectroscopy shows two negative transients in reflectance with local maxima at ˜2.5 eV and ˜3.5 eV which correspond to two optical transitions in LFO as determined by ellipsometry. The kinetics at these transients were best fit with an exponential decay model with fast (5-40 ps), medium (˜200 ps), and slow (˜ 3 ns) components that we attribute mainly to recombination of photoexcited carriers. Moreover, these reflectance transients did not completely decay within the observable time window, indicating that ˜10% of photoexcited carriers exist for at least 3 ns. This work illustrates that TR spectroscopy can be performed on thin (<20 nm) epitaxial oxide films to provide a quantitative understanding of recombination lifetimes, which are important parameters for the potential utilization of perovskite films in photovoltaic and photocatalytic applications.

  7. Fiber-supported perovskites for catalytic combustion of natural gas

    Klvana, D.; Kirchnerova, J.; Chaouki, J.; Delval, J. [Department of Chemical Engineering, Ecole Polytechnique, PO Box 6079, Station Centre-Ville, Montreal (Canada); Yaieci, W. [Centre des technologies du gaz naturel, 1350, rue Nobel, Boucherville (Canada)

    1999-01-01

    Based on previous work, highly performing combustion catalyst consisting of an iron doped nickel-cobalt-based perovskite supported on commercial fiber blankets has been developed. The catalyst is particularly suitable for use in combustion of lean natural gas mixtures. With 12-15wt% perovskite loadings the catalyst exhibits activities comparable to those of commercial fiber-supported platinum. At temperatures below 1000K the catalyst activity seems stable, and resistant to low levels of mercaptan used as an odorant. Unlike platinum (or palladium) the catalyst promotes deep methane oxidation, i.e. no carbon monoxide formation, even in methane-rich mixtures. The combustion is inhibited by carbon dioxide, but water has no measurable influence. A simple kinetic model which takes the inhibition effect of carbon dioxide into account and permits more realistic conversion estimates is proposed: r{sub CO{sub 2}}=k{sub CH{sub 4}}P{sub CH{sub 4}}/(1+k{sub CO{sub 2}}P{sub CO{sub 2}})

  8. Manganese perovskites for room temperature magnetic refrigeration applications

    Phan, Manh-Huong; Peng, Hua-Xin; Yu, Seong-Cho; Tho, Nguyen Duc; Nhat, Hoang Nam; Chau, Nguyen

    2007-09-01

    We found the large magnetocaloric effect (MCE) in La 0.6Ca 0.3Pb 0.1MnO 3 (sample No. 1), La 0.7Ca 0.2Pb 0.1MnO 3 (sample No. 2), and La 0.7Ca 0.1Pb 0.2MnO 3 (sample No. 3) perovskites, which were prepared by a conventional ceramic method. For a magnetic field change of 13.5 kOe, the magnetic entropy change (Δ SM) reached values of 2.55, 2.53 and 3.72 J/kg K for samples Nos. 1, 2 and 3, respectively. Interestingly, the large Δ SM was found to occur around 300 K for all samples investigated, which allows magnetic refrigeration at room temperature. These perovskites have the large magnetic entropy changes induced by low magnetic field change, which is beneficial for the household application of active magnetic refrigerant (AMR) materials.

  9. Combustion synthesis and characterization of porous perovskite catalysts

    Yuehui Wu-Laitao Luo; Wei Liu

    2007-05-01

    Porous perovskite-type complex oxides LaCoO3 and La0.95Sr0.05Ni0.05Co0.95O3 were produced by combustion method. The properties of these porous materials such as crystal structures, particle sizes, surface patterns, pore size, surface area and pore volume were characterized by X-ray diffraction( XRD), scanning electron microscopy(SEM) and BET measurements. The results indicated that all porous materials are of the perovskite-type complex oxides. Doping Sr2+ ions on site A and doping Ni2+ ions on site B entered the crystal lattices of LaCoO3 in the place of La3+ and Co3+, respectively, and the maximum peak of XRD patterns of doping sample was weaken and broaden. Morphological microscopy demonstrated agglomerates involved mostly thin smooth flakes and layers perforated by a large number of pores and its lamella decreased with the introduction of Sr2+ and Ni2+. Hysteresis loop in the N2 adsorption-desorption isotherm of samples indicated its porous structures and the doping effect on its pore size, surface area and pore volume were improved. The porous catalysts have been tested for methane catalytic combustion and the results showed that these catalysts possessed high catalytic activity.

  10. Lead iodide perovskite light-emitting field-effect transistor

    Chin, Xin Yu; Cortecchia, Daniele; Yin, Jun; Bruno, Annalisa; Soci, Cesare

    2015-06-01

    Despite the widespread use of solution-processable hybrid organic-inorganic perovskites in photovoltaic and light-emitting applications, determination of their intrinsic charge transport parameters has been elusive due to the variability of film preparation and history-dependent device performance. Here we show that screening effects associated to ionic transport can be effectively eliminated by lowering the operating temperature of methylammonium lead iodide perovskite (CH3NH3PbI3) field-effect transistors. Field-effect carrier mobility is found to increase by almost two orders of magnitude below 200 K, consistent with phonon scattering-limited transport. Under balanced ambipolar carrier injection, gate-dependent electroluminescence is also observed from the transistor channel, with spectra revealing the tetragonal to orthorhombic phase transition. This demonstration of CH3NH3PbI3 light-emitting field-effect transistors provides intrinsic transport parameters to guide materials and solar cell optimization, and will drive the development of new electro-optic device concepts, such as gated light-emitting diodes and lasers operating at room temperature.

  11. Perovskite-type oxides - Oxygen electrocatalysis and bulk structure

    Carbonio, R. E.; Fierro, C.; Tryk, D.; Scherson, D.; Yeager, E.

    1988-01-01

    Perovskite type oxides were considered for use as oxygen reduction and generation electrocatalysts in alkaline electrolytes. Perovskite stability and electrocatalytic activity are studied along with possible relationships of the latter with the bulk solid state properties. A series of compounds of the type LaFe(x)Ni1(-x)O3 was used as a model system to gain information on the possible relationships between surface catalytic activity and bulk structure. Hydrogen peroxide decomposition rate constants were measured for these compounds. Ex situ Mossbauer effect spectroscopy (MES), and magnetic susceptibility measurements were used to study the solid state properties. X ray photoelectron spectroscopy (XPS) was used to examine the surface. MES has indicated the presence of a paramagnetic to magnetically ordered phase transition for values of x between 0.4 and 0.5. A correlation was found between the values of the MES isomer shift and the catalytic activity for peroxide decomposition. Thus, the catalytic activity can be correlated to the d-electron density for the transition metal cations.

  12. Perovskite Photovoltachromic Supercapacitor with All-Transparent Electrodes.

    Zhou, Feichi; Ren, Zhiwei; Zhao, Yuda; Shen, Xinpeng; Wang, Aiwu; Li, Yang Yang; Surya, Charles; Chai, Yang

    2016-06-28

    Photovoltachromic cells (PVCCs) are of great interest for the self-powered smart windows of architectures and vehicles, which require widely tunable transmittance and automatic color change under photostimuli. Organolead halide perovskite possesses high light absorption coefficient and enables thin and semitransparent photovoltaic device. In this work, we demonstrate co-anode and co-cathode photovoltachromic supercapacitors (PVCSs) by vertically integrating a perovskite solar cell (PSC) with MoO3/Au/MoO3 transparent electrode and electrochromic supercapacitor. The PVCSs provide a seamless integration of energy harvesting/storage device, automatic and wide color tunability, and enhanced photostability of PSCs. Compared with conventional PVCC, the counter electrodes of our PVCSs provide sufficient balancing charge, eliminate the necessity of reverse bias voltage for bleaching the device, and realize reasonable in situ energy storage. The color states of PVCSs not only indicate the amount of energy stored and energy consumed in real time, but also enhance the photostability of photovoltaic component by preventing its long-time photoexposure under fully charged state of PVCSs. This work designs PVCS devices for multifunctional smart window applications commonly made of glass. PMID:27159013

  13. Perovskite enhanced solid state ZnO solar cells

    This paper will report on the design, fabrication and testing of a solid-state perovskite enhanced ZnO solar cell. The p-type perovskite material used is bismuth ferrite (BFO) which has an absorption range within the blue range of the visible light spectrum. The solid state solar cell, was sensitized with N719 dye and used a CuSCN hole conductor. A disadvantage of ZnO is its poor chemical stability in acidic and corrosive environments. As chemical solution techniques were used in depositing BFO, a buffer method using an aminosilane ((3-aminopropyltrimethoxysilane or H2N(CH2)3Si(OCH3)3)) coating was used to provide a protective coating on the ZnO nanorods before the BFO film was spin coated onto the ZnO nanorods. The photovoltaic performance of the solar cells were tested using a Keithley 2400 source meter under 100mW/cm2, AM 1.5G simulated sunlight, where improvements in Jsc and efficiency were observed. The BFO was able to harness more electrons and also acted as a buffer from electron recombination

  14. Light induced polaron formation in perovskite solar cell devices

    Neukirch, Amanda; Nie, Wanyi; Blancon, Jean-Christophe; Appavoo, Kannatassen; Tsai, Hsinhan; Chhowalla, Manish; Alam, Muhammad; Sfeir, Matthew; Katan, Claudine; Even, Jacky; Crochet, Jared; Gupta, Gautum; Mohite, Aditya; Tretiak, Sergei

    The need for a low-cost, clean, and abundant source of energy has generated large amounts of research in solution processed solar cell materials. The lead halide perovskite has rapidly developed as a serious candidate for the active layer of photovoltaic devices. The efficiencies of devices made with this material have increased from 3.5% to over 20% in around 5 years. Despite the remarkable progress associated with perovskite materials, there are still fundamental questions regarding their lack of photo-stability over prolonged solar irradiation that need to be addressed. Recent experiments on photo-degradation under constant illumination have found fast self-healing by resting the device in the dark for less than 1 minute. Density functional theory and symmetry analysis show that localized charge states couple to local structural lattice distortions and methyl ammonium quasistatic configurations. Once translational symmetry is lost, additional bonding configurations become symmetry allowed, triggering localized charges in the vicinity over time under constant illumination, thus seeding the formation of macroscopic charged domains and preventing efficient charge extraction. Here we present an in-depth study of polaron formation and binding energy at the atomistic level.

  15. Perovskite Nanocrystals as a Color Converter for Visible Light Communication

    Dursun, Ibrahim

    2016-05-31

    Visible light communication (VLC) is an emerging technology that uses light-emitting diodes (LEDs) or laser diodes for simultaneous illumination and data communication. This technology is envisioned to be a major part of the solution to the current bottlenecks in data and wireless communication. However, the conventional lighting phosphors that are typically integrated with LEDs have limited modulation bandwidth and thus cannot provide the bandwidth required to realize the potential of VLC. In this work, we present a promising light converter for VLC by designing solution-processed CsPbBr3 perovskite nanocrystals (NCs) with a conventional red phosphor. The fabricated CsPbBr3 NCs phosphor-based white light converter exhibits an unprecedented modulation bandwidth of 491 MHz, which is ~ 40 times greater than that of conventional phosphors, and the capability to transmit a high data rate of up to 2 Gbit/s. Moreover, this perovskite enhanced white light source combines ultrafast response characteristics with a high color rendering index of 89 and a low correlated color temperature of 3236 K, thereby enabling dual VLC and solid-state lighting functionalities.

  16. Growing perovskite into polymers for easy-processable optoelectronic devices

    Masi, Sofia; Colella, Silvia; Listorti, Andrea; Roiati, Vittoria; Liscio, Andrea; Palermo, Vincenzo; Rizzo, Aurora; Gigli, Giuseppe

    2015-01-01

    Here we conceive an innovative nanocomposite to endow hybrid perovskites with the easy processability of polymers, providing a tool to control film quality and material crystallinity. We verify that the employed semiconducting polymer, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), controls the self-assembly of CH3NH3PbI3 (MAPbI3) crystalline domains and favors the deposition of a very smooth and homogenous layer in one straightforward step. This idea offers a new paradigm for the implementation of polymer/perovskite nanocomposites towards versatile optoelectronic devices combined with the feasibility of mass production. As a proof-of-concept we propose the application of such nanocomposite in polymer solar cell architecture, demonstrating a power conversion efficiency up to 3%, to date the highest reported for MEH-PPV. On-purpose designed polymers are expected to suit the nanocomposite properties for the integration in diverse optoelectronic devices via facile processing condition.

  17. Methane combustion over lanthanum-based perovskite mixed oxides

    Arandiyan, Hamidreza [New South Wales Univ., Sydney (Australia). School of Chemical Engineering

    2015-11-01

    This book presents current research into the catalytic combustion of methane using perovskite-type oxides (ABO{sub 3}). Catalytic combustion has been developed as a method of promoting efficient combustion with minimum pollutant formation as compared to conventional catalytic combustion. Recent theoretical and experimental studies have recommended that noble metals supported on (ABO{sub 3}) with well-ordered porous networks show promising redox properties. Three-dimensionally ordered macroporous (3DOM) materials with interpenetrated and regular mesoporous systems have recently triggered enormous research activity due to their high surface areas, large pore volumes, uniform pore sizes, low cost, environmental benignity, and good chemical stability. These are all highly relevant in terms of the utilization of natural gas in light of recent catalytic innovations and technological advances. The book is of interest to all researchers active in utilization of natural gas with novel catalysts. The research covered comes from the most important industries and research centers in the field. The book serves not only as a text for researcher into catalytic combustion of methane, 3DOM perovskite mixed oxide, but also explores the field of green technologies by experts in academia and industry. This book will appeal to those interested in research on the environmental impact of combustion, materials and catalysis.

  18. Ultrafast transient reflectance of epitaxial semiconducting perovskite thin films

    Ultrafast pump-probe transient reflectance (TR) spectroscopy was used to study carrier dynamics in an epitaxial perovskite oxide thin film of LaFeO3 (LFO) with a thickness of 40 unit cells (16 nm) grown by molecular beam epitaxy on (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT). TR spectroscopy shows two negative transients in reflectance with local maxima at ∼2.5 eV and ∼3.5 eV which correspond to two optical transitions in LFO as determined by ellipsometry. The kinetics at these transients were best fit with an exponential decay model with fast (5–40 ps), medium (∼200 ps), and slow (∼ 3 ns) components that we attribute mainly to recombination of photoexcited carriers. Moreover, these reflectance transients did not completely decay within the observable time window, indicating that ∼10% of photoexcited carriers exist for at least 3 ns. This work illustrates that TR spectroscopy can be performed on thin (<20 nm) epitaxial oxide films to provide a quantitative understanding of recombination lifetimes, which are important parameters for the potential utilization of perovskite films in photovoltaic and photocatalytic applications.

  19. Scattering of fast N-2 from Pd(111) : Orientational influences on the interaction dynamics

    Schlatholter, T; Vicanek, M; Heiland, W

    1997-01-01

    Classical trajectory studies of grazing incidence, N-2 scattering from Pd(111) surfaces in the keV rang are performed. We use an analytical six-dimensional potential energy surface based on ab initio density-functional-theory-calculations and experimental data to describe the molecule-surface intera

  20. 111 oriented gold nanoplatelets on multilayer graphene as visible light photocatalyst for overall water splitting

    Mateo, Diego; Esteve-Adell, Iván; Albero, Josep; Royo, Juan F. Sánchez; Primo, Ana; Garcia, Hermenegildo

    2016-06-01

    Development of renewable fuels from solar light appears as one of the main current challenges in energy science. A plethora of photocatalysts have been investigated to obtain hydrogen and oxygen from water and solar light in the last decades. However, the photon-to-hydrogen molecule conversion is still far from allowing real implementation of solar fuels. Here we show that 111 facet-oriented gold nanoplatelets on multilayer graphene films deposited on quartz is a highly active photocatalyst for simulated sunlight overall water splitting into hydrogen and oxygen in the absence of sacrificial electron donors, achieving hydrogen production rate of 1.2 molH2 per gcomposite per h. This photocatalytic activity arises from the gold preferential orientation and the strong gold-graphene interaction occurring in the composite system.

  1. Threshold voltage modeling in (100, (110 and (111 oriented nanoscale MOSFET substrates

    Chaudhry Amit

    2011-01-01

    Full Text Available An analytical model for the inversion layer quantization for nanoscale - Metal Oxide Semiconductor Field Effect Transistor (MOSFET with different crystallographic substrate orientations, such as (100, (110 and (111 has been developed. The threshold voltage analysis has been studied using the quantum inversion charge model under three substrate orientations. The results indicate a significant impact of crystal orientation on the threshold voltage and the inversion charge density. The results have also been compared with the numerically reported results and show good agreement.

  2. Perovskite at high P-T conditions: An in situ synchrotron X ray diffraction study of NaMgF3 perovskite

    Zhao, Yusheng; Weidner, Donald J.; Ko, Jiadong; Leinenweber, Kurt; Liu, Xing; Li, Baosheng; Meng, Yue; Pacalo, Rosemary E. G.; Vaughan, Michael T.; Wang, Yanbin

    1994-02-01

    The lattice distortion and structural phase transition of NaMgF3 perovskite (Neighborite) have been studied using synchrotron X ray powder diffraction at high pressure and temperature. Changes in the unit cell dimensions of the perovskite are determined by conventional peak indexing and least squares routines. The stress field within the high-pressure cell assembly is analyzed, and the yield strength of the NaMgF3 perovskite is determined at high P and T. The pressure- and temperature-induced dimensional changes of the NaMgF3 perovskite structure are expressed empirically as a combination of compression/expansion of the (Mg-F) bond length and tilting of the MgF6 octahedral framework. The linear thermal expansions of the NaMgF3 perovskite observed at different pressures show significant anisotropy with alpha(sub a) is greater than alpha(sub c) is greater than alpha(sub b), which reflects the decrease of structural distortion and the development of a phase transition in the perovskite with increasing temperature. The tilting angle of the MgF6 octahedral framework is observed to decrease rapidly toward zero, in a manner expected for a ferroelastic phase transition, as the temperature approaches the transition point T(sub c). The apparent (Mg-F) bond lengths of the MgF6 octahedra experience drastic shrinkage with increasing temperature just prior to the transition. Despite a 12% change in volume due to compression, the experimental results on NaMgF3 perovskite show that the thermal expansivity is independent of pressure, i.e., d(alpha)/dP is approximately equal to 0, and, compatibly, that the compressibility is independent of temperature, i.e., d(beta)/dT is approximately equal to 0. However, the dominant compression mechanism is the compression of the octahedral bond length, whereas the dominant mechanism for thermal expansion is the diminishing of octahedral tilting. The Earth's mantle may be isochemical if the thermal expansion of MgSiO3 perovskite at high pressure

  3. Dynamical Origin of the Rashba Effect in Organohalide Lead Perovskites: A Key to Suppressed Carrier Recombination in Perovskite Solar Cells?

    Etienne, Thibaud; Mosconi, Edoardo; De Angelis, Filippo

    2016-05-01

    The presence of a Rashba band-splitting mechanism mediated by spin-orbit coupling and breaking of inversion symmetry has been suggested as a possible cause for the reduced recombination rates observed in organohalide perovskites. Here, we investigate the interplay of electronic and nuclear degrees of freedom in defining the Rashba splitting in realistic MAPbI3 models. Our simulations disclose a "dynamical Rashba effect", allowing for a quantification of its magnitude under thermal conditions. We find that even in globally centrosymmetric structures the dynamics of the coupled inorganic-organic degrees of freedom give rise to a spatially local Rashba effect which fluctuates on the subpicosecond time scale typical of the methylammonium cation dynamics. This effect is progressively quenched in globally centrosymmetric structures, likely representing the MAPbI3 perovskite at room temperature, on increasing the probed spatial scale up to 32 MAPbI3 units (∼3 nm size) because of the incoherent nuclear thermal motion mediated by the disorder of the organic cations. PMID:27062910

  4. Phase Boundary between MgSiO3 Perovskite and Post-perovskite from Quantum Monte Carlo Simulations

    Lin, Yangzheng; Cohen, R. E.; Stackhouse, Stephen; Driver, Kevin P.; Militzer, Burkhard; Shulenburger, Luke; Kim, Jeongnim

    2015-03-01

    Accurate prediction of the phase boundary between perovskite (pv) and post-perovskite (ppv) phases of MgSiO3 is important to explain many unusual properties of the Earth's D'' layer, such as lateral variations in the depth of the observed seismic discontinuity and seismic anisotropy. We have performed quantum Monte Carlo (QMC) simulations with the QMCPACK code on GPU clusters to obtain the ground state equation of state. Density functional perturbation theory (DFPT) computations were performed to obtain the thermal pressure within quasiharmonic lattice dynamics. The equations of state for both phases of MgSiO3 and their phase boundary from our QMC simulations agree well with experiment results and better than previous DFT calculations. Double-crossing of the pv-ppv boundary along Earth's geotherm depends on the effects of iron on the transition. Computations were performed on XSEDE machine Stampede, and on the Oak Ridge Leadership Computing Facility (OLCF) machine Titan from INCITE program. This work is supported by NSF.

  5. High-pressure physical properties of magnesium silicate post-perovskite from ab initio calculations

    Zi-Jiang Liu; Xiao-Wei Sun; Cai-Rong Zhang; Jian-Bu Hu; Ling-Cang Cai; Qi-Feng Chen

    2012-08-01

    The structure, thermodynamic and elastic properties of magnesium silicate (MgSiO3) post-perovskite at high pressure are investigated with quasi-harmonic Debye model and ab initio method based on the density functional theory (DFT). The calculated structural parameters of MgSiO3 post-perovskite are consistent with the available experimental results and the recent theoretical results. The Debye temperature, heat capacity and thermal expansion coefficient at high pressures and temperatures are predicted using the quasi-harmonic Debye model. The elastic constants are calculated using stress–strain relations. A complete elastic tensor of MgSiO3 post-perovskite is determined in the wide pressure range. The calculated elastic anisotropic factors and directional bulk modulus show that MgSiO3 post-perovskite possesses high elastic anisotropy.

  6. Methane partial oxidation by the lattice oxygen of the lanio₃δ perovskite. a pulse study

    SIERRA GALLEGO, GERMÁN; BATIOT-DUPEYRAT, CATHERINE; MONDRAGÓN, FANOR

    2011-01-01

    LaNiO₃ perovskite was prepared by the selfcombustion method and tested as catalyst for CH4 activation using the oxygen lattice at 700°C and 800°C. Based on the non-stoichiometry experiments, the perovskite formula is written as La³⁺+ Ni³⁺ 0.37Ni²⁺ 0.63O2.68. When unreduced LaNiO3d perovskite is used, only type oxygen species were responsible for the partial CH₄ oxidation. Over non reduced perovskite high CH4 conversions to H₂ and CO were obtained. CH4 conversion and H₂, CO and CO₂, selectivit...

  7. Thermally induced structural evolution and performance of mesoporous block copolymer-directed alumina perovskite solar cells.

    Tan, Kwan Wee

    2014-04-11

    Structure control in solution-processed hybrid perovskites is crucial to design and fabricate highly efficient solar cells. Here, we utilize in situ grazing incidence wide-angle X-ray scattering and scanning electron microscopy to investigate the structural evolution and film morphologies of methylammonium lead tri-iodide/chloride (CH3NH3PbI(3-x)Cl(x)) in mesoporous block copolymer derived alumina superstructures during thermal annealing. We show the CH3NH3PbI(3-x)Cl(x) material evolution to be characterized by three distinct structures: a crystalline precursor structure not described previously, a 3D perovskite structure, and a mixture of compounds resulting from degradation. Finally, we demonstrate how understanding the processing parameters provides the foundation needed for optimal perovskite film morphology and coverage, leading to enhanced block copolymer-directed perovskite solar cell performance.

  8. Ultrathin Cu2O as an efficient inorganic hole transporting material for perovskite solar cells

    Yu, Weili

    2016-02-18

    We demonstrate that ultrathin P-type Cu2O thin films fabricated by a facile thermal oxidation method can serve as a promising hole-transporting material in perovskite solar cells. Following a two-step method, inorganic-organic hybrid perovskite solar cells were fabricated and a power conversion efficiency of 11.0% was achieved. We find that the thickness and properties of Cu2O layers must be precisely tuned in order to achieve the optimal solar cell performance. The good performance of such perovskite solar cells can be attributed to the unique properties of ultrathin Cu2O, including high hole mobility, good energy level alignment with CH3NH3PbI3, and longer lifetime of photo-excited carriers. Combining merits of low cost, facile synthesis, and high device performance, ultrathin Cu2O films fabricated via thermal oxidation hold promise for facilitating the developments of industrial-scale perovskite solar cells.

  9. Electrochemical reduction of nitrous oxide on La1-xSrxFeO3 perovskites

    Kammer Hansen, Kent

    2010-01-01

    The electrochemical reduction of nitrous oxide and oxygen has been studied on cone-shaped electrodes of La1-xSrxFeO3-delta perovskites in an all solid state cell, using cyclic voltammetry. It was shown that the activity of the La1-xSrxFeO3-delta perovskites for the electrochemical reduction of...... nitrous oxide mainly depends on the amount of Fe(III) and oxide ion vacancies. The activity of the La1-xSrxFeO3-delta perovskites towards the electrochemical reduction of nitrous oxide is much lower than the activity of the La1-xSrxFeO3-delta perovskites towards the electrochemical reduction of oxygen...

  10. Wire-shaped perovskite solar cell based on TiO2 nanotubes

    Wang, Xiaoyan; Kulkarni, Sneha A.; Li, Zhen; Xu, Wenjing; Batabyal, Sudip K.; Zhang, Sam; Cao, Anyuan; Wong, Lydia Helena

    2016-05-01

    In this work, a wire-shaped perovskite solar cell based on TiO2 nanotube (TNT) arrays is demonstrated for the first time by integrating a perovskite absorber on TNT-coated Ti wire. Anodization was adopted for the conformal growth of TNTs on Ti wire, together with the simultaneous formation of a compact TiO2 layer. A sequential step dipping process is employed to produce a uniform and compact perovskite layer on top of TNTs with conformal coverage as the efficient light absorber. Transparent carbon nanotube film is wrapped around Ti wire as the hole collector and counter electrode. The integrated perovskite solar cell wire by facile fabrication approaches shows a promising future in portable and wearable textile electronics.

  11. Towards printed perovskite solar cells with cuprous oxide hole transporting layers

    Wang, Yan; Xia, Zhonggao; Liang, Jun;

    2015-01-01

    Solution-processed p-type metal oxide materials have shown great promise in improving the stability of perovskite-based solar cells and offering the feasibility for a low cost printing fabrication process. Herein, we performed a device modeling study on planar perovskite solar cells with cuprous...... oxide (Cu2O) hole transporting layers (HTLs) by using a solar cell simulation program, wxAMPS. The performance of a Cu2O/perovskite solar cell was correlated to the material properties of the Cu2O HTL, such as thickness, carrier mobility, mid-gap defect, and doping...... concentrations. The effect of interfacial defect densities on the solar cell performance was also investigated. Our simulation indicates that, with an optimized Cu2O HTL, high performance perovskite solar cells with efficiencies above 13% could be achieved, which shows the potential of using Cu2...

  12. Influence of the orientation of methylammonium lead iodide perovskite crystals on solar cell performance

    Pablo Docampo

    2014-08-01

    Full Text Available Perovskite solar cells are emerging as serious candidates for thin film photovoltaics with power conversion efficiencies already exceeding 16%. Devices based on a planar heterojunction architecture, where the MAPbI3 perovskite film is simply sandwiched between two charge selective extraction contacts, can be processed at low temperatures (<150 °C, making them particularly attractive for tandem and flexible applications. However, in this configuration, the perovskite crystals formed are more or less randomly oriented on the surface. Our results show that by increasing the conversion step temperature from room temperature to 60 °C, the perovskite crystal orientation on the substrate can be controlled. We find that films with a preferential orientation of the long axis of the tetragonal unit cell parallel to the substrate achieve the highest short circuit currents and correspondingly the highest photovoltaic performance.

  13. Hydrophobic Organic Hole Transporters for Improved Moisture Resistance in Metal Halide Perovskite Solar Cells.

    Leijtens, Tomas; Giovenzana, Tommaso; Habisreutinger, Severin N; Tinkham, Jonathan S; Noel, Nakita K; Kamino, Brett A; Sadoughi, Golnaz; Sellinger, Alan; Snaith, Henry J

    2016-03-01

    Solar cells based on organic-inorganic perovskite semiconductor materials have recently made rapid improvements in performance, with the best cells performing at over 20% efficiency. With such rapid progress, questions such as cost and solar cell stability are becoming increasingly important to address if this new technology is to reach commercial deployment. The moisture sensitivity of commonly used organic-inorganic metal halide perovskites has especially raised concerns. Here, we demonstrate that the hygroscopic lithium salt commonly used as a dopant for the hole transport material in perovskite solar cells makes the top layer of the devices hydrophilic and causes the solar cells to rapidly degrade in the presence of moisture. By using novel, low cost, and hydrophobic hole transporters in conjunction with a doping method incorporating a preoxidized salt of the respective hole transporters, we are able to prepare efficient perovskite solar cells with greatly enhanced water resistance. PMID:26859777

  14. Energetics and dynamics in organic-inorganic halide perovskite photovoltaics and light emitters.

    Sum, Tze Chien; Chen, Shi; Xing, Guichuan; Liu, Xinfeng; Wu, Bo

    2015-08-28

    The rapid transcendence of organic-inorganic metal halide perovskite solar cells to above the 20% efficiency mark has captivated the broad photovoltaic community. As the efficiency race continues unabated, it is essential that fundamental studies keep pace with these developments. Further gains in device efficiencies are expected to be increasingly arduous and harder to come by. The key to driving the perovskite solar cell efficiencies towards their Shockley-Queisser limit is through a clear understanding of the interfacial energetics and dynamics between perovskites and other functional materials in nanostructured- and heterojunction-type devices. In this review, we focus on the current progress in basic characterization studies to elucidate the interfacial energetics (energy-level alignment and band bending) and dynamical processes (from the ultrafast to the ultraslow) in organic-inorganic metal halide perovskite photovoltaics and light emitters. Major findings from these studies will be distilled. Open questions and scientific challenges will also be highlighted. PMID:26234397

  15. Morphological Control for High Performance, Solution-Processed Planar Heterojunction Perovskite Solar Cells

    Eperon, Giles E.

    2013-09-09

    Organometal trihalide perovskite based solar cells have exhibited the highest efficiencies to-date when incorporated into mesostructured composites. However, thin solid films of a perovskite absorber should be capable of operating at the highest efficiency in a simple planar heterojunction configuration. Here, it is shown that film morphology is a critical issue in planar heterojunction CH3NH3PbI3-xCl x solar cells. The morphology is carefully controlled by varying processing conditions, and it is demonstrated that the highest photocurrents are attainable only with the highest perovskite surface coverages. With optimized solution based film formation, power conversion efficiencies of up to 11.4% are achieved, the first report of efficiencies above 10% in fully thin-film solution processed perovskite solar cells with no mesoporous layer. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Wire-shaped perovskite solar cell based on TiO2 nanotubes.

    Wang, Xiaoyan; Kulkarni, Sneha A; Li, Zhen; Xu, Wenjing; Batabyal, Sudip K; Zhang, Sam; Cao, Anyuan; Wong, Lydia Helena

    2016-05-20

    In this work, a wire-shaped perovskite solar cell based on TiO2 nanotube (TNT) arrays is demonstrated for the first time by integrating a perovskite absorber on TNT-coated Ti wire. Anodization was adopted for the conformal growth of TNTs on Ti wire, together with the simultaneous formation of a compact TiO2 layer. A sequential step dipping process is employed to produce a uniform and compact perovskite layer on top of TNTs with conformal coverage as the efficient light absorber. Transparent carbon nanotube film is wrapped around Ti wire as the hole collector and counter electrode. The integrated perovskite solar cell wire by facile fabrication approaches shows a promising future in portable and wearable textile electronics. PMID:27070991

  17. One-Step Facile Synthesis of a Simple Hole Transport Material for Efficient Perovskite Solar Cells

    Chen, Hu

    2016-04-04

    A hole transporting material was designed for use in perovskite solar cells, with a facile one-step synthesis from inexpensive, com-mercially available reagents. The molecule comprises a central fluorinated phenyl core with pendant aryl amines, namely, 3,6-difluoro-N1,N1,N2,N2,N4,N4,N5,N5-octakis(4-methoxyphenyl)benzene-1,2,4,5-tetraamine (DFTAB). A power conversion efficiency of up to 10.4% was achieved in a mesoporous perovskite device architecture. The merits of a simple and potentially low cost syn-thetic route as well as promising performance in perovskite devices, encourages further development of this materials class as new low-cost hole transporting materials for the scale up of perovskite solar cells.

  18. Influence of iridium on the reactivity of LaFeO3 base perovskites

    Kindermann, L.; Das, D.; Bahadur, D.; Nickel, H.

    The influence of iridium on the reactivity of powder mixtures made of perovskites and 8 mol% yttria stabilized zirconia (8 YSZ) is reported. Iridium is added to the perovskites of the composition (La0.6M0.4)(z)Fe0.8TM0.2O3-delta (M = Sr, Ca; TM = Mn, Co; z = 0.90, 1.00) via the gaseous phase....... Iridium is present in the perovskite lattice as Ir4+ replacing iron as is evident from XRD and TEM/EDX results. Compatibility studies carried out at 1000 degrees C demonstrate that iridium has considerable influence on the reactivity. The results are discussed with respect to the stability of the...... perovskites, thermodynamic activities, Ir(IV)-O bonding, tolerance factor and oxygen migration....

  19. Bifacial Si Heterojunction-Perovskite Organic-Inorganic Tandem to Produce Highly Efficient Solar Cell

    Asadpour, Reza; Khan, M Ryyan; Alam, Muhammad A

    2015-01-01

    As single junction thin-film technologies, both Si heterojunction (HIT) and Perovskite based solar cells promise high efficiencies at low cost. One expects that a tandem cell design with these cells connected in series will improve the efficiency further. Using a self-consistent numerical modeling of optical and transport characteristics, however, we find that a traditional series connected tandem design suffers from low Jsc due to band-gap mismatch and current matching constraints. It requires careful thickness optimization of Perovskite to achieve any noticeable efficiency gain. Specifically, a traditional tandem cell with state-of-the-art HIT (24%) and Perovskite (20%) sub-cells provides only a modest tandem efficiency of ~25%. Instead, we demonstrate that a bifacial HIT/Perovskite tandem design decouples the optoelectronic constraints and provides an innovative path for extraordinary efficiencies. In the bifacial configuration, the same state-of the-art sub-cells achieve a normalized output of 33%, exceed...

  20. High-pressure phase transitions of CaRhO3 perovskite

    Shirako, Yuichi; Kojitani, Hiroshi; Akaogi, Masaki; Yamaura, Kazunari; Takayama-Muromachi, Eiji

    2009-09-01

    High-pressure phase transitions of CaRhO3 perovskite were examined at pressures of 6-27 GPa and temperatures of 1,000-1,930°C, using a multi-anvil apparatus. The results indicate that CaRhO3 perovskite successively transforms to two new high-pressure phases with increasing pressure. Rietveld analysis of powder X-ray diffraction data indicated that, in the two new phases, the phase stable at higher pressure possesses the CaIrO3-type post-perovskite structure (space group Cmcm) with lattice parameters: a = 3.1013(1) Å, b = 9.8555(2) Å, c = 7.2643(1) Å, V m = 33.43(1) cm3/mol. The Rietveld analysis also indicated that CaRhO3 perovskite has the GdFeO3-type structure (space group Pnma) with lattice parameters: a = 5.5631(1) Å, b = 7.6308(1) Å, c = 5.3267(1) Å, V m = 34.04(1) cm3/mol. The third phase stable in the intermediate P, T conditions between perovskite and post-perovskite has monoclinic symmetry with the cell parameters: a = 12.490(3) Å, b = 3.1233(3) Å, c = 8.8630(7) Å, β = 103.96(1)°, V m = 33.66(1) cm3/mol ( Z = 6). Molar volume changes from perovskite to the intermediate phase and from the intermediate phase to post-perovskite are -1.1 and -0.7%, respectively. The equilibrium phase relations determined indicate that the boundary slopes are large positive values: 29 ± 2 MPa/K for the perovskite—intermediate phase transition and 62 ± 6 MPa/K for the intermediate phase—post-perovskite transition. The structural features of the CaRhO3 intermediate phase suggest that the phase has edge-sharing RhO6 octahedra and may have an intermediate structure between perovskite and post-perovskite.

  1. Experimental Evidence for Anisotropic Diffusion in Post-Perovskite Phases

    McCormack, R.; Dobson, D. P.; Heidelbach, F.; Beard, A.; Ammann, M. W.; Brodholt, J. P.

    2010-12-01

    Diffusion is an extremely important process which exerts influence over the rheological behaviour of the Earth’s interior. A good understanding of the rates of diffusion in the minerals composing the Earth’s mantle is essential to quantitatively understand the viscosity of the lower mantle which, in turn, controls a host of dynamic phenomena from the thermal and chemical coupling with the core to the formation of plumes. Ammann et al., 2010a suggest, based on first principles calculations, that the anisotropy in the diffusivity of the lower mantle MgSiO3 post-perovskite phase is extremely high. Furthermore, the diffusivity in the a-direction is predicted to be almost eight orders of magnitude higher than that in the b- and c-directions. Unfortunately, experimental verification of these results on MgSiO3 post-perovskite is prohibitively difficult. In this study we therefore performed experiments to measure the Ir-Pt interdiffusion tensor in single crystals of the low-pressure post-perovskite analogue CaIrO3. In addition we have calculated the activation energy for migration of iridium in CaIrO3 using the technique described in Ammann et al., 2010b. Experiments and simulations agree in giving the relative speed of diffusion in the axial directions as Da>Db>Dc in this system. Preliminary experimental results give Arrhenius parameters of Ir-Pt interdiffusion in the axial directions of CaIrO3 of: D0 (a)=4.0(2)e-12 m2/s; H*(a)=132(26) kJ/mol D0 (b)=1.2(7)e-12 m2/s; H* (b)=124(32) kJ/mol D0 (c)=1.1(5)e-9 m2/s; H* (c)=195(19) kJ/mol Ammann, M.W., Brodholt, J.P., Wookey, J. and Dobson, D.P. (2010) First Principles Constraints on Diffusion in Lower Mantle Minerals and a Weak D’’ Layer. Nature, 465, 462-465. Ammann, M.W., Brodholt, J.P. and Dobson, D.P. (2010) Simulating Diffusion. Reviews in Mineralogy and Geochemistry; v. 71;1; p. 201-224

  2. Interplay of octahedral rotations and breathing distortions in charge ordering perovskite oxides

    Balachandran, Prasanna V.; James M. Rondinelli

    2013-01-01

    We investigate the structure--property relationships in $AB$O$_3$ perovskites exhibiting octahedral rotations and cooperative octahedral breathing distortions (CBD) using group theoretical methods. Rotations of octahedra are ubiquitous in the perovskite family, while the appearance of breathing distortions -- oxygen displacement patterns that lead to approximately uniform dilation and contraction of the $B$O$_6$ octahedra -- are rarer in compositions with a single, chemically unique $B$-site....

  3. Low-temperature solution-processed p-type vanadium oxide for perovskite solar cells.

    Sun, Haocheng; Hou, Xiaomeng; Wei, Qiulong; Liu, Huawei; Yang, Kecheng; Wang, Wei; An, Qinyou; Rong, Yaoguang

    2016-06-21

    A low-temperature solution-processed inorganic p-type contact material of vanadium oxide (VOx) was developed to fabricate planar-heterojunction perovskite solar cells. Using a solvent-assisted process, high-quality uniform and compact perovskite (CH3NH3PbI3) films were deposited on VOx coated substrates. Due to the high transmittance and quenching efficiency of VOx layers, a power conversion efficiency of over 14% was achieved. PMID:27263631

  4. Conjugated polyelectrolyte hole transport layer for inverted-type perovskite solar cells

    Choi, Hyosung; Mai, Cheng-Kang; Kim, Hak-Beom; Jeong, Jaeki; Song, Seyeong; Bazan, Guillermo C.; Kim, Jin Young; Heeger, Alan J.

    2015-01-01

    Organic–inorganic hybrid perovskite materials offer the potential for realization of low-cost and flexible next-generation solar cells fabricated by low-temperature solution processing. Although efficiencies of perovskite solar cells have dramatically improved up to 19% within the past 5 years, there is still considerable room for further improvement in device efficiency and stability through development of novel materials and device architectures. Here we demonstrate that inverted-type perov...

  5. The Stability of Zirconia-Saturated Perovskite and Conditions in the Early Solar System

    Beckett, J. R.; Harvey, J.-P.; Ma, C.; Stolper, E. M.

    2015-01-01

    Perovskite and tazheranite (cubic zirconia) are among the most refractory oxides in nebular vapors [1] and important repositories for several refractory elements whose concentrations can potentially be used to constrain the environments of formation. There are numerous studies on the phase relations and thermodynamic properties of zirconias containing Al, Ca, Mg, Sc, Ti, and the REE [e.g., 2-4], but meteoritic zirconia is rare [5]. Meteoritic perovskite is much more commo...

  6. Highly Efficient Perovskite Nanocrystal Light-Emitting Diodes Enabled by a Universal Crosslinking Method.

    Li, Guangru; Rivarola, Florencia Wisnivesky Rocca; Davis, Nathaniel J L K; Bai, Sai; Jellicoe, Tom C; de la Peña, Francisco; Hou, Shaocong; Ducati, Caterina; Gao, Feng; Friend, Richard H; Greenham, Neil C; Tan, Zhi-Kuang

    2016-05-01

    The preparation of highly efficient perovskite nanocrystal light-emitting diodes is shown. A new trimethylaluminum vapor-based crosslinking method to render the nanocrystal films insoluble is applied. The resulting near-complete nanocrystal film coverage, coupled with the natural confinement of injected charges within the perovskite crystals, facilitates electron-hole capture and give rise to a remarkable electroluminescence yield of 5.7%. PMID:26990965

  7. Interplays between charge and electric field in perovskite solar cells: charge transport, recombination and hysteresis

    Shi, Jiangjian; Zhang, Huiyin; Xu, Xin; Li, Dongmei; Luo, Yanhong; Meng, Qingbo

    2016-01-01

    Interplays between charge and electric field, which play a critical role in determining the charge transport, recombination, storage and hysteresis in the perovskite solar cell, have been systematically investigated by both electrical transient experiments and theoretical calculations. It is found that the light illumination can increase the carrier concentration in the perovskite absorber, thus enhancing charge recombination and causing the co-existence of high electric field and free carrie...

  8. Spectral splitting photovoltaics using perovskite and wideband dye-sensitized solar cells

    Kinoshita, Takumi; Nonomura, Kazuteru; Joong Jeon, Nam; Giordano, Fabrizio; Abate, Antonio; Uchida, Satoshi; Kubo, Takaya; Seok, Sang Il; Nazeeruddin, Mohammad Khaja; Hagfeldt, Anders; Grätzel, Michael; Segawa, Hiroshi

    2015-01-01

    The extension of the light absorption of photovoltaics into the near-infrared region is important to increase the energy conversion efficiency. Although the progress of the lead halide perovskite solar cells is remarkable, and high conversion efficiency of >20% has been reached, their absorption limit on the long-wavelength side is ∼800 nm. To further enhance the conversion efficiency of perovskite-based photovoltaics, a hybridized system with near-infrared photovoltaics is a useful approach....

  9. Fabrication of efficient planar perovskite solar cells using a one-step chemical vapor deposition method

    Mohammad Mahdi Tavakoli; Leilei Gu; Yuan Gao; Claas Reckmeier; Jin He; Rogach, Andrey L; Yan Yao; Zhiyong Fan

    2015-01-01

    Organometallic trihalide perovskites are promising materials for photovoltaic applications, which have demonstrated a rapid rise in photovoltaic performance in a short period of time. We report a facile one-step method to fabricate planar heterojunction perovskite solar cells by chemical vapor deposition (CVD), with a solar power conversion efficiency of up to 11.1%. We performed a systematic optimization of CVD parameters such as temperature and growth time to obtain high quality films of CH...

  10. Current progress and future perspectives for organic/inorganic perovskite solar cells

    Boix, Pablo P.; Kazuteru Nonomura; Nripan Mathews; Subodh G. Mhaisalkar

    2014-01-01

    The recent emergence of efficient solar cells based on organic/inorganic lead halide perovskite absorbers promises to transform the fields of dye-sensitized, organic, and thin film solar cells. Solution processed photovoltaics incorporating perovskite absorbers have achieved efficiencies of 15% [1] in solid-state device configurations, superseding liquid dye sensitized solar cell (DSC), evaporated and tandem organic solar cells, as well as various thin film photovoltaics; thus establishing pe...

  11. Intrinsic femtosecond charge generation dynamics in a single crystal organometal halide perovskite

    Valverde-Chávez, David A.; Ponseca Jr., Carlito; Stoumpos, Constantinos; Yartsev, Arkady; Kanatzidis, Mercouri G.; Sundström, Villy; Cooke, David G.

    2015-01-01

    Hybrid metal-organic perovskite solar cells have astounded the solar cell community with their rapid rise in efficiency over the past three years. Despite this success, the basic processes governing the photogeneration of free charges, particularly their dynamics and efficiency, remain unknown. Here we use ultrabroadband pulses of THz frequency light to see the intrinsic photophysical properties of single crystal lead halide perovskite just femtoseconds after a photon is first absorbed. Our s...

  12. Equations of state of magnesium perovskite and postperovskite: diagnostics from ab initio simulations

    Belousov, Roman; Prencipe, Mauro

    2014-01-01

    The isothermal compression of magnesium perovskite and postperovskite is examined through the F-f plot and the diagnostic plot of Vinet universal model theoretically from the ab initio quantum-mechanical calculations at the hybrid Hartree-Fock / Density Functional Theory level. A purely numerical approach, first time applied in this paper, shows that the discrepancies largely observed between studies on the perovskite and criticized in geophysical applications are due to the inadequate choice...

  13. Application of Secondary Neutral Mass Spectrometry in the investigation of doped perovskites

    Vad, K.; Hakl, J.; Csik, A.; S. MESZAROS; Kis-Varga, M.; Langer, G A; Pallinger, A.; Bodog, M.

    2009-01-01

    Electromagnetic properties of doped perovskites depend sensitively on the doping level. Both the superconducting transition temperature of Bi2Sr2Ca(Pr)Cu2O8+d compounds and the magnetic and electronic transport properties of La(Sr)Co(Fe)O3 perovskites change dramatically with the doping level. Apart from doping, oxygen deficiency is influenced by the details of preparation processes such as calcination and sintering. Simultaneous determination of constituents is of crucial importance from sam...

  14. Perovskite Solar Cells Employing Dopant-Free Organic Hole Transport Materials with Tunable Energy Levels.

    Liu, Yongsheng; Hong, Ziruo; Chen, Qi; Chen, Huajun; Chang, Wei-Hsuan; Yang, Yang Michael; Song, Tze-Bin; Yang, Yang

    2016-01-20

    Conjugated small-molecule hole-transport materials (HTMs) with tunable energy levels are designed and synthesized for efficient perovskite solar cells. A champion device with efficiency of 16.2% is demonstrated using a dopant-free DERDTS-TBDT HTM, while the DORDTS-DFBT-HTM-based device shows an inferior performance of 6.2% due to its low hole mobility and unmatched HOMO level with the valence band of perovskite film. PMID:26588665

  15. Towards optical optimization of planar monolithic perovskite/silicon-heterojunction tandem solar cells

    Albrecht, Steve; Saliba, Michael; Correa-Baena, Juan-Pablo; Jäger, Klaus; Korte, Lars; Hagfeldt, Anders; Grätzel, Michael; Rech, Bernd

    2016-06-01

    Combining inorganic–organic perovskites and crystalline silicon into a monolithic tandem solar cell has recently attracted increased attention due to the high efficiency potential of this cell architecture. Promising results with published efficiencies above 21% have been reported so far. To further increase the device performance, optical optimizations enabling device related guidelines are highly necessary. Here we experimentally show the optical influence of the ITO thickness in the interconnecting layer and fabricate an efficient monolithic tandem cell with a reduced ITO layer thickness that shows slightly improved absorption within the silicon sub-cell and a stabilized power output of 17%. Furthermore we present detailed optical simulations on experimentally relevant planar tandem stacks to give practical guidelines to reach efficiencies above 25%. By optimizing the thickness of all functional and the perovskite absorber layers, together with the optimization of the perovskite band-gap, we present a tandem stack that can yield ca 17.5 mA cm‑ 2 current in both sub-cells at a perovskite band-gap of 1.73 eV including losses from reflection and parasitic absorption. Assuming that the higher band-gap of the perovskite absorber directly translates into a higher open circuit voltage, the perovskite sub-cell should be able to reach a value of 1.3 V. With that, realistic efficiencies above 28% are within reach for planar monolithic tandem cells in which the thickness of the perovskite top-cell and the perovskite band-gap are highly optimized. When applying light trapping schemes such as textured surfaces and by reducing the parasitic absorption of the functional layers, for example in spiro-OMeTAD, this monolithic tandem can overcome 30% power conversion efficiency.

  16. Structural and Chemical Evolution of Methylammonium Lead Halide Perovskites during Thermal Processing from Solution

    Nenon, David P.; Christians, Jeffrey A.; Wheeler, Lance M.; Blackburn, Jeffrey L.; Sanehira, Erin M.; Dou, Benjia; Olsen, Michele L.; Zhu, Kai; Berry, Joseph J.; Luther, Joseph M.

    2016-06-01

    Following the prominent success of CH3NH3PbI3 in photovoltaics and other optoelectronic applications, focus has been placed on better understanding perovskite crystallization from precursor and intermediate phases in order to facilitate improved crystallinity often desirable for advancing optoelectronic properties. Understanding of stability and degradation is also of critical importance as these materials seek commercial applications. In this study, we investigate the evolution of perovskites formed from targeted precursor chemistries by correlating in situ temperature-dependent X-ray diffraction, thermogravimetric analysis, and mass spectral analysis of the evolved species. This suite of analyses reveals important precursor composition-induced variations in the processes underpinning perovskite formation and degradation. The addition of Cl- leads to widely different precursor evolution and perovskite formation kinetics, and results in significant changes to the degradation mechanism, including suppression of crystalline PbI2 formation and modification of the thermal stability of the perovskite phase. This work highlights the role of perovskite precursor chemistry in both its formation and degradation.

  17. pH dependence of the aqueous dissolution rates of perovskite and zirconolite at 90 C

    Perovskite and zirconolite are two of the major phases of the Synroc titanate mineral assemblage. Their aqueous durability under a range of pH conditions at 90 C has been examined. Solution analysis, electron microscopy and X-ray diffraction have been used to investigate the dissolution behavior of these phases, and a perovskite phase doped with Nd, Sr and Al, using buffered solutions at pH levels of 2.1, 3.7, 6.1, 7.9 and 12.9. After 43 days of leaching, Ca and Ti extractions from perovskite and zirconolite show only a weak pH-dependence. SEM investigation of the samples leached at pH 2.1, 6.1 and 12.9 showed that a titanaceous surface layer formed on the perovskite specimens. XRD analysis of the perovskite samples showed that anatase formed on the leached surface at acidic and neutral pHs, but not under alkaline conditions, and that minor amounts of rutile also formed. In the leached perovskite specimens doped with Nd, Sr and Al, no rule was found by XRD and anatase was only detected in the sample leached at pH 2.1. There were no detectable changes in the leached zirconolite samples examined by SEM and XRD

  18. Color-Pure Violet-Light-Emitting Diodes Based on Layered Lead Halide Perovskite Nanoplates.

    Liang, Dong; Peng, Yuelin; Fu, Yongping; Shearer, Melinda J; Zhang, Jingjing; Zhai, Jianyuan; Zhang, Yi; Hamers, Robert J; Andrew, Trisha L; Jin, Song

    2016-07-26

    Violet electroluminescence is rare in both inorganic and organic light-emitting diodes (LEDs). Low-cost and room-temperature solution-processed lead halide perovskites with high-efficiency and color-tunable photoluminescence are promising for LEDs. Here, we report room-temperature color-pure violet LEDs based on a two-dimensional lead halide perovskite material, namely, 2-phenylethylammonium (C6H5CH2CH2NH3(+), PEA) lead bromide [(PEA)2PbBr4]. The natural quantum confinement of two-dimensional layered perovskite (PEA)2PbBr4 allows for photoluminescence of shorter wavelength (410 nm) than its three-dimensional counterpart. By converting as-deposited polycrystalline thin films to micrometer-sized (PEA)2PbBr4 nanoplates using solvent vapor annealing, we successfully integrated this layered perovskite material into LEDs and achieved efficient room-temperature violet electroluminescence at 410 nm with a narrow bandwidth. This conversion to nanoplates significantly enhanced the crystallinity and photophysical properties of the (PEA)2PbBr4 samples and the external quantum efficiency of the violet LED. The solvent vapor annealing method reported herein can be generally applied to other perovskite materials to increase their grain size and, ultimately, improve the performance of optoelectronic devices based on perovskite materials. PMID:27336850

  19. Perovskite-supported palladium for methane oxidation - structure-activity relationships.

    Eyssler, Arnim; Lu, Ye; Matam, Santhosh Kumar; Weidenkaff, Anke; Ferri, Davide

    2012-01-01

    Palladium is the precious metal of choice for methane oxidation and perovskite-type oxides offer the possibility to stabilize it as PdO, considered crucial for catalytic activity. Pd can adopt different oxidation and coordination states when associated with perovskite-type oxides. Here, we review our work on the effect of perovskite composition on the oxidation and coordination states of Pd and its influence on catalytic activity for methane oxidation in the case of typical Mn, Fe and Co perovskite-based oxidation catalysts. Especially X-ray absorption near edge structure (XANES) spectroscopy is shown to be crucial to fingerprint the different coordination states of Pd. Pd substitutes Fe and Co in the octahedral sites but without modifying catalytic activity with respect to the Pd-free perovskite. On LaMnO(3) palladium is predominantly exposed at the surface thus bestowing catalytic activity for methane oxidation. However, the occupancy of B-cation sites of the perovskite structure by Pd can be exploited to cyclically activate Pd and to protect it from particle growth. This is explicitly demonstrated for La(Fe, Pd)O(3), where catalytic activity for methane oxidation is enhanced under oscillating redox conditions at 500 °C, therefore paving the way to the practical application in three-way catalysts for stoichiometric natural gas engines. PMID:23211725

  20. Ambient Engineering for High-Performance Organic-Inorganic Perovskite Hybrid Solar Cells.

    Huang, Jiabin; Yu, Xuegong; Xie, Jiangsheng; Xu, Dikai; Tang, Zeguo; Cui, Can; Yang, Deren

    2016-08-24

    Considering the evaporation of solvents during fabrication of perovskite films, the organic ambience will present a significant influence on the morphologies and properties of perovskite films. To clarify this issue, various ambiences of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and chlorobenzene (CBZ) are introduced during fabrication of perovskite films by two-step sequential deposition method. The results reveal that an ambient CBZ atmosphere is favorable to control the nucleation and growth of CH3NH3PbI3 grains while the others present a negative effect. The statistical results show that the average efficiencies of perovskite solar cells processed in an ambient CBZ atmosphere can be significantly improved by a relatively average value of 35%, compared with those processed under air. The efficiency of the best perovskite solar cells can be improved from 10.65% to 14.55% by introducing this ambience engineering technology. The CH3NH3PbI3 film with large-size grains produced in an ambient CBZ atmosphere can effectively reduce the density of grain boundaries, and then the recombination centers for photoinduced carriers. Therefore, a higher short-circuit current density is achieved, which makes main contribution to the improvement in efficiency. These results provide vital progress toward understanding the role of ambience in the realization of highly efficient perovskite solar cells. PMID:27489961

  1. The efficiency limit of CH3NH3PbI3 perovskite solar cells

    Sha, Wei E. I.; Ren, Xingang; Chen, Luzhou; Choy, Wallace C. H.

    2015-06-01

    With the consideration of photon recycling effect, the efficiency limit of methylammonium lead iodide (CH3NH3PbI3) perovskite solar cells is predicted by a detailed balance model. To obtain convincing predictions, both AM 1.5 spectrum of Sun and experimentally measured complex refractive index of perovskite material are employed in the detailed balance model. The roles of light trapping and angular restriction in improving the maximal output power of thin-film perovskite solar cells are also clarified. The efficiency limit of perovskite cells (without the angular restriction) is about 31%, which approaches to Shockley-Queisser limit (33%) achievable by gallium arsenide (GaAs) cells. Moreover, the Shockley-Queisser limit could be reached with a 200 nm-thick perovskite solar cell, through integrating a wavelength-dependent angular-restriction design with a textured light-trapping structure. Additionally, the influence of the trap-assisted nonradiative recombination on the device efficiency is investigated. The work is fundamentally important to high-performance perovskite photovoltaics.

  2. Oxygen reduction and evolution reactions of air electrodes using a perovskite oxide as an electrocatalyst

    Nishio, Koji; Molla, Sergio; Okugaki, Tomohiko; Nakanishi, Shinji; Nitta, Iwao; Kotani, Yukinari

    2015-03-01

    The oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) of air electrodes consisting of La0.5Sr0.5CoO3 and/or carbon in the electrocatalyst layer are studied by using two types of gas diffusion electrodes. Cyclic voltammetry and square wave voltammetry studies reveal very low ORR activity of carbon-free perovskite and remarkably enhanced ORR of perovskite-carbon composites. The ORR current density at -0.5 V vs. Hg/HgO is higher than 200 mA cm-2 in a wide range of perovskite-carbon composition, suggesting good peroxide reducing capability of the perovskite. The ORR mechanisms of perovskite-carbon composites are consistent with the 2+2-electron mechanisms. The ORR and OER properties of perovskite-carbon composite electrodes are significantly influenced by the carbon species. The electrode exhibits a higher ORR current density, but inferior cycling performances when a carbon material with a higher specific surface area is used, and vice versa. Under a current density of 20 mA cm-2 and ORR and OER durations of 30 min, a gas diffusion type electrode consists of La0.5Sr0.5CoO3 and a low surface area carbon are capable of more than 150 cycles.

  3. Interfacial Study To Suppress Charge Carrier Recombination for High Efficiency Perovskite Solar Cells.

    Adhikari, Nirmal; Dubey, Ashish; Khatiwada, Devendra; Mitul, Abu Farzan; Wang, Qi; Venkatesan, Swaminathan; Iefanova, Anastasiia; Zai, Jiantao; Qian, Xuefeng; Kumar, Mukesh; Qiao, Qiquan

    2015-12-01

    We report effects of an interface between TiO2-perovskite and grain-grain boundaries of perovskite films prepared by single step and sequential deposited technique using different annealing times at optimum temperature. Nanoscale kelvin probe force microscopy (KPFM) measurement shows that charge transport in a perovskite solar cell critically depends upon the annealing conditions. The KPFM results of single step and sequential deposited films show that the increase in potential barrier suppresses the back-recombination between electrons in TiO2 and holes in perovskite. Spatial mapping of the surface potential within perovskite film exhibits higher positive potential at grain boundaries compared to the surface of the grains. The average grain boundary potential of 300-400 mV is obtained upon annealing for sequentially deposited films. X-ray diffraction (XRD) spectra indicate the formation of a PbI2 phase upon annealing which suppresses the recombination. Transient analysis exhibits that the optimum device has higher carrier lifetime and short carrier transport time among all devices. An optimum grain boundary potential and proper band alignment between the TiO2 electron transport layer (ETL) and the perovskite absorber layer help to increase the overall device performance. PMID:26579732

  4. The efficiency limit of CH3NH3PbI3 perovskite solar cells

    With the consideration of photon recycling effect, the efficiency limit of methylammonium lead iodide (CH3NH3PbI3) perovskite solar cells is predicted by a detailed balance model. To obtain convincing predictions, both AM 1.5 spectrum of Sun and experimentally measured complex refractive index of perovskite material are employed in the detailed balance model. The roles of light trapping and angular restriction in improving the maximal output power of thin-film perovskite solar cells are also clarified. The efficiency limit of perovskite cells (without the angular restriction) is about 31%, which approaches to Shockley-Queisser limit (33%) achievable by gallium arsenide (GaAs) cells. Moreover, the Shockley-Queisser limit could be reached with a 200 nm-thick perovskite solar cell, through integrating a wavelength-dependent angular-restriction design with a textured light-trapping structure. Additionally, the influence of the trap-assisted nonradiative recombination on the device efficiency is investigated. The work is fundamentally important to high-performance perovskite photovoltaics

  5. Acetate Salts as Nonhalogen Additives To Improve Perovskite Film Morphology for High-Efficiency Solar Cells.

    Wu, Qiliang; Zhou, Pengcheng; Zhou, Weiran; Wei, Xiangfeng; Chen, Tao; Yang, Shangfeng

    2016-06-22

    A two-step method has been popularly adopted to fabricate a perovskite film of planar heterojunction organo-lead halide perovskite solar cells (PSCs). However, this method often generates uncontrollable film morphology with poor coverage. Herein, we report a facile method to improve perovskite film morphology by incorporating a small amount of acetate (CH3COO(-), Ac(-)) salts (NH4Ac, NaAc) as nonhalogen additives in CH3NH3I solution used for immersing PbI2 film, resulting in improved CH3NH3PbI3 film morphology. Under the optimized NH4Ac additive concentration of 10 wt %, the best power conversion efficiency (PCE) reaches 17.02%, which is enhanced by ∼23.2% relative to that of the pristine device without additive, whereas the NaAc additive does not lead to an efficiency enhancement despite the improvement of the CH3NH3PbI3 film morphology. SEM study reveals that NH4Ac and NaAc additives can both effectively improve perovskite film morphology by increasing the surface coverage via diminishing pinholes. The improvement on CH3NH3PbI3 film morphology is beneficial for increasing the optical absorption of perovskite film and improving the interfacial contact at the perovskite/spiro-OMeTAD interface, leading to the increase of short-circuit current and consequently efficiency enhancement of the PSC device for NH4Ac additive only. PMID:27253082

  6. Two-Dimensional CH3NH3PbI3 Perovskite: Synthesis and Optoelectronic Application.

    Liu, Jingying; Xue, Yunzhou; Wang, Ziyu; Xu, Zai-Quan; Zheng, Changxi; Weber, Bent; Song, Jingchao; Wang, Yusheng; Lu, Yuerui; Zhang, Yupeng; Bao, Qiaoliang

    2016-03-22

    Hybrid organic-inorganic perovskite materials have received substantial research attention due to their impressively high performance in photovoltaic devices. As one of the oldest functional materials, it is intriguing to explore the optoelectronic properties in perovskite after reducing it into a few atomic layers in which two-dimensional (2D) confinement may get involved. In this work, we report a combined solution process and vapor-phase conversion method to synthesize 2D hybrid organic-inorganic perovskite (i.e., CH3NH3PbI3) nanocrystals as thin as a single unit cell (∼1.3 nm). High-quality 2D perovskite crystals have triangle and hexagonal shapes, exhibiting tunable photoluminescence while the thickness or composition is changed. Due to the high quantum efficiency and excellent photoelectric properties in 2D perovskites, a high-performance photodetector was demonstrated, in which the current can be enhanced significantly by shining 405 and 532 nm lasers, showing photoresponsivities of 22 and 12 AW(-1) with a voltage bias of 1 V, respectively. The excellent optoelectronic properties make 2D perovskites building blocks to construct 2D heterostructures for wider optoelectronic applications. PMID:26910395

  7. Modeling the PbI2 formation in perovskite solar cells using XRD/XPS patterns

    Sohrabpoor, Hamed; Elyasi, Majid; Aldosari, Marouf; Gorji, Nima E.

    2016-09-01

    The impact of prolonged irradiation and air humidity on the stability of perovskite solar cells is modeled using X-ray diffraction and X-ray photoelectron spectroscopy patterns reported in the literature. Light or air-moisture causes the formation of a thin PbI2 or oxide defective layers (in nanoscale) at the interface of perovskite/hole-transport-layer or at the junction with metallic back contact. This thin layer blocks the carrier transport/passivation at the interfaces and cause degradation of device parameters. Variation in thickness of defective layers, changes the XRD and XPS peaks. This allows detection and estimation of the type, crystallinity and thickness of the defective layer. A simple model is developed here to extract the thickness of such thin defective layers formed in nanometer scale at the back region of several perovskite devices. Based on this information, corrected energy band diagram of every device before and after degradation/aging is drawn and discussed in order to obtain insight into the carrier transport and charge collection at the barrier region. In addition, graphene contacted perovskite devices are investigated showing that honey-comb network of graphene contact reduces the effect of aging leading to formation of a thinner defective layer at the perovskite surface compared to perovskite devices with conventional inorganic contacts i.e. Au, Al.

  8. Crystallographic and Electronic Structure of the Sr3Sb2CoO9 Triple Perovskite

    Compounds The perovskites are materials with physical and chemical characteristics that make them optimal for application in the technological and scientist. When the ideal formula of perovskite ABO3 is modified by introducing a special structural arrangement can get to get triple perovskites, which correspond to the formula A3B2B'O9. In this work we report the synthesis process and the study of electronic structure and crystal Sr3Sb2CoO9 new triple perovskite. From the experiments of X-ray Diffraction and the application of the Rietveld refinement method was revealed that the system crystallizes in a perovskite structure with a characteristic triple given by the space group Immm (#71) and lattice parameters a=9.791(9) Å, b=5.656(7) Å and c=16.957(8) Å. Ab initio calculations of density of states (DOS) and electronic structure were carried out for this perovskite-like system by using the Quantum EXPRESSO code. The exchange-correlation potential was treated using the Generalized Gradient Approximation (GGA). All calculations were carried-out using spin polarization.

  9. Comparison of different advanced oxidation processes (AOPs) in the presence of perovskites

    The efficacy of the oxidation systems: O3, UV radiation, O3/UV radiation, O3/perovskite, UV radiation/perovskite, O3/UV radiation/perovskite, H2O2/UV radiation, H2O2/UV radiation/perovskite, has been investigated by using pyruvic acid as probe compound. Under the operating conditions used, the combination of UV radiation and hydrogen peroxide (with or without perovskites) leads to the fastest pyruvic acid removal while the best results in terms of mineralization degree are obtained when combining O3/UV radiation/perovskite. The effect of the variables: inlet ozone (15-75 mg L-1) and initial pyruvic acid (10-3 to 10-2 M) concentrations, catalyst load (0.01-1.5 g L-1) and pH (2-9) was investigated for the photocatalytic ozonation. The most influencing parameter was the ozone concentration fed to the photoreactor. A zero order was observed for pyruvic acid concentration and close to zero for catalyst load. Some deactivation is observed after reusing the catalyst, likely due to leaching of the active phase

  10. Performance Improvement of CH3NH3PbI3 Perovskite Solar Cell by CH3SH Doping

    Hong Li; Yingguo Yang; Xiao Feng; Kongchao Shen; Haiyang Li; Jiong Li; Zheng Jiang; Fei Song

    2016-01-01

    Organometal halide perovskites have recently emerged as an appealing candidate in photovoltaic devices due to their excellent properties. Therefore, intense efforts have been devoted to find the ideal organics for perovskite solar cells. In response, we investigate the doping effect of CH3SH organic on the structure and related performance of a CH3NH3PbI3 perovskite solar cell, via in situ synchrotron- based grazing incidence X-ray diffraction (GIXRD), together with scanning electron microsco...

  11. Material Innovation in Advancing Organometal Halide Perovskite Functionality.

    Zheng, Fan; Saldana-Greco, Diomedes; Liu, Shi; Rappe, Andrew M

    2015-12-01

    Organometal halide perovskites (OMHPs) have garnered much attention recently for their unprecedented rate of increasing power conversion efficiency (PCE), positioning them as a promising basis for the next-generation photovoltaic devices. However, the gap between the rapid increasing PCE and the incomplete understanding of the structure-property-performance relationship prevents the realization of the true potential of OMHPs. This Perspective aims to provide a concise overview of the current status of OMHP research, highlighting the unique properties of OMHPs that are critical for solar applications but still not adequately explained. Stability and performance challenges of OMHP solar cells are discussed, calling upon combined experimental and theoretical efforts to address these challenges for pioneering commercialization of OMHP solar cells. Various material innovation strategies for improving the performance and stability of OMHPs are surveyed, showing that the OMHP architecture can serve as a promising and robust platform for the design and optimization of materials with desired functionalities. PMID:26631361

  12. Ferroelectric phase formation with perovskite structure containing niobates

    Compounds of the perovskite type with general formulation Pb(AB)O3 are very useful for application on multylayers ceramic capacitors. They can show high dielectric constants, how temperature. The objetive of this work is to study the variables of the preparation process of the Pb (Mg1/3 Nb2/3)O3 phase (PMN) and to minimize the pyroclore Pb3Nb2O8 P3N formation. Using salts as Mg(NO3)2.6H2O, Pb(NO3)2, Nb2O5. nH2O, NH4N2 (NbO(C2O4)3). 3H2O, we tyed to optimize the time, the temperature and the obtaining process of the PMN phase. The obtained powders were characterized by X-ray diffraction and specific surface area measurements. (author)

  13. Gaps and pseudogaps in perovskite rare earth nickelates

    Allen, S. James; Ouellette, Daniel G.; Kally, James; Kozhanov, Alex [Department of Physics, University of California, Santa Barbara, California 93106 (United States); Hauser, Adam J.; Mikheev, Evgeny; Zhang, Jack Y.; Moreno, Nelson E.; Son, Junwoo; Stemmer, Susanne [Materials Department, University of California, Santa Barbara, California 93106 (United States); Balents, Leon [Department of Physics, University of California, Santa Barbara, California 93106 (United States); Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States)

    2015-06-01

    We report on tunneling measurements that reveal the evolution of the quasiparticle state density in two rare earth perovskite nickelates, NdNiO{sub 3} and LaNiO{sub 3}, that are close to a bandwidth controlled metal to insulator transition. We measure the opening of a sharp gap of ∼30 meV in NdNiO{sub 3} in its insulating ground state. LaNiO{sub 3}, which remains a correlated metal at all practical temperatures, exhibits a pseudogap of the same order. The results point to both types of gaps arising from a common origin, namely, a quantum critical point associated with the T = 0 K metal-insulator transition. The results support theoretical models of the quantum phase transition in terms of spin and charge instabilities of an itinerant Fermi surface.

  14. Antiferromagnetic resonance in the cubic perovskite KNiF3

    Yamaguchi, H.; Katsumata, K.; Hagiwara, M.; Tokunaga, M.; Liu, H. L.; Zibold, A.; Tanner, D. B.; Wang, Y. J.

    1999-03-01

    Low-temperature high-magnetic-field far-infrared spectroscopy and electron-spin-resonance measurements have been performed on single crystals of the cubic perovskite KNiF3. We found the absorption at 48.7+/-0.3 cm-1 observed by Richards [P. L. Richards, J. Appl. Phys. 34, 1237 (1963)] that was attributed to antiferromagnetic resonance (AFMR) is not magnetic in origin. Instead, a different absorption is well fit by a theory of AFMR with uniaxial anisotropy. Analysis yields an anisotropy energy of 8.7×10-3 cm-1. The ratio between the anisotropy field and the exchange field is 2.4×10-5. Thus, KNiF3 is an excellent example of a Heisenberg antiferromagnet.

  15. Improving the Performance of Perovskite in Nonaqueous Oxygen Electrocatalysis.

    Lu, Meihua; Xu, Chaohe; Zhan, Yi; Lee, Jim Yang

    2016-04-20

    Nanoparticle (NP) aggregates of lanthanum cobalt oxide perovskite (LCO) were compounded with reduced graphene oxide (rGO) nanosheets and used as the cathode catalyst for nonaqueous lithium-oxygen batteries (LOBs). The LCO NP aggregates were completely surrounded by rGO nanosheets in the composite with 10.5 wt % of rGO (LCO-rGO-10.5) but were partially exposed in the composite with 7.5 wt % of rGO (LCO-rGO-7.5). Both composites performed better than pristine LCO NPs and rGO nanosheets in nonaqueous oxygen electrocatalysis. The LCO-rGO-7.5 composite excelled at capacity and rate performance, while the LCO-rGO-10.5 composite was better at cycle stability. The good performance of the LCO-rGO composites was due to the synergy of functions of LCO and rGO. PMID:26663461

  16. Giant photostriction in organic-inorganic lead halide perovskites

    Zhou, Yang; You, Lu; Wang, Shiwei; Ku, Zhiliang; Fan, Hongjin; Schmidt, Daniel; Rusydi, Andrivo; Chang, Lei; Wang, Le; Ren, Peng; Chen, Liufang; Yuan, Guoliang; Chen, Lang; Wang, Junling

    2016-04-01

    Among the many materials investigated for next-generation photovoltaic cells, organic-inorganic lead halide perovskites have demonstrated great potential thanks to their high power conversion efficiency and solution processability. Within a short period of about 5 years, the efficiency of solar cells based on these materials has increased dramatically from 3.8 to over 20%. Despite the tremendous progress in device performance, much less is known about the underlying photophysics involving charge-orbital-lattice interactions and the role of the organic molecules in this hybrid material remains poorly understood. Here, we report a giant photostrictive response, that is, light-induced lattice change, of >1,200 p.p.m. in methylammonium lead iodide, which could be the key to understand its superior optical properties. The strong photon-lattice coupling also opens up the possibility of employing these materials in wireless opto-mechanical devices.

  17. Defect density and dielectric constant in perovskite solar cells

    We report on measurement of dielectric constant, mid-gap defect density, Urbach energy of tail states in CH3NH3PbIxCl1−x perovskite solar cells. Midgap defect densities were estimated by measuring capacitance vs. frequency at different temperatures and show two peaks, one at 0.66 eV below the conduction band and one at 0.24 eV below the conduction band. The attempt to escape frequency is in the range of 2 × 1011/s. Quantum efficiency data indicate a bandgap of 1.58 eV. Urbach energies of valence and conduction band are estimated to be ∼16 and ∼18 meV. Measurement of saturation capacitance indicates that the relative dielectric constant is ∼18.

  18. Charge Trapping in Photovoltaically Active Perovskites and Related Halogenoplumbate Compounds.

    Shkrob, Ilya A; Marin, Timothy W

    2014-04-01

    Halogenoplumbate perovskites (MeNH3PbX3, where X is I and/or Br) have emerged as promising solar panel materials. Their limiting photovoltaic efficiency depends on charge localization and trapping processes that are presently insufficiently understood. We demonstrate that in halogenoplumbate materials the holes are trapped by organic cations (that deprotonate from their oxidized state) and Pb(2+) cations (as Pb(3+) centers), whereas the electrons are trapped by several Pb(2+) cations, forming diamagnetic lead clusters that also serve as color centers. In some cases, paramagnetic variants of these clusters can be observed. We suggest that charge separation in the halogenoplumbates resembles latent image formation in silver halide photography. Electron and hole trapping by lead clusters in extended dislocations in the bulk may be responsible for accumulation of trapped charge observed in this photovoltaic material. PMID:26274450

  19. Defect density and dielectric constant in perovskite solar cells

    Samiee, Mehran; Konduri, Siva; Abbas, Hisham A.; Joshi, Pranav; Zhang, Liang; Dalal, Vikram, E-mail: vdalal@iastate.edu [Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011 (United States); Ganapathy, Balaji; Kottokkaran, Ranjith; Noack, Max [Microelectronics Research Center, Iowa State University, Ames, Iowa 50011 (United States); Kitahara, Andrew [Department of Materials Science and Engineering, Iowa State University, Ames, Iowa 50011 (United States)

    2014-10-13

    We report on measurement of dielectric constant, mid-gap defect density, Urbach energy of tail states in CH{sub 3}NH{sub 3}PbI{sub x}Cl{sub 1−x} perovskite solar cells. Midgap defect densities were estimated by measuring capacitance vs. frequency at different temperatures and show two peaks, one at 0.66 eV below the conduction band and one at 0.24 eV below the conduction band. The attempt to escape frequency is in the range of 2 × 10{sup 11}/s. Quantum efficiency data indicate a bandgap of 1.58 eV. Urbach energies of valence and conduction band are estimated to be ∼16 and ∼18 meV. Measurement of saturation capacitance indicates that the relative dielectric constant is ∼18.

  20. Performance of genetic algorithms in search for water splitting perovskites

    Jain, A.; Castelli, Ivano Eligio; Hautier, G.;

    2013-01-01

    We examine the performance of genetic algorithms (GAs) in uncovering solar water light splitters over a space of almost 19,000 perovskite materials. The entire search space was previously calculated using density functional theory to determine solutions that fulfill constraints on stability, band...... performance of the GA can be further improved to approximately 12–17 better than random search. We discuss the effect of population size, selection function, crossover function, mutation rate, fitness function, and elitism on the final result, finding that selection function and elitism are especially...... important to GA performance. In addition, we determine that parameters that perform well in finding solar water splitters can also be applied to discovering transparent photocorrosion shields. Our results indicate that coupling GAs to high-throughput density functional calculations presents a promising...