ODH, oxygen deficiency hazard cryogenic analysis

International Nuclear Information System (INIS)

Augustynowicz, S.D.

1994-01-01

An oxygen deficiency exists when the concentration of oxygen, by volume, drops to a level at which atmosphere supplying respiratory protection must be provided. Since liquid cryogens can expand by factors of 700 (LN 2 ) to 850 (LH e ), the uncontrolled release into an enclosed space can easily cause an oxygen-deficient condition. An oxygen deficiency hazard (ODH) fatality rate per hour (OE) is defined as: OE = Σ N i P i F i , where N i = number of components, P i = probability of failure or operator error, and F i = fatality factor. ODHs range from open-quotes unclassifiedclose quotes (OE -9 1/h) to class 4, which is the most hazardous (OE>10 -1 1/h). For Superconducting Super Collider Laboratory (SSCL) buildings where cryogenic systems exist, failure rate, fatality factor, reduced oxygen ratio, and fresh air circulation are examined

Perovskite-related oxide materials for oxygen-permeable electrochemical membrans

OpenAIRE

Naumovich, E. N.; Yaremchenko, A. A.; Viskup, A. P.; Kharton, V. V.

2003-01-01

This brief review is focused on the studies of mixed ionic-electronic conductors on the basis of lanthanum gallate doped with transition metal cations in the В sublattice. The substitution of gallium with iron, cobalt or nickel results in greater electronic conductivity, simultaneously keeping high level of the oxy-gen ionic transport. In particular, La0 90Sr0 10Ga0 65Ni0 20Mg0 1503d perovskite exhib-its attractive oxygen permeability, which is quite similar to that of La2Ni04- and (...

Investigation of ferromagnetism in oxygen deficient hafnium oxide thin films

Energy Technology Data Exchange (ETDEWEB)

Hildebrandt, Erwin; Kurian, Jose; Krockenberger, Yoshiharu; Alff, Lambert [Institut fuer Materialwissenschaft, TU Darmstadt (Germany); Suter, Andreas [PSI, Villingen (Switzerland); Wilhelm, Fabrice; Rogalev, Andrei [ESRF, Grenoble (France)

2008-07-01

Oxygen deficient thin films of hafnium oxide were grown on single crystal r-cut and c-cut sapphire by reactive molecular beam epitaxy. RF-activated oxygen was used for the in situ oxidation of hafnium oxide thin films. Oxidation conditions were varied substantially in order to create oxygen deficiency in hafnium oxide films intentionally. The films were characterized by X-ray and magnetic measurements. X-ray diffraction studies show an increase in lattice parameter with increasing oxygen deficiency. Oxygen deficient hafnium oxide thin films also showed a decreasing bandgap with increase in oxygen deficiency. The magnetisation studies carried out with SQUID did not show any sign of ferromagnetism in the whole oxygen deficiency range. X-ray magnetic circular dichroism measurements also confirmed the absence of ferromagnetism in oxygen deficient hafnium oxide thin films.

Activity and stability trends of perovskite oxides for oxygen evolution catalysis at neutral pH

OpenAIRE

Ling, Chen; Jia, Hongfei; Han, Binghong; Risch, Marcel; Lee, Yueh Lin; Shao-Horn, Yang

2015-01-01

Perovskite oxides (ABO[subscript 3]) have been studied extensively to promote the kinetics of the oxygen evolution reaction (OER) in alkaline electrolytes. However, developing highly active catalysts for OER at near-neutral pH is desirable for many photoelectrochemical/electrochemical devices. In this paper, we systematically studied the activity and stability of well-known perovskite oxides for OER at pH 7. Previous activity descriptors established for perovskite oxides at pH 13, such as hav...

Synthesis and Structure of A New Perovskite, SrCuO 2.5

Science.gov (United States)

Chen, Bai-Hao; Walker, Dave; Scott, Bruce A.; Mitzi, David B.

1996-02-01

A new oxygen-deficient perovskite, SrCuO2.5, was prepared at 950°C and 100 kbar pressure in a multianvil apparatus. Rietveld profile analysis, using X-ray powder diffraction data, was employed for the structural determination. SrCuO2.5is orthorhombic,Pbam(No. 55),Z= 4,a= 5.424(2) Â,b= 10.837(4) Â, andc= 3.731(1) Â, which is related to the perovskite subcell by root{2}ap× 2root{2}ap×ap, whereapis the simple cubic perovskite lattice parameter. It consists of corner-shared CuO5square pyramids with oxygen vacancy ordering in the CuO2layers. The ordered oxygen vacancies create parallel pseudo-hexagonal tunnels where the Sr atoms reside, forming SrO10polyhedra. Structural features with respect to oxygen vacancies, superstructures, and distortions are analogous to the type of ordering observed in Sr2CuO3+δ. Superconductivity was not observed in SrCuO2.5down to 5 K.

Factors Controlling the Redox Activity of Oxygen in Perovskites: From Theory to Application for Catalytic Reactions

Directory of Open Access Journals (Sweden)

Chunzhen Yang

2017-05-01

Full Text Available Triggering the redox reaction of oxygens has become essential for the development of (electro catalytic properties of transition metal oxides, especially for perovskite materials that have been envisaged for a variety of applications such as the oxygen evolution or reduction reactions (OER and ORR, respectively, CO or hydrocarbons oxidation, NO reduction and others. While the formation of ligand hole for perovskites is well-known for solid state physicists and/or chemists and has been widely studied for the understanding of important electronic properties such as superconductivity, insulator-metal transitions, magnetoresistance, ferroelectrics, redox properties etc., oxygen electrocatalysis in aqueous media at low temperature barely scratches the surface of the concept of oxygen ions oxidation. In this review, we briefly explain the electronic structure of perovskite materials and go through a few important parameters such as the ionization potential, Madelung potential, and charge transfer energy that govern the oxidation of oxygen ions. We then describe the surface reactivity that can be induced by the redox activity of the oxygen network and the formation of highly reactive surface oxygen species before describing their participation in catalytic reactions and providing mechanistic insights and strategies for designing new (electro catalysts. Finally, we give a brief overview of the different techniques that can be employed to detect the formation of such transient oxygen species.

Perovskite oxides: Oxygen electrocatalysis and bulk structure

Science.gov (United States)

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.

The lanthanum gallate-based mixed conducting perovskite ceramics

International Nuclear Information System (INIS)

Politova, E.D.; Stefanovich, S.Yu.; Aleksandrovskii, V.V.; Kaleva, G.M.; Mosunov, A.V.; Avetisov, A.K.; Sung, J.S.; Choo, K.Y.; Kim, T.H.

2005-01-01

The structure, microstructure, dielectric, and transport properties of the anion deficient perovskite solid solutions (La,Sr)(Ga,Mg,M)O 3-δ with M=Fe, Ni have been studied. Substitution of iron and nickel for gallium up to about 20 and 40 at.% respectively, leads to the perovskite lattice contraction due to the cation substitutions by the transition elements. The transition from pure ionic to mixed ionic-electronic conductivity was observed for both the systems studied. Both the enhancement of total conductivity and increasing in the thermal expansion coefficient values has been proved to correlate with the increasing amount of weakly bounded oxygen species in the Fe or Ni-doped ceramics. The oxygen ionic conductivity has been estimated from the kinetic experiments using the dc-conductivity and dilatometry methods under the condition of the stepwise change of the atmosphere from nitrogen to oxygen. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

The lanthanum gallate-based mixed conducting perovskite ceramics

Energy Technology Data Exchange (ETDEWEB)

Politova, E.D.; Stefanovich, S.Yu.; Aleksandrovskii, V.V.; Kaleva, G.M.; Mosunov, A.V.; Avetisov, A.K. [L.Ya. Karpov Institute of Physical Chemistry, Vorontsovo pole 10, 105064 Moscow (Russian Federation); Sung, J.S.; Choo, K.Y.; Kim, T.H. [Korea Institute of Energy Research, 71-2 Jang-dong Yooseong, Daejeon (Korea)

2005-01-01

The structure, microstructure, dielectric, and transport properties of the anion deficient perovskite solid solutions (La,Sr)(Ga,Mg,M)O{sub 3-{delta}} with M=Fe, Ni have been studied. Substitution of iron and nickel for gallium up to about 20 and 40 at.% respectively, leads to the perovskite lattice contraction due to the cation substitutions by the transition elements. The transition from pure ionic to mixed ionic-electronic conductivity was observed for both the systems studied. Both the enhancement of total conductivity and increasing in the thermal expansion coefficient values has been proved to correlate with the increasing amount of weakly bounded oxygen species in the Fe or Ni-doped ceramics. The oxygen ionic conductivity has been estimated from the kinetic experiments using the dc-conductivity and dilatometry methods under the condition of the stepwise change of the atmosphere from nitrogen to oxygen. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Oxygen doping of the high T/sub c/ superconducting perovskites

International Nuclear Information System (INIS)

Tarascon, J.M.; McKinnon, W.R.; Greene, L.H.; Hull, G.W.; Bagley, B.G.; Vogel, E.M.; Le Page, Y.

1987-01-01

Oxygen defect perovskites are studied because of their ability to reversibly intercalate oxygen atoms. Our previous studies of the La/sub 2-y/Sr/sub y/CuO/sub 4-x/ system shows that T/sub c/ is dramatically affected by subtle changes in oxygen content. However since this study did not achieve large values of x, a systematic study was not undertaken. The authors have found by thermogravimetric analysis (TGA) that a wide range of oxygen non-stoichiometry in the 90K superconductor YBa/sub 2/Cu/sub 3/O/sub 7-x/ is obtainable. This study of the effect of oxygen doping on the transport properties of the 40K material, and a systematic analysis of this over a broader range in the 90K superconductor is presented

Oxygen deficiency at CERN: Hazards, risks & mitigation measures

CERN Multimedia

CERN. Geneva

2016-01-01

Compressed and liquified gases are used at many places at CERN. If they are introduced to the atmosphere, they can present an oxygen deficiency hazard (ODH) and lead to reduced abilities, unconsciousness or even death. The CERN method for ODH risk assessments is done on a case-by-case basis as each situation is unique. It is crucial to make sure the personnel can evacuate safely in case of an ODH situation. My talk will explain human reactions to reduced oxygen levels and I will give some practical examples on how one can assess and control the hazards from a possible oxygen deficient atmosphere. Some real accidents involving oxygen deficiency will also be mentioned.

Carbon-Coated Perovskite BaMnO3 Porous Nanorods with Enhanced Electrocatalytic Perporites for Oxygen Reduction and Oxygen Evolution

International Nuclear Information System (INIS)

Xu, Yujiao; Tsou, Alvin; Fu, Yue; Wang, Jin; Tian, Jing-Hua; Yang, Ruizhi

2015-01-01

A thin carbon layer has been introduced to coat on the perovskite BaMnO 3 nanorods by a facile method, which exhibit significantly enhanced electrocatalytic activity for both the ORR and OER with excellent stability. - Highlights: • A non-rare-earth element based perovskite BaMnO 3 nanorods as an active electrocatalyst for the ORR and OER have been prepared and investigated for the first time. • A thin carbon-coating layer with thickness of approximately 10 nm has been successfully introduced to enhance the electrical conductivity and the electrocatalytic activities of the bare perovskite for both ORR and OER. • The stabilities of bare BaMnO 3 nanorods for both ORR and OER have also been improved dramatically with the help of carbon coating, especially for the OER process. - Abstract: Highly efficient, low-cost catalysts, especially with bifunctional electrocatalytic capabilities for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are vital for the wide commercialization of fuel cells and metal-air batteries. In this study, BaMnO 3 - a non-rare-earth element based perovskite nanorods have been prepared and investigated for the first time, and a thin carbon-coating with a thickness of approximately 10 nm has been successfully introduced to enhance the electrical conductivity of the bare perovskite. Electrochemical tests reveal that bare BaMnO 3 nanorods exhibit very good catalytic activity. More interestingly, a remarkably enhanced ORR activity for the perovskite BaMnO 3 nanorods was observed after coating with a thin layer of carbon, which dominated with a direct four-electron pathway. Meanwhile, the OER process has also been enhanced extraordinarily with the carbon-coating, reaching a maximum of 14.8 mA cm −2 at 1.0 V (vs. Ag/AgCl), which is far superior to both the bare BaMnO 3 nanorods and commercial Pt/C (20 wt%) catalysts. Furthermore, the stabilities of bare BaMnO 3 nanorods for both ORR and OER have also been improved

Surface strontium enrichment on highly active perovskites for oxygen electrocatalysis in solid oxide fuel cells

KAUST Repository

Crumlin, Ethan J.; Mutoro, Eva; Liu, Zhi; Grass, Michael E.; Biegalski, Michael D.; Lee, Yueh-Lin; Morgan, Dane; Christen, Hans M.; Bluhm, Hendrik; Shao-Horn, Yang

2012-01-01

Perovskite oxides have high catalytic activities for oxygen electrocatalysis competitive to platinum at elevated temperatures. However, little is known about the oxide surface chemistry that influences the activity near ambient oxygen partial pressures, which hampers the design of highly active catalysts for many clean-energy technologies such as solid oxide fuel cells. Using in situ synchrotron-based, ambient pressure X-ray photoelectron spectroscopy to study the surface chemistry changes, we show that the coverage of surface secondary phases on a (001)-oriented La 0.8Sr 0.2CoO 3-δ (LSC) film becomes smaller than that on an LSC powder pellet at elevated temperatures. In addition, strontium (Sr) in the perovskite structure enriches towards the film surface in contrast to the pellet having no detectable changes with increasing temperature. We propose that the ability to reduce surface secondary phases and develop Sr-enriched perovskite surfaces of the LSC film contributes to its enhanced activity for O 2 electrocatalysis relative to LSC powder-based electrodes. © 2012 The Royal Society of Chemistry.

A-Site Deficient (Pr0.6Sr0.4)(1-s)Fe0.8Co0.2O3-delta Perovskites as Solid Oxide Fuel Cell Cathodes

DEFF Research Database (Denmark)

Kammer Hansen, Kent

2009-01-01

Five A-site deficient (Pr0.6Sr0.4)1−sFe0.8Co0.2O3− perovskites (s=0.01, 0.05, 0.10, 0.15, and 0.20) were synthesized using the glycine-nitrate process. The perovskites were characterized with powder X-ray diffraction (XRD), dilatometry, four-point dc conductivity measurements, and electrochemical...... resistance more than 3 times lower than the weakly A-site deficient (Pr0.6Sr0.4)0.99Fe0.8Co0.2O3− perovskite. ©2009 The Electrochemical Society...

Formation and Migration of Oxygen Vacancies in SrCoO3 and their effect on Oxygen Evolution Reactions

KAUST Repository

Tahini, Hassan A.; Tan, Xin; Schwingenschlö gl, Udo; Smith, Sean C.

2016-01-01

Perovskite SrCoO3 is a potentially useful material for promoting the electrocatalytic oxygen evolution reaction, with high activities predicted theoretically and observed experimentally for closely related doped perovskite materials. However, complete stoichiometric oxidation is very difficult to realize experimentally – in almost all cases there are significant fractions of oxygen vacancies present. Here, using first principles calculations we study oxygen vacancies in perovskite SrCoO3 from thermodynamic, electronic and kinetic points of view. We find that an oxygen vacancy donates two electrons to neighboring Co sites in the form of localized charge. The formation energy of a single vacancy is very low and estimated to be 1.26 eV in the dilute limit. We find that a vacancy is quite mobile with a migration energy of ~0.5 eV. Moreover, we predict that oxygen vacancies exhibit a tendency towards clustering which is in accordance with the material’s ability to form a variety of oxygen-deficient structures. These vacancies have a profound effect on the material’s ability to facilitate OER, increasing the overpotential from ~0.3 V for the perfect material to ~0.7 for defective surfaces. A moderate compressive biaxial strain (2%) is predicted here to increase the surface oxygen vacancy formation energy by ca. 30%, thus reducing the concentration of surface vacancies and thereby preserving the OER activity of the material.

Formation and Migration of Oxygen Vacancies in SrCoO3 and their effect on Oxygen Evolution Reactions

KAUST Repository

Tahini, Hassan A.

2016-07-18

Perovskite SrCoO3 is a potentially useful material for promoting the electrocatalytic oxygen evolution reaction, with high activities predicted theoretically and observed experimentally for closely related doped perovskite materials. However, complete stoichiometric oxidation is very difficult to realize experimentally – in almost all cases there are significant fractions of oxygen vacancies present. Here, using first principles calculations we study oxygen vacancies in perovskite SrCoO3 from thermodynamic, electronic and kinetic points of view. We find that an oxygen vacancy donates two electrons to neighboring Co sites in the form of localized charge. The formation energy of a single vacancy is very low and estimated to be 1.26 eV in the dilute limit. We find that a vacancy is quite mobile with a migration energy of ~0.5 eV. Moreover, we predict that oxygen vacancies exhibit a tendency towards clustering which is in accordance with the material’s ability to form a variety of oxygen-deficient structures. These vacancies have a profound effect on the material’s ability to facilitate OER, increasing the overpotential from ~0.3 V for the perfect material to ~0.7 for defective surfaces. A moderate compressive biaxial strain (2%) is predicted here to increase the surface oxygen vacancy formation energy by ca. 30%, thus reducing the concentration of surface vacancies and thereby preserving the OER activity of the material.

CaCu3Ti4O12: A Bifunctional Perovskite Electrocatalyst for Oxygen Evolution and Reduction Reaction in Alkaline Medium

International Nuclear Information System (INIS)

Kushwaha, H.S.; Halder, Aditi; Thomas, P.; Vaish, Rahul

2017-01-01

Highlights: •A cost effective double perovskite CaCu 3 Ti 4 O 12 have been synthesized using oxalate precursor method. •CCTO electrocatalyst exhibit enhanced bifunctional electrocatalytic activities. •CCTO electrocatalyst have lower overpotential and higher mass activity as compared to noble metal oxide and well-known perovskite catalysts. •Electrochemical impedance spectroscopy investigations of oxygen reactions on perovskite surfaces. -- Abstract: Perovskite oxides are prominent materials as the bifunctional electrocatalysts for both oxygen reduction/evolution reactions (ORR/OER) for the electrochemical energy conversion and storage using regenerative fuel cells and rechargeable metal-air batteries. In this work, a quadruple perovskite CaCu 3 Ti 4 O 12 has been synthesized oxalate precursor route. X-ray diffraction pattern shows phase purity of the synthesized electrocatalyst. The synthesized CCTO electrocatalyst have crystallite size of 26 nm. Electrochemical investigations reveal that CCTO exhibit efficient catalytic activity. More interestingly, an extremely high OER activity is observed for CCTO electrocatalysts which is found superior than similar class of perovskites. Additionally, CCTO shows efficient ORR activity with an onset potential of 0.83 V which is better than that of Pt/C catalyst (≈0.94 V). These results demonstrate the significant potential of CCTO perovskite as a bifunctional electrode material for alkaline fuel cells and metal-air batteries.

Oxygen evolution studies on perovskite films in alkaline media

Energy Technology Data Exchange (ETDEWEB)

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.

A novel zincum-doped perovskite-type ceramic membrane for oxygen separation

Energy Technology Data Exchange (ETDEWEB)

Chen Xinzhi; Liu Hongfei; Wei Yanying [School of Chemistry and Chemical Engineering, South China University of Technology, No. 381 Wushan Road, 510640 Guangzhou (China); Caro Juergen [Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Callinstr. 3-3A D-30179 Hannover (Germany); Wang Haihui, E-mail: hhwang@scut.edu.c [School of Chemistry and Chemical Engineering, South China University of Technology, No. 381 Wushan Road, 510640 Guangzhou (China)

2009-09-18

Zincum-doped ceramic membrane materials based on BaCo{sub 0.4}Fe{sub 0.4}Zn{sub x}Zr{sub (0.2-x)}O{sub 3-delta} with 0 <= x <= 0.2 were synthesized by combining citric acid and ethylene-diamine-tetraacetic acid (EDTA) complexing method. X-ray diffraction (XRD) patterns show that the BaCo{sub 0.4}Fe{sub 0.4}Zn{sub 0.2}O{sub 3-delta} ceramic oxide exhibits a pure cubic perovskite structure. Oxygen temperature-programmed desorption (O{sub 2}-TPD) profile indicates that BaCo{sub 0.4}Fe{sub 0.4}Zn{sub 0.2}O{sub 3-delta} possesses a good phase reversibility. An oxygen permeation flux of 0.65 ml/min cm{sup 2} was obtained at 950 deg. C and a single activation energy of 67 kJ/mol was observed for the oxygen permeation in the temperature range of 600-950 deg. C. No decline was found during more than 100 h oxygen permeation.

Oxygen permeability of perovskite-type BaBi1-xLaxO3-δ

International Nuclear Information System (INIS)

Yaremchenko, A.A.; Kharton, V.V.; Viskup, A.P.; Naumovich, E.N.; Samokhval, V.V.

1998-01-01

Oxygen permeability, electrical conductivity, and thermal expansion of BaBi 1-x La x O 3-δ (x = 0, 0.2, and 0.4) perovskite-like solid solutions have been found to decrease with lanthanum content. Thermal expansion coefficients of the ceramics are (11.9--12.8) x 10 -6 K -1 . Oxygen transport through the BaBi(La)O 3-δ dense ceramic membranes within the membrane thickness range of 0.6 < d < 1.2 mm has been shown to be limited by both bulk ionic conductivity and surface exchange rate

Analysis of heterogeneous oxygen exchange and fuel oxidation on the catalytic surface of perovskite membranes

KAUST Repository

Hong, Jongsup

2013-10-01

The catalytic kinetics of oxygen surface exchange and fuel oxidation for a perovskite membrane is investigated in terms of the thermodynamic state in the immediate vicinity of or on the membrane surface. Perovskite membranes have been shown to exhibit both oxygen perm-selectivity and catalytic activity for hydrocarbon conversion. A fundamental description of their catalytic surface reactions is needed. In this study, we infer the kinetic parameters for heterogeneous oxygen surface exchange and catalytic fuel conversion reactions, based on permeation rate measurements and a spatially resolved physical model that incorporates detailed chemical kinetics and transport in the gas-phase. The conservation equations for surface and bulk species are coupled with those of the gas-phase species through the species production rates from surface reactions. It is shown that oxygen surface exchange is limited by dissociative/associative adsorption/desorption of oxygen molecules onto/from the membrane surface. On the sweep side, while the catalytic conversion of methane to methyl radical governs the overall surface reactions at high temperature, carbon monoxide oxidation on the membrane surface is dominant at low temperature. Given the sweep side conditions considered in ITM reactor experiments, gas-phase reactions also play an important role, indicating the significance of investigating both homogeneous and heterogeneous chemistry and their coupling when examining the results. We show that the local thermodynamic state at the membrane surface should be considered when constructing and examining models of oxygen permeation and heterogeneous chemistry. © 2013 Elsevier B.V.

Analysis of heterogeneous oxygen exchange and fuel oxidation on the catalytic surface of perovskite membranes

KAUST Repository

Hong, Jongsup; Kirchen, Patrick; Ghoniem, Ahmed F.

2013-01-01

The catalytic kinetics of oxygen surface exchange and fuel oxidation for a perovskite membrane is investigated in terms of the thermodynamic state in the immediate vicinity of or on the membrane surface. Perovskite membranes have been shown to exhibit both oxygen perm-selectivity and catalytic activity for hydrocarbon conversion. A fundamental description of their catalytic surface reactions is needed. In this study, we infer the kinetic parameters for heterogeneous oxygen surface exchange and catalytic fuel conversion reactions, based on permeation rate measurements and a spatially resolved physical model that incorporates detailed chemical kinetics and transport in the gas-phase. The conservation equations for surface and bulk species are coupled with those of the gas-phase species through the species production rates from surface reactions. It is shown that oxygen surface exchange is limited by dissociative/associative adsorption/desorption of oxygen molecules onto/from the membrane surface. On the sweep side, while the catalytic conversion of methane to methyl radical governs the overall surface reactions at high temperature, carbon monoxide oxidation on the membrane surface is dominant at low temperature. Given the sweep side conditions considered in ITM reactor experiments, gas-phase reactions also play an important role, indicating the significance of investigating both homogeneous and heterogeneous chemistry and their coupling when examining the results. We show that the local thermodynamic state at the membrane surface should be considered when constructing and examining models of oxygen permeation and heterogeneous chemistry. © 2013 Elsevier B.V.

The effect of oxygen molecule adsorption on lead iodide perovskite surface by first-principles calculation

Science.gov (United States)

Ma, Xia-Xia; Li, Ze-Sheng

2018-01-01

Oxygen molecule has a negative effect on perovskite solar cells, which has been investigated experimentally. However, detailed theoretical research is still rare. This study presents a microscopic view to reveal the interaction mechanism between O2 and perovskite based on the first-principles calculation. The results show that O2 is adsorbed on the (100) surface of MAPbI3 perovskite mainly by Van der Waals force. O2 adsorption makes the MAPbI3 surface generate a small number of positive charges, which leads to the increase of the work function of the MAPbI3 surface. This is in agreement with the experimental measurement. And increased work function of MAPbI3 surface is not beneficial to electron transfer from perovskite to electronic extraction layer (such as TiO2). Comparison of the density of states (DOS) of the clean (100) surface and the adsorbed system shows that an in-gap state belonging to O2 appears, which can explain the phenomenon observed from experiments that electron transfers from the surface of perovskite to O2 to form superoxide. The theoretical power conversion efficiency of the system with and without O2 adsorption is evaluated, and it turns out that the power conversion efficiency of the system with O2 adsorption is slightly lower than that of the system without O2 adsorption. This result indicates that avoiding the introduction of O2 molecules between perovskite and electronic extraction layer is beneficial to the perovskite solar cell.

Comparative DFT+U and HSE Study of the Oxygen Evolution Electrocatalysis on Perovskite Oxides

DEFF Research Database (Denmark)

Tripkovic, Vladimir; Hansen, Heine Anton; García Lastra, Juan Maria

2018-01-01

+U functional and the amount of exact exchange, α, in the hybrid HSE functional on the structural stability, catalytic activity and electronic conductivity of pure and doped perovskite oxides, ABO3, (A = La, Ca, Sr and Ba, B = Cr, Mn, Fe, Co, Ni and Cu) for oxygen evolution electrocatalysis. We find a strong...

Oxygen rocking aqueous batteries utilizing reversible topotactic oxygen insertion/extraction in iron-based perovskite oxides Ca1-xLaxFeO3-δ

Science.gov (United States)

Hibino, Mitsuhiro; Kimura, Takeshi; Suga, Yosuke; Kudo, Tetsuichi; Mizuno, Noritaka

2012-08-01

Developments of large-scale energy storages with not only low cost and high safety but also abundant metals are significantly demanded. While lithium ion batteries are the most successful method, they cannot satisfy all conditions. Here we show the principle of novel lithium-free secondary oxygen rocking aqueous batteries, in which oxygen shuttles between the cathode and anode composed of iron-based perovskite-related oxides Ca0.5La0.5FeOz (2.5 topotactic oxygen extraction and reinsertion during discharge and charge processes.

Enhanced magnetoresistance induced by oxygen deficiency in La0.4Ca0.6MnO3-δ oxides

International Nuclear Information System (INIS)

Triki, M.; Dhahri, E.; Hlil, E. K.; Garden, J. L.

2014-01-01

We report electrical features and magnetoresistance behavior of the oxygen deficient La 0.4 Ca 0.6 MnO 3-δ perovskites (δ = 0, 0.15, and 0.2). These samples will be referred to as S0, S15, and S20, respectively. The dependence of electrical transport on temperature and magnetic field is systematically investigated between 2 K and 400 K in magnetic field ranging up to 5 T. The parent compound shows a stable charge ordering/antiferromagnetic state with a semiconductor-like behavior in all considered temperature range. The variable range hopping and thermally activated hopping models are found to fit well with the electrical resistivity data at low and high temperatures, respectively. Oxygen deficiency tends to weaken the charge ordering and induce ferromagnetism and metallicity at low temperature. Metal insulator transition appears at higher fields for lower oxygen deficit (S15 sample) and without field for the S20 sample. The resistivity data for S15 sample are discussed in the framework of the variable-range hopping model. Abnormal transport properties were observed in the S20 sample, characterized by the double metal-insulator transitions and low minimum behavior. These results are discussed in terms of phenomenological percolation model, based on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions. While the parent compound shows no magnetoresistance, a large magnetoresistance is observed in the deficient samples at low temperature reaching 90% and 75% at 2 T for S15 and S20 samples, respectively. Noticeably, these values reached 98% and 91% at 5 T. The appearance of colossal magnetoresistance is attributed to the spin dependent hopping between spin clusters and/or ferromagnetic domains

Are macroinvertebrates in high altitude streams affected by oxygen deficiency?

DEFF Research Database (Denmark)

Jacobsen, Dean; Rostgaard, S.; Vásconez, J. J.

2003-01-01

1. The solubility of oxygen in water increases with decreasing temperature. This has led to a general perception of cold, high mountain streams as more oxygen rich than warmer lowland streams, and that macroinvertebrates inhabiting high altitude streams have had no need to adapt to critical oxygen...... conditions. However, this fails to take into account that oxygen solubility declines with decreasing atmospheric pressure, which may be of importance at high altitudes. 2. Based on samples of macroinvertebrate benthos and in situ measurements of respiratory oxygen demand of macroinvertebrates in small...... the mean weight-specific respiratory rate of macroinvertebrates declined by only 50%, from 400 to 3800 m. We suggest that this disproportionately large gap between availability and demand of oxygen at high altitudes may imply a potential oxygen deficiency for the fauna, and we discuss how oxygen deficiency...

Electrocatalysis of oxygen electrode reactions by some perovskite oxides based on lanthanum manganate

International Nuclear Information System (INIS)

Raj, I.A.; Rao, K.V.; Venkatesan, V.K.

1984-01-01

In recent years, several electrocatalyst materials based on platinum, silver, tungsten bronzes, spinels, metal chelates, etc., have been studied for use as oxygen diffusion electrodes in alkaline fuel cells, secondary metal-air batteries, and water electrolyzers. However, virtually all catalysts of commercial importance are semiconducting transition metal oxides. The various oxide catalysts that have been studied can be grouped under mixed oxides, spinels, and perovskites

Thermal conductivity reduction in oxygen-deficient strontium titanates

NARCIS (Netherlands)

Yu, Choongho; Scullin, Matthew L.; Huijben, Mark; Ramesh, Ramamoorthy; Majumdar, Arun

2008-01-01

We report significant thermal conductivity reduction in oxygen-deficient lanthanum-doped strontium titanate (Sr1−xLaxTiO3−δ) films as compared to unreduced strontium titanates. Our experimental results suggest that the oxygen vacancies could have played an important role in the reduction. This could

Ordered oxygen deficient '112' perovskites, LnBaCo2 : complex ...

Indian Academy of Sciences (India)

Administrator

are labeled on the graph. .... in agreement with Kanamori Goodenough rules. In sum- mary, these results ... exhibit very rich phase diagrams as illustrated in figure 9. The latter .... which make that the control of oxygen content in these phases is ...

High-throughput DFT calculations of formation energy, stability and oxygen vacancy formation energy of ABO3 perovskites

Science.gov (United States)

Emery, Antoine A.; Wolverton, Chris

2017-10-01

ABO3 perovskites are oxide materials that are used for a variety of applications such as solid oxide fuel cells, piezo-, ferro-electricity and water splitting. Due to their remarkable stability with respect to cation substitution, new compounds for such applications potentially await discovery. In this work, we present an exhaustive dataset of formation energies of 5,329 cubic and distorted perovskites that were calculated using first-principles density functional theory. In addition to formation energies, several additional properties such as oxidation states, band gap, oxygen vacancy formation energy, and thermodynamic stability with respect to all phases in the Open Quantum Materials Database are also made publicly available. This large dataset for this ubiquitous crystal structure type contains 395 perovskites that are predicted to be thermodynamically stable, of which many have not yet been experimentally reported, and therefore represent theoretical predictions. The dataset thus opens avenues for future use, including materials discovery in many research-active areas.

Mineralogy and Oxygen Isotope Compositions of an Unusual Hibonite-Perovskite Refractory Inclusion from Allende

Science.gov (United States)

Keller, L. P.; Snead, C.; Rahman, Z.; McKeegan, K. D.

2012-01-01

Hibonite-rich Ca- and Al-rich inclusions (CAIs) are among the earliest formed solids that condensed in the early nebula. We discovered an unusual refractory inclusion from the Allende CV3 chondrite (SHAL) containing an approx 500 micron long single crystal of hibonite and co-existing coarse-grained perovskite. The mineralogy and petrography of SHAL show strong similarities to some FUN inclusions, especially HAL. Here we report on the mineralogy, petrography, mineral chemistry and oxygen isotopic compositions in SHAL.

In Operando Self-Healing of Perovskite Electrocatalysts: A Case Study of SrCoO3 for the Oxygen Evolution Reaction

KAUST Repository

Tahini, Hassan A.; Tan, Xin; Schwingenschlö gl, Udo; Smith, Sean C.

2017-01-01

Perovskites are promising catalysts for oxygen evolution reactions (OER); among them, SrCoO3 is one of the best for these reactions. We study the O* intermediates and the role of surface oxygen vacancies of SrCoO3 during OER. A self-healing mechanism is proposed in which O* are incorporated into the surface to recover the redox capabilities of the material.

In Operando Self-Healing of Perovskite Electrocatalysts: A Case Study of SrCoO3 for the Oxygen Evolution Reaction

KAUST Repository

Tahini, Hassan A.

2017-01-24

Perovskites are promising catalysts for oxygen evolution reactions (OER); among them, SrCoO3 is one of the best for these reactions. We study the O* intermediates and the role of surface oxygen vacancies of SrCoO3 during OER. A self-healing mechanism is proposed in which O* are incorporated into the surface to recover the redox capabilities of the material.

Strontium-free rare earth perovskite ferrites with fast oxygen exchange kinetics: Experiment and theory

Science.gov (United States)

Berger, Christian; Bucher, Edith; Windischbacher, Andreas; Boese, A. Daniel; Sitte, Werner

2018-03-01

The Sr-free mixed ionic electronic conducting perovskites La0.8Ca0.2FeO3-δ (LCF82) and Pr0.8Ca0.2FeO3-δ (PCF82) were synthesized via a glycine-nitrate process. Crystal structure, phase purity, and lattice constants were determined by XRD and Rietveld analysis. The oxygen exchange kinetics and the electronic conductivity were obtained from in-situ dc-conductivity relaxation experiments at 600-800 °C and 1×10-3≤pO2/bar≤0.1. Both LCF82 and PCF82 show exceptionally fast chemical surface exchange coefficients and chemical diffusion coefficients of oxygen. The oxygen nonstochiometry of LCF82 and PCF82 was determined by precision thermogravimetry. A point defect model was used to calculate the thermodynamic factors of oxygen and to estimate self-diffusion coefficients and ionic conductivities. Density Functional Theory (DFT) calculations on the crystal structure, oxygen vacancy formation as well as oxygen migration energies are in excellent agreement with the experimental values. Due to their favourable properties both LCF82 and PCF82 are of interest for applications in solid oxide fuel cell cathodes, solid oxide electrolyser cell anodes, oxygen separation membranes, catalysts, or electrochemical sensors.

Effect of lone-electron-pair cations on the orientation of crystallographic shear planes in anion-deficient perovskites.

Science.gov (United States)

Batuk, Dmitry; Batuk, Maria; Abakumov, Artem M; Tsirlin, Alexander A; McCammon, Catherine; Dubrovinsky, Leonid; Hadermann, Joke

2013-09-03

Factors affecting the structure and orientation of the crystallographic shear (CS) planes in anion-deficient perovskites were investigated using the (Pb(1-z)Sr(z))(1-x)Fe(1+x)O(3-y) perovskites as a model system. The isovalent substitution of Sr(2+) for Pb(2+) highlights the influence of the A cation electronic structure because these cations exhibit very close ionic radii. Two compositional ranges have been identified in the system: 0.05 ≤ z ≤ 0.2, where the CS plane orientation gradually varies but stays close to (203)p, and 0.3 ≤ z ≤ 0.45 with (101)p CS planes. The incommensurately modulated structure of Pb0.792Sr0.168Fe1.040O2.529 was refined from neutron powder diffraction data using the (3 + 1)D approach (space group X2/m(α0γ), X = (1/2, 1/2, 1/2, 1/2), a = 3.9512(1) Å, b = 3.9483(1) Å, c = 3.9165(1) Å, β = 93.268(2)°, q = 0.0879(1)a* + 0.1276(1)c*, RF = 0.023, RP = 0.029, and T = 900 K). A comparison of the compounds with different CS planes indicates that the orientation of the CS planes is governed mainly by the stereochemical activity of the lone-electron-pair cations inside the perovskite blocks.

Non-hydrolytic metal oxide films for perovskite halide overcoating and stabilization

Science.gov (United States)

Martinson, Alex B.; Kim, In Soo

2017-09-26

A method of protecting a perovskite halide film from moisture and temperature includes positioning the perovskite halide film in a chamber. The chamber is maintained at a temperature of less than 200 degrees Celsius. An organo-metal compound is inserted into the chamber. A non-hydrolytic oxygen source is subsequently inserted into the chamber. The inserting of the organo-metal compound and subsequent inserting of the non-hydrolytic oxygen source into the chamber is repeated for a predetermined number of cycles. The non-hydrolytic oxygen source and the organo-metal compound interact in the chamber to deposit a non-hydrolytic metal oxide film on perovskite halide film. The non-hydrolytic metal oxide film protects the perovskite halide film from relative humidity of greater than 35% and a temperature of greater than 150 degrees Celsius, respectively.

Oxygen rocking aqueous batteries utilizing reversible topotactic oxygen insertion/extraction in iron-based perovskite oxides Ca(1-x)La(x)FeO(3-δ).

Science.gov (United States)

Hibino, Mitsuhiro; Kimura, Takeshi; Suga, Yosuke; Kudo, Tetsuichi; Mizuno, Noritaka

2012-01-01

Developments of large-scale energy storages with not only low cost and high safety but also abundant metals are significantly demanded. While lithium ion batteries are the most successful method, they cannot satisfy all conditions. Here we show the principle of novel lithium-free secondary oxygen rocking aqueous batteries, in which oxygen shuttles between the cathode and anode composed of iron-based perovskite-related oxides Ca(0.5)La(0.5)FeO(z) (2.5 ≤ z ≤ 2.75 and 2.75 ≤ z ≤ 3.0). Compound Ca(0.5)La(0.5)FeO(z) can undergo two kinds of reduction and reoxidation of Fe(4+)/Fe(3+) and Fe(3+)/Fe(2+), that are accompanied by reversible and repeatable topotactic oxygen extraction and reinsertion during discharge and charge processes.

Ultrafast atomic layer-by-layer oxygen vacancy-exchange diffusion in double-perovskite LnBaCo2O5.5+δ thin films.

Science.gov (United States)

Bao, Shanyong; Ma, Chunrui; Chen, Garry; Xu, Xing; Enriquez, Erik; Chen, Chonglin; Zhang, Yamei; Bettis, Jerry L; Whangbo, Myung-Hwan; Dong, Chuang; Zhang, Qingyu

2014-04-22

Surface exchange and oxygen vacancy diffusion dynamics were studied in double-perovskites LnBaCo2O5.5+δ (LnBCO) single-crystalline thin films (Ln = Er, Pr; -0.5 atoms in the LnBCO thin films is taking the layer by layer oxygen-vacancy-exchange mechanism. The first principles density functional theory calculations indicate that hydrogen atoms are present in LnBCO as bound to oxygen forming O-H bonds. This unprecedented oscillation phenomenon provides the first direct experimental evidence of the layer by layer oxygen vacancy exchange diffusion mechanism.

Oxygen vacancies at the spinel/perovskite γ-Al{sub 2}O{sub 3}/SrTiO{sub 3} heterointerface probed by resonant photoelectron spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Schuetz, Philipp; Pfaff, Florian; Zapf, Michael; Gabel, Judith; Dudy, Lenart; Berner, Goetz; Sing, Michael; Claessen, Ralph [Physikalisches Institut and Roentgen Center for Complex Material Systems (RCCM), Universitaet Wuerzburg (Germany); Chen, Yunzhong; Pryds, Nini [Department of Energy Conversion and Storage, Technical University of Denmark, Risoe (Denmark); Schlueter, Christoph; Lee, Tien-Lin [Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot (United Kingdom)

2016-07-01

The spinel/perovskite heterointerface between the band insulators γ-Al{sub 2}O{sub 3} and SrTiO{sub 3} hosts a two-dimensional electron system (2DES) with exceptionally high electron mobility. Soft x-ray resonant photoelectron spectroscopy at the Ti L absorption edge is used to probe the Ti 3d derived interface states. Marked differences in the resonance behavior are found for the SrTiO{sub 3} valence band and the different interface states, which are observed in the band gap of SrTiO{sub 3}. A comparison to X-ray absorption spectra of Ti 3d{sup 0} and Ti 3d{sup 1} systems reveals the presence of different types of electronic states with Ti 3d character, i.e., oxygen vacancy induced, trapped in-gap states and itinerant states contributing to the 2DES. Exposure to low doses of oxygen during irradiation allows for the reversible manipulation of the oxygen stoichiometry, thus revealing the presence of an oxygen vacancy-induced state, which is characteristic for this spinel/perovskite interface.

Development of Perovskite-Type Materials for Thermoelectric Application

Directory of Open Access Journals (Sweden)

Tingjun Wu

2018-06-01

Full Text Available Oxide perovskite materials have a long history of being investigated for thermoelectric applications. Compared to the state-of-the-art tin and lead chalcogenides, these perovskite compounds have advantages of low toxicity, eco-friendliness, and high elemental abundance. However, because of low electrical conductivity and high thermal conductivity, the total thermoelectric performance of oxide perovskites is relatively poor. Variety of methods were used to enhance the TE properties of oxide perovskite materials, such as doping, inducing oxygen vacancy, embedding crystal imperfection, and so on. Recently, hybrid perovskite materials started to draw attention for thermoelectric application. Due to the low thermal conductivity and high Seebeck coefficient feature of hybrid perovskites materials, they can be promising thermoelectric materials and hold the potential for the application of wearable energy generators and cooling devices. This mini-review will build a bridge between oxide perovskites and burgeoning hybrid halide perovskites in the research of thermoelectric properties with an aim to further enhance the relevant performance of perovskite-type materials.

Oxygen rocking aqueous batteries utilizing reversible topotactic oxygen insertion/extraction in iron-based perovskite oxides Ca1–xLaxFeO3−δ

Science.gov (United States)

Hibino, Mitsuhiro; Kimura, Takeshi; Suga, Yosuke; Kudo, Tetsuichi; Mizuno, Noritaka

2012-01-01

Developments of large-scale energy storages with not only low cost and high safety but also abundant metals are significantly demanded. While lithium ion batteries are the most successful method, they cannot satisfy all conditions. Here we show the principle of novel lithium-free secondary oxygen rocking aqueous batteries, in which oxygen shuttles between the cathode and anode composed of iron-based perovskite-related oxides Ca0.5La0.5FeOz (2.5 ≤ z ≤ 2.75 and 2.75 ≤ z ≤ 3.0). Compound Ca0.5La0.5FeOz can undergo two kinds of reduction and reoxidation of Fe4+/Fe3+ and Fe3+/Fe2+, that are accompanied by reversible and repeatable topotactic oxygen extraction and reinsertion during discharge and charge processes. PMID:22924108

Oxygen deficiency impacts on burying habitats for lesser sandeel, Ammodytes tobianus, in the inner Danish waters

DEFF Research Database (Denmark)

Behrens, Jane; Ærtebjerg, Gunni; Petersen, Jens Kjerulf

2009-01-01

Starting in 1980s, the inner Danish waters have yearly been exposed to seasonal oxygen deficiency (hypoxia). Through spatial–temporal interpolation of monitoring data (1998–2005), we investigated oxygen deficiency impacts on suitable burying habitats for lesser sandeel (Ammodytes tobianus...

Synthesis, structure and total conductivity of A-site doped LaTiO3−δ perovskites

International Nuclear Information System (INIS)

Bradha, M.; Hussain, S.; Chakravarty, Sujay; Amarendra, G.; Ashok, Anuradha

2015-01-01

Highlights: • A-site divalent alkaline earth metal doped LaTiO 3−δ perovskites were synthesised by sol–gel method. • Structural studies revealed no change in crystal symmetry but change in cell dimensions after doping. • After doping divalent cations in A-site, an enhancement in total conductivity was observed in LaTiO 3−δ . • Temperature dependent electrical property was observed in all synthesised perovskites. - Abstract: Oxygen deficient perovskites LaTiO 3−δ and La 0.8 A 0.2 TiO 3−δ (A = Ba, Sr, Ca) were synthesized by sol–gel method. The effect of divalent dopants on microstructure is investigated in detail using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The oxidation states of La 3+ and Ti 3+ ions have been deduced using X-ray Photoelectron Spectroscopy (XPS). Impedance spectroscopy was used to analyze the total conductivity, an increase in conductivity was observed after doping in the A-site with divalent cations Ba, Ca and Sr. Among the investigated perovskites La 0.8 Ca 0.2 TiO 3−δ exhibited the maximum conductivity of 1.22 × 10 −2 S/cm in air atmosphere at 650 °C

Hafnium carbide formation in oxygen deficient hafnium oxide thin films

Energy Technology Data Exchange (ETDEWEB)

Rodenbücher, C. [Forschungszentrum Jülich GmbH, Peter Grünberg Institute (PGI-7), JARA-FIT, 52425 Jülich (Germany); Hildebrandt, E.; Sharath, S. U.; Kurian, J.; Komissinskiy, P.; Alff, L. [Technische Universität Darmstadt, Institute of Materials Science, 64287 Darmstadt (Germany); Szot, K. [Forschungszentrum Jülich GmbH, Peter Grünberg Institute (PGI-7), JARA-FIT, 52425 Jülich (Germany); University of Silesia, A. Chełkowski Institute of Physics, 40-007 Katowice (Poland); Breuer, U. [Forschungszentrum Jülich GmbH, Central Institute for Engineering, Electronics and Analytics (ZEA-3), 52425 Jülich (Germany); Waser, R. [Forschungszentrum Jülich GmbH, Peter Grünberg Institute (PGI-7), JARA-FIT, 52425 Jülich (Germany); RWTH Aachen, Institute of Electronic Materials (IWE 2), 52056 Aachen (Germany)

2016-06-20

On highly oxygen deficient thin films of hafnium oxide (hafnia, HfO{sub 2−x}) contaminated with adsorbates of carbon oxides, the formation of hafnium carbide (HfC{sub x}) at the surface during vacuum annealing at temperatures as low as 600 °C is reported. Using X-ray photoelectron spectroscopy the evolution of the HfC{sub x} surface layer related to a transformation from insulating into metallic state is monitored in situ. In contrast, for fully stoichiometric HfO{sub 2} thin films prepared and measured under identical conditions, the formation of HfC{sub x} was not detectable suggesting that the enhanced adsorption of carbon oxides on oxygen deficient films provides a carbon source for the carbide formation. This shows that a high concentration of oxygen vacancies in carbon contaminated hafnia lowers considerably the formation energy of hafnium carbide. Thus, the presence of a sufficient amount of residual carbon in resistive random access memory devices might lead to a similar carbide formation within the conducting filaments due to Joule heating.

Oxygen-perovskites with fourvalent rare earth metals

Energy Technology Data Exchange (ETDEWEB)

Kristen, H R

1978-01-01

The quadrivalent oxidation stage of the elements praseodymium and terbium can be easily prepared as oxides BaPrO/sub 3/ and BaTbO/sub 3/ crystallizing with the Perovskite structure. From this observation one has tried to stabilize the elements neodymium and dysprosium in the lanthanide series by including a host lattice with Perovskite structure. BaCeO/sub 3/, BaPrO/sub 3/, BaZrO/sub 3/, BaThO/sub 3/, BaTbO/sub 3/, SrCeO/sub 3/ and SrTbO/sub 3/ are used as host lattices. The preparation was carried out by simple annealing of the corresponding oxides with BaCO/sub 3/ or SrCO/sub 3/ in air at 1350/sup 0/C. X-ray and analytical characterization showed that Nd(IV) and Dy(IV) were partly taken up by a few host lattices.

Oxygen-perovskites with fourvalent rare earth metals

Energy Technology Data Exchange (ETDEWEB)

Kristen, H R

1978-01-01

The quadrivalent oxidation stage of the elements praseodymium and terbium can be easily prepared as oxides BaPrO/sub 3/ and BaTbO/sub 3/ crystallizing with the Perovskite structure. From this observation one has tried to stabilize the elements neodymium and dysprosium in the lanthanide series by including a host lattice with Perovskite structure. BaCeO/sub 3/, BaPrO/sub 3/, BaZrO/sub 3/, BaThO/sub 3/, BaTbO/sub 3/, SrCeO/sub 3/ and SrTbO/sub 3/ are used as host lattices. The preparation was carried out by simple annealing of the corresponding oxides with BaCO/sub 3/ or SrCO/sub 3/ in air at 1350/sup 0/C. X-ray and analytical characterization showed that Nd(IV) and Dy(IV) were partly taken up by a few host lattices. (orig./HBR).

A high reliability oxygen deficiency monitoring system

International Nuclear Information System (INIS)

Parry, R.; Claborn, G.; Haas, A.; Landis, R.; Page, W.; Smith, J.

1993-05-01

The escalating use of cryogens at national laboratories in general and accelerators in particular, along with the increased emphasis placed on personnel safety, mandates the development and installation of oxygen monitoring systems to insure personnel safety in the event of a cryogenic leak. Numerous vendors offer oxygen deficiency monitoring systems but fail to provide important features and/or flexibility. This paper describes a unique oxygen monitoring system developed for the Magnet Test Laboratory (MTL) at the Superconducting Super Collider Laboratory (SSCL). Features include: high reliability, oxygen cell redundancy, sensor longevity, simple calibration, multiple trip points, offending sensor audio and visual indication, global alarms for building evacuation, local and remote analog readout, event and analog data logging, EMAIL event notification, phone line voice status system, and multi-drop communications network capability for reduced cable runs. Of particular importance is the distributed topology of the system which allows it to operate in a stand-alone configuration or to communicate with a host computer. This flexibility makes it ideal for small applications such as a small room containing a cryogenic dewar, as well as larger systems which monitor many offices and labs in several buildings

A high reliability oxygen deficiency monitoring system

International Nuclear Information System (INIS)

Parry, R.; Claborn, G.; Haas, A.; Landis, R.; Page, W.; Smith, J.

1993-01-01

The escalating use of cryogens at national laboratories in general and accelerators in particular, along with the increased emphasis placed on personnel safety, mandates the development and installation of oxygen monitoring systems to insure personnel safety in the event of a cryogenic leak. Numerous vendors offer oxygen deficiency monitoring systems but fail to provide important features and/or flexibility. This paper describes a unique oxygen monitoring system developed for the Magnet Test Laboratory (MTL) at the Superconducting Super Collider Laboratory (SSCL). Features include: high reliability, oxygen cell redundancy, sensor longevity, simple calibration, multiple trip points, offending sensor audio and visual indication, global alarms for building evacuation, local and remote analog readout, event and analog data logging, EMAIL event notification, phone line voice status system, and multi-drop communications network capability for reduced cable runs. Of particular importance is the distributed topology of the system which allows it to operate in a stand-alone configuration or to communicate with a host computer. This flexibility makes it ideal for small applications such as a small room containing a cryogenic dewar, as well as larger systems which monitor many offices and labs in several buildings

Temperature-independent sensors based on perovskite-type oxides

International Nuclear Information System (INIS)

Zaza, F.; Frangini, S.; Masci, A.; Leoncini, J.; Pasquali, M.; Luisetto, I.; Tuti, S.

2013-01-01

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 La 0.7 Sr 0.3 FeO 3 , 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 (La 0.7 Sr 0.3 )(Al x Fe 1−x )O 3 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 Fe 4+ and Fe 3+ , 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 (La 0.7 Sr 0.3 )(Al x Fe 1−x )O 3 perovskites have temperature-independence conductivity from 900 K

Temperature-independent sensors based on perovskite-type oxides

Energy Technology Data Exchange (ETDEWEB)

Zaza, F.; Frangini, S.; Masci, A. [ENEA-Casaccia R.C., Via Anguillarese 301, 00123 S.Maria di Galeria, Rome (Italy); Leoncini, J.; Pasquali, M. [University La Sapienza, Piazza Via del Castro Laurenziano 7, 00161 Rome (Italy); Luisetto, I.; Tuti, S. [University RomaTre, Rome 00146 (Italy)

2014-06-19

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 La{sub 0.7}Sr{sub 0.3}FeO{sub 3}, 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 (La{sub 0.7}Sr{sub 0.3})(Al{sub x}Fe{sub 1−x})O{sub 3} 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 Fe{sup 4+} and Fe{sup 3+}, 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 (La{sub 0.7}Sr{sub 0.3})(Al{sub x}Fe{sub 1−x})O{sub 3} perovskites have temperature-independence conductivity from 900 K.

Formation of Two-Dimensional Homologous Faults and Oxygen Electrocatalytic Activities in a Perovskite Nickelate.

Science.gov (United States)

Bak, Jumi; Bae, Hyung Bin; Kim, Jaehoon; Oh, Jihun; Chung, Sung-Yoon

2017-05-10

Atomic-scale direct probing of active sites and subsequent elucidation of the structure-activity relationship are important issues involving oxide-based electrocatalysts to achieve better electrochemical conversion efficiency. By generating Ruddlesden-Popper (RP) two-dimensional homologous faults via simple control of the cation nonstoichiometry in LaNiO 3 thin films, we demonstrate that strong tetragonal distortion of [NiO 6 ] octahedra is induced by more than 20% elongation of Ni-O bonds in the faults. In addition to direct visualization of the elongation by scanning transmission electron microscopy, we identify that the distorted [NiO 6 ] octahedra in the faults show considerably higher electrocatalytic activities than other surface sites during the electrochemical oxygen evolution reaction. This unequivocal evidence of the octahedral distortion and its impact on electrocatalysis in LaNiO 3 suggests that the formation of RP-type faults can provide an efficient way to control the octahedral geometry and thereby remarkably enhance the oxygen catalytic performance of perovskite oxides.

Characterisation of perovskite-type high-temperature membranes used for oxygen supply in fossil fuelled power plant processes; Charakterisierung perowskitischer Hochtemperaturmembranen zur Sauerstoffbereitstellung fuer fossil gefeuerte Kraftwerksprozesse

Energy Technology Data Exchange (ETDEWEB)

Moebius, Sigrid Annett

2010-03-12

In this thesis thermochemical properties of mixed conducting perovskite-type materials were investigated. Those materials are assumed to be applicable as gas separation membranes in the oxyfuel process. Here, the materials are aimed to produce the required oxygen for the combustion more energy-efficient than using cryogenic air separation. High-temperature materials which are applicable for this purpose must be gastight and should exhibit a high oxygen permeation rate and a preferably low thermal expansion coefficient. Moreover, the materials need to be long-term stable under power plant relevant conditions. The aim of this work is a better understanding of the material behaviour. Furthermore, on the basis of the results it should be possible to draw conclusions concerning the suitability of the material for application in oxyfuel power plant processes. Therefor, the influence of the chemical composition (doping elements and stoichiometry) of the perovskites, the temperature and the oxygen content in the ambient atmosphere on the thermochemical properties are studied systematically. In the framework of this thesis it could be stated that the thermochemical behaviour of prospective membrane materials strongly depends on the above mentioned parameters. In addition, the degradation behaviour (thermochemical stability) of the materials was investigated. The degradation behaviour influences the suitability of the material to be used in oxyfuel power plant processes. Here, the influence of the chemical composition of the perovskites, the temperature and the CO{sub 2}-concentration in dry and humid atmospheres was also studied. On the basis of the results it could be stated that the thermochemical stability strongly depends on the surrounding atmosphere and on the chemical composition of the perovskites. (orig.)

Large isosymmetric reorientation of oxygen octahedra rotation axes in epitaxially strained perovskites.

Science.gov (United States)

Rondinelli, James M; Coh, Sinisa

2011-06-10

Using first-principles density functional theory calculations, we discover an anomalously large biaxial strain-induced octahedral rotation axis reorientation in orthorhombic perovskites with tendency towards rhombohedral symmetry. The transition between crystallographically equivalent (isosymmetric) structures with different octahedral rotation magnitudes originates from strong strain-octahedral rotation coupling available to perovskites and the energetic hierarchy among competing octahedral tilt patterns. By elucidating these criteria, we suggest many functional perovskites would exhibit the transition in thin film form, thus offering a new landscape in which to tailor highly anisotropic electronic responses.

Copper-substituted perovskite compositions for solid oxide fuel cell cathodes and oxygen reduction electrodes in other electrochemical devices

Science.gov (United States)

Rieke, Peter C [Pasco, WA; Coffey, Gregory W [Richland, WA; Pederson, Larry R [Kennewick, WA; Marina, Olga A [Richland, WA; Hardy, John S [Richland, WA; Singh, Prabhaker [Richland, WA; Thomsen, Edwin C [Richland, WA

2010-07-20

The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells. Also provided are electrochemical devices that include active oxygen reduction electrodes, such as solid oxide fuel cells, sensors, pumps and the like. The compositions comprises a copper-substituted ferrite perovskite material. The invention also provides novel methods for making and using the electrode compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having cathodes comprising the compositions.

Dinitrogen Fixation Within and Adjacent to Oxygen Deficient Waters of the Eastern Tropical South Pacific Ocean

Science.gov (United States)

Widner, B.; Mulholland, M. R.; Bernhardt, P. W.; Chang, B. X.; Jayakumar, A.

2016-02-01

Recent work suggests that planktonic diazotrophs are geographically more widely distributed than previously thought including relatively warm (14-23oC) aphotic oxygenated pelagic waters and in aphotic waters within oxygen deficient zones. Because the volume of aphotic water in the ocean is large and may increase in the future, if dinitrogen (N2) fixation is widely occurring at sub-euphotic depths, this could result in a dramatic upward revision of global nitrogen (N) inputs via this process. N2 fixation rates were measured during a cruise in the Eastern Tropical South Pacific using stable isotope tracer techniques that account for slow gas dissolution. Results are compared with light, nutrient, and oxygen gradients (and necessarily temperature gradients). In addition, rates of N2 fixation made in vertical profiles within and above oxygen deficient waters are compared with those measured in vertical profiles adjacent to oxygen deficient waters. Results suggest that while rates of N2 fixation were measurable in deeper anoxic waters, volumetric N2 fixation rates were higher in surface waters.

Oxygen deficiency in MoO{sub 3} polycrystalline nanowires and nanotubes

Energy Technology Data Exchange (ETDEWEB)

Varlec, Ana, E-mail: ana.varlec@ijs.si [Condensed Matter Physics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Arčon, Denis [Condensed Matter Physics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Faculty of Mathematics and Physics, University of Ljubljana, Jadranska cesta 19, SI-1000 Ljubljana (Slovenia); Škapin, Srečo D. [Advanced Materials Department, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Remškar, Maja [Condensed Matter Physics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia)

2016-02-15

We report on the synthesis of polycrystalline molybdenum oxide (MoO{sub 3}) nanowires via oxidation of molybdenum-sulfur-iodine (Mo{sub 6}S{sub 2}I{sub 8}) nanowires. This unique synthesis route results in an interesting morphology comprising porous nanowires and nanotubes. We found the nanowires to have the orthorhombic MoO{sub 3} structure. The structure is slightly oxygen deficient which results in the appearance of a new resonant Raman band (1004 cm{sup −1}) and paramagnetic defects (Mo{sup 5+}) of both the point and crystallographic shear plane nature. - Highlights: • Polycrystalline MoO{sub 3} nanowires were obtained via oxidation of Mo{sub 6}S{sub 2}I{sub 8} nanowires. • Nanowires are porous and tubular with either filled or empty interior. • Nanowires are slightly oxygen deficient which leads to a new Raman band.

Energetics of magnesium, strontium, and barium doped lanthanum gallate perovskites

International Nuclear Information System (INIS)

Cheng Jihong; Navrotsky, Alexandra

2004-01-01

LaGaO 3 perovskites doped with Sr or Ba at the La site and Mg at the Ga site were prepared by solid-state reaction or sol-gel method and characterized. Enthalpies of formation from constituent oxides at 298 K were determined by high-temperature oxide melt solution calorimetry. Energetic trends are discussed in terms of defect chemistry. As oxygen deficiency increases, formation enthalpies define three trends, LaGa 1-y Mg y O 3-δ (LGM), La 1-x Sr x Ga 1-y Mg y O 3-δ (LSGM), and La 1-x Ba x Ga 1-y Mg y O 3-δ (LBGM). They become less exothermic with increasing doping, suggesting a dominant destabilization effect from oxygen vacancies. The endothermic enthalpy of vacancy formation is 275±37, 166±18 and 138±12 kJ/mol of V O ·· for LGM, LBGM and LSGM, respectively. Tolerance factor and ion size mismatch also affect enthalpies. In terms of energetics, Sr is the best dopant for the La site and Mg for the Ga site, supporting earlier studies, including oxygen ion conductivity and computer modeling

Energetics of magnesium, strontium, and barium doped lanthanum gallate perovskites

Science.gov (United States)

Cheng, Jihong; Navrotsky, Alexandra

2004-01-01

LaGaO 3 perovskites doped with Sr or Ba at the La site and Mg at the Ga site were prepared by solid-state reaction or sol-gel method and characterized. Enthalpies of formation from constituent oxides at 298 K were determined by high-temperature oxide melt solution calorimetry. Energetic trends are discussed in terms of defect chemistry. As oxygen deficiency increases, formation enthalpies define three trends, LaGa 1- yMg yO 3- δ (LGM), La 1- xSr xGa 1- yMg yO 3- δ (LSGM), and La 1- xBa xGa 1- yMg yO 3- δ (LBGM). They become less exothermic with increasing doping, suggesting a dominant destabilization effect from oxygen vacancies. The endothermic enthalpy of vacancy formation is 275±37, 166±18 and 138±12 kJ/mol of VO·· for LGM, LBGM and LSGM, respectively. Tolerance factor and ion size mismatch also affect enthalpies. In terms of energetics, Sr is the best dopant for the La site and Mg for the Ga site, supporting earlier studies, including oxygen ion conductivity and computer modeling.

Electrochemical reduction of nitrous oxide on La1-xSrxFeO3 perovskites

DEFF Research Database (Denmark)

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...

Oxygen perovskites with tetravalent neodymium

Energy Technology Data Exchange (ETDEWEB)

Brauer, G; Kristen, H [Freiburg Univ. (Germany, F.R.)

1979-09-01

Neodymium could be stabilized by incorporating it in host-lattices with the perovskite structure. BaCeO/sub 3/, BaPrO/sub 3/, BaThO/sub 3/, and BaZrO/sub 3/ have been used for host-lattices. The samples were prepared by heating the corresponding oxides on air and at 1250-1400 /sup 0/C. X-ray diffraction and chemical analysis showed that Nd(IV) has been stabilized in different rates by these four host-lattices. BaCeO/sub 3/ is able to incorporate Nd(IV) up to 30%. BaPrO/sub 3/ up to 18%, BaThO/sub 3/ up to 17% and BaZrO/sub 3/ up to 4%.

Synthesis, structure and total conductivity of A-site doped LaTiO{sub 3−δ} perovskites

Energy Technology Data Exchange (ETDEWEB)

Bradha, M. [Nanotech Research Facility, PSG Institute of Advanced Studies, Coimbatore 641 004, TN (India); Hussain, S.; Chakravarty, Sujay [UGC-DAE CSR, Kalpakkam Node, Kokilamedu 603 104, TN (India); Amarendra, G. [UGC-DAE CSR, Kalpakkam Node, Kokilamedu 603 104, TN (India); Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, TN (India); Ashok, Anuradha, E-mail: anu.machina@gmail.com [Nanotech Research Facility, PSG Institute of Advanced Studies, Coimbatore 641 004, TN (India)

2015-03-25

Highlights: • A-site divalent alkaline earth metal doped LaTiO{sub 3−δ} perovskites were synthesised by sol–gel method. • Structural studies revealed no change in crystal symmetry but change in cell dimensions after doping. • After doping divalent cations in A-site, an enhancement in total conductivity was observed in LaTiO{sub 3−δ}. • Temperature dependent electrical property was observed in all synthesised perovskites. - Abstract: Oxygen deficient perovskites LaTiO{sub 3−δ} and La{sub 0.8}A{sub 0.2}TiO{sub 3−δ} (A = Ba, Sr, Ca) were synthesized by sol–gel method. The effect of divalent dopants on microstructure is investigated in detail using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The oxidation states of La{sup 3+} and Ti{sup 3+} ions have been deduced using X-ray Photoelectron Spectroscopy (XPS). Impedance spectroscopy was used to analyze the total conductivity, an increase in conductivity was observed after doping in the A-site with divalent cations Ba, Ca and Sr. Among the investigated perovskites La{sub 0.8}Ca{sub 0.2}TiO{sub 3−δ} exhibited the maximum conductivity of 1.22 × 10{sup −2} S/cm in air atmosphere at 650 °C.

Magnetism and metal-insulator transition in oxygen deficient SrTiO3

Science.gov (United States)

Lopez-Bezanilla, Alejandro; Ganesh, P.; Littlewood, Peter

2015-03-01

We report new findings in the electronic structure and magnetism of oxygen vacancies in SrTiO3. By means of first-principles calculations we show that the appearance of magnetism in oxygen-deficient SrTiO3 is not determined solely by the presence of a single oxygen vacancy but by the density of free carriers and the relative proximity of the vacant sites. While an isolated vacancy behaves as a non-magnetic double donor, manipulation of the doping conditions allows the stability of a single donor state with emergent local moments. Strong local lattice distortions enhance the binding of this state. Consequently we find that the free-carrier density and strain are fundamental components to obtaining trapped spin-polarized electrons in oxygen-deficient SrTiO3, which may have important implications in the design of switchable magneto-optic devices. AL-B and PBL were supported by DOE-BES under Contract No. DE-AC02-06CH11357. PG was sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT- Battelle, LLC, for the US Department of Energy.

Effect of oxygen deficiency on electronic properties and local structure of amorphous tantalum oxide thin films

Energy Technology Data Exchange (ETDEWEB)

Denny, Yus Rama [Department of Physics Education, University of Sultan Ageng Tirtayasa, Banten 42435 (Indonesia); Firmansyah, Teguh [Department of Electrical Engineering, University of Sultan Ageng Tirtayasa, Banten 42435 (Indonesia); Oh, Suhk Kun [Department of Physics, Chungbuk National University, Cheongju 28644 (Korea, Republic of); Kang, Hee Jae, E-mail: hjkang@cbu.ac.kr [Department of Physics, Chungbuk National University, Cheongju 28644 (Korea, Republic of); Yang, Dong-Seok [Department of Physics Education, Chungbuk National University, Cheongju 28644 (Korea, Republic of); Heo, Sung; Chung, JaeGwan; Lee, Jae Cheol [Analytical Engineering Center, Samsung Advanced Institute of Technology, Suwon 16678 (Korea, Republic of)

2016-10-15

Highlights: • The effect of oxygen flow rate on electronic properties and local structure of tantalum oxide thin films was studied. • The oxygen deficiency induced the nonstoichiometric state a-TaOx. • A small peak at 1.97 eV above the valence band side appeared on nonstoichiometric Ta{sub 2}O{sub 5} thin films. • The oxygen flow rate can change the local electronic structure of tantalum oxide thin films. - Abstract: The dependence of electronic properties and local structure of tantalum oxide thin film on oxygen deficiency have been investigated by means of X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and X-ray absorption spectroscopy (XAS). The XPS results showed that the oxygen flow rate change results in the appearance of features in the Ta 4f at the binding energies of 23.2 eV, 24.4 eV, 25.8, and 27.3 eV whose peaks are attributed to Ta{sup 1+}, Ta{sup 2+}, Ta{sup 3+}/Ta{sup 4+}, and Ta{sup 5+}, respectively. The presence of nonstoichiometric state from tantalum oxide (TaOx) thin films could be generated by the oxygen vacancies. In addition, XAS spectra manifested both the increase of coordination number of the first Ta-O shell and a considerable reduction of the Ta-O bond distance with the decrease of oxygen deficiency.

Crystal structure and lithium ion conductivity of A-site deficient perovskites La1/3-xLi3xTaO3

International Nuclear Information System (INIS)

Mizumoto, Katsuyoshi; Hayashi, Shinsuke

1997-01-01

The crystal structure and lithium ion conductivity of La 1/3-x Li 3x TaO 3 solid solutions with the A-site deficient perovskite structure have been studied. Single phase solid solutions were obtained in the range of x=0 to 1/6. Change from tetragonal to cubic structure and decrease in the lattice volume were observed with increasing the x value. The maximum conductivity obtained was 7 x 10 -3 S·m -1 at x=0.06. The composition-dependence on the carrier concentration was calculated and compared with conductivity data. (author)

Effect of oxygen deficiency on the magnetic field-dependent entropy ...

Indian Academy of Sciences (India)

Moreover, to account for the applicability of the theory at high field, we have incorporated the effect of vortex overlapping in the London theory done by Nanda (1995). Here, we have presented the variation of change in entropy (S) with magnetic field for different oxygen deficiencies = 0, 0.04, and 0.06. On comparison ...

Facile Aluminum Reduction Synthesis of Blue TiO2 with Oxygen Deficiency for Lithium-Ion Batteries.

Science.gov (United States)

Zheng, Jing; Ji, Guangbin; Zhang, Peng; Cao, Xingzhong; Wang, Baoyi; Yu, Linghui; Xu, Zhichuan J

2015-12-07

An ultrafacile aluminum reduction method is reported herein for the preparation of blue TiO2 nanoparticles (donated as Al-TiO2 , anatase phase) with abundant oxygen deficiency for lithium-ion batteries. Under aluminum reduction, the morphology of the TiO2 nanosheets changes from well-defined rectangular into uniform round or oval nanoparticles and the particle size also decreases from 60 to 31 nm, which can aggressively accelerate the lithium-ion diffusion. Electron paramagnetic resonance (EPR) and positron annihilation lifetime spectroscopy (PALS) results reveal that plentiful oxygen deficiencies relative to the Ti(3+) species were generated in blue Al-TiO2 ; this effectively enhances the electron conductivity of the TiO2 . X-ray photoelectron spectrometry (XPS) analysis indicates that a small peak is observed for the Al-O bond, which probably plays a very important role in the stabilization of the oxygen deficiencies/Ti(3+) species. As a result, the blue Al-TiO2 possesses significantly higher capacity, better rate performance, and a longer cycle life than the white pure TiO2 . Such improvements can be attributed to the decreased particle size, as well as the existence of the oxygen deficiencies/Ti(3+) species. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crystal structure and surface characteristics of Sr-doped GdBaCo2O6−δ double perovskites: oxygen evolution reaction and conductivity

KAUST Repository

Pramana, Stevin S.

2017-12-04

A cheap and direct solution towards engineering better catalysts through identification of novel materials is required for a sustainable energy system. Perovskite oxides have emerged as potential candidates to replace the less economically attractive Pt and IrO2 water splitting catalysts. In this work, excellent electrical conductivity (980 S cm−1) was found for the double perovskite of composition GdBa0.6Sr0.4Co2O6−δ which is consistent with a better oxygen evolution reaction activity with the onset polarisation of 1.51 V with respect to a reversible hydrogen electrode (RHE). GdBa1−xSrxCo2O6−δ with increasing Sr content was found to crystallise in the higher symmetry tetragonal P4/mmm space group in comparison with the undoped GdBaCo2O6−δ which is orthorhombic (Pmmm), and yields higher oxygen uptake, accompanied by higher Co oxidation states. This outstanding electrochemical performance is explained by the wider carrier bandwidth, which is a function of Co–O–Co buckling angles and Co–O bond lengths. Furthermore the higher oxygen evolution activity was observed despite the formation of non-lattice oxides (mainly hydroxide species) and enrichment of alkaline earth ions on the surface.

Crystal structure and surface characteristics of Sr-doped GdBaCo2O6−δ double perovskites: oxygen evolution reaction and conductivity

KAUST Repository

Pramana, Stevin S.; Cavallaro, Andrea; Li, Cheng; Handoko, Albertus D.; Chan, Kuang Wen; Walker, Robert J.; Regoutz, Anna; Herrin, Jason S.; Yeo, Boon Siang; Payne, David J.; Kilner, John A.; Ryan, Mary P.; Skinner, Stephen J.

2017-01-01

A cheap and direct solution towards engineering better catalysts through identification of novel materials is required for a sustainable energy system. Perovskite oxides have emerged as potential candidates to replace the less economically attractive Pt and IrO2 water splitting catalysts. In this work, excellent electrical conductivity (980 S cm−1) was found for the double perovskite of composition GdBa0.6Sr0.4Co2O6−δ which is consistent with a better oxygen evolution reaction activity with the onset polarisation of 1.51 V with respect to a reversible hydrogen electrode (RHE). GdBa1−xSrxCo2O6−δ with increasing Sr content was found to crystallise in the higher symmetry tetragonal P4/mmm space group in comparison with the undoped GdBaCo2O6−δ which is orthorhombic (Pmmm), and yields higher oxygen uptake, accompanied by higher Co oxidation states. This outstanding electrochemical performance is explained by the wider carrier bandwidth, which is a function of Co–O–Co buckling angles and Co–O bond lengths. Furthermore the higher oxygen evolution activity was observed despite the formation of non-lattice oxides (mainly hydroxide species) and enrichment of alkaline earth ions on the surface.

Oxygen Stoichiometry in Cation Deficient (La,Sr)_{1-z}MnO_3 SOFC Cathode Materials

DEFF Research Database (Denmark)

Zachau-Christiansen, Birgit; Jacobsen, Torben; Skaarup, Steen

1997-01-01

by the imposed potential.It is found that the oxygen stoichiometry and hence the defect chemistry is different whether A-site charge deficiency is established by Sr-doping or by A-site vacancies. Furthermore,A-site deficient lanthanum strontium manganates expel a secondary phase of manganese oxide when exposed...... to low oxygen partial pressures. The presence of small amounts of secondary phase isobserved and identified by its reoxidation peak. The amount of this foreign phase is determined by the charge used for its oxidation....

High-temperature vaporization behavior of oxygen-deficient thoria

International Nuclear Information System (INIS)

Ackermann, R.J.; Tetenbaum, M.

1979-01-01

The experimental results of the present study on the vaporization behavior of oxygen-deficient thoria are directed toward a more precise and detailed study of the lower phase boundary (l.p.b.) and congruently vaporizing composition (c.v.c), and intermediate compositions, and the corresponding oxygen potentials and total pressure at temperatures above 2000K. The l.p.b. and c.v.c. values were found to fit an equation of the form log x = A + (B/T), where x is the stoichiometric defect in ThO 2 -x. Oxygen potentials corresponding to the l.p.b. and c.v.c. have been estimated from vapor pressures and thermodynamic data. A very sharp decrease in oxygen potential occurs when thoria isreduced only slightly from the stoichiometric composition. In the temperature range from 2400 to 2655 K, the oxygen partial pressure dependency of x in ThO 2 -x was found to be approximately proportional to PO 2 - 1 /4to PO 2 - 1 /. The small extent of reduction over a wide range of oxygen potentials at these temperatures is a clear illustration of the higher stability of the ThO 2 -x phase compared with that of UO 2 -x. Values of ΔHO 2 and ΔSO 2 have been estimated for selected compositions from the dependence of the measured oxygen potential on temperature. Estimates of the standard free energy of formation of bivariant ThO 2 -x compositions have been made. A substantial increase in the total pressure of thorium-bearing species occurs when stoichiometric thoria is reduced toward the lower phase boundary. (orig.) [de

Perovskite Catalysts—A Special Issue on Versatile Oxide Catalysts

Directory of Open Access Journals (Sweden)

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. [...

High-resolution spectra of stars in globular clusters. VI - Oxygen-deficient red giant stars in M13

International Nuclear Information System (INIS)

Brown, J.A.; Wallerstein, G.; Oke, J.B.

1991-01-01

From high-resolution, high signal-to-noise spectra, abundances of carbon, nitrogen, and oxygen and the C-12/C-13 ratio for five red giants in M13, including star II-67, which has previously been reported to be deficient in oxygen have been determined. Three of the five stars exhibit substantial oxygen deficiencies; O/Fe values range from +0.5 to less than about 0.3. The sum of the CNO nuclides is the same for all stars, which is interpreted as evidence that mixing of CNO-cycled material into the envelope is the cause of the variations in oxygen abundance. 41 refs

Oxygen-deficient hematite nanorods as high-performance and novel negative electrodes for flexible asymmetric supercapacitors.

Science.gov (United States)

Lu, Xihong; Zeng, Yinxiang; Yu, Minghao; Zhai, Teng; Liang, Chaolun; Xie, Shilei; Balogun, Muhammad-Sadeeq; Tong, Yexiang

2014-05-21

Oxygen-deficient α-Fe2 O3 nanorods with outstanding capacitive performance are developed and demonstrated as novel negative electrodes for flexible asymmetric supercapacitors. The asymmetric-supercapacitor device based on the oxygen-deficient α-Fe2 O3 nanorod negative electrode and a MnO2 positive electrode achieves a maximum energy density of 0.41 mW·h/cm(3) ; it is also capable of charging a mobile phone and powering a light-emitting diode indicator. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phase stability study of Bi0.15Sr0.85-xAexCoO3-δ (x = 0 and Ae = Ba0.28; Ca0.17) perovskites by in-situ neutron diffraction

International Nuclear Information System (INIS)

Eriksson, A.K.; Eriksson, S.G.; Chapon, L.C.; Knee, C.S.

2010-01-01

The oxygen deficient perovskites, Bi 0.15 Sr 0.85-x Ae x CoO 3-δ , x = 0 and Ae x = Ba 0.28 , Ca 0.17 , were studied with in-situ neutron powder diffraction and combined TGA/DSC in order to investigate their behaviour at elevated temperatures in oxidising conditions. The phase stability of the I4/mmm supercell structure adopted by Bi 0.15 Sr 0.85 CoO 3-δ is shown to be dependent on temperature and the oxygen content of the phase, with three structural events, at T ∼ 250, 590 and 880 o C, detected. The first transition occurs as the perovskite supercell vanishes due to oxygen absorption; the second transition is also associated with oxidation and involves the decomposition of the perovskite phase via an exothermic process to yield a dominant hexagonal phase. Finally, at T ∼ 900 o C the perovskite phase re-forms. For the Ba and Ca containing materials the decomposition to the hexagonal phase occurs at T ∼ 600 o C and ∼ 650 o C respectively. The presence of Ca at the A-site is found to stabilise the I4/mmm supercell structure in the range RT - 650 o C. The antiferromagnetic to paramagnetic transitions occur at T N ∼ 250 o C, T N ∼ 175 o C and T N ∼ 145 o C for the samples with Ae x = Ba 0.28 , x = 0 and Ae x = Ca 0.17 , respectively.

Perovskite-Perovskite Homojunctions via Compositional Doping.

Science.gov (United States)

Dänekamp, Benedikt; Müller, Christian; Sendner, Michael; Boix, Pablo P; Sessolo, Michele; Lovrincic, Robert; Bolink, Henk J

2018-05-11

One of the most important properties of semiconductors is the possibility of controlling their electronic behavior via intentional doping. Despite the unprecedented progress in the understanding of hybrid metal halide perovskites, extrinsic doping of perovskite remains nearly unexplored and perovskite-perovskite homojunctions have not been reported. Here we present a perovskite-perovskite homojunction obtained by vacuum deposition of stoichiometrically tuned methylammonium lead iodide (MAPI) films. Doping is realized by adjusting the relative deposition rates of MAI and PbI 2 , obtaining p-type (MAI excess) and n-type (MAI defect) MAPI. The successful stoichiometry change in the thin films is confirmed by infrared spectroscopy, which allows us to determine the MA content in the films. We analyzed the resulting thin-film junction by cross-sectional scanning Kelvin probe microscopy (SKPM) and found a contact potential difference (CPD) of 250 mV between the two differently doped perovskite layers. Planar diodes built with the perovskite-perovskite homojunction show the feasibility of our approach for implementation in devices.

Curtailing Perovskite Processing Limitations via Lamination at the Perovskite/Perovskite Interface

Energy Technology Data Exchange (ETDEWEB)

Van Hest, Marinus F [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Moore, David [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Klein, Talysa [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Christians, Jeffrey A [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Beard, Matthew C [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Berry, Joseph J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Dunfield, Sean P. [University of Colorado; Fabian, David M. [University of California Irvine; Dixon, Alex G. [University of Colorado; Dou, Benjia [University of Colorado; Ardo, Shane [University of California Irvine; Shaheen, Sean E. [University of Colorado

2018-04-24

Standard layer-by-layer solution processing methods constrain lead-halide perovskite device architectures. The layer below the perovskite must be robust to the strong organic solvents used to form the perovskite while the layer above has a limited thermal budget and must be processed in nonpolar solvents to prevent perovskite degradation. To circumvent these limitations, we developed a procedure where two transparent conductive oxide/transport material/perovskite half stacks are independently fabricated and then laminated together at the perovskite/perovskite interface. Using ultraviolet-visible absorption spectroscopy, external quantum efficiency, X-ray diffraction, and time-resolved photoluminesence spectroscopy, we show that this procedure improves photovoltaic properties of the perovskite layer. Applying this procedure, semitransparent devices employing two high-temperature oxide transport layers were fabricated, which realized an average efficiency of 9.6% (maximum: 10.6%) despite series resistance limitations from the substrate design. Overall, the developed lamination procedure curtails processing constraints, enables new device designs, and affords new opportunities for optimization.

Ethanol flame synthesis of carbon nanotubes in deficient oxygen environments

Science.gov (United States)

Hu, Wei-Chieh; Lin, Ta-Hui

2016-04-01

In this study, carbon nanotubes (CNTs) were synthesized using ethanol diffusion flames in a stagnation-flow system composed of an upper oxidizer duct and a lower liquid pool. In the experiments, a gaseous mixture of oxygen and nitrogen flowed from the upper oxidizer duct, and then impinged onto the vertically aligned ethanol pool to generate a planar and steady diffusion flame in a deficient oxygen environment. A nascent nickel mesh was used as the catalytic metal substrate to collect deposited materials. The effect of low oxygen concentration on the formation of CNTs was explored. The oxygen concentration significantly influenced the flame environment and thus the synthesized carbon products. Lowering the oxygen concentration increased the yield, diameter, and uniformity of CNTs. The optimal operating conditions for CNT synthesis were an oxygen concentration in the range of 15%-19%, a flame temperature in the range of 460 °C-870 °C, and a sampling position of 0.5-1 mm below the upper edge of the blue flame front. It is noteworthy that the concentration gradient of C2 species and CO governed the CNT growth directly. CNTs were successfully fabricated in regions with uniform C2 species and CO distributions.

Synthesis of surface oxygen-deficient BiPO{sub 4} nanocubes with enhanced visible light induced photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Shi, Bingtao; Yin, Haoyong; Li, Tao; Gong, Jianying; Lv, Shumei; Nie, Qiulin, E-mail: yhy@hdu.edu.cn [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou (China)

2017-05-15

The visible light driven BiPO{sub 4} nanocubes with sufficient surface oxygen deficiency were fabricated by a hydrothermal process and subsequently ultrasonic assistant Fe reduction process. The products were characterized by XRD, DRS, XPS, SEM and TEM which showed that the BiPO{sub 4} had cuboid-like shape with a smooth surface and clear edges and the oxygen vacancies were successfully introduced on the surface of the BiPO{sub 4} nanocubes. The as prepared oxygen-deficient BiPO{sub 4} nanocubes showed greatly enhanced visible light induced photocatalytic activity in degradation of Rhodamine B. The enhanced photocatalytic performance and expanded visible light response of BiPO{sub 4} may be due to the introduction of surface oxygen vacancies which can generate the oxygen vacancies mid-gap states lower to the conduction band of BiPO{sub 4}. (author)

Hybrid Perovskite/Perovskite Heterojunction Solar Cells.

Science.gov (United States)

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.

Nature of potential barrier in (Ca 1/4,Cu 3/4)TiO 3 polycrystalline perovskite

Science.gov (United States)

Marques, V. P. B.; Bueno, P. R.; Simões, A. Z.; Cilense, M.; Varela, J. A.; Longo, E.; Leite, E. R.

2006-04-01

The nonohmic electrical features of (Ca 1/4,Cu 3/4)TiO 3 perovskite ceramics, which have very strong gigantic dielectric is believed originate from potential barriers at the grain boundaries. In the present study, we used the admittance and impedance spectroscopy technique to investigate (Ca 1/4,Cu 3/4)TiO 3 perovskite ceramics with low nonohmic electrical properties. The study was conducted under two different conditions: on as-sintered ceramics and on ceramics thermally treated in an oxygen-rich atmosphere. The results confirm that thermal treatment in oxygen-rich atmospheres influence the nonohmic properties. Annealing at oxygen-rich atmospheres improve the nonohmic behavior and annealing at oxygen-poor atmospheres decrease the nonohmic properties, a behavior already reported for common metal oxide nonohmic devices and here firstly evidenced for the (Ca 1/4,Cu 3/4)TiO 3 perovskite related materials. The results show that oxygen also influences the capacitance values at low frequencies, a behavior that is indicative of the Schottky-type nature of the potential barrier.

A study on oxygen-deficient YBa2Cu3O7-δ superconductors by positron lifetime spectroscopy

International Nuclear Information System (INIS)

Zhang Jincang; Liu Fengqi; Liu Junzheng; Cao Shixun; Cheng Guosheng

1995-01-01

Positron lifetime spectroscopy has been used for studying various oxygen-deficient YBa 2 Cu 3 O 7 - δ (δ = 0.06-0.68) at normal state (300 K) and Superconducting state (77 K). Using the two-state trapping model, the experimental results were analysed and there exists a typical positron annihilation characteristics in this systems. The local electron density n e and vacancy concentration C v are calculated as a function of oxygen-deficiency δ. The mechanism of positron annihilation and the correlation with superconductivity are also discussed

Molecular diversity of fungi from marine oxygen-deficient environments (ODEs)

Digital Repository Service at National Institute of Oceanography (India)

Manohar, C.S.; Forster, D.; Kauff, F.; Stoeck, T.

. Sparrow Jr F K (1936) Biological observations of the marine fungi of woods hole waters. Biol Bull 70: 236-263. States JS & Christensen M (2001) Fungi Associated with Biological Soil Crusts in Desert Grasslands of Utah and Wyoming. Mycologia 93: 432... version: Biology of marine fungi. Ed. by: Raghukumar, C. (Prog. Mol. Subcellular Biol). Springer, vol.53 (Chap 10); 2012; 189-208 Chapter # 10 Molecular diversity of fungi from marine oxygen-deficient environments (ODEs) Cathrine S. Jebaraj 1...

Tolerance factor rules for Sr1-x-yCaxBayMnO3 perovskites

International Nuclear Information System (INIS)

Dabrowski, B.; Chmaissem, O.; Mais, J.; Kolesnik, S.; Jorgensen, J.D.; Short, S.

2003-01-01

Synthesis of new perovskite Sr 1-x-y Ca x Ba y MnO 3-δ compounds is described in detail and dependence of their phase stability and structural distortions on the tolerance factor is discussed. Oxygen contents have been measured over extended temperature and composition ranges. Neutron powder diffraction was used to precisely measure the A-O and Mn-O bond lengths and derive accurate interatomic distances [Ca-O], [Sr-O], [Ba-O], and [Mn-O]. By using these parameters instead of tabulated ionic radii we have derived the functional dependence of the tolerance factor t=t(x,y,T,δ) on composition, temperature, and oxygen content. At a fixed oxygen content, the tolerance factor is an increasing function of temperature as a result of greater thermal expansion of the average bond relative to the bond. We find that the stability of the perovskite phase at high temperature is governed, as expected, by the magnitude of tolerance factor (t≤1) which can be adjusted by controlling the oxygen content 3-δ. This dependence of the tolerance factor on oxygen content and temperature can be utilized to design synthesis conditions for the controlled formation of the new, kinetically stable, perovskite phases

Oxygen Evolution at Manganite Perovskite Ruddlesden-Popper Type Particles: Trends of Activity on Structure, Valence and Covalence

Directory of Open Access Journals (Sweden)

Majid Ebrahimizadeh Abrishami

2016-11-01

Full Text Available An improved understanding of the correlation between the electronic properties of Mn-O bonds, activity and stability of electro-catalysts for the oxygen evolution reaction (OER is of great importance for an improved catalyst design. Here, an in-depth study of the relation between lattice structure, electronic properties and catalyst performance of the perovskite Ca1−xPrxMnO3 and the first-order RP-system Ca2−xPrxMnO4 at doping levels of x = 0, 0.25 and 0.5 is presented. Lattice structure is determined by X-ray powder diffraction and Rietveld refinement. X-ray absorption spectroscopy of Mn-L and O-K edges gives access to Mn valence and covalency of the Mn-O bond. Oxygen evolution activity and stability is measured by rotating ring disc electrode studies. We demonstrate that the highest activity and stability coincidences for systems with a Mn-valence state of +3.7, though also requiring that the covalency of the Mn-O bond has a relative minimum. This observation points to an oxygen evolution mechanism with high redox activity of Mn. Covalency should be large enough for facile electron transfer from adsorbed oxygen species to the MnO6 network; however, it should not be hampered by oxidation of the lattice oxygen, which might cause a crossover to material degradation. Since valence and covalency changes are not entirely independent, the introduction of the energy position of the eg↑ pre-edge peak in the O-K spectra as a new descriptor for oxygen evolution is suggested, leading to a volcano-like representation of the OER activity.

Solution processed deposition of electron transport layers on perovskite crystal surface—A modeling based study

Energy Technology Data Exchange (ETDEWEB)

Mortuza, S.M.; Taufique, M.F.N.; Banerjee, Soumik, E-mail: soumik.banerjee@wsu.edu

2017-02-01

Highlights: • The model determined the surface coverage of solution-processed film on perovskite. • Calculated surface density map provides insight into morphology of the monolayer. • Carbonyl oxygen atom of PCBM strongly attaches to the (110) surface of perovskite. • Uniform distribution of clusters on perovskite surface at lower PCBM concentration. • Deposition rate of PCBM on the surface is very high at initial stage of film growth. - Abstract: The power conversion efficiency (PCE) of planar perovskite solar cells (PSCs) has reached up to ∼20%. However, structural and chemicals defects that lead to hysteresis in the perovskite based thin film pose challenges. Recent work has shown that thin films of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) deposited on the photo absorption layer, using solution processing techniques, minimize surface pin holes and defects thereby increasing the PCE. We developed and employed a multiscale model based on molecular dynamics (MD) and kinetic Monte Carlo (kMC) to establish a relationship between deposition rate and surface coverage on perovskite surface. The MD simulations of PCBMs dispersed in chlorobenzene, sandwiched between (110) perovskite substrates, indicate that PCBMs are deposited through anchoring of the oxygen atom of carbonyl group to the exposed lead (Pb) atom of (110) perovskite surface. Based on rates of distinct deposition events calculated from MD, kMC simulations were run to determine surface coverage at much larger time and length scales than accessible by MD alone. Based on the model, a generic relationship is established between deposition rate of PCBMs and surface coverage on perovskite crystal. The study also provides detailed insights into the morphology of the deposited film.

Solution processed deposition of electron transport layers on perovskite crystal surface—A modeling based study

International Nuclear Information System (INIS)

Mortuza, S.M.; Taufique, M.F.N.; Banerjee, Soumik

2017-01-01

Highlights: • The model determined the surface coverage of solution-processed film on perovskite. • Calculated surface density map provides insight into morphology of the monolayer. • Carbonyl oxygen atom of PCBM strongly attaches to the (110) surface of perovskite. • Uniform distribution of clusters on perovskite surface at lower PCBM concentration. • Deposition rate of PCBM on the surface is very high at initial stage of film growth. - Abstract: The power conversion efficiency (PCE) of planar perovskite solar cells (PSCs) has reached up to ∼20%. However, structural and chemicals defects that lead to hysteresis in the perovskite based thin film pose challenges. Recent work has shown that thin films of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) deposited on the photo absorption layer, using solution processing techniques, minimize surface pin holes and defects thereby increasing the PCE. We developed and employed a multiscale model based on molecular dynamics (MD) and kinetic Monte Carlo (kMC) to establish a relationship between deposition rate and surface coverage on perovskite surface. The MD simulations of PCBMs dispersed in chlorobenzene, sandwiched between (110) perovskite substrates, indicate that PCBMs are deposited through anchoring of the oxygen atom of carbonyl group to the exposed lead (Pb) atom of (110) perovskite surface. Based on rates of distinct deposition events calculated from MD, kMC simulations were run to determine surface coverage at much larger time and length scales than accessible by MD alone. Based on the model, a generic relationship is established between deposition rate of PCBMs and surface coverage on perovskite crystal. The study also provides detailed insights into the morphology of the deposited film.

Research Update: Strategies for improving the stability of perovskite solar cells

Directory of Open Access Journals (Sweden)

Severin N. Habisreutinger

2016-09-01

Full Text Available The power-conversion efficiency of perovskite solar cells has soared up to 22.1% earlier this year. Within merely five years, the perovskite solar cell can now compete on efficiency with inorganic thin-film technologies, making it the most promising of the new, emerging photovoltaic solar cell technologies. The next grand challenge is now the aspect of stability. The hydrophilicity and volatility of the organic methylammonium makes the work-horse material methylammonium lead iodide vulnerable to degradation through humidity and heat. Additionally, ultraviolet radiation and oxygen constitute stressors which can deteriorate the device performance. There are two fundamental strategies to increasing the device stability: developing protective layers around the vulnerable perovskite absorber and developing a more resilient perovskite absorber. The most important reports in literature are summarized and analyzed here, letting us conclude that any long-term stability, on par with that of inorganic thin-film technologies, is only possible with a more resilient perovskite incorporated in a highly protective device design.

Processing and characterization of Sr2−xVMoO6−δ double perovskites

International Nuclear Information System (INIS)

Weisentein, A.J.; Childs, N.; Amendola, R.; Driscoll, D.; Sofie, S.W.; Gannon, P.; Smith, R.

2013-01-01

In this study, the analysis and characterization of the processing and sintering of Sr 2−x VMoO 6−δ perovskites, where x = 0.0, 0.1 and 0.2, was investigated with application potential in high temperature fuel cell electrodes and electro-catalysts. Sr 2−x VMoO 6−δ substrates were sintered in a reducing (5%H 2 95%N 2 ) atmosphere at 1100 °C, 1200 °C, and 1300 °C. The X-ray diffraction patterns indicate that the double perovskite is the primary phase for Sr 2−x VMoO 6−δ pellets sintered at 1200 °C and 1300 °C for 20 h; however, these pellets show a secondary phase of SrMoO 4−δ . X-ray photoelectron spectroscopy revealed a deficiency of vanadium on the pellet surfaces, in which samples yielded surface vanadium concentrations of less than 5%. The vanadium inhomogeneity can be explained by the formation of the SrMoO 4−δ scheelite phase (ABO 4 ) due to oxygen exposure on the surface of the pellets, which indicates inward vanadium migration to the bulk, and was exhibited in redox cycling. Sr 2−x VMoO 6−δ pellets sintered at 1300 °C showed the lowest resistivity at both SOFC operating temperature (800 °C) and room temperature. The resistivity tests also show a semiconductor to metallic transition for all double perovskites, from heating up to 800 °C to cooling down to room temperature in a reducing atmosphere, related to the reduction of Mo 6+ to Mo 4+ . - Highlights: ► Primary Sr 2−x VMoO 6−δ phase only shown to form in excess of 1300 °C in reducing. ► Surface formation of secondary phase SrMoO 4−δ (Mo 6+ ) observed at RT in air. ► Surface vanadium deficiency induced by inward atomic diffusion. ► Semiconductor to metallic transition is related to the reduction of Mo 6+ to Mo 4+

LSFM perovskites as cathodes for the electrochemical reduction of NO

DEFF Research Database (Denmark)

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

2005-01-01

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...... 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....

Thermal engineering of lead-free nanostructured CH3NH3SnCl3 perovskite material for thin-film solar cell

Science.gov (United States)

Moyez, Sk Abdul; Roy, Subhasis

2018-01-01

Perovskite solar cell is a kind of revolutionary investigation in the field of renewable energy which is capable of mitigates the deficiencies of silicon solar cell and its uprising efficiency can bring blessing to society. The presence of lead (Pb) in perovskite solar cell can make worst and negative impact on environment and is not desirable for our society. In this paper, general plans are anticipated by replacement of Pb with tin (Sn) in open atmosphere to fabricate the CH3NH3SnCl3 photovoltaic cells in chlorine (Cl)-rich environment. Excess uses of Cl has positive influences on morphological growth of the film and it also suppresses the oxidation tendency of tin (Sn) with existing oxygen in atmosphere and maintains same chemical atmosphere as bulk. Various characterization tools like X-ray diffraction, scanning electron microscope (SEM) have been used to study the effect of annealing temperature on crystal stricture, phase formation, impurities, and morphologies of the film. Finally, photovoltaic performance was reported using the solar simulator under 1.5 sun illumination.

Lack of oxygen effect in glutathione-deficient human cells in culture

International Nuclear Information System (INIS)

Edgren, M.; Larsson, A.; Nilsson, K.; Revesz, L.; Scott, O.C.A.

1980-01-01

The frequency of X-ray-induced DNA breaks was determined in human cell lines which are deficient in glutathione synthetase and have a greatly reduced glutathione content. Hydroxyapatite chromatography was used for the estimation of the DNA breaks in cell cultures, which were derived either from lymphoblasts transformed by infection with EB virus or from fibroblasts. The dose-effect relationship for the induction of breaks when radiation exposure was made in argon, was similar to that found when exposure was made in air. In control cultures with normal glutathione content, the induction of breaks was enhanced when irradiation was made under aerobic, instead of anaerobic, conditions. Treatment of the glutathione-deficient cells with the hypoxic radiosensitizer misonidazole did not enhance the induction of breaks by radiation delivered either in air or in argon. In control cultures, radiation induction of breaks was enhanced by misonidazole under anaerobic but not under aerobic conditions. When the glutathione-deficient cells were pretreated with cysteamine however, irradiation in the absence of oxygen resulted in a decreased frequency of DNA breaks. (author)

K{sub 2}NaOsO{sub 5.5} and K{sub 3}NaOs{sub 2}O{sub 9}: The first osmium perovskites containing alkali cations at the 'A' site

Energy Technology Data Exchange (ETDEWEB)

Mogare, Kailash M.; Klein, Wilhelm [Stuttgart, Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, 70569 Stuttgart (Germany); Jansen, Martin, E-mail: M.Jansen@fkf.mpg.de [Stuttgart, Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, 70569 Stuttgart (Germany)

2012-07-15

K{sub 2}NaOsO{sub 5.5} and K{sub 3}NaOs{sub 2}O{sub 9} were obtained from solid-state reactions of potassium superoxide, sodium peroxide and osmium metal at elevated oxygen pressures. K{sub 2}NaOsO{sub 5.5} crystallizes as an oxygen-deficient cubic double perovskite in space group Fm3{sup Macron }m with a=8.4184(5) A and contains isolated OsO{sub 6} octahedra. K{sub 3}NaOs{sub 2}O{sub 9} crystallizes hexagonally in P6{sub 3}/mmc with a=5.9998(4) A and c=14.3053(14) A. K{sub 3}NaOs{sub 2}O{sub 9} consists of face sharing Os{sub 2}O{sub 9} pairs of octahedra. According to magnetic measurements K{sub 2}NaOsO{sub 5.5} is diamagnetic, whereas K{sub 3}NaOs{sub 2}O{sub 9} displays strong antiferromagnetic coupling (T{sub N}=140 K), indicating enhanced magnetic interactions within the octahedral pair. - Graphical abstract: High oxidation states of Os, obtained by high oxygen pressure synthesis, are accommodated in double and triple perovskite matrices. K{sub 3}NaOs{sub 2}O{sub 9} displays enhanced magnetic interactions. Highlights: Black-Right-Pointing-Pointer New osmates containing highly oxidized Os were obtained by high O{sub 2} pressure synthesis. Black-Right-Pointing-Pointer High oxidation states of Os are accommodated in double and triple perovskite matrices. Black-Right-Pointing-Pointer Both compounds represent the first Os perovskites with an alkali metal at the A site. Black-Right-Pointing-Pointer K{sub 3}NaOs{sub 2}O{sub 9} displays enhanced magnetic interactions within the octahedral pair.

Influence of iridium on the reactivity of LaFeO3 base perovskites

DEFF Research Database (Denmark)

Kindermann, L.; Das, D.; Bahadur, D.

1998-01-01

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....

Tilts and Ionic Shifts in Rhombohedral Perovskites

NARCIS (Netherlands)

Noheda, Beatriz; Duan, Ning; Cereceda, Noé; Gonzalo, Julio A.

1998-01-01

We make a comparative analysis of rhombohedral perovskites (ABO3) with/without oxygen rotations and ionic shifts, within the framework of a generalised effective field approach. We analyse available data on LaAlO3 and LiTaO3 and new data on Zr-rich PZT, examples of three different ways of structural

Persistent optically induced magnetism in oxygen-deficient strontium titanate.

Science.gov (United States)

Rice, W D; Ambwani, P; Bombeck, M; Thompson, J D; Haugstad, G; Leighton, C; Crooker, S A

2014-05-01

Strontium titanate (SrTiO3) is a foundational material in the emerging field of complex oxide electronics. Although its bulk electronic and optical properties are rich and have been studied for decades, SrTiO3 has recently become a renewed focus of materials research catalysed in part by the discovery of superconductivity and magnetism at interfaces between SrTiO3 and other non-magnetic oxides. Here we illustrate a new aspect to the phenomenology of magnetism in SrTiO3 by reporting the observation of an optically induced and persistent magnetization in slightly oxygen-deficient bulk SrTiO3-δ crystals using magnetic circular dichroism (MCD) spectroscopy and SQUID magnetometry. This zero-field magnetization appears below ~18 K, persists for hours below 10 K, and is tunable by means of the polarization and wavelength of sub-bandgap (400-500 nm) light. These effects occur only in crystals containing oxygen vacancies, revealing a detailed interplay between magnetism, lattice defects, and light in an archetypal complex oxide material.

Ab initio study of perovskite type oxide materials for solid oxide fuel cells

Science.gov (United States)

Lee, Yueh-Lin

2011-12-01

Perovskite type oxides form a family of materials of significant interest for cathodes and electrolytes of solid oxide fuel cells (SOFCs). These perovskites not only are active catalysts for surface oxygen reduction (OR) reactions but also allow incorporating the spilt oxygen monomers into their bulk, an unusual and poorly understood catalytic mechanism that couples surface and bulk properties. The OR mechanisms can be influenced strongly by defects in perovskite oxides, composition, and surface defect structures. This thesis work initiates a first step in developing a general strategy based on first-principles calculations for detailed control of oxygen vacancy content, transport rates of surface and bulk oxygen species, and surface/interfacial reaction kinetics. Ab initio density functional theory methods are used to model properties relevant for the OR reactions on SOFC cathodes. Three main research thrusts, which focus on bulk defect chemistry, surface defect structures and surface energetics, and surface catalytic properties, are carried to investigate different level of material chemistry for improved understanding of key physics/factors that govern SOFC cathode OR activity. In the study of bulk defect chemistry, an ab initio based defect model is developed for modeling defect chemistry of LaMnO 3 under SOFC conditions. The model suggests an important role for defect interactions, which are typically excluded in previous defect models. In the study of surface defect structures and surface energetics, it is shown that defect energies change dramatically (1˜2 eV lower) from bulk values near surfaces. Based on the existing bulk defect model with the calculated ab initio surface defect energetics, we predict the (001) MnO 2 surface oxygen vacancy concentration of (La0.9Sr0.1 )MnO3 is about 5˜6 order magnitude higher than that of the bulk under typical SOFC conditions. Finally, for surface catalytic properties, we show that area specific resistance, oxygen

Study on the effects of fluorine and oxygen deficiency on YBa2Cu3O7 by ab initio method

Institute of Scientific and Technical Information of China (English)

刘洪霖; 曹晓卫; 瞿丽曼; 陈念贻

1997-01-01

The calculations of clusters modeling the fluorine-doping and oxygen deficiency of YBa2Cu3O2,have been performed by the method of all-electron ab initio Hartree-Fock with self-consistent crystal field Results show that in CuO planes electric charge significantly increases,the chemical valence of Cu decreases and the covalent bonding of Cu-O greatly weakens owing to oxygen deficiency,while the effect of F restores the local electronic structure of YBa2Cu3O7 The reported opinion that F occupied the oxygen vacancy in Cu-O chains seems disputable according to the calculated bonding characteristics.

The oxygen deficient Ruddlesden-Popper La3Ni2O7-δ (δ = 0.65) phase: Structure and properties

International Nuclear Information System (INIS)

Poltavets, Viktor V.; Lokshin, Konstantin A.; Egami, Takeshi; Greenblatt, Martha

2006-01-01

La 3 Ni 2 O 7-δ (δ = 0.65) was synthesized by hydrogen reduction of the parent La 3 Ni 2 O 7 Ruddlesden-Popper nickelate. The crystal structure of La 3 Ni 2 O 6.35 (space group: I4/mmm, a = 3.8742 (1) A and c = 20.055 (1) A) has been determined from powder neutron diffraction data by the Rietveld method for the first time. The oxygen vacancies are located in the LaO x planes between two of the NiO 2 layers. Removal of these oxygen atoms from the parent phase results in a significant (∼0.4 A) shrinkage of the perovskite block along c-direction and splitting of the Ni position. The major part of Ni cations is surrounded by five oxygen atoms forming square pyramids, while the rest are coordinated to six octahedrally arranged oxygen atoms. Over the 170-400 K temperature range, the conductivity of La 3 Ni 2 O 6.35 follows Mott's variable range hopping model modified for a 2D case

Effects of sintering temperature on the pyrochlore phase in PZT nanotubes and their transformation to the perovskite phase by coating with PbO multilayers.

Science.gov (United States)

Han, Jin Kyu; Choi, Yong Chan; Jeon, Do Hyen; Lee, Min Ku; Bu, Sang Don

2014-11-01

We report the phase evolution of Pb(Zr0.52Ti0.48)O3 nanotubes (PZT-NTs), from the pyrochlore to perovskite phase, with an outer diameter of about 420 nm and a wall thickness of about 10 nm. The PZT-NTs were fabricated in pores of porous anodic alumina membrane (PAM) using a spin coating of PZT sol-gel solution and subsequent annealing at 500-700 degrees C in oxygen gas. The pyrochlore phase was found to be formed at 500 degrees C, and also found not to be transformed into the perovskite phase, even though annealing was performed at higher temperatures to 700 degrees C. Elementary distribution analysis of PZT-NTs embedded in PAM reveal that Pb diffusion from nanotubes into pore walls of PAM is one of the main reasons. By employing firstly an additional PbO coating on the pyrochlore nanotubes and then subsequent annealing at 700 degrees C, we have successfully achieved an almost pure perovskite phase in nanotubes. These results suggest that PbO acts as a Pb-compensation agent in the Pb- deficient PZT-NTs. Moreover, our method can be used in the synthesis of all metal-oxide materials, including volatile elements.

Environmental Effects on the Photophysics of Organic-Inorganic Halide Perovskites.

Science.gov (United States)

Galisteo-López, Juan F; Anaya, M; Calvo, M E; Míguez, H

2015-06-18

The photophysical properties of films of organic-inorganic lead halide perovskites under different ambient conditions are herein reported. We demonstrate that their luminescent properties are determined by the interplay between photoinduced activation and darkening processes, which strongly depend on the atmosphere surrounding the samples. We have isolated oxygen and moisture as the key elements in each process, activation and darkening, both of which involve the interaction with photogenerated carriers. These findings show that environmental factors play a key role in the performance of lead halide perovskites as efficient luminescent materials.

Positron-annihilation study of oxygen-deficient YBa2Cu3Ox (6.3

International Nuclear Information System (INIS)

Tang, C.Q.; Li, B.R.; Chen, A.

1990-01-01

We have measured the positron-lifetime spectra of oxygen-deficient YBa 2 Cu 3 O x for 6.3 m , τ 1 , τ 2 , and I 2 have a significant oxygen-content dependence. It is suggested that there are many kinds of positron states in polycrystalline YBa 2 Cu 3 O x , the disordering of O(1) vacancies strongly affects positron lifetime, and with gradually decreasing x the average electronic density decreases and the configuration and/or the charge states of the oxygen vacancies change in the region containing Cu(1)-O(1) chains

High-pressure BaCrO_3 polytypes and the 5H–BaCrO_2_._8 phase

International Nuclear Information System (INIS)

Arévalo-López, Angel M.; Paul Attfield, J.

2015-01-01

Polytypism of BaCrO_3 perovskites has been investigated at 900–1100 °C and pressures up to 22 GPa. Hexagonal 5H, 4H, and 6H perovskites are observed with increasing pressure, and the cubic 3C perovskite (a=3.99503(1) Å) is observed in bulk form for the first time at 19–22 GPa. An oxygen-deficient material with limiting composition 5H–BaCrO_2_._8 is synthesised at 1200 °C under ambient pressure. This contains double tetrahedral Cr"4"+ layers and orders antiferromagnetically below 260 K with a (0 0 1/2) magnetic structure. - Graphical abstract: Hexagonal 5H, 4H, and 6H perovskites polytypes of BaCrO_3 are observed with increasing pressure and the cubic 3C perovskite is stabilised in bulk form for the first time at 19–22 GPa. Oxygen-deficient 5H–BaCrO_2_._8 synthesised at ambient pressure contains double tetrahedral Cr"4"+ layers and orders antiferromagnetically below 260 K with a (0 0 1/2) magnetic structure.

Resistance switching memory in perovskite oxides

International Nuclear Information System (INIS)

Yan, Z.B.; Liu, J.-M.

2015-01-01

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

Charge doping and large lattice expansion in oxygen-deficient heteroepitaxial WO3

Science.gov (United States)

Mattoni, Giordano; Filippetti, Alessio; Manca, Nicola; Zubko, Pavlo; Caviglia, Andrea D.

2018-05-01

Tungsten trioxide (WO3) is a versatile material with widespread applications ranging from electrochromics and optoelectronics to water splitting and catalysis of chemical reactions. For technological applications, thin films of WO3 are particularly appealing, taking advantage from a high surface-to-volume ratio and tunable physical properties. However, the growth of stoichiometric crystalline thin films is challenging because the deposition conditions are very sensitive to the formation of oxygen vacancies. In this paper, we show how background oxygen pressure during pulsed laser deposition can be used to tune the structural and electronic properties of WO3 thin films. By performing x-ray diffraction and low-temperature electrical transport measurements, we find changes in the WO3 lattice volume of up to 10% concomitantly with a resistivity drop of more than five orders of magnitude at room temperature as a function of increased oxygen deficiency. We use advanced ab initio calculations to describe in detail the properties of the oxygen vacancy defect states and their evolution in terms of excess charge concentration. Our results depict an intriguing scenario where structural, electronic, optical, and transport properties of WO3 single-crystal thin films can all be purposely tuned by controlling the oxygen vacancy formation during growth.

Microscopic origin of the mobility enhancement at a spinel/perovskite oxide heterointerface revealed by photoemission spectroscopy

DEFF Research Database (Denmark)

Schuetz, P.; Christensen, Dennis Valbjørn; Borisov, V.

2017-01-01

The spinel/perovskite heterointerface γ−Al2O3/SrTiO3 hosts a two-dimensional electron system (2DES) with electron mobilities exceeding those in its all-perovskite counterpart LaAlO3/SrTiO3 by more than an order of magnitude, despite the abundance of oxygen vacancies which act as electron donors a...

Decreasing the Hydroxylation Affinity of La _1–x Sr _x MnO ₃ Perovskites To Promote Oxygen Reduction Electrocatalysis

Energy Technology Data Exchange (ETDEWEB)

Stoerzinger, Kelsey A.; Hong, Wesley T.; Wang, Xiao Renshaw; Rao, Reshma R.; Bengaluru Subramanyam, Srinivas; Li, Changjian; Ariando,; Venkatesan, T.; Liu, Qiang [Advanced; Crumlin, Ethan J. [Advanced; Varanasi, Kripa K.; Shao-Horn, Yang

2017-11-17

Understanding the interaction between oxides and water is critical to design many of their functionalities, including the electrocatalysis of molecular oxygen reduction. In this study, we probed the hydroxylation of model (001)-oriented La(1-x)SrxMnO3 (LSMO) perovskite surfaces, where the electronic structure and manganese valence was controlled by five substitution levels of lanthanum with strontium, using ambient pressure X-ray photoelectron spectroscopy in a humid environment. The degree of hydroxyl formation on the oxide surface correlated with the proximity of the valence band center relative to the Fermi level. LSMO perovskites with a valence band center closer to the Fermi level were more reactive toward water, forming more hydroxyl species at a given relative humidity. More hydroxyl species correlate with greater electron-donating character to the surface free energy in wetting, and reduce the activity to catalyze oxygen reduction reaction (ORR) kinetics in basic solution. New strategies to design more active catalysts should include design of electronically conducting oxides with lower valence band centers relative to the Fermi level at ORR-relevant potentials.

Accumulation of Fe oxyhydroxides in the Peruvian oxygen deficient zone implies non-oxygen dependent Fe oxidation

Science.gov (United States)

Heller, Maija I.; Lam, Phoebe J.; Moffett, James W.; Till, Claire P.; Lee, Jong-Mi; Toner, Brandy M.; Marcus, Matthew A.

2017-08-01

Oxygen minimum zones (OMZs) have been proposed to be an important source of dissolved iron (Fe) into the interior ocean. However, previous studies in OMZs have shown a sharp decrease in total dissolved Fe (dFe) and/or dissolved Fe(II) (dFe(II)) concentrations at the shelf-break, despite constant temperature, salinity and continued lack of oxygen across the shelf-break. The loss of both total dFe and dFe(II) suggests a conversion of the dFe to particulate form, but studies that have coupled the reduction-oxidation (redox) speciation of both dissolved and particulate phases have not previously been done. Here we have measured the redox speciation and concentrations of both dissolved and particulate forms of Fe in samples collected during the U.S. GEOTRACES Eastern tropical Pacific Zonal Transect (EPZT) cruise in 2013 (GP16). This complete data set allows us to assess possible mechanisms for loss of dFe. We observed an offshore loss of dFe(II) within the oxygen deficient zone (ODZ), where dissolved oxygen is undetectable, accompanied by an increase in total particulate Fe (pFe). Total pFe concentrations were highest in the upper ODZ. X-ray absorption spectroscopy revealed that the pFe maximum was primarily in the Fe(III) form as Fe(III) oxyhydroxides. The remarkable similarity in the distributions of total particulate iron and nitrite suggests a role for nitrite in the oxidation of dFe(II) to pFe(III). We present a conceptual model for the rapid redox cycling of Fe that occurs in ODZs, despite the absence of oxygen.

Vacancy ordering and superstructure formation in dry and hydrated strontium tantalate perovskites: A TEM perspective

DEFF Research Database (Denmark)

Ashok, Anuradha M.; Haavik, Camilla; Norby, Poul

2014-01-01

Crystal structures of Sr4(Sr2Ta2)O11 and Sr4(Sr1.92Ta2.08)O11.12, synthesized by solid state reaction technique in dry and hydrated state have been studied mainly using Transmission Electron Microscopy. Due to the lesser ability of X-rays to probe details in oxygen sublattice, the change in crystal...... and 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...

Oxygen Transport Membranes

Energy Technology Data Exchange (ETDEWEB)

S. Bandopadhyay

2008-08-30

small polaron conduction mechanism. Scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) were used to develop strategies to detect and characterize vacancy creation, dopant segregations and defect association in the oxygen conducting membrane material. The pO{sub 2} and temperature dependence of the conductivity, non-stoichiometry and thermal-expansion behavior of compositions with increasing complexity of substitution on the perovskite A and B sites were studied. Studies with the perovskite structure show anomalous behavior at low oxygen partial pressures (<10{sup -5} atm). The anomalies are due to non-equilibrium effects and can be avoided by using very strict criteria for the attainment of equilibrium. The slowness of the oxygen equilibration kinetics arises from two different mechanisms. In the first, a two phase region occurs between an oxygen vacancy ordered phase such as brownmillerite SrFeO{sub 2.5} and perovskite SrFeO{sub 3-x}. The slow kinetics is associated with crossing the two phase region. The width of the miscibility gap decreases with increasing temperature and consequently the effect is less pronounced at higher temperature. The preferred kinetic pathway to reduction of perovskite ferrites when the vacancy concentration corresponds to the formation of significant concentrations of Fe{sup 2+} is via the formation of a Ruddlesden-Popper (RP) phases as clearly observed in the case of La{sub 0.5}Sr{sub 0.5}FeO{sub 3-x} where LaSrFeO{sub 4} is found together with Fe. In more complex compositions, such as LSFTO, iron or iron rich phases are observed locally with no evidence for the presence of discrete RP phase. Fracture strength of tubular perovskite membranes was determined in air and in reducing atmospheric conditions. The strength of the membrane decreased with temperature and severity of reducing conditions although the strength distribution (Weibull parameter, m) was relatively unaltered. Surface and volume

Passivation of interstitial and vacancy mediated trap-states for efficient and stable triple-cation perovskite solar cells

Science.gov (United States)

Mahmud, Md Arafat; Elumalai, Naveen Kumar; Upama, Mushfika Baishakhi; Wang, Dian; Gonçales, Vinicius R.; Wright, Matthew; Xu, Cheng; Haque, Faiazul; Uddin, Ashraf

2018-04-01

The current work reports the concurrent passivation of interstitial and oxygen vacancy mediated defect states in low temperature processed ZnO electron transport layer (ETL) via Ultraviolet-Ozone (UVO) treatment for fabricating highly efficient (maximum efficiency: 16.70%), triple cation based MA0.57FA0.38Rb0.05PbI3 (MA: methyl ammonium, FA: formamidinium, Rb: rubidium) perovskite solar cell (PSC). Under UV exposure, ozone decomposes to free atomic oxygen and intercalates into the interstitial and oxygen vacancy induced defect sites in the ZnO lattice matrix, which contributes to suppressed trap-assisted recombination phenomena in perovskite device. UVO treatment also reduces the content of functional hydroxyl group on ZnO surface, that increases the inter-particle connectivity and grain size of perovskite film on UVO treated ZnO ETL. Owing to this, the perovskite film atop UVO treated ZnO film exhibits reduced micro-strain and dislocation density values, which contribute to the enhanced photovoltaic performance of PSC with modified ZnO ETL. The modified PSCs exhibit higher recombination resistance (RRec) ∼40% compared to pristine ZnO ETL based control devices. Adding to the merit, the UVO treated ZnO PSC also demonstrates superior device stability, retaining about 88% of its initial PCE in the course of a month-long, systematic degradation study.

Hierarchically porous LaFeO3 perovskite prepared from the pomelo peel bio-template for catalytic oxidation of NO

Science.gov (United States)

Zhao, Shaojun; Wang, Li; Wang, Ying; Li, Xing

2018-05-01

In this paper, pomelo peel was used as biological template to obtain hierarchically porous LaFeO3 perovskite for the catalytic oxidation of NO to NO2. In addition, X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption-desorption analyses, X-ray photoelectron spectra (XPS), NO temperature-programmed desorption (NO-TPD), oxygen temperature-programmed desorption (O2-TPD) and hydrogen temperature-programmed reduction (H2-TPR) were used to investigate the micro-structure and the redox properties of the hierarchically porous LaFeO3 perovskite prepared from pomelo peel biological template and the LaFeO3 perovskite without the biological template. The results indicated that the hierarchically porous LaFeO3 perovskite successfully replicated the porous structure of pomelo peel with high specific surface area. Compared to the LaFeO3 perovskite prepared without the pomelo peel template, the hierarchically porous LaFeO3 perovskite showed better catalytic oxidization of NO to NO2 under the same conditions. The maximum NO conversions for LaFeO3 prepared with and without template were 90% at 305 °C and 76% at 313 °C, respectively. This is mainly attributed to the higher ratio of Fe4+/Fe3+, the hierarchically porous structure with more adsorbed oxygen species and higher surface area for the hierarchically porous LaFeO3 perovskite compared with the sample prepared without the pomelo peel template.

Hexagonal perovskites with cationic vacancies. 29. Structure of Ba/sub 4/ScReWvacantO/sub 12/ - on the function of octahedral cationic vacancies in perovskite stacking polytypes

Energy Technology Data Exchange (ETDEWEB)

Kemmler-Sack, S; Herrmann, M [Tuebingen Univ. (Germany, F.R.). Lehrstuhl fuer Anorganische Chemie 2

1981-09-01

The hexagonal perovskite stacking polytype Ba/sub 4/ScReWvacantO/sub 12/ crystallizes in a rhombohedral 12 L structure (space group R-3m; sequence (hhcc)/sub 3/). The refined, intensity related R' value is 6.6%. The octahedral net consists of blocks of three face connected octahedra with a central vacancy, in the two outer positions the rhenium and tungsten atoms are located; these units are linked via common corners by single octahedra, occupied with scandium. The construction principles of hexagonal oxygen perovskites with octahedral, cationic vacancies are reported.

Constructing Efficient and Stable Perovskite Solar Cells via Interconnecting Perovskite Grains.

Science.gov (United States)

Hou, Xian; Huang, Sumei; Ou-Yang, Wei; Pan, Likun; Sun, Zhuo; Chen, Xiaohong

2017-10-11

A high-quality perovskite film with interconnected perovskite grains was obtained by incorporating terephthalic acid (TPA) additive into the perovskite precursor solution. The presence of TPA changed the crystallization kinetics of the perovskite film and promoted lateral growth of grains in the vicinity of crystal boundaries. As a result, sheet-shaped perovskite was formed and covered onto the bottom grains, which made some adjacent grains partly merge together to form grains-interconnected perovskite film. Perovskite solar cells (PSCs) with TPA additive exhibited a power conversion efficiency (PCE) of 18.51% with less hysteresis, which is obviously higher than that of pristine cells (15.53%). PSCs without and with TPA additive retain 18 and 51% of the initial PCE value, respectively, aging for 35 days exposed to relative humidity 30% in air without encapsulation. Furthermore, MAPbI 3 film with TPA additive shows superior thermal stability to the pristine one under 100 °C baking. The results indicate that the presence of TPA in perovskite film can greatly improve the performance of PSCs as well as their moisture resistance and thermal stability.

Synthesis and characterization of a-site doped LaTiO3 nano perovskites

International Nuclear Information System (INIS)

Bradha, M.; Ashok, Anuradha

2013-01-01

Nano-sized lanthanum titanate perovskites (La (1-x) A x TiO 3 ) (A= Ba, Sr, Ca) were prepared by sol-gel method and calcined at 800℃. The synthesised perovskites were characterized by Thermogravimetry/ Differential thermal analysis (TGA/DTA), X-ray diffraction (XRD) and High Resolution Transmission Electron Microscopy (HRTEM) etc. LaTiO 3 is a perovskite having prominent interest for a variety of applications such as dielectric, insulators, charge-transport properties etc. It is a defect perovskite, with transport properties varying from insulating to metallic based on oxygen stoichiometry. In a quest to observe the effect of the nano size on its properties, lanthanum titanate (LaTiO 3 ) nano perovskites with different dopants on the A-site were prepared by using sol-gel method. In the present work we discuss the synthesis and structural analysis of (La 0.8 A 0.2 TiO 3 ). Phase purity and structural analysis of the calcined samples were performed by powder X-ray diffraction (XRD, with CuKα radiation). In addition to this, morphology and crystal structure was examined by Transmission Electron Microscopy (TEM) using a JEOL JEM 2100 HRTEM. HRTEM studies indicate that the nano perovskites are of size around 20 nm. Ring pattern in SAED also confirms that the perovskite is polycrystalline/nanocrystalline. More detailed study on high resolution images and crystal structure shed light on the reason for the properties exhibited by this perovskites

Enhanced metabolic versatility of planktonic sulfur-oxidizing γ-proteobacteria in an oxygen-deficient coastal ecosystem

Directory of Open Access Journals (Sweden)

Alejandro A. Murillo

2014-07-01

Full Text Available Sulfur-oxidizing Gamma-proteobacteria are abundant in marine oxygen-deficient waters, and appear to play a key role in a previously unrecognized cryptic sulfur cycle. Metagenomic analyses of members of the uncultured SUP05 lineage in the Canadian seasonally anoxic fjord Saanich Inlet (SI, hydrothermal plumes in the Guaymas Basin (GB and single cell genomics analysis of two ARCTIC96BD-19 representatives from the South Atlantic Sub-Tropical Gyre (SASG have shown them to be metabolically versatile. However, SI and GB SUP05 bacteria seem to be obligate chemolithoautotrophs, whereas ARCTIC96BD-19 has the genetic potential for aerobic respiration. Here, we present results of a metagenomic analysis of sulfur-oxidizing Gamma-proteobacteria (GSO, closely related to the SUP05/ARCTIC96BD-19 clade, from a coastal ecosystem in the eastern South Pacific (ESP. This ecosystem experiences seasonal anoxia and accumulation of nitrite and ammonium at depth, with a corresponding increase in the abundance of GSO representatives. The ESP-GSOs appear to have a significantly different gene complement than those from Saanich Inlet, Guaymas Basin and SASG. Genomic analyses of de novo assembled contigs indicate the presence of a complete aerobic respiratory complex based on the cytochrome bc1 oxidase. Furthermore, they appear to encode a complete TCA cycle and several transporters for dissolved organic carbon species, suggesting a mixotrophic lifestyle. Thus, the success of sulfur-oxidizing Gamma-proteobacteria in oxygen-deficient marine ecosystems appears due not only to their previously recognized anaerobic metabolic versatility, but also to their capacity to function under aerobic conditions using different carbon sources. Finally, members of ESP-GSO cluster also have the genetic potential for reducing nitrate to ammonium based on the nirBD genes, and may therefore facilitate a tighter coupling of the nitrogen and sulfur cycles in oxygen-deficient waters.

Factors controlling the oxide ion conductivity of fluorite and perovskite structured oxides

DEFF Research Database (Denmark)

Mogensen, Mogens Bjerg; Lybye, D.; Bonanos, N.

2004-01-01

Many metal oxides of fluorite and perovskite related structures are oxide ion conductors, which have practical applications in devices such as oxygen sensors, solid oxide fuel cells (SOFC) and electrolysers. Several structural and thermodynamic parameters such as (1) critical radius of the pathway...... such parameters for fluorite and perovskite oxides by considering their sensitivities to the individual ionic radii. Based on experimental data available in the literature, it is argued that lattice distortion (lattice stress and deviation from cubic symmetry) due to ion radii mismatch determines the ionic...... conductivity to a very large extent, and that lattice distortion is of much greater importance than many other proposed parameters. In case of the perovskites, the charge of the B-site ion is also of major importance. (C) 2004 Published by Elsevier B.V....

Synthesis, stability range and characterization of Pr2Cu2O5

Science.gov (United States)

Fernández-Sanjulián, Javier; Morán, Emilio; Ángel Alario-Franco, Miguel

2010-03-01

A novel Pr2Cu2O5 phase has been prepared under high-pressure and high-temperature conditions (P ∼6 GPa and T ∼1673 K) in a Belt-type apparatus and characterized by X-ray diffraction and electron microscopy. The crystal structure appears to be an orthorhombic "oxygen-deficient perovskite" (M.T. Anderson, J.T. Vaughey, and K.R. Poeppelmeier, Structural similarities among oxygen-deficient perovskites, Chem. Mater. 5 (1993), pp. 151-165) isostructural with La2Cu2O5 (J.F. Bringley, B.A. Scott, S.J. La Placa, R.F. Boheme, T.M. Shaw, M.W. McElfresh, S.S. Trail, and D.E. Cox, Synthesis of the defect perovskite series LaCuO 3-δ with copper valence varying from 2+to 3+, Nature 347 (1990), pp. 263-265) and Nd2Cu2O5 (B.-H. Chen, D. Walker, E. Suard, B.A. Scott, B. Mercey, M. Hervieu, and B. Raveau, High pressure synthesis of NdCuO3-δ perovskites (0≤δ≤0.5). Inorg. Chem. 34 (1995), pp. 2077-2083).

Recent progress in stabilizing hybrid perovskites for solar cell applications

Science.gov (United States)

Chen, Jianqing; Cai, Xin; Yang, Donghui; Song, Dan; Wang, Jiajia; Jiang, Jinghua; Ma, Aibin; Lv, Shiquan; Hu, Michael Z.; Ni, Chaoying

2017-07-01

Hybrid inorganic-organic perovskites have quickly evolved as a promising group of materials for solar cells and optoelectronic applications mainly owing to the inexpensive materials, relatively simple and versatile fabrication and high power conversion efficiency (PCE). The certified energy conversion efficiency for perovskite solar cell (PSC) has reached above 20%, which is compatible to the current best for commercial applications. However, long-term stabilities of the materials and devices remain to be the biggest challenging issue for realistic implementation of the PSCs. This article discusses the key issues related to the stability of perovskite absorbing layer including crystal structural stability, chemical stability under moisture, oxygen, illumination and interface reaction, effects of electron-transporting materials (ETM), hole-transporting materials (HTM), contact electrodes, ion migration and preparation conditions. Towards the end, prospective strategies for improving the stability of PSCs are also briefly discussed and summarized. We focus on recent understanding of the stability of materials and devices and our perspectives about the strategies for the stability improvement.

Processing and characterization of Sr{sub 2−x}VMoO{sub 6−δ} double perovskites

Energy Technology Data Exchange (ETDEWEB)

Weisentein, A.J., E-mail: a.weisenstein@gmail.com [Department of Mechanical and Industrial Engineering, Montana State University, Bozeman, MT 59717-3800 (United States); Childs, N., E-mail: nick.childs@msu.montana.edu [Department of Physics, Montana State University, Bozeman, MT 59717-3804 (United States); Amendola, R., E-mail: roberta.amendola@coe.montana.edu [Department of Chemical and Biological Engineering, Montana State University, Bozeman, MT 59717-3920 (United States); Driscoll, D., E-mail: davidrobertdriscoll@gmail.com [Department of Mechanical and Industrial Engineering, Montana State University, Bozeman, MT 59717-3800 (United States); Sofie, S.W., E-mail: ssofie@me.montana.edu [Department of Mechanical and Industrial Engineering, Montana State University, Bozeman, MT 59717-3800 (United States); Gannon, P., E-mail: pgannon@coe.montana.edu [Department of Chemical and Biological Engineering, Montana State University, Bozeman, MT 59717-3920 (United States); Smith, R., E-mail: smith@physics.montana.edu [Department of Physics, Montana State University, Bozeman, MT 59717-3804 (United States)

2013-05-15

In this study, the analysis and characterization of the processing and sintering of Sr{sub 2−x}VMoO{sub 6−δ} perovskites, where x = 0.0, 0.1 and 0.2, was investigated with application potential in high temperature fuel cell electrodes and electro-catalysts. Sr{sub 2−x}VMoO{sub 6−δ} substrates were sintered in a reducing (5%H{sub 2} 95%N{sub 2}) atmosphere at 1100 °C, 1200 °C, and 1300 °C. The X-ray diffraction patterns indicate that the double perovskite is the primary phase for Sr{sub 2−x}VMoO{sub 6−δ} pellets sintered at 1200 °C and 1300 °C for 20 h; however, these pellets show a secondary phase of SrMoO{sub 4−δ}. X-ray photoelectron spectroscopy revealed a deficiency of vanadium on the pellet surfaces, in which samples yielded surface vanadium concentrations of less than 5%. The vanadium inhomogeneity can be explained by the formation of the SrMoO{sub 4−δ} scheelite phase (ABO{sub 4}) due to oxygen exposure on the surface of the pellets, which indicates inward vanadium migration to the bulk, and was exhibited in redox cycling. Sr{sub 2−x}VMoO{sub 6−δ} pellets sintered at 1300 °C showed the lowest resistivity at both SOFC operating temperature (800 °C) and room temperature. The resistivity tests also show a semiconductor to metallic transition for all double perovskites, from heating up to 800 °C to cooling down to room temperature in a reducing atmosphere, related to the reduction of Mo{sup 6+} to Mo{sup 4+}. - Highlights: ► Primary Sr{sub 2−x}VMoO{sub 6−δ} phase only shown to form in excess of 1300 °C in reducing. ► Surface formation of secondary phase SrMoO{sub 4−δ} (Mo{sup 6+}) observed at RT in air. ► Surface vanadium deficiency induced by inward atomic diffusion. ► Semiconductor to metallic transition is related to the reduction of Mo{sup 6+} to Mo{sup 4+}.

Magnesium and Titanium Isotopic Compositions of an Unusual Hibonite-Perovskite Refractory Inclusion from Allende: It Is Fun

Science.gov (United States)

Liu, M.-C.; Keller, L. P.; McKeegan, K. D.

2016-01-01

Introduction: Hibonite-rich refractory inclusions are among the first solids that formed in the solar nebula, and thus provide constraints on the earliest environment in the Solar System. An unusual hibonite-perovskite inclusion from Allende, SHAL, consists of a large (approximately 500 by 200 microns) single hibonite crystal and coexisting blocky perovskite (approximately 200 microns in size). The hibonite is characterized by chemical and oxygen isotopic compositions similar to those in the FUN (Fractionated and Unknown Nuclear anomalies) inclusion HAL. However, the rare earth element (REE) patterns measured at different spots of SHAL hibonite are highly variable, ranging from Group II-like (light REEs enriched relative to heavy REEs) to Group III-like (relatively flat with slight Eu depletions), but overall contrast largely with that of HAL, especially in the Ce and Yb abundances. This implies that SHAL hibonite formed and underwent distillation processes under more reducing conditions. Interestingly, the accompanying perovskite has uniform, unfractionated oxygen isotopic compositions (averaging delta (sup 17) O equals delta (sup 18) O equals -7 per mille) and REE abundances that are completely different from those of SHAL hibonite. This has been interpreted that perovskite and hibonite may not be co-genetic. Here we performed Al-Mg and Ti isotopic measurements of SHAL hibonite and perovskite to determine if the FUN characteristics are observed in these two isotope systems, and to further constrain the origin and evolution of SHAL. Results: Isotopic measurements of Al-Mg and Ti in SHAL were performed on the UCLA CAMECA ims-1290 ion microprobe by following the analytical protocols described in [1]. The Al-Mg and Ti data obtained in both terrestrial standards and SHAL hibonite and perovskite are shown below. Both SHAL hibonite and perovskite, despite very high (sup 27) Al to (sup 24) Mg ratios, are devoid of (sup 26) Mg excesses that can be attributed to the decay

A family of oxide ion conductors based on the ferroelectric perovskite Na0.5Bi0.5TiO3.

Science.gov (United States)

Li, Ming; Pietrowski, Martha J; De Souza, Roger A; Zhang, Huairuo; Reaney, Ian M; Cook, Stuart N; Kilner, John A; Sinclair, Derek C

2014-01-01

Oxide ion conductors find important technical applications in electrochemical devices such as solid-oxide fuel cells (SOFCs), oxygen separation membranes and sensors. Na0.5Bi0.5TiO3 (NBT) is a well-known lead-free piezoelectric material; however, it is often reported to possess high leakage conductivity that is problematic for its piezo- and ferroelectric applications. Here we report this high leakage to be oxide ion conduction due to Bi-deficiency and oxygen vacancies induced during materials processing. Mg-doping on the Ti-site increases the ionic conductivity to ~0.01 S cm(-1) at 600 °C, improves the electrolyte stability in reducing atmospheres and lowers the sintering temperature. This study not only demonstrates how to adjust the nominal NBT composition for dielectric-based applications, but also, more importantly, gives NBT-based materials an unexpected role as a completely new family of oxide ion conductors with potential applications in intermediate-temperature SOFCs and opens up a new direction to design oxide ion conductors in perovskite oxides.

Quasiparticle Interference on Cubic Perovskite Oxide Surfaces.

Science.gov (United States)

Okada, Yoshinori; Shiau, Shiue-Yuan; Chang, Tay-Rong; Chang, Guoqing; Kobayashi, Masaki; Shimizu, Ryota; Jeng, Horng-Tay; Shiraki, Susumu; Kumigashira, Hiroshi; Bansil, Arun; Lin, Hsin; Hitosugi, Taro

2017-08-25

We report the observation of coherent surface states on cubic perovskite oxide SrVO_{3}(001) thin films through spectroscopic-imaging scanning tunneling microscopy. A direct link between the observed quasiparticle interference patterns and the formation of a d_{xy}-derived surface state is supported by first-principles calculations. We show that the apical oxygens on the topmost VO_{2} plane play a critical role in controlling the coherent surface state via modulating orbital state.

Enhanced oxygen reduction activity on surface-decorated perovskite thin films for solid oxide fuel cells

KAUST Repository

Mutoro, Eva; Crumlin, Ethan J.; Biegalski, Michael D.; Christen, Hans M.; Shao-Horn, Yang

2011-01-01

Surface-decoration of perovskites can strongly affect the oxygen reduction activity, and therefore is a new and promising approach to improve SOFC cathode materials. In this study, we demonstrate that a small amount of secondary phase on a (001) La 0.8Sr 0.2CoO 3-δ (LSC) surface can either significantly activate or passivate the electrode. LSC (001) microelectrodes prepared by pulsed laser deposition on a (001)-oriented yttria-stabilized zirconia (YSZ) substrate were decorated with La-, Co-, and Sr-(hydr)oxides/carbonates. "Sr"-decoration with nanoparticle coverage in the range from 50% to 80% of the LSC surface enhanced the surface exchange coefficient, k q, by an order of magnitude while "La"- decoration and "Co"-decoration led to no change and reduction in k q, respectively. Although the physical origin for the enhancement is not fully understood, results from atomic force microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy suggest that the observed k q enhancement for "Sr"-decorated surfaces can be attributed largely to catalytically active interface regions between surface Sr-enriched particles and the LSC surface. © 2011 The Royal Society of Chemistry.

Sorbent-based Oxygen Production for Energy Systems

Energy Technology Data Exchange (ETDEWEB)

Sethi, Vijay [Western Research Inst. (WRI), Laramie, WY (United States)

2017-01-31

Project DE-FE0024075 deals with the development of a moderate-temperature sorbent-based oxygen production technology. Sorbent-based oxygen production process utilizes oxygen-storage properties of Perovskites to (1) adsorb oxygen from air in a solid sorbent, and (2) release the adsorbed oxygen into a sweep gas such as CO₂ and/or steam for gasification systems or recycled flue gas for oxy-combustion systems. Pure oxygen can be produced by the use of vacuum instead of a sweep gas to affect the pressure swing. By developing more efficient and stable, higher sorption capacity, newer class of materials operating at moderate temperatures this process represents a major advancement in air separation technology. Newly developed perovskite ceramic sorbent materials with order-disorder transition have a higher O₂ adsorption capacity, potentially 200 °C lower operating temperatures, and up to two orders of magnitude faster desorption rates than those used in earlier development efforts. The performance advancements afforded by the new materials lead to substantial savings in capital investment and operational costs. Cost of producing oxygen using sorbents could be as much as 26% lower than VPSA and about 13% lower than a large cryogenic air separation unit. Cost advantage against large cryogenic separation is limited because sorbent-based separation numbers up sorbent modules for achieving the larger capacity.

Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes

Directory of Open Access Journals (Sweden)

Nicola H. Perry

2016-10-01

Full Text Available Mixed conducting perovskite oxides and related structures serving as electrodes for electrochemical oxygen incorporation and evolution in solid oxide fuel and electrolysis cells, respectively, play a significant role in determining the cell efficiency and lifetime. Desired improvements in catalytic activity for rapid surface oxygen exchange, fast bulk transport (electronic and ionic, and thermo-chemo-mechanical stability of oxygen electrodes will require increased understanding of the impact of both bulk and surface chemistry on these properties. This review highlights selected work at the International Institute for Carbon-Neutral Energy Research (I2CNER, Kyushu University, set in the context of work in the broader community, aiming to characterize and understand relationships between bulk and surface composition and oxygen electrode performance. Insights into aspects of bulk point defect chemistry, electronic structure, crystal structure, and cation choice that impact carrier concentrations and mobilities, surface exchange kinetics, and chemical expansion coefficients are emerging. At the same time, an understanding of the relationship between bulk and surface chemistry is being developed that may assist design of electrodes with more robust surface chemistries, e.g., impurity tolerance or limited surface segregation. Ion scattering techniques (e.g., secondary ion mass spectrometry, SIMS, or low energy ion scattering spectroscopy, LEIS with high surface sensitivity and increasing lateral resolution are proving useful for measuring surface exchange kinetics, diffusivity, and corresponding outer monolayer chemistry of electrodes exposed to typical operating conditions. Beyond consideration of chemical composition, the use of strain and/or a high density of active interfaces also show promise for enhancing performance.

Morphology modification of perovskite film by a simple post-treatment process in perovskite solar cell

Energy Technology Data Exchange (ETDEWEB)

Song, J.; Yang, Y.; Zhao, Y.L., E-mail: sdyulong@cumt.edu.cn; Che, M.; Zhu, L.; Gu, X.Q.; Qiang, Y.H., E-mail: yhqiang@cumt.edu.cn

2017-03-15

Highlights: • Perovskite films were post-treated by DMF/CBZ, DMSO/CBZ, or GBL/CBZ blend solvents. • This process could repair pinholes and enhance coverage in perovskite film. • This technique could modify charge transfer process at TiO{sub 2}/perovskite interface. - Abstract: A homogenous perovskite thin film with high coverage is a determining factor for high performance perovskite solar cells. Unlike previous pre-treatments aiming at perovskite precursor, we proposed a simple method to modify the morphology of perovskite films by post-treatment process using mixed solvents of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or 1,4-butyrolactone (GBL) with chlorobenzene (CBZ) in this paper. As good solvent of perovskite, DMF, DMSO, and GBL could dissolve the formed perovskite film. Meanwhile, CBZ, anti-solvent of perovskite film, could decrease the dissolving capacity of these good solvents. Therefore, the perovskite film coverage might be improved by the partial dissolution and recrystallization after solvent post-treatment process. Electrochemical impedance spectrometry (EIS) and time-resolved photoluminescence (TRPL) indicated that this post-treatment process could enhance charge transfer at TiO{sub 2}/perovskite interface. Finally, the conversion efficiency increased from 10.10% to 11.82%, 11.68%, and 10.66% using perovskite films post-treated by DMF/CBZ, DMSO/CBZ, and GBL/CBZ blend solvents, respectively.

Hybrid Organic-Inorganic Perovskite Photodetectors.

Science.gov (United States)

Tian, Wei; Zhou, Huanping; Li, Liang

2017-11-01

Hybrid organic-inorganic perovskite materials garner enormous attention for a wide range of optoelectronic devices. Due to their attractive optical and electrical properties including high optical absorption coefficient, high carrier mobility, and long carrier diffusion length, perovskites have opened up a great opportunity for high performance photodetectors. This review aims to give a comprehensive summary of the significant results on perovskite-based photodetectors, focusing on the relationship among the perovskite structures, device configurations, and photodetecting performances. An introduction of recent progress in various perovskite structure-based photodetectors is provided. The emphasis is placed on the correlation between the perovskite structure and the device performance. Next, recent developments of bandgap-tunable perovskite and hybrid photodetectors built from perovskite heterostructures are highlighted. Then, effective approaches to enhance the stability of perovskite photodetector are presented, followed by the introduction of flexible and self-powered perovskite photodetectors. Finally, a summary of the previous results is given, and the major challenges that need to be addressed in the future are outlined. A comprehensive summary of the research status on perovskite photodetectors is hoped to push forward the development of this field. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The spatial distribution of temperature and oxygen deficiency in spark-plasma sintered superconducting Bi-based materials

International Nuclear Information System (INIS)

Govea-Alcaide, E.; Pérez-Fernández, J.E.; Machado, I.F.; Jardim, R.F.

2014-01-01

Pre-reacted powders of (Bi–Pb) 2 Sr 2 Ca 2 Cu 3 O 10+δ (Bi-2223) were consolidated by using the spark plasma sintering (SPS) technique under vacuum and at different consolidate temperatures T D . X-ray diffraction patterns revealed that the dominant phase in all SPS samples is the Bi-2223 phase, but traces of the Bi 2 Sr 2 CaCu 2 O 10+x (Bi-2212) phase were identified. We have found that the transport properties of SPS samples depend on their oxygen content because the SPS process is performed under vacuum. Simulations by using the finite element method (FEM) were performed for determining the actual temperature in which powders are consolidated. From these results we have inferred that SPS samples are oxygen deficient and such a deficiency is more marked near the grain boundaries, suggesting the occurrence of grains with core–shell morphology. We also argued that the width of the shell depends on the consolidation temperature, a feature corroborated by the FEM simulations

Both AtrbohD and AtrbohF are essential for mediating responses to oxygen deficiency in Arabidopsis.

Science.gov (United States)

Liu, Bo; Sun, Lirong; Ma, Liya; Hao, Fu-Shun

2017-06-01

Both AtrbohD and AtrbohF promote the increases in activities of ADH, PDC, LDH, and Ca 2+ levels, and induce the expression of multiple hypoxia response genes, thus improving Arabidopsis adaptation to oxygen deficiency. NADPH oxidase AtrbohD and AtrbohF cooperatively play key roles in regulation of growth and stress signaling in Arabidopsis. However, reports on AtrbohD and AtrbohF functioning together in hypoxia signaling are scarce, and the underlying mechanisms remain elusive. Here, we show that the double null mutant atrbohD/F is more sensitive to oxygen deprivation compared with wild type (WT) and the single mutant atrbohD and atrbohF. Under oxygen deficiency, enhancements of the transcripts of alcohol dehydrogenase 1 (ADH1) and pyruvate decarboxylase 1 (PDC1) and the activities of ADH, PDC and lactate dehydrogenase in WT are clearly reduced in the single mutants, and more strongly reduced in the double mutant. Moreover, increases in the production of ATP, H 2 O 2 and Ca 2+ in WT are significantly arrested in atrbohD, atrbohF, and especially in atrbohD/F. Hypoxia-promoted rise in the expression of some hypoxic responsive genes is also inhibited in atrbohD/F relative to WT, atrbohD and atrbohF. These genes include ethylene response factor 73, lactate dehydrogenase, MYB transcription factor 2, sucrose synthase 1 (SUS1), SUS4, heat stress transcription factor A2 and heat-shock protein 18.2. These results suggest that both AtrbohD and AtrbohF are essential for mediating hypoxia signaling. H 2 O 2 derived from AtrbohD and AtrbohF triggers the Ca 2+ increase and induces the expression of multiple hypoxia response genes, thus improving Arabidopsis tolerance to low-oxygen stress. These findings provide new insights into the mechanisms of AtrbohF in regulating the responses to oxygen deprivation in Arabidopsis.

Self-propagating high-temperature synthesis of LaMO{sub 3} perovskite-type oxide using heteronuclearcyano metal complex precursors

Energy Technology Data Exchange (ETDEWEB)

Sánchez-Rodríguez, Daniel, E-mail: daniel.sanchez@udg.edu [GRMT, Department of Physics, University of Girona, Campus Montilivi, Edif.PII, E17071 Girona, Catalonia (Spain); Wada, Hiroki; Yamaguchi, Syuhei [Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan); Farjas, Jordi [GRMT, Department of Physics, University of Girona, Campus Montilivi, Edif.PII, E17071 Girona, Catalonia (Spain); Yahiro, Hidenori, E-mail: yahiro.hidenori.me@ehime-u.ac.jp [Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan)

2015-11-15

The decomposition of La[Fe(CN){sub 6}]·5H{sub 2}O and La[Co(CN){sub 6}]·5H{sub 2}O under different atmospheres has been analyzed by thermogravimetry (TG) and differential thermal analysis (DTA). In addition, the decomposition temperature at different sample locations was monitored for sample masses around 2 g of La[Fe(CN){sub 6}]·5H{sub 2}O and La[Co(CN){sub 6}]·5H{sub 2}O, when they were calcined for 1 h at temperatures ranging from 200 to 400 °C in a controlled gas-flow system. Results showed that, the large enough of the cyano complex precursors undergo combustion when they are decomposed under oxygen atmosphere. X-ray diffraction results revealed that perovskite-type oxides crystallize due to the overheating of the process. As a result, it has been possible to produce LaFeO{sub 3} and LaCoO{sub 3} perovskite-type oxide powders by SHS under oxygen atmosphere using La[Fe(CN){sub 6}]·5H{sub 2}O and La[Co(CN){sub 6}]·5H{sub 2}O as a precursor. The effect of the ignition temperature has been investigated. The specific surface area of the perovskite-type oxides produced via SHS using heteronuclearcyano metal complex as a precursor is significantly higher than that of other LaMO{sub 3} produced using the same technique but obtained from other type of precursors. - Highlights: • The decomposition of La[Fe(CN){sub 6}] and La[Co(CN){sub 6}] precursors was analyzed. • The combustion process proceeded under oxygen when sample was large enough. • Perovskite oxides via SHS from the cyano complex precursors were synthesized. • LaMO{sub 3} perovskite oxides via SHS was obtained with high specific surface area.

What makes the difference in perovskite titanates?

Science.gov (United States)

Bussmann-Holder, Annette; Roleder, Krystian; Ko, Jae-Hyeon

2018-06-01

We have investigated in detail the lattice dynamics of five different perovskite titanates ATiO3 (A = Ca, Sr, Ba, Pb, Eu) where the A sites are occupied by +2 ions. In spite of the largely ionic character of these ions, the properties of these compounds differ substantially. They range from order/disorder like, to displacive ferroelectric, quantum paraelectric, and antiferromagnetic. All compounds crystallize in the cubic structure at high temperature and undergo structural phase transitions to tetragonal symmetry, partly followed by further transitions to lower symmetries. Since the TiO6 moiety is the essential electronic and structural unit, the question arises, what makes the significant difference between them. It is shown that the lattice dynamics of these compounds are very different, and that mode-mode coupling effects give rise to many distinct properties. In addition, the oxygen ion nonlinear polarizability plays a key role since it dominates the anharmonicity of these perovskites and determines the structural instability.

Perovskite electrodes and method of making the same

Science.gov (United States)

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.

Survival curves of irradiated glutathione-deficient human fibroblasts: indication of a reduced enhancement of radiosensitivity by oxygen and misonidazole

International Nuclear Information System (INIS)

Midander, J.; Deschavanne, P.J.; Malaise, E.P.; Revesz, L.

1982-01-01

Fibroblasts derived from a patient with 5-oxoprolinuria are genetically deficient in glutathione synthetase. This deficiency causes a dramatic decrease in intracellular glutathione (GSH) level. The radiosensitivity of GSH deficient cells (GSH) was studied in vitro using colony forming ability as an endpoint. Cells with normal GSH level, obtained from the healthy brother of the patient, were used as controls. When irradiated in 95% air-5% CO 2 , GSH - cells are slightly but significantly more radiosensitive than GSH + controls (dose modifying factor (DMF) of 1.2). When irradiated in argon, the survival curve of GSH - cells indicates an oxygen enhancement ratio (OER) of 1.5 when compared to the curve obtained in oxic conditions. The OER of control cells in the same conditions is 2.9. In comparison to results obtained in air, 100% oxygen moderately increases the radiosensitivity of GSH + cells (DMF 1,23), while it has a very low effect on GSH - cells (DMF 1.06). These results suggest that intracellular GSH plays an essential protective role in hypoxia, its effect is reduced in air and practically disappears in 100% oxygen. When cells are incubated with 8 mM misonidazole 2 hours before irradiation, the drug has a much greater sensitizing effect on GSH + cells (DMF 2.33) than on GSH - cells (DMF 1.55). The results demonstrate that intracellular GSH level plays a major role in the response of hypoxic cells, irradiated either alone or in the presence of misonidazole

Cardiomyocyte hypertrophy induced by Endonuclease G deficiency requires reactive oxygen radicals accumulation and is inhibitable by the micropeptide humanin.

Science.gov (United States)

Blasco, Natividad; Cámara, Yolanda; Núñez, Estefanía; Beà, Aida; Barés, Gisel; Forné, Carles; Ruíz-Meana, Marisol; Girón, Cristina; Barba, Ignasi; García-Arumí, Elena; García-Dorado, David; Vázquez, Jesús; Martí, Ramon; Llovera, Marta; Sanchis, Daniel

2018-06-01

The endonuclease G gene (Endog), which codes for a mitochondrial nuclease, was identified as a determinant of cardiac hypertrophy. How ENDOG controls cardiomyocyte growth is still unknown. Thus, we aimed at finding the link between ENDOG activity and cardiomyocyte growth. Endog deficiency induced reactive oxygen species (ROS) accumulation and abnormal growth in neonatal rodent cardiomyocytes, altering the AKT-GSK3β and Class-II histone deacethylases (HDAC) signal transduction pathways. These effects were blocked by ROS scavengers. Lack of ENDOG reduced mitochondrial DNA (mtDNA) replication independently of ROS accumulation. Because mtDNA encodes several subunits of the mitochondrial electron transport chain, whose activity is an important source of cellular ROS, we investigated whether Endog deficiency compromised the expression and activity of the respiratory chain complexes but found no changes in these parameters nor in ATP content. MtDNA also codes for humanin, a micropeptide with possible metabolic functions. Nanomolar concentrations of synthetic humanin restored normal ROS levels and cell size in Endog-deficient cardiomyocytes. These results support the involvement of redox signaling in the control of cardiomyocyte growth by ENDOG and suggest a pathway relating mtDNA content to the regulation of cell growth probably involving humanin, which prevents reactive oxygen radicals accumulation and hypertrophy induced by Endog deficiency. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Electric and magnetic properties of oxidic titanium bronzes of rare earths Lnsub(2/3+x)TiOsub(3+-y) with perovskite structure

International Nuclear Information System (INIS)

Bazuev, G.V.; Makarova, O.V.; Shvejkin, G.P.

1983-01-01

A study was made on electric and magnetic properties of oxidic titanium bronzes of rare earths and their dependence on rare earth nature and the degree of rare earth sublattice filling was followed. Data on Lnsub(2/3)TiOsub(3-y) (Ln-Ce, Nd) anion-deficient perovskites are given as well. Investigated Cesub(2/3)TiOsub(2.985) and Ndsub(2/3)TiOsub(2.875) phases as well as defectless with respect to oxygen Lnsub(2/3)TiOsub(3) phases have rhombic structure of perovskite type with ordered position of Ln 3 + cations and vacancies. Specific electric resistance and thermoelectromotive force factor were determined in vacuum at 290-1173 K for samples in the form of parallelepiped of 3x5x25 mm 3 size. Magnetic susceptibility chi was determined at 77-300 K by Faraday method using a device based on magnetic balancewith electromagnetic compensation. Relative error during chi measuring didn't exceed +-2%. Collectivized behaviour of d-electrons of Ti 3 + cations in oxidic titanium bronzes of rare earths: Lnsub(2/3+x)TiOsub(3+-y) (Ln-La, Ce, Nd; 0 < x < 1/3), conditioned by formation of narrow, partly filled π*-zone, was established on the basis of measuring specific electric resistance and magnetic susceptibility

Resonant halide perovskite nanoparticles

Science.gov (United States)

Tiguntseva, Ekaterina Y.; Ishteev, Arthur R.; Komissarenko, Filipp E.; Zuev, Dmitry A.; Ushakova, Elena V.; Milichko, Valentin A.; Nesterov-Mueller, Alexander; Makarov, Sergey V.; Zakhidov, Anvar A.

2017-09-01

The hybrid halide perovskites is a prospective material for fabrication of cost-effective optical devices. Unique perovskites properties are used for solar cells and different photonic applications. Recently, perovskite-based nanophotonics has emerged. Here, we consider perovskite like a high-refractive index dielectric material, which can be considered to be a basis for nanoparticles fabrication with Mie resonances. As a result, we fabricate and study resonant perovskite nanoparticles with different sizes. We reveal, that spherical nanoparticles show enhanced photoluminescence signal. The achieved results lay a cornerstone in the field of novel types of organic-inorganic nanophotonics devices with optical properties improved by Mie resonances.

On the oxygen deficiency of high-Tc Y1Ba2Cu3O7-μ ceramics

International Nuclear Information System (INIS)

Szasz, A.; Dankhazi, Z.; Kojnok, J.; Trager, T.; Matrai, J.; Gyorgy, I.; Kirchmayr, H.; Mueller, H.; Watson, L.M.

1991-01-01

The role of oxygen deficiency in Y 1 Ba 2 Cu 3 O 7-μ ceramics was investigated by differential thermal analysis (DTA), differential thermogravimetry (DTG), linear thermal expansion (LTE), and by soft x-ray fluorescence spectroscopy (SXFS). The interdependence of the measured parameters and some of the stability criteria are discussed

High-temperature electromass transfer in the perovskite La-Sr-Ga-Fe-Mg-O ceramics

International Nuclear Information System (INIS)

Aleksandrovskij, V.V.; Kaleva, G.M.; Mosunov, A.V.; Politova, E.D.; Stefanovich, S.Yu.; Avetistov, A.K.; Venskovskij, N.U.

2001-01-01

Physicochemical mechanism of oxygen-ion transfer in perovskite-like solid solutions within La-Sr-Ga-Fe-Mg-O system was studied using kinetic dependences of oxygen deficit at variation of gas medium composition. One discusses relation between the phenomenon of mass loss, linear deformation and conducting features of a ceramic material. Oxygen-ion transfer was determined to proceed by vacancy jumping mechanism. On the basis of data on dielectric relaxation in lanthanum gallate base solid solutions one obtained new evidences of vacancy correlation under high temperature [ru

Electrochemical properties of mixed conducting (La,M)(CoFe) oxide perovskites (M=3DSr, Ca, and Ba)

Energy Technology Data Exchange (ETDEWEB)

Stevenson, J.W.; Armstrong, T.R.; Bates, J.L. [and others

1996-04-01

Electrical properties and oxygen permeation properties of solid mixed-conducting electrolytes (La,M)(CoFe) oxide perovskites (M=3DSr, Ca, and Ba) have been characterized. These materials are potentially useful as passive membranes to separate high purity oxygen from air and as the cathode in a fuel cell. Dilatometric linear expansion measurements were performed as a function of temperature and oxygen partial pressure to evaluate the stability.

Humidity-Induced Photoluminescence Hysteresis in Variable Cs/Br Ratio Hybrid Perovskites.

Science.gov (United States)

Howard, John M; Tennyson, Elizabeth M; Barik, Sabyasachi; Szostak, Rodrigo; Waks, Edo; Toney, Michael F; Nogueira, Ana F; Neves, Bernardo R A; Leite, Marina S

2018-06-12

Hybrid organic-inorganic perovskites containing Cs are a promising new material for light-absorbing and light-emitting optoelectronics. However, the impact of environmental conditions on their optical properties is not fully understood. Here, we elucidate and quantify the influence of distinct humidity levels on the charge carrier recombination in Cs x FA 1- x Pb(I y Br 1- y ) 3 perovskites. Using in situ environmental photoluminescence (PL), we temporally and spectrally resolve light emission within a loop of critical relative humidity (rH) levels. Our measurements show that exposure up to 35% rH increases the PL emission for all Cs (10-17%) and Br (17-38%) concentrations investigated here. Spectrally, samples with larger Br concentrations exhibit PL redshift at higher humidity levels, revealing water-driven halide segregation. The compositions considered present hysteresis in their PL intensity upon returning to a low-moisture environment due to partially reversible hydration of the perovskites. Our findings demonstrate that the Cs/Br ratio strongly influences both the spectral stability and extent of light emission hysteresis. We expect our method to become standard when testing the stability of emerging perovskites, including lead-free options, and to be combined with other parameters known for affecting material degradation, e.g., oxygen and temperature.

Oxygen enhancement ratios for glutathione-deficient human fibroblasts determined from the frequency of radiation induced micronuclei

International Nuclear Information System (INIS)

Midander, J.

1982-01-01

The yield of micronuclei (MN) was determined to study the radiosensitizing effect of oxygen on three human fibroblast strains, characterized by genetically defined differences in their glutathione (GSH) level. Cells were irradiated in paired experiments with x-ray doses of 2.66 and 6.65 gy in their exponential growth phase in a monolayer under oxic and anoxic conditions. Results indicated a reduced oxygen effect for the GSH deficient cells, the reduction of o.e.r. being most pronounced in the case of GSHsup(-/-) cells, when it was close to unity. The o.e.r. value was intermediate for the GSHsup(+/-) in comparison with the two other cell strains. It is concluded that the data indicate a correlation between the cellular content of GSH and the oxygen enhancement of the formation of micronuclei after irradiation. (U.K.)

Evolution of Oxygen Deficiency Center on Fused Silica Surface Irradiated by Ultraviolet Laser and Posttreatment

Directory of Open Access Journals (Sweden)

Hai-Bing Lü

2014-01-01

Full Text Available Evolution of oxygen deficiency centers (ODCs on a fused silica surface irradiated using a 355 nm ultraviolet (UV laser beam in both vacuum and atmospheric conditions was quantitatively studied using photoluminescence and X-ray photoelectron spectroscopy. When the fusedsilica surface was exposed to the UV laser in vacuum, the laser damage threshold was decreased whereas the concentration of the ODCs was increased. For the fuse silica operated under the high power lasers, creation of ODCs on their surface resulted from the UV laser irradiation, and this is more severe in a high vacuum. The laser fluence and/or laser intensity have significant effects on the increase of the ODCs concentration. The ODCs can be effectively repaired using postoxygen plasma treatment and UV laser irradiation in an excessive oxygen environment. Results also demonstrated that the “gain” and “loss” of oxygen at the silica surface is a reversible and dynamic process.

Novel Solvent-free Perovskite Deposition in Fabrication of Normal and Inverted Architectures of Perovskite Solar Cells

Science.gov (United States)

Nejand, Bahram Abdollahi; Gharibzadeh, Saba; Ahmadi, Vahid; Shahverdi, H. Reza

2016-01-01

We introduced a new approach to deposit perovskite layer with no need for dissolving perovskite precursors. Deposition of Solution-free perovskite (SFP) layer is a key method for deposition of perovskite layer on the hole or electron transport layers that are strongly sensitive to perovskite precursors. Using deposition of SFP layer in the perovskite solar cells would extend possibility of using many electron and hole transport materials in both normal and invert architectures of perovskite solar cells. In the present work, we synthesized crystalline perovskite powder followed by successful deposition on TiO2 and cuprous iodide as the non-sensitve and sensitive charge transport layers to PbI2 and CH3NH3I solution in DMF. The post compressing step enhanced the efficiency of the devices by increasing the interface area between perovskite and charge transport layers. The 9.07% and 7.71% cell efficiencies of the device prepared by SFP layer was achieved in respective normal (using TiO2 as a deposition substrate) and inverted structure (using CuI as deposition substrate) of perovskite solar cell. This method can be efficient in large-scale and low cost fabrication of new generation perovskite solar cells. PMID:27640991

An experimental study of perovskite-structured mixed ionic- electronic conducting oxides and membranes

Science.gov (United States)

Zeng, Pingying

In recent decades, ceramic membranes based on mixed ionic and electronic conducting (MIEC) perovskite-structured oxides have received many attentions for their applications for air separation, or as a membrane reactor for methane oxidation. While numerous perovskite oxide materials have been explored over the past two decades; there are hardly any materials with sufficient practical economic value and performance for large scale applications, which justifies continuing the search for new materials. The main purposes of this thesis study are: (1) develop several novel SrCoO3-delta based MIEC oxides, SrCoCo1-xMxO3-delta, based on which membranes exhibit excellent oxygen permeability; (2) investigate the significant effects of the species and concentration of the dopants M (metal ions with fixed valences) on the various properties of these membranes; (3) investigate the significant effects of sintering temperature on the microstructures and performance of oxygen permeation membranes; and (4) study the performance of oxygen permeation membranes as a membrane reactor for methane combustion. To stabilize the cubic phase structure of the SrCoO3-delta oxide, various amounts of scandium was doped into the B-site of SrCoO 3-delta to form a series of new perovskite oxides, SrScxCoCo 1-xO3-delta (SSCx, x = 0-0.7). The significant effects of scandium-doping concentration on the phase structure, electrical conductivity, sintering performance, thermal and structural stability, cathode performance, and oxygen permeation performance of the SSCx membranes, were systematically studied. Also for a more in-depth understanding, the rate determination steps for the oxygen transport process through the membranes were clarified by theoretical and experimental investigation. It was found that only a minor amount of scandium (5 mol%) doping into the B-site of SrCoO3-delta can effectively stabilize the cubic phase structure, and thus significantly improve the electrical conductivity and

High-pressure stability relations, crystal structures, and physical properties of perovskite and post-perovskite of NaNiF3

International Nuclear Information System (INIS)

Shirako, Y.; Shi, Y.G.; Aimi, A.; Mori, D.; Kojitani, H.; Yamaura, K.; Inaguma, Y.; Akaogi, M.

2012-01-01

NaNiF 3 perovskite was found to transform to post-perovskite at 16–18 GPa and 1273–1473 K. The equilibrium transition boundary is expressed as P (GPa)=−2.0+0.014×T (K). Structure refinements indicated that NaNiF 3 perovskite and post-perovskite have almost regular NiF 6 octahedra consistent with absence of the first-order Jahn–Teller active ions. Both NaNiF 3 perovskite and post-perovskite are insulators. The perovskite underwent a canted antiferromagnetic transition at 156 K, and the post-perovskite antiferromagnetic transition at 22 K. Magnetic exchange interaction of NaNiF 3 post-perovskite is smaller than that of perovskite, reflecting larger distortion of Ni–F–Ni network and lower dimension of octahedral arrangement in post-perovskite than those in perovskite. - Graphical abstract: Perovskite–post-perovskite transition in NaNiF 3 at high pressure Highlights: ► NaNiF 3 perovskite (Pv) transforms to post-perovskite (pPv) at 16 GPa and 1300 K. ► The equilibrium transition boundary is expressed as P (GPa)=−2.0+0.014 T (K). ► Antiferromagnetic transition occurs at 156 K in Pv and 22 K in pPv.

Mixed oxygen ion/electron-conducting ceramics for oxygen separation

Energy Technology Data Exchange (ETDEWEB)

Stevenson, J.W.; Armstrong, T.R.; Armstrong, B.L. [Pacific Northwest National Lab., Richland, WA (United States)

1996-08-01

Mixed oxygen ion and electron-conducting ceramics are unique materials that can passively separate high purity oxygen from air. Oxygen ions move through a fully dense ceramic in response to an oxygen concentration gradient, charge-compensated by an electron flux in the opposite direction. Compositions in the system La{sub 1{minus}x}M{sub x}Co{sub 1{minus}y{minus}z}Fe{sub y}N{sub z}O{sub 3{minus}{delta}}, perovskites where M=Sr, Ca, and Ba, and N=Mn, Ni, Cu, Ti, and Al, have been prepared and their electrical, oxygen permeation, oxygen vacancy equilibria, and catalytic properties evaluated. Tubular forms, disks, and asymmetric membrane structures, a thin dense layer on a porous support of the same composition, have been fabricated for testing purposes. In an oxygen partial gradient, the passive oxygen flux through fully dense structures was highly dependent on composition. An increase in oxygen permeation with increased temperature is attributed to both enhanced oxygen vacancy mobility and higher vacancy populations. Highly acceptor-doped compositions resulted in oxygen ion mobilities more than an order of magnitude higher than yttria-stabilized zirconia. The mixed conducting ceramics have been utilized in a membrane reactor configuration to upgrade methane to ethane and ethylene. Conditions were established to balance selectivity and throughput in a catalytic membrane reactor constructed from mixed conducting ceramics.

Highly Efficient Perovskite-Perovskite Tandem Solar Cells Reaching 80% of the Theoretical Limit in Photovoltage.

Science.gov (United States)

Rajagopal, Adharsh; Yang, Zhibin; Jo, Sae Byeok; Braly, Ian L; Liang, Po-Wei; Hillhouse, Hugh W; Jen, Alex K-Y

2017-09-01

Organic-inorganic hybrid perovskite multijunction solar cells have immense potential to realize power conversion efficiencies (PCEs) beyond the Shockley-Queisser limit of single-junction solar cells; however, they are limited by large nonideal photovoltage loss (V oc,loss ) in small- and large-bandgap subcells. Here, an integrated approach is utilized to improve the V oc of subcells with optimized bandgaps and fabricate perovskite-perovskite tandem solar cells with small V oc,loss . A fullerene variant, Indene-C 60 bis-adduct, is used to achieve optimized interfacial contact in a small-bandgap (≈1.2 eV) subcell, which facilitates higher quasi-Fermi level splitting, reduces nonradiative recombination, alleviates hysteresis instabilities, and improves V oc to 0.84 V. Compositional engineering of large-bandgap (≈1.8 eV) perovskite is employed to realize a subcell with a transparent top electrode and photostabilized V oc of 1.22 V. The resultant monolithic perovskite-perovskite tandem solar cell shows a high V oc of 1.98 V (approaching 80% of the theoretical limit) and a stabilized PCE of 18.5%. The significantly minimized nonideal V oc,loss is better than state-of-the-art silicon-perovskite tandem solar cells, which highlights the prospects of using perovskite-perovskite tandems for solar-energy generation. It also unlocks opportunities for solar water splitting using hybrid perovskites with solar-to-hydrogen efficiencies beyond 15%. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and structural study of the transition metal doped rhodium perovskites

International Nuclear Information System (INIS)

Ting, J.; Kennedy, B.; Zhang, Z.

2009-01-01

Full text: One of the most common structures encountered in solid state chemistry is the perovskite structure. With a general formula of AB0 3, the A-type cations are 12-coordinate within a cubo-octahedral environment, while the B-type cations are 6-coordinate, forming an interconnecting three-dimensional octahedral network with neighbouring oxygen anions. While the ideal perovskite structure is cubic in Pm 3 m, many perovskites exhibit symmetry lowering tilting of the corner-sharing B0 6o ctahedral units as a result of A- and B-type cation size disparity. This is also evident in substituted perovskites, where two cations occupy the smaller octahedral site, AB 1- xB' x0 3' Electronic effects can also lower the symmetry. The two most commonly observed effects are the polarisation of the B-cation with a d 0 electronic configuration and Jahn-Teller distortion where the B-cation has a d 4 or d 9 electronic configuration, such as Mn 3+ or Cu 2+ respectively. Manganese containing perovskites have been shown in some compounds to exhibit long-range orbital ordering, giving rise to interesting properties. Heavier transition metals such as ruthenium and iridium have been previously incorporated into these perovskites as an avenue to regulate the properties of these materials. Two orthorhombic rhodium perovskite structures are presented, LaMn 0 . 5 Rh 0 . 5 O 3 and LaCu 05 Rh 0 . 5 O 3 ' A combination of synchrotron x-ray and neutron powder diffraction has been used to elucidate their structures, and have shown both B- and B'-type cations to be disordered across the same crystallographic site for both compounds. x-ray absorption spectroscopy measurements have been used to provide an insight into the valence states of the cations, which show a valency of +3.5 for rhodium due to an extensive charge delocalisation between copper and rhodium.

CaMn0.875Ti0.125O3 as oxygen carrier for chemical-looping combustion with oxygen uncoupling (CLOU)—Experiments in a continuously operating fluidized-bed reactor system

KAUST Repository

Rydé n, Magnus; Lyngfelt, Anders; Mattisson, Tobias

2011-01-01

Particles of the perovskite material CaMn0.875Ti0.125O3 has been examined as oxygen carrier for chemical-looping with oxygen uncoupling, and for chemical-looping combustion of natural gas, by 70h of experiments in a circulating fluidized-bed reactor

TrxR2 deficiencies promote chondrogenic differentiation and induce apoptosis of chondrocytes through mitochondrial reactive oxygen species

International Nuclear Information System (INIS)

Yan, Jidong; Xu, Jing; Fei, Yao; Jiang, Congshan; Zhu, Wenhua; Han, Yan; Lu, Shemin

2016-01-01

Thioredoxin reductase 2 (TrxR2) is a selenium (Se) containing protein. Se deficiency is associated with an endemic osteoarthropathy characterized by impaired cartilage formation. It is unclear whether TrxR2 have roles in cartilage function. We examined the effects of TrxR2 on chondrogenic ATDC5 cells through shRNA-mediated gene silencing of TrxR2. We demonstrated TrxR2 deficiencies could enhance chondrogenic differentiation and apoptosis of ATDC5 cells. TrxR2 deficiencies increased accumulation of cartilage glycosaminoglycans (GAGs) and mineralization. TrxR2 deficiencies also stimulated expression of extracellular (ECM) gene including Collagen II and Aggrecan. The enhanced chondrogenic properties were further confirmed by activation of Akt signaling which are required for chondrogenesis. In addition, TrxR2 deficiencies promoted chondrocyte proliferation through acceleration of cell cycle progression by increase in both S and G2/M phase cell distribution accompanied with induction of parathyroid hormone-related protein (PTHrP). Moreover, TrxR2 deficiencies induced chondrocyte death via apoptosis and increased cell sensitivity to exogenous oxidative stress. Furthermore, TrxR2 deficiencies induced emission of mitochondrial reactive oxygen species (ROS) without alteration of mitochondrial membrane potential and intracellular ATP content. Finally, treatment of TrxR2 deficiency cells with N-acetylcysteine (NAC) inhibited mitochondrial ROS production and chondrocyte apoptosis. NAC also prevented chondrogenic differentiation of TrxR2 deficiency cells by suppression of ECM gene expression, GAGs accumulation and mineralization, as well as attenuation of Akt signaling. Thus, TrxR2-mediated mitochondrial integrity is indispensable for chondrogenic differentiation of ATDC5 cells. TrxR2 deficiency-induced impaired proliferation and death of chondrocytes may be the pathological mechanism of the osteoarthropathy due to Se deficiency. Notably, this study also uncover the roles of

TrxR2 deficiencies promote chondrogenic differentiation and induce apoptosis of chondrocytes through mitochondrial reactive oxygen species

Energy Technology Data Exchange (ETDEWEB)

Yan, Jidong [Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an, Shaanxi 710061 (China); Xu, Jing [Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an, Shaanxi 710061 (China); Fei, Yao [College of Life Sciences, Northwest University, Xi’an, Shaanxi Province 710069 (China); Jiang, Congshan; Zhu, Wenhua; Han, Yan [Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an, Shaanxi 710061 (China); Lu, Shemin, E-mail: lushemin@xjtu.edu.cn [Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an, Shaanxi 710061 (China); Key Laboratory of Environment and Genes Related to Diseases, Xi’an Jiaotong University, Ministry of Education of China (China)

2016-05-15

Thioredoxin reductase 2 (TrxR2) is a selenium (Se) containing protein. Se deficiency is associated with an endemic osteoarthropathy characterized by impaired cartilage formation. It is unclear whether TrxR2 have roles in cartilage function. We examined the effects of TrxR2 on chondrogenic ATDC5 cells through shRNA-mediated gene silencing of TrxR2. We demonstrated TrxR2 deficiencies could enhance chondrogenic differentiation and apoptosis of ATDC5 cells. TrxR2 deficiencies increased accumulation of cartilage glycosaminoglycans (GAGs) and mineralization. TrxR2 deficiencies also stimulated expression of extracellular (ECM) gene including Collagen II and Aggrecan. The enhanced chondrogenic properties were further confirmed by activation of Akt signaling which are required for chondrogenesis. In addition, TrxR2 deficiencies promoted chondrocyte proliferation through acceleration of cell cycle progression by increase in both S and G2/M phase cell distribution accompanied with induction of parathyroid hormone-related protein (PTHrP). Moreover, TrxR2 deficiencies induced chondrocyte death via apoptosis and increased cell sensitivity to exogenous oxidative stress. Furthermore, TrxR2 deficiencies induced emission of mitochondrial reactive oxygen species (ROS) without alteration of mitochondrial membrane potential and intracellular ATP content. Finally, treatment of TrxR2 deficiency cells with N-acetylcysteine (NAC) inhibited mitochondrial ROS production and chondrocyte apoptosis. NAC also prevented chondrogenic differentiation of TrxR2 deficiency cells by suppression of ECM gene expression, GAGs accumulation and mineralization, as well as attenuation of Akt signaling. Thus, TrxR2-mediated mitochondrial integrity is indispensable for chondrogenic differentiation of ATDC5 cells. TrxR2 deficiency-induced impaired proliferation and death of chondrocytes may be the pathological mechanism of the osteoarthropathy due to Se deficiency. Notably, this study also uncover the roles of

Selective oxidation of n-butane to maleic anhydride under oxygen-deficient conditions over V-P-O mixed oxides

NARCIS (Netherlands)

Bosch, H.; Bruggink, A.A.; Ross, J.R.H.

1987-01-01

The selective oxidation of n-butane to maleic anhydride over V-P-O mixed oxides was studied under oxygen deficient conditions. The mixed oxides were prepared with P/V atomic ratios ranging from 0.7 to 1.0. Catalysts with P/V <1.0 did not show any selectivity to maleic anhydride formation, regardless

CO2 absorption of perovskites as seen by positron lifetime spectroscopy

International Nuclear Information System (INIS)

Suevegh, K.; Nomura, K.; Juhasz, G.; Homonnay, Z.; Vertes, A.

2000-01-01

The CO 2 absorption of several ABO 3 type perovskites was studied by positron lifetime spectroscopy. The longer positron lifetime was associated with positrons trapped by A site vacancies. The evaluated positron lifetime data indicated the relative stability of the crystal structure of Sr(Co 0.5 Fe 0.5 )O 3-δ against Ca doping at low Ca concentrations. Oxygen desorption and CO 2 absorption/desorption could also be followed by positron lifetime spectroscopy. It was shown that the concentration of oxygen vacancies has a large effect on positron lifetime data through the electron density of A site vacancies.

A preliminary X-ray diffraction study of the tetragonal superconducting oxide LaBa2Cu3O7-δ

International Nuclear Information System (INIS)

Hervieu, M.; Nguyen, N.; Michel, C.

1987-01-01

X-ray diffraction study of LaBa 2 Cu 3 O 7-δ showed that this tetragonal oxide exhibits an ordered oxygen deficient perovskite structure. It appears that the oxygen vacancy distribution differs from that observed for the orthorhombic superconductor YBa 2 Cu 3 O 7-δ . A structural model is proposed and discussed [fr

Planar structured perovskite solar cells by hybrid physical chemical vapor deposition with optimized perovskite film thickness

Science.gov (United States)

Wei, Xiangyang; Peng, Yanke; Jing, Gaoshan; Cui, Tianhong

2018-05-01

The thickness of perovskite absorber layer is a critical parameter to determine a planar structured perovskite solar cell’s performance. By modifying the spin coating speed and PbI2/N,N-dimethylformamide (DMF) solution concentration, the thickness of perovskite absorber layer was optimized to obtain high-performance solar cells. Using a PbI2/DMF solution of 1.3 mol/L, maximum power conversion efficiency (PCE) of a perovskite solar cell is 15.5% with a perovskite film of 413 nm at 5000 rpm, and PCE of 14.3% was also obtained for a solar cell with a perovskite film of 182 nm thick. It is derived that higher concentration of PbI2/DMF will result in better perovskite solar cells. Additionally, these perovskite solar cells are highly uniform. In 14 sets of solar cells, standard deviations of 11 sets of solar cells were less than 0.50% and the smallest standard deviation was 0.25%, which demonstrates the reliability and effectiveness of hybrid physical chemical vapor deposition (HPCVD) method.

Enhanced planar perovskite solar cell efficiency and stability using a perovskite/PCBM heterojunction formed in one step.

Science.gov (United States)

Zhou, Long; Chang, Jingjing; Liu, Ziye; Sun, Xu; Lin, Zhenhua; Chen, Dazheng; Zhang, Chunfu; Zhang, Jincheng; Hao, Yue

2018-02-08

Perovskite/PCBM heterojunctions are efficient for fabricating perovskite solar cells with high performance and long-term stability. In this study, an efficient perovskite/PCBM heterojunction was formed via conventional sequential deposition and one-step formation processes. Compared with conventional deposition, the one-step process was more facile, and produced a perovskite thin film of substantially improved quality due to fullerene passivation. Moreover, the resulting perovskite/PCBM heterojunction exhibited more efficient carrier transfer and extraction, and reduced carrier recombination. The perovskite solar cell device based on one-step perovskite/PCBM heterojunction formation exhibited a higher maximum PCE of 17.8% compared with that from the conventional method (13.7%). The device also showed exceptional stability, retaining 83% of initial PCE after 60 days of storage under ambient conditions.

μSR in oxygen deficient YBa2Cu3Ox (6.5≤x≤7.0)

International Nuclear Information System (INIS)

Puempin, B.; Keller, H.; Kuendig, W.; Savic, I.M.; Schneider, J.W.; Simmler, H.; Zimmermann, P.; Kaldis, E.; Rusiecki, S.; Rossel, C.

1991-01-01

A systematic μSR study of the local magnetic field distribution in a series of oxygen deficient YBa 2 Cu 3 O x samples with 6.5≤x≤7.0 is reported. Special attention was given to perform the experiments under the same conditions, so that the oxygen content of the measured samples was the only parameter varied. The behavior of the depolarization rate σ as a function of the oxygen content x was found to have strong similarities with the behavior of the critical temperature Tc as a function of x. In particular, two step-like increases of σ were observed above x=6.7 and 6.9. The temperature dependence of the normalized depolarization rate σ(T)/σ(0) is well described by the two-fluid model for x≥6.781(1) and clearly deviates from this behavior for x≤6.704(1). Our results are compared to those obtained by other groups. (orig.)

Antimony doped barium strontium ferrite perovskites as novel cathodes for intermediate-temperature solid oxide fuel cells

Energy Technology Data Exchange (ETDEWEB)

Ling, Yihan, E-mail: lyhyy@mail.ustc.edu.cn [School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, 221116 (China); Lu, Xiaoyong [China Anhui Key Laboratory of Low Temperature Co-fired Materials, Department of Chemistry, Huainan Normal University, Huainan, Anhui, 232001 (China); Niu, Jinan; Chen, Hui [School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, 221116 (China); Ding, Yanzhi [China Anhui Key Laboratory of Low Temperature Co-fired Materials, Department of Chemistry, Huainan Normal University, Huainan, Anhui, 232001 (China); Ou, Xuemei [School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, 221116 (China); Zhao, Ling [Department of Material Science and Chemistry, China University of Geosciences, Wuhan, 430074 (China)

2016-05-05

Antimony was doped to barium strontium ferrite to produce ferrite-based perovskites with a composition of Ba{sub 0.5}Sr{sub 0.5}Fe{sub 1−x}Sb{sub x}O{sub 3−δ} (x = 0.0, 0.05, 0.1) as novel cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The perovskite properties including oxygen nonstoichiometry (δ), mean valence of B-site, tolerance factors, thermal expansion coefficient (TEC) and electrical conductivity (σ) are explored as a function of antimony content. By defect chemistry analysis, the TECs decrease since the variable oxygen vacancy concentration is decreased by Sb doping, and σ decreases with x due to the reduced charge concentration of Fe{sup 4+} content. Consequently, the electrochemical performance was substantially improved and the interfacial polarization resistance was reduced from 0.213 to 0.120 Ωcm{sup 2} at 700 °C with Sb doping. The perovskite with x = 1.0 is suggested as the most promising composition as SOFC cathode material. - Highlights: • Antimony is doped to barium strontium ferrite to produce novel cathodes. • δ, TECs and σ are evaluated as a function of antimony content. • The electrochemical performance is substantially improved with antimony doping.

Electric and magnetic properties of oxidic titanium bronzes of rare earths Lnsub(2/3+x)TiOsub(3+-y) with perovskite structure

Energy Technology Data Exchange (ETDEWEB)

Bazuev, G V; Makarova, O V; Shvejkin, G P [AN SSSR, Sverdlovsk. Inst. Khimii

1983-01-01

A study was made on electric and magnetic properties of oxidic titanium bronzes of rare earths and their dependence on rare earth nature and the degree of rare earth sublattice filling was followed. Data on Lnsub(2/3)TiOsub(3-y) (Ln-Ce, Nd) anion-deficient perovskites are given as well. Investigated Cesub(2/3)TiOsub(2.985) and Ndsub(2/3)TiOsub(2.875) phases as well as defectless with respect to oxygen Lnsub(2/3)TiOsub(3) phases have rhombic structure of perovskite type with ordered position of Ln/sup 3 +/ cations and vacancies. Specific electric resistance and thermoelectromotive force factor were determined in vacuum at 290-1173 K for samples in the form of parallelepiped of 3x5x25 mm/sup 3/ size. Magnetic susceptibility chi was determined at 77-300 K by Faraday method using a device based on magnetic balance with electromagnetic compensation. Relative error during chi measuring didn't exceed +-2%. Collectivized behaviour of d-electrons of Ti/sup 3 +/ cations in oxidic titanium bronzes of rare earths: Lnsub(2/3+x)TiOsub(3+-y) (Ln-La, Ce, Nd; 0 < x < 1/3), conditioned by formation of narrow, partly filled ..pi..*-zone, was established on the basis of measuring specific electric resistance and magnetic susceptibility.

Ab initio Defect Energetics in LaBO3 Perovskite Solid Oxide Fuel Cell Materials

DEFF Research Database (Denmark)

Lee, Yueh-Lin; Morgan, Dane; Kleis, Jesper

2009-01-01

Perovskite materials of the form ABO3 are a promising family of compounds for use in solid oxide fuel cell (SOFC) cathodes. Study of the physics of these compounds under SOFC conditions with ab initio methods is particularly challenging due to high temperatures, exchange of oxygen with O2 gas...

Proton-oxygen conductivity in substituted perovskites ATi0.95Mo0.05O3-α (A = Ca, Sr, Ba; M = Sc, Mg) in the reducing hydrogen-containing atmospheres

International Nuclear Information System (INIS)

Gorelov, V.P.; Balakireva, V.B.; Sharova, N.V.

1999-01-01

Electric conductivity depending on temperature, oxygen partial pressure, as well as the number of t i ion transfer and transfer hydrogen numbers in the perovskites ATi 0.95 Mo 0.05 O 3-α (A = Ca, Sr, Ba; M = Sc, Mg) in reducing hydrogen-containing atmospheres in the temperature range of 450-850 deg C have been measured. With the temperature decrease t i increases reaching 1.0 at a temperature of 550 deg C for all compositions. Proton conductivity under conditions of assumed concomitant transfer of either O 2- or OH - has been ascertained [ru

Stability Issues on Perovskite Solar Cells

Directory of Open Access Journals (Sweden)

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.

Oxygen perovskites of type Ba/sub 3/Bsup(III)RuIrO/sub 9/

Energy Technology Data Exchange (ETDEWEB)

Duerrschmidt, E; Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Lehrstuhl fuer Anorganische Chemie 2

1980-11-01

The black perovskites Ba/sub 3/Bsup(III)RuIrO/sub 9/ with Bsup(III) = La, Nd, Sm, Gd, Dy, Er, Yb, In, Sc are isotypic. They crystallize in a hexagonal BaTiO/sub 3/ structure (sequence (hcc)/sub 2/). The mean oxydation state of the noble metal ions is +4.5.

Ligand-Stabilized Reduced-Dimensionality Perovskites

KAUST Repository

Quan, Li Na; Yuan, Mingjian; Comin, Riccardo; Voznyy, Oleksandr; Beauregard, Eric M.; Hoogland, Sjoerd; Buin, Andrei; Kirmani, Ahmad R.; Zhao, Kui; Amassian, Aram; Kim, Dong Ha; Sargent, Edward H.

2016-01-01

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.

Ligand-Stabilized Reduced-Dimensionality Perovskites

KAUST Repository

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.

Colour centre-free perovskite single crystals

International Nuclear Information System (INIS)

Petit, Pierre-Olivier; Petit, Johan; Goldner, Philippe; Viana, Bruno

2009-01-01

Yb 3+ :YAlO 3 (YAP) and Yb 3+ :GdAlO 3 (GAP) are interesting 1 μm high-power laser media thanks to their very good thermo-mechanical properties. However, as-grown perovskite single crystals exhibit colour centres. Parasitic thermal load generated by these centres is deleterious for high-power laser action and can lead to crystal damages. Moreover these defects decrease Yb 3+ lifetime. They are related to trapped holes on the oxygen network. In the present work, several schemes to remove colour centres are presented. Attention is focused on cerium codoping, thermal annealing under reducing atmosphere and growth of non-stoechiometric compounds.

Improving the Morphology of the Perovskite Absorber Layer in Hybrid Organic/Inorganic Halide Perovskite MAPbI3 Solar Cells

Directory of Open Access Journals (Sweden)

I. J. Ogundana

2017-01-01

Full Text Available Recently, perovskite solar cells have attracted tremendous attention due to their excellent power conversion efficiency, low cost, simple fabrications, and high photovoltaic performance. Furthermore, the perovskite solar cells are lightweight and possess thin film and semitransparency. However, the nonuniformity in perovskite layer constitutes a major setback to the operation mechanism, performance, reproducibility, and degradation of perovskite solar cells. Therefore, one of the main challenges in planar perovskite devices is the fabrication of high quality films with controlled morphology and least amount of pin-holes for high performance thin film perovskite devices. The poor reproducibility in perovskite solar cells hinders the accurate fabrication of practical devices for use in real world applications, and this is primarily as a result of the inability to control the morphology of perovskites, leading to large variability in the characteristics of perovskite solar cells. Hence, the focus of research in perovskites has been mostly geared towards improving the morphology and crystallization of perovskite absorber by selecting the optimal annealing condition considering the effect of humidity. Here we report a controlled ambient condition that is necessary to grow uniform perovskite crystals. A best PCE of 7.5% was achieved along with a short-circuit current density of 15.2 mA/cm2, an open-circuit voltage of 0.81 V, and a fill factor of 0.612 from the perovskite solar cell prepared under 60% relative humidity.

Structural and chemical reactivity modifications of a cobalt perovskite induced by Sr-substitution. An in situ XAS study

International Nuclear Information System (INIS)

Hueso, Jose L.; Holgado, Juan P.; Pereñíguez, Rosa; Gonzalez-DelaCruz, V.M.; Caballero, Alfonso

2015-01-01

LaCoO 3 and La 0.5 Sr 0.5 CoO 3−δ perovskites have been studied by in situ Co K-edge XAS. Although the partial substitution of La(III) by Sr(II) species induces an important increase in the catalytic oxidation activity and modifies the electronic state of the perovskite, no changes could be detected in the oxidation state of cobalt atoms. So, maintaining the electroneutrality of the perovskite requires the generation of oxygen vacancies in the network. The presence of these vacancies explains that the substituted perovskite is now much more reducible than the original LaCoO 3 perovskite. As detected by in situ XAS, after a consecutive reduction and oxidation treatment, the original crystalline structure of the LaCoO 3 perovskite is maintained, although in a more disordered state, which is not the case for the Sr doped perovskite. So, the La 0.5 Sr 0.5 CoO 3−δ perovskite submitted to the same hydrogen reduction treatment produces metallic cobalt, while as determined by in situ XAS spectroscopy the subsequent oxidation treatment yields a Co(III) oxide phase with spinel structure. Surprisingly, no Co(II) species are detected in this new spinel phase. - Highlights: • A Sr-substituted lanthanum cobalt perovskite has been prepared by spray pyrolysis. • It has been established that Co(III) cations are present in both perovskites. • LaCoO 3 is a less reducible phase than the substituted La 0.5 Sr 0.5 CoO 3−δ . • After reoxidation of reduced La 0.5 Sr 0.5 CoO 3−δ , a 100% Co(III) spinel is obtained

Iron deficiency in childhood

NARCIS (Netherlands)

Uijterschout, L.

2015-01-01

Iron deficiency (ID) is the most common micronutrient deficiency in the world. Iron is involved in oxygen transport, energy metabolism, immune response, and plays an important role in brain development. In infancy, ID is associated with adverse effects on cognitive, motor, and behavioral development

Artificial oxygen transport protein

Science.gov (United States)

Dutton, P. Leslie

2014-09-30

This invention provides heme-containing peptides capable of binding molecular oxygen at room temperature. These compounds may be useful in the absorption of molecular oxygen from molecular oxygen-containing atmospheres. Also included in the invention are methods for treating an oxygen transport deficiency in a mammal.

Perovskite Solar Cell

Indian Academy of Sciences (India)

Organic–inorganic halide perovskite, a newcomerin the solar cell industry has proved its potential forincreasing efficiency rapidly from 3.8% in 2009 to 22.1% in2016. High efficiency, flexibility, and cell architecture of theemerging hybrid halide perovskite have caught the attentionof researchers and technologists in the field.

Topotactic phase transformation of the brownmillerite SrCoO2.5 to the perovskite SrCoO3- δ.

Science.gov (United States)

Jeen, H; Choi, W S; Freeland, J W; Ohta, H; Jung, C U; Lee, H N

2013-07-19

Pulsed laser epitaxy of brownmillerite SrCoO2.5 thin films and their phase transformation to the perovskite SrCoO3-δ are investigated. While the direct growth of the fully oxidized perovskite films is found to be an arduous task, filling some of oxygen vacancies into SrCoO2.5 by topotactic oxidation accompanies systematic evolution of electronic, magnetic, and thermoelectric properties, useful for many information and energy technologies. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Intracellular nitrate in sediments of an oxygen-deficient marine basin is linked to pelagic diatoms

DEFF Research Database (Denmark)

Kamp, Anja; Petro, Caitlin; Røy, Hans

2018-01-01

Intracellular nitrate is an important electron acceptor in oxygen-deficient aquatic environments, either for the nitrate-storing microbes themselves, or for ambient microbial communities through nitrate leakage. This study links the spatial distribution of intracellular nitrate with the abundance...... and identity of nitrate-storing microbes in sediments of the Bornholm Basin, an environmental showcase for severe hypoxia. Intracellular nitrate (up to 270 nmol cm−3 sediment) was detected at all 18 stations along a 35-km transect through the basin and typically extended as deep as 1.6 cm into the sediment...

Electrochemical reduction of oxygen and nitric oxide at low temperature on La1−xSrxMnO3+δ cathodes

DEFF Research Database (Denmark)

Kammer Hansen, Kent

2013-01-01

in the nitric oxide containing atmosphere compared to the activity in the oxygen containing atmosphere at 200°C. At 300 and 400°C the activity in the nitric oxide and oxygen containing atmospheres were similar. The highest ratio between the cathodic current densities in the nitric oxide and oxygen containing......Six La1−xSrxMnO3+δ (x=0, 0.05, 0.15, 0.25, 0.35, 0.50) perovskites were synthesised and characterised by powder XRD and cyclic voltammetry on cone-shaped electrodes in 10% oxygen in argon or 1% nitric oxide in argon at 200, 300 and 400°C. The activity of the manganite based perovskites were highest...

Combined effect of oxygen deficient point defects and Ni doping in radio frequency magnetron sputtering deposited ZnO thin films

Energy Technology Data Exchange (ETDEWEB)

Saha, B., E-mail: biswajit.physics@gmail.com [Thin Film and Nano Science Laboratory, Department of Physics, Jadavpur University, 700 032 Kolkata (India); Department of Physics, National Institute of Technology Agartala, Jirania 799046, Tripura (India); Das, N.S.; Chattopadhyay, K.K. [Thin Film and Nano Science Laboratory, Department of Physics, Jadavpur University, 700 032 Kolkata (India)

2014-07-01

Ni doped ZnO thin films with oxygen deficiency have been synthesized on glass substrates by radio frequency magnetron sputtering technique using argon plasma. The combined effect of point defects generated due to oxygen vacancies and Ni doping on the optical and electrical properties of ZnO thin films has been studied in this work. Ni doping concentrations were varied and the structural, optical and electrical properties of the films were studied as a function of doping concentrations. The films were characterized with X-ray diffractometer, UV–Vis–NIR spectrophotometer, X-ray photoelectron spectroscopy, atomic force microscopy and electrical conductivity measurements. Oxygen deficient point defects (Schottky defects) made the ZnO thin film highly conducting while incorporation of Ni dopant made it more functional regarding their electrical and optical properties. The films were found to have tunable electrical conductivity with Ni doping concentrations. - Highlights: • ZnO thin films prepared by radio frequency magnetron sputtering technique • Synthesis process was stimulated to introduce Schottky-type point defects. • Point defects and external doping of Ni made ZnO thin films more functional. • Point defect induced high electrical conductivity in ZnO thin film. • Significant shift in optical bandgap observed in ZnO with Ni doping concentrations.

O3 perovskite ceramic

Indian Academy of Sciences (India)

The prepared sample remains as double phases with the perovskite struc- ture. The structure ... Ferroelectric oxides with perovskite structure are the subject of many investigations. ... in optical devices and heterojunction solar cells. 1765 ...

Perovskite classification: An Excel spreadsheet to determine and depict end-member proportions for the perovskite- and vapnikite-subgroups of the perovskite supergroup

Science.gov (United States)

Locock, Andrew J.; Mitchell, Roger H.

2018-04-01

Perovskite mineral oxides commonly exhibit extensive solid-solution, and are therefore classified on the basis of the proportions of their ideal end-members. A uniform sequence of calculation of the end-members is required if comparisons are to be made between different sets of analytical data. A Microsoft Excel spreadsheet has been programmed to assist with the classification and depiction of the minerals of the perovskite- and vapnikite-subgroups following the 2017 nomenclature of the perovskite supergroup recommended by the International Mineralogical Association (IMA). Compositional data for up to 36 elements are input into the spreadsheet as oxides in weight percent. For each analysis, the output includes the formula, the normalized proportions of 15 end-members, and the percentage of cations which cannot be assigned to those end-members. The data are automatically plotted onto the ternary and quaternary diagrams recommended by the IMA for depiction of perovskite compositions. Up to 200 analyses can be entered into the spreadsheet, which is accompanied by data calculated for 140 perovskite compositions compiled from the literature.

Transport and magnetoresistance effect in an oxygen-deficient SrTiO3/La0.67Sr0.33MnO3 heterojunction

International Nuclear Information System (INIS)

Wang Jing; Chen Chang-Le; Yang Shi-Hai; Luo Bing-Cheng; Duan Meng-Meng; Jin Ke-Xin

2013-01-01

An oxygen-deficient SrTiO 3 /La 0.67 Sr 0.33 MnO 3 heterojunction is fabricated on an SrTiO 3 (001) substrate by a pulsed laser deposition method. The electrical characteristics of the heterojunction are studied systematically in a temperature range from 80 K to 300 K. The transport mechanism follows I ∞ exp(eV/nkT) under small forward bias, while it becomes space charge limited and follows I ∞ V m(T) with 1.49 < m < 1.99 under high bias. Such a heterojunction also exhibits magnetoresistance (MR) effect. The absolute value of negative MR monotonically increases with temperature decreasing and reaches 26.7% at 80 K under H = 0.7 T. Various factors, such as strain and oxygen deficiency play dominant roles in the characteristics. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

New Hypothesis for SOFC Ceramic Oxygen Electrode Mechanisms

DEFF Research Database (Denmark)

Mogensen, Mogens Bjerg; Chatzichristodoulou, Christodoulos; Graves, Christopher R.

2016-01-01

A new hypothesis for the electrochemical reaction mechanism in solid oxide cell ceramic oxygen electrodes is proposed based on literature including our own results. The hypothesis postulates that the observed thin layers of SrO-La2O3 on top of ceramic perovskite and other Ruddlesden-Popper...

Hybrid perovskites: Approaches towards light-emitting devices

KAUST Repository

Alias, Mohd Sharizal

2016-10-06

The high optical gain and absorption of organic-inorganic hybrid perovskites have attracted extensive research for photonic device applications. Using the bromide halide as an example, we present key approaches of our work towards realizing efficient perovskites based light-emitters. The approaches involved determination of optical constants for the hybrid perovskites thin films, fabrication of photonic nanostructures in the form of subwavelength grating reflector patterned directly on the hybrid perovskites as light manipulation layer, and enhancing the emission property of the hybrid perovskites by using microcavity structure. Our results provide a platform for realization of hybrid perovskites based light-emitting devices for solid-state lighting and display applications. © 2016 IEEE.

Hybrid perovskites: Approaches towards light-emitting devices

KAUST Repository

Alias, Mohd Sharizal; Dursun, Ibrahim; Priante, Davide; Saidaminov, Makhsud I.; Ng, Tien Khee; Bakr, Osman; Ooi, Boon S.

2016-01-01

The high optical gain and absorption of organic-inorganic hybrid perovskites have attracted extensive research for photonic device applications. Using the bromide halide as an example, we present key approaches of our work towards realizing efficient perovskites based light-emitters. The approaches involved determination of optical constants for the hybrid perovskites thin films, fabrication of photonic nanostructures in the form of subwavelength grating reflector patterned directly on the hybrid perovskites as light manipulation layer, and enhancing the emission property of the hybrid perovskites by using microcavity structure. Our results provide a platform for realization of hybrid perovskites based light-emitting devices for solid-state lighting and display applications. © 2016 IEEE.

Light-Independent Ionic Transport in Inorganic Perovskite and Ultrastable Cs-Based Perovskite Solar Cells.

Science.gov (United States)

Zhou, Wenke; Zhao, Yicheng; Zhou, Xu; Fu, Rui; Li, Qi; Zhao, Yao; Liu, Kaihui; Yu, Dapeng; Zhao, Qing

2017-09-07

Due to light-induced effects in CH 3 NH 3 -based perovskites, such as ion migration, defects formation, and halide segregation, the degradation of CH 3 NH 3 -based perovskite solar cells under maximum power point is generally implicated. Here we demonstrated that the effect of light-enhanced ion migration in CH 3 NH 3 PbI 3 can be eliminated by inorganic Cs substitution, leading to an ultrastable perovskite solar cell. Quantitatively, the ion migration barrier for CH 3 NH 3 PbI 3 is 0.62 eV under dark conditions, larger than that of CsPbI 2 Br (0.45 eV); however, it reduces to 0.07 eV for CH 3 NH 3 PbI 3 under illumination, smaller than that for CsPbI 2 Br (0.43 eV). Meanwhile, photoinduced halide segregation is also suppressed in Cs-based perovskites. Cs-based perovskite solar cells retained >99% of the initial efficiency (10.3%) after 1500 h of maximum power point tracking under AM1.5G illumination, while CH 3 NH 3 PbI 3 solar cells degraded severely after 50 h of operation. Our work reveals an uncovered mechanism for stability improvement by inorganic cation substitution in perovskite-based optoelectronic devices.

New vanadium oxides with perovskite type structure: AThV/sub 2/O/sub 6/ (A=Ca,Sr)

Energy Technology Data Exchange (ETDEWEB)

Vidyasagar, K; Gopalakrishnan, J

1982-07-01

New perovskite oxides of the formula AThV/sub 2/O/sub 6/ (A=Ca,Sr) have been prepared by reduction of the corresponding AThV/sub 2/O/sub 8/ under hydrogen atmosphere. CaThV/sub 2/O/sub 6/ crystallizes in an orthorhombic LaVO/sub 3/ type structure, while the strontium compound exhibiting cation-deficient nonstoichiometry. SrThsub(1-x)V/sub 2/O/sub 6/ (x approx. 0.4), is cubic. The magnetic susceptibility behaviour of the calcium compound is similar to that of V/sup 3 +/ perovskites, while the strontium compound exhibits a large increase in susceptibility below 130K, the behaviour being likely to be associated with the mixed-valence character of vanadium.

Cerium luminescence in nd0 perovskites

International Nuclear Information System (INIS)

Setlur, A.A.; Happek, U.

2010-01-01

The luminescence of Ce 3+ in perovskite (ABO 3 ) hosts with nd 0 B-site cations, specifically Ca(Hf,Zr)O 3 and (La,Gd)ScO 3 , is investigated in this report. The energy position of the Ce 3+ excitation and emission bands in these perovskites is compared to those of typical Al 3+ perovskites; we find a Ce 3+ 5d 1 centroid shift and Stokes shift that are larger versus the corresponding values for the Al 3+ perovskites. It is also shown that Ce 3+ luminescence quenching is due to Ce 3+ photoionization. The comparison between these perovskites shows reasonable correlations between Ce 3+ luminescence quenching, the energy position of the Ce 3+ 5d 1 excited state with respect to the host conduction band, and the host composition. - Graphical abstract: Ce 3+ decay times versus temperature for perovskites with nd 0 B-site cations.

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

Science.gov (United States)

Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

2013-01-01

For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1 − xSrxFeyMn1 − yO3 − δ (0 ≤ x ≤ 1, 0.2 ≤ y ≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst with that of an industrial potassium promoted iron (Fe–K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst showed higher initial activity than the industrial Fe–K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe–K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ and the Fe–K catalysts in a H2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst while the Fe–K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst had higher potential for activating the steam than the Fe–K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ was superior to that of Fe–K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ perovskite oxide. PMID:24790949

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

Directory of Open Access Journals (Sweden)

Ryo eWatanabe

2013-10-01

Full Text Available For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1–xSrxFeyMn1–yO3–d(0 ≤ x≤ 1, 0.2 ≤ y≤ 0.8, perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3–d catalyst with that of an industrial potassium promoted iron (Fe–K catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3–d catalyst showed higher initial activity than the industrial Fe–K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3–d catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe–K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3–d and the Fe–K catalysts in aH2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3–d catalyst while the Fe–K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3–d catalyst had higher potential for activating the steam than the Fe–K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3–d was superior to that of Fe–K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3–d perovskite oxide.

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

Science.gov (United States)

Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

2013-10-01

For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1-xSrxFeyMn1-yO3-d(0 ≤ x≤ 1, 0.2 ≤ y≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst with that of an industrial potassium promoted iron (Fe-K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed higher initial activity than the industrial Fe-K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe-K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d and the Fe-K catalysts in aH2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst while the Fe-K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst had higher potential for activating the steam than the Fe-K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3-d was superior to that of Fe-K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d perovskite oxide.

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism.

Science.gov (United States)

Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

2013-01-01

For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1 - x SrxFe y Mn1 - y O3 - δ (0 ≤ x ≤ 1, 0.2 ≤ y ≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst with that of an industrial potassium promoted iron (Fe-K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst showed higher initial activity than the industrial Fe-K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe-K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ and the Fe-K catalysts in a H2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst while the Fe-K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst had higher potential for activating the steam than the Fe-K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ was superior to that of Fe-K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ perovskite oxide.

Non-collinear magnetism in multiferroic perovskites.

Science.gov (United States)

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.

Synthesis and characterization of perovskite-type Sr{sub x}Y{sub 1−x}FeO{sub 3−δ} (0.63≤x<1.0) and Sr{sub 0.75}Y{sub 0.25}Fe{sub 1−y}M{sub y}O{sub 3−δ} (M=Cr, Mn, Ni), (y=0.2, 0.33, 0.5)

Energy Technology Data Exchange (ETDEWEB)

Biendicho, J.J. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); The ISIS Facility, STFC Rutherford Appleton Laboratory, Didcot, OX11 0QX Oxfordshire (United Kingdom); Shafeie, S. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Frenck, L. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Université Pierre et Marie Curie, 75005 Paris (France); Gavrilova, D. [M.V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Böhme, S. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Technische Universität Chemnitz, Institut für Chemie, Straße der Nationen 62, D-09111 Chemnitz (Germany); Bettanini, A.M. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Department of Molecular Sciences and Nanosystems, University Ca’ Foscari of Venice, 30123 Venice (Italy); Svedlindh, P. [Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala (Sweden); Hull, S. [The ISIS Facility, STFC Rutherford Appleton Laboratory, Didcot, OX11 0QX Oxfordshire (United Kingdom); Zhao, Z. [School of Industrial Engineering and Management, Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Istomin, S.Ya., E-mail: istomin@icr.chem.msu.ru [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); M.V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Grins, J.; Svensson, G. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden)

2013-04-15

Oxygen-deficient ferrates with the cubic perovskite structure Sr{sub x}Y{sub 1−x}FeO{sub 3−δ} were prepared in air (0.71≤x≤0.91) as well as in N{sub 2} (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 Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} 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 Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} reveal a modulation along 〈1 0 0〉{sub p} with G± ∼0.4〈1 0 0〉{sub 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, Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} 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 Sr{sub 0.75}Y{sub 0.25}Fe{sub 1−y}M{sub y}O{sub 3−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 Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79}. Only M=Ni has increased electrical conductivity compared to un-doped Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79}. - Graphical abstract: Oxygen-deficient ferrates with the cubic perovskite structure Sr{sub x}Y{sub 1−x}FeO{sub 3−δ} were prepared both in air (0.71≤x≤0.91) and N{sub 2} (x=0.75 and 0.79) at 1573 K. Refinement of the

Perovskite Solar Cells: Progress and Advancements

Directory of Open Access Journals (Sweden)

Naveen Kumar Elumalai

2016-10-01

Full Text Available Organic–inorganic hybrid perovskite solar cells (PSCs have emerged as a new class of optoelectronic semiconductors that revolutionized the photovoltaic research in the recent years. The perovskite solar cells present numerous advantages include unique electronic structure, bandgap tunability, superior charge transport properties, facile processing, and low cost. Perovskite solar cells have demonstrated unprecedented progress in efficiency and its architecture evolved over the period of the last 5–6 years, achieving a high power conversion efficiency of about 22% in 2016, serving as a promising candidate with the potential to replace the existing commercial PV technologies. This review discusses the progress of perovskite solar cells focusing on aspects such as superior electronic properties and unique features of halide perovskite materials compared to that of conventional light absorbing semiconductors. The review also presents a brief overview of device architectures, fabrication methods, and interface engineering of perovskite solar cells. The last part of the review elaborates on the major challenges such as hysteresis and stability issues in perovskite solar cells that serve as a bottleneck for successful commercialization of this promising PV technology.

Magnetic Modes in Rare Earth Perovskites: A Magnetic-Field-Dependent Inelastic Light Scattering study.

Science.gov (United States)

Saha, Surajit; Cao, Bing-Chen; Motapothula, M; Cong, Chun-Xiao; Sarkar, Tarapada; Srivastava, Amar; Sarkar, Soumya; Patra, Abhijeet; Ghosh, Siddhartha; Ariando; Coey, J M D; Yu, Ting; Venkatesan, T

2016-11-15

Here, we report the presence of defect-related states with magnetic degrees of freedom in crystals of LaAlO 3 and several other rare-earth based perovskite oxides using inelastic light scattering (Raman spectroscopy) at low temperatures in applied magnetic fields of up to 9 T. Some of these states are at about 140 meV above the valence band maximum while others are mid-gap states at about 2.3 eV. No magnetic impurity could be detected in LaAlO 3 by Proton-Induced X-ray Emission Spectroscopy. We, therefore, attribute the angular momentum-like states in LaAlO 3 to cationic/anionic vacancies or anti-site defects. Comparison with the other rare earth perovskites leads to the empirical rule that the magnetic-field-sensitive transitions require planes of heavy elements (e.g. lanthanum) and oxygen without any other light cations in the same plane. These magnetic degrees of freedom in rare earth perovskites with useful dielectric properties may be tunable by appropriate defect engineering for magneto-optic applications.

CO sub 2 absorption of perovskites as seen by positron lifetime spectroscopy

CERN Document Server

Suevegh, K; Juhasz, G; Homonnay, Z; Vertes, A

2000-01-01

The CO sub 2 absorption of several ABO sub 3 type perovskites was studied by positron lifetime spectroscopy. The longer positron lifetime was associated with positrons trapped by A site vacancies. The evaluated positron lifetime data indicated the relative stability of the crystal structure of Sr(Co sub 0 sub . sub 5 Fe sub 0 sub . sub 5)O sub 3 sub - subdelta against Ca doping at low Ca concentrations. Oxygen desorption and CO sub 2 absorption/desorption could also be followed by positron lifetime spectroscopy. It was shown that the concentration of oxygen vacancies has a large effect on positron lifetime data through the electron density of A site vacancies.

Ambipolar solution-processed hybrid perovskite phototransistors

KAUST Repository

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.

Intrinsic ZnO films fabricated by DC sputtering from oxygen-deficient targets for Cu(In,Ga)Se2 solar cell application

Institute of Scientific and Technical Information of China (English)

Chongyin Yang; DongyunWan; Zhou Wang; Fuqiang Huang

2011-01-01

Intrinsic zinc oxide films, normally deposited by radio frequency (RF) sputtering, are fabricated by direct current (DC) sputtering. The oxygen-deficient targets are prepared via a newly developed double crucible method. The 800-nm-thick film obtaines significantly higher carrier mobility compareing with that of the 800-nm-thick ZnO film. This is achieved by the widely used RF sputtering, which favors the prevention of carrier recombination at the interfaces and reduction of the series resistance of solar cells. The optimal ZnO film is used in a Cu (In, Ga) Se2 (CIGS) solar cell with a high efficiency of 11.57%. This letter demonstrates that the insulating ZnO films can be deposited by DC sputtering from oxygen-deficient ZnO targets to lower the cost of thin film solar cells.%Intrinsic zinc oxide films,normally deposited by radio frequency (RF) sputtering,are fabricated by direct current (DC) sputtering.The oxygen-deficient targets are prepared via a newly developed double crucible method.The 800-nm-thick film obtaines significantly higher carrier mobility compareing with that of the 800-nm-thick ZnO film.This is achieved by the widely used RF sputtering,which favors the prevention of carrier recombination at the interfaces and reduction of the series resistance of solar cells.The optimal ZnO film is used in a Cu (In,Ga) Se2 (C1GS) solar cell with a high efficiency of 11.57％.This letter demonstrates that the insulating ZnO films can be deposited by DC sputtering from oxygen-deficient ZnO targets to lower the cost of thin film solar cells.High resistance transparent intrinsic zinc oxide (i-ZnO)thin film has been widely nsed as the front electrode in transparent electronics and photovoltaic devices because of its low cost and nontoxicity.Owing to its unique characteristics of high transparency and adjustable resistivity in a certain range,the use of i-ZnO thin films as diffusion barrier layers of a-Si/μc-Si,CdTe,and CIGS thin-film solar cells has been advantageous

Phase transition of a cobalt-free perovskite as a high-performance cathode for intermediate-temperature solid oxide fuel cells.

Science.gov (United States)

Jiang, Shanshan; Zhou, Wei; Niu, Yingjie; Zhu, Zhonghua; Shao, Zongping

2012-10-01

It is generally recognized that the phase transition of a perovskite may be detrimental to the connection between cathode and electrolyte. Moreover, certain phase transitions may induce the formation of poor electronic and ionic conducting phase(s), thereby lowering the electrochemical performance of the cathode. Here, we present a study on the phase transition of a cobalt-free perovskite (SrNb(0.1)Fe(0.9)O(3-δ), SNF) and evaluate its effect on the electrochemical performance of the fuel cell. SNF exists as a primitive perovskite structure with space group P4mm (99) at room temperature. As evidenced by in situ high-temperature X-ray diffraction measurements over the temperature range of 600 to 1000 °C, SNF undergoes a transformation to a tetragonal structure with a space group I4/m (87). This phase transition is accompanied by a moderate change in the volume, allowing a good cathode/electrolyte interface on thermal cycling. According to the electrochemical impedance spectroscopy evaluation, the I4/m phase exhibits positive effects on the cathode's performance, showing the highest oxygen reduction reaction activity of cobalt-free cathodes reported so far. This activity improvement is attributed to enhanced oxygen surface processes. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photovoltaic Effect of 2D Homologous Perovskites

International Nuclear Information System (INIS)

Jung, Mi-Hee

2017-01-01

Highlights: • The mixed perovskite was prepared by exposure of MAI gas on the BAPbI_4 film. • The increased dimensional perovskite shows a smaller band gap than 2D perovskite. • The mixed perovskite system shows the vertical crystal orientation. • The mixed perovskite cell exhibits the higher Jsc and FF than 2D perovskite cell. - Abstract: The controlled growth of mixed dimensional perovskite structures, (C_6H_5CH_2NH_2)(CH_3NH_3)_n_-_1Pb_nI_3_n_+_1, through the introduction of CH_3NH_3I molecule vapor into the two-dimensional perovskite C_6H_5CH_2NH_3PbI_4 structure and its application in photovoltaic devices is reported. The dimensionality of (C_6H_5CH_2NH_2)(CH_3NH_3)_n_-_1Pb_nI_3_n_+_1 is controlled using the exposure time to the CH_3NH_3I vapor on the C_6H_5CH_2NH_3PbI_4 perovskite film. As the stacking of the lead iodide lattice increases, the crystallographic planes of the inorganic perovskite compound exhibit vertical growth in order to facilitate efficient charge transport. Furthermore, the devices have a smaller band gap, which offers broader absorption and the potential to increase the photocurrent density in the solar cell. As a result, the photovoltaic device based on the (C_6H_5CH_2NH_2)(CH_3NH_3)_n_-_1Pb_nI_3_n_+_1 perovskite exhibits a power conversion efficiency of 5.43% with a short circuit current density of 14.49 mA cm"−"2, an open circuit voltage of 0.85 V, and a fill factor of 44.30 for the best power conversion efficiency under AM 1.5G solar irradiation (100 mW cm"−"2), which is significantly higher than the 0.34% of the pure two-dimensional BAPbI_4 perovskite-based solar cell.

Stable and Efficient Organo-Metal Halide Hybrid Perovskite Solar Cells via π-Conjugated Lewis Base Polymer Induced Trap Passivation and Charge Extraction.

Science.gov (United States)

Qin, Ping-Li; Yang, Guang; Ren, Zhi-Wei; Cheung, Sin Hang; So, Shu Kong; Chen, Li; Hao, Jianhua; Hou, Jianhui; Li, Gang

2018-03-01

High-quality pinhole-free perovskite film with optimal crystalline morphology is critical for achieving high-efficiency and high-stability perovskite solar cells (PSCs). In this study, a p-type π-conjugated polymer poly[(2,6-(4,8-bis(5-(2-ethylhexyl) thiophen-2-yl)-benzo[1,2-b:4,5-b'] dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl) benzo[1',2'-c:4',5'-c'] dithiophene-4,8-dione))] (PBDB-T) is introduced into chlorobenzene to form a facile and effective template-agent during the anti-solvent process of perovskite film formation. The π-conjugated polymer PBDB-T is found to trigger a heterogeneous nucleation over the perovskite precursor film and passivate the trap states of the mixed perovskite film through the formation of Lewis adducts between lead and oxygen atom in PBDB-T. The p-type semiconducting and hydrophobic PBDB-T polymer fills in the perovskite grain boundaries to improve charge transfer for better conductivity and prevent moisture invasion into the perovskite active layers. Consequently, the PSCs with PBDB-T modified anti-solvent processing leads to a high-efficiency close to 20%, and the devices show excellent stability, retaining about 90% of the initial power conversion efficiency after 150 d storage in dry air. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication and processing of next-generation oxygen carrier materials for chemical looping combustion

Energy Technology Data Exchange (ETDEWEB)

Nadarajah, Arunan [Univ. of Toledo, OH (United States)

2017-04-26

Among numerous methods of controlling the global warming effect, Chemical Looping Combustion is known to be the most viable option currently. A key factor to a successful chemical looping process is the presence of highly effective oxygen carriers that enable fuel combustion by going through oxidation and reduction in the presence of air and fuel respectively. In this study, CaMnO_3-δ was used as the base material and doped on the A-site (Sr or La) and B-site (Fe, Ti, Zn and Al) by 10 mol % of dopants. Solid state reaction followed by mechanical extrusion (optimized paste formula) was used as the preparation method A series of novel doped perovskite-type oxygen carrier particles (Ca_xLa (Or Sa)_1-x Mn_1-yByO_3-δ (B-site = Fe, Ti, Al, or Zr)) were synthesized by the proposed extrusion formula. The produced samples were characterized with XRD, SEM, BET and TGA techniques. According to the results obtained from TGA analysis, the oxygen capacity of the samples ranged between 1.2 for CLMZ and 1.75 for CSMF. Reactivity and oxygen uncoupling behaviors of the prepared samples were also evaluated using a fluidized bed chemical looping reactor using methane as the fuel at four different temperatures (800, 850, 900, 950 °C). All of the oxygen carriers showed oxygen uncoupling behavior and they were able to capture and release oxygen. Mass-based conversion of the perovskites was calculated and temperature increase proved to increase the mass-based conversion rate in all of the samples under study. Gas yield was calculated at 950 °C as well, and results showed that CLMZ, CM and CSMF showed 100% gas yields and CLMF and CSMZ showed approximately 85% yield in fluidized bed reactor, which is a high and acceptable quantity. Based on extended reactor tests the modified calcium manganese perovskite structures (CSMF) can be a good candidate for future pilot tests.

Topotactic oxidative and reductive control of the structures and properties of layered manganese oxychalcogenides.

Science.gov (United States)

Hyett, Geoffrey; Barrier, Nicolas; Clarke, Simon J; Hadermann, Joke

2007-09-12

Topotactic modification, by both oxidation and reduction, of the composition, structures, and magnetic properties of the layered oxychalcogenides Sr4Mn3O7.5Cu2Ch2 (Ch=S, Se) is described. These Mn3+ compounds are composed of alternating perovskite-type strontium manganese oxide slabs separated by anti-fluorite-type copper chalcogenide layers and are intrinsically oxide deficient in the central layer of the perovskite slabs. The systems are unusual examples of perovskite-related compounds that may topotactically be both oxidized by fluorination and reduced by deintercalation of oxygen from the oxide-deficient part of the structure. The compounds exhibit antiferromagnetic ordering of the manganese magnetic moments in the outer layers of the perovskite slabs, while the other moments, in the central layers, exhibit spin-glass-like behavior. Fluorination has the effect of increasing the antiferromagnetic ordering temperature and the size of the ordered moment, whereas reduction destroys magnetic long-range order by introducing chemical disorder which leads to both further disorder and frustration of the magnetic interactions in the manganese oxide slab.

Amine treatment induced perovskite nanowire network in perovskite solar cells: efficient surface passivation and carrier transport

Science.gov (United States)

Xiao, Ke; Cui, Can; Wang, Peng; Lin, Ping; Qiang, Yaping; Xu, Lingbo; Xie, Jiangsheng; Yang, Zhengrui; Zhu, Xiaodong; Yu, Xuegong; Yang, Deren

2018-02-01

In the fabrication of high efficiency organic-inorganic metal halide perovskite solar cells (PSCs), an additional interface modifier is usually applied for enhancing the interface passivation and carrier transport. In this paper, we develop an innovative method with in-situ growth of one-dimensional perovskite nanowire (1D PNW) network triggered by Lewis amine over the perovskite films. To our knowledge, this is the first time to fabricate PSCs with shape-controlled perovskite surface morphology, which improved power conversion efficiency (PCE) from 14.32% to 16.66% with negligible hysteresis. The amine molecule can passivate the trap states on the polycrystalline perovskite surface to reduce trap-state density. Meanwhile, as a fast channel, the 1D PNWs would promote carrier transport from the bulk perovskite film to the electron transport layer. The PSCs with 1D PNW modification not only exhibit excellent photovoltaic performances, but also show good stability with only 4% PCE loss within 30 days in the ambient air without encapsulation. Our results strongly suggest that in-situ grown 1D PNW network provides a feasible and effective strategy for nanostructured optoelectronic devices such as PSCs to achieve superior performances.

A Study on Organic-Metal Halide Perovskite Film Morphology, Interfacial Layers, Tandem Applications, and Encapsulation

Science.gov (United States)

Fisher, Dallas A.

decreased drastically due to poor band alignment. Fe2O3 appears to be better suited to a narrower band gap material than methylammonium lead iodide perovskite. Finally, encapsulation of perovskite devices with epoxy coatings is explored as a method to improve long-term stability. Perovskites are sensitive to a variety of conditions, but most importantly water and polar molecules. Encapsulants act as a moisture/oxygen barrier, but also prevent outgassing of the organic components. Three epoxies were tested in high heat and high humidity conditions. Important factors in the curing process were uncovered such as the sensitivity of UV-epoxies to amine functional groups found in common p-type dopants and perovskite layers. Moisture ingress was the failure point for high-humidity/heat devices which was confirmed through conversion to yellow lead iodide. A revised device fabrication method is proposed to reduce moisture ingress for future experiments.

Investigation on the structural, magnetic and magnetocaloric properties of nanocrystalline Pr-deficient Pr1-xSrxMnO3-δ manganites

Science.gov (United States)

Arun, B.; Athira, M.; Akshay, V. R.; Sudakshina, B.; Mutta, Geeta R.; Vasundhara, M.

2018-02-01

We have investigated the structural, magnetic and magnetocaloric properties of nanocrystalline Pr-deficient Pr1-xSrxMnO3-δ Perovskite manganites. Rietveld refinement of the X-ray powder diffraction patterns confirms that all the studied compounds have crystallized into an orthorhombic structure with Pbnm space group. Transmission electron microscopy analysis reveals nanocrystalline compounds with crystallite size less than 50 nm. The selected area electron diffraction patterns reveal the highly crystalline nature of the compounds and energy dispersive X-ray spectroscopic analysis shows that the obtained compositions are nearly identical with the nominal one. The oxygen stoichiometry is estimated by iodometric titration method and stoichiometric compositions are confirmed by X-ray Fluorescence Spectrometry analysis. A large bifurcation is observed in the ZFC/FC curves and Arrott plots not show a linear relation but have a convex curvature nature. The temperature dependence of inverse magnetic susceptibility at higher temperature confirms the existence of ferromagnetic clusters. The experimental results reveal that the reduction of crystallite size to nano metric scale in Pr-deficient manganites adversely influences structural, magnetic and magnetocaloric properties as compared to its bulk counterparts reported earlier.

Incorporation effect of nanosized perovskite LaFe₀.₇Co₀.₃O₃ on the electrochemical activity of Pt nanoparticles-multi walled carbon nanotube composite toward methanol oxidation

Energy Technology Data Exchange (ETDEWEB)

Noroozifar, Meissam, E-mail: mnoroozifar@chem.usb.ac.ir [Department of Chemistry, University of Sistan and Baluchestan, PO Box 98155-147, Zahedan (Iran, Islamic Republic of); Khorasani-Motlagh, Mozhgan; Khaleghian-Moghadam, Roghayeh; Ekrami-Kakhki, Mehri-Saddat; Shahraki, Mohammad [Department of Chemistry, University of Sistan and Baluchestan, PO Box 98155-147, Zahedan (Iran, Islamic Republic of)

2013-05-01

Nanosized perovskite LaFe₀.₇Co₀.₃O₃ (LFCO) is synthesized through conventional co-precipitation method and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques. The incorporation effect of the mentioned perovskite to catalytic activity of the PtNPs-MWCNTs-nafion (or -chitosan) catalyst toward methanol oxidation has been studied by cyclic voltammetry. Based on the electrochemical studies, all MWCNTs-PtNPs-nafion (or chitosan) and MWCNTs-PtNPs-LFCO-nafion (or chitosan) catalysts show a considerable activity for methanol oxidation. However, a synergistic effect is observed when LFCO is added to the catalyst by decreasing the poisoning rate of the Pt catalyst. - Graphical abstract: Nanosized perovskite LaFe₀.₇Co₀.₃O₃ is synthesized and characterized. The incorporation effect of the mentioned perovskite to catalytic activity of the PtNPS-MWCNTs-nafion (or -chitosan) catalyst toward methanol oxidation is studied. Highlights: • Nanocrystalline LaFe₀.₇Co₀.₃O₃ (LFCO) is prepared by a new simple co-precipitation method. • Effect of LFCO to catalytic activity of PtNPS for methanol oxidation is studied. • A synergistic effect is observed when LFCO is added to the Pt catalyst. • Oxygen of LFCO could be considered as active oxygen to remove CO intermediates.

Cooperative Couplings between Octahedral Rotations and Ferroelectricity in Perovskites and Related Materials

Science.gov (United States)

Gu, Teng; Scarbrough, Timothy; Yang, Yurong; Íñiguez, Jorge; Bellaiche, L.; Xiang, H. J.

2018-05-01

The structure of AB O 3 perovskites is dominated by two types of unstable modes, namely, the oxygen octahedral rotation (AFD) and ferroelectric (FE) mode. It is generally believed that such AFD and FE modes tend to compete and suppress each other. Here we use first-principles methods to show that a dual nature of the FE-AFD coupling, which turns from competitive to cooperative as the AFD mode strengthens, occurs in numerous perovskite oxides. We provide a unified model of such a dual interaction by introducing novel high-order coupling terms and explain the atomistic origin of the resulting new form of ferroelectricity in terms of universal steric mechanisms. We also predict that such a novel form of ferroelectricity leads to atypical behaviors, such as an enhancement of all the three Cartesian components of the electric polarization under hydrostatic pressure and compressive epitaxial strain.

A new route of synthesizing perovskite nanotubes by templating approach

Science.gov (United States)

Habiballah, Anisah Shafiqah; Osman, Nafisah; Jani, Abdul Mutalib Md

2017-09-01

A perovskite oxide for example Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) has attracted growing attention due to its high catalytic activity and mixed ionic/electronic conductivity. Recent research of BSCF is more comprehensively based on a remarkable trajectory of innovation, in particular with regards to the synthesis of perovskite structures in one-dimensional (1-D) nanometric scales as they promote not only to increase an active electrode area for the oxygen reduction reaction, but also allow the tailoring of electrode's architecture. Nevertheless, achieving the desired 1-D structure by a conventional method such as hydrothermal, solvothermal, or sonochemical are far from satisfactory. Herein, the aim of this work is to synthesize the BSCF perovskite nanotubes via soft templating approach, particularly using anodic aluminium oxide (AAO) as a template, focusing on the morphology, composition and structural properties were demonstrated. After the AAO template was anodized at 80 V, the fabricated template was clamped between apair of spectroscopic cells containing BSCF sol and deionized water (with a hole of both sides) for 24 hours. After that, the sample was removed from the cells followed by heat treatment process. The FESEM images showed that BSCF nanotubes were successfully achieved, with the diameter of the nanotubes' approximately 80 nm. The EDX result also confirmed the nominal stoichiometry of Ba0.5Sr0.5Co0.8Fe0.2O3-δ. Meanwhile, the XRD pattern confirmed a single crystalline phase of BSCF nanotubes was successfully obtained and congruent to a cubic perovskite structure of BSCF. Possible formation mechanism,as well as the schematic illustration of BSCF nanotubes inside the template was also discussed in this paper.

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

KAUST Repository

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.

Paintable Carbon-Based Perovskite Solar Cells with Engineered Perovskite/Carbon Interface Using Carbon Nanotubes Dripping Method.

Science.gov (United States)

Ryu, Jaehoon; Lee, Kisu; Yun, Juyoung; Yu, Haejun; Lee, Jungsup; Jang, Jyongsik

2017-10-01

Paintable carbon electrode-based perovskite solar cells (PSCs) are of particular interest due to their material and fabrication process costs, as well as their moisture stability. However, printing the carbon paste on the perovskite layer limits the quality of the interface between the perovskite layer and carbon electrode. Herein, an attempt to enhance the performance of the paintable carbon-based PSCs is made using a modified solvent dripping method that involves dripping of the carbon nanotubes (CNTs), which is dispersed in chlorobenzene solution. This method allows CNTs to penetrate into both the perovskite film and carbon electrode, facilitating fast hole transport between the two layers. Furthermore, this method is results in increased open circuit voltage (V oc ) and fill factor (FF), providing better contact at the perovskite/carbon interfaces. The best devices made with CNT dripping show 13.57% power conversion efficiency and hysteresis-free performance. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

KAUST Repository

Bera, Ashok; Wu, Kewei; Sheikh, Arif D.; Alarousu, Erkki; Mohammed, Omar F.; Wu, Tao

2014-01-01

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.

Organic-inorganic perovskites containing trivalent metal halide layers: the templating influence of the organic cation layer.

Science.gov (United States)

Mitzi, D B

2000-12-25

Thin sheetlike crystals of the metal-deficient perovskites (H2AEQT)M2/3I4 [M = Bi or Sb; AEQT = 5,5"'-bis-(aminoethyl)-2,2':5',2'':5'',2'''-quaterthiophene] were formed from slowly cooled ethylene glycol/2-butanol solutions containing the bismuth(III) or antimony(III) iodide and AEQT.2HI salts. Each structure was refined in a monoclinic (C2/m) subcell, with the lattice parameters a = 39.712(13) A, b = 5.976(2) A, c = 6.043(2) A, beta = 92.238(5) degrees, and Z = 2 for M = Bi and a = 39.439(7) A, b = 5.952(1) A, c = 6.031(1) A, beta = 92.245(3) degrees, and Z = 2 for M = Sb. The trivalent metal cations locally adopt a distorted octahedral coordination, with M-I bond lengths ranging from 3.046(1) to 3.218(3) A (3.114 A average) for M = Bi and 3.012(1) to 3.153(2) A (3.073 A average) for M = Sb. The new organic-inorganic hybrids are the first members of a metal-deficient perovskite family consisting of (Mn+)2/nV(n-2)/nX4(2-) sheets, where V represents a vacancy (generally left out of the formula) and the metal cation valence, n, is greater than 2. The organic layers in the AEQT-based organic-inorganic hybrids feature edge-to-face aromatic interactions among the rigid, rodlike quaterthiophene moieties, which may help to stabilize the unusual metal-deficient layered structures.

Ordered perovskites with cationic vacancies. 11. System Ba/sub 2/Gd/sub 2/3/vacant/sub 1/3/U/sub 1-x/W/sub x/O/sub 6/

Energy Technology Data Exchange (ETDEWEB)

Wischert, W; Oelkrug, D; Schittenhelm, H J; Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Lehrstuhl fuer Anorganische Chemie 2

1982-12-01

The cation deficient polymorphic perovskites Ba/sub 2/Gd/sub 2/3/vacant/sub 1/3/UO/sub 6/ and Ba/sub 2/Gd/sub 2/3/vacant/sub 1/3/WO/sub 6/ form a continuous series of mixed crystals, which crystallize over a wide range (x = 0.1 up to 0.99) in a cubic 1:1 ordered perovskite lattice. According to the investigations of the vibrational spectra, the diffuse reflectance spectra, and the photoluminescence - opposite to isostructural perovskites wihout vacancies - different species of UO/sub 6/ and WO/sub 6/ octahedra are present. Numerous differences in properties - e.g. an orange emission colour in comparison with a green one by absence of vacancies - are based upon that.

Oxyfluoride Chemistry of Layered Perovskite Compounds

Directory of Open Access Journals (Sweden)

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.

Perovskite Superlattices as Tunable Microwave Devices

Science.gov (United States)

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.

Efficient Luminescence from Perovskite Quantum Dot Solids

KAUST Repository

Kim, Younghoon; Yassitepe, Emre; Voznyy, Oleksandr; Comin, Riccardo; Walters, Grant; Gong, Xiwen; Kanjanaboos, Pongsakorn; Nogueira, Ana F.; Sargent, Edward H.

2015-01-01

© 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.

Efficient Luminescence from Perovskite Quantum Dot Solids

KAUST Repository

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.

Neutral- and Multi-Colored Semitransparent Perovskite Solar Cells.

Science.gov (United States)

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

2016-04-11

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 solar cells with distinctive color generation, which are enabled by engineering the band gap of the perovskite light-harvesting semiconductors with chemical management and integrating with photonic nanostructures, including microcavity, are discussed. We conclude by providing future research directions toward further performance improvements of the semitransparent perovskite solar cells.

Development of High Efficiency Four-Terminal Perovskite-Silicon Tandems

Science.gov (United States)

Duong, The Duc

This thesis is concerned with the development of high efficiency four-terminal perovskite-silicon tandem solar cells with the potential to reduce the cost of solar energy. The work focuses on perovskite top cells and can be divided into three main parts: developing low parasitic absorption and efficient semi-transparent perovskite cells, doping perovskite materials with rubidium, and optimizing perovskite material's bandgap with quadruple-cation and mixed-halide. A further section investigates the light stability of optimized bandgap perovskite cells. In a four-terminal mechanically stacked tandem, the perovskite top cell requires two transparent contacts at both the front and rear sides. Through detailed optical and electrical power loss analysis of the tandem efficiency due to non-ideal properties of the two transparent contacts, optimal contact parameters in term of sheet resistance and transparency are identified. Indium doped tin oxide by sputtering is used for both two transparent contacts and their deposition parameters are optimized separately. The semi-transparent perovskite cell using MAPbI3 has an efficiency of more than 12% with less than 12% parasitic absorption and up to 80% transparency in the long wavelength region. Using a textured foil as anti-reflection coating, an outstanding average transparency of 84% in the long wavelength is obtained. The low parasitic absorption allows an opaque version of the semi-transparent perovskite cell to operate efficiently in a filterless spectrum splitting perovskite-silicon tandem configuration. To further enhance the performance of perovskite cells, it is essential to improve the quality of perovskite films. This can be achieved with mixed-perovskite FAPbI3/MAPbBr3. However, mixed-perovskite films normally contain small a small amount of a non-perovskite phase, which is detrimental for the cell performance. Rb-doping is found to eliminate the formation of the non-perovskite phase and enhance the crystallinity of

Environmentally Friendly Plasma-Treated PEDOT:PSS as Electrodes for ITO-Free Perovskite Solar Cells.

Science.gov (United States)

Vaagensmith, Bjorn; Reza, Khan Mamun; Hasan, Md Nazmul; Elbohy, Hytham; Adhikari, Nirmal; Dubey, Ashish; Kantack, Nick; Gaml, Eman; Qiao, Qiquan

2017-10-18

Solution processed poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) transparent electrodes (TEs) offer great potential as a low cost alternative to expensive indium tin oxide (ITO). However, strong acids are typically used for enhancing the conductivity of PEDOT:PSS TEs, which produce processing complexity and environmental issues. This work presents an environmentally friendly acid free approach to enhance the conductivity of PEDOT:PSS using a light oxygen plasma treatment, in addition to solvent blend additives and post treatments. The plasma treatment was found to significantly reduce the sheet resistance of PEDOT:PSS TEs from 85 to as low as 15 Ω sq -1 , which translates to the highest reported conductivity of 5012 S/cm for PEDOT:PSS TEs. The plasma treated PEDOT:PSS TE resulted in an ITO-free perovskite solar cell efficiency of 10.5%, which is the highest reported efficiency for ITO-free perovskite solar cells with a PEDOT:PSS electrode that excludes the use of acid treatments. This research presents the first demonstration of this technology. Moreover, the PEDOT:PSS TEs enabled better charge extraction from the perovskite solar cells and reduced hysteresis in the current density-voltage (J-V) curves.

In Situ Studies of the Temperature-Dependent Surface Structure and Chemistry of Single-Crystalline (001)-Oriented La 0.8 Sr 0.2 CoO 3−δ Perovskite Thin Films

KAUST Repository

Feng, Zhenxing; Crumlin, Ethan J.; Hong, Wesley T.; Lee, Dongkyu; Mutoro, Eva; Biegalski, Michael D.; Zhou, Hua; Bluhm, Hendrik; Christen, Hans M.; Shao-Horn, Yang

2013-01-01

Perovskites are used to promote the kinetics of oxygen electrocatalysis in solid oxide fuel cells and oxygen permeation membranes. Little is known about the surface structure and chemistry of perovskites at high temperatures and partial oxygen pressures. Combining in situ X-ray reflectivity (XRR) and in situ ambient pressure X-ray photoelectron spectroscopy (APXPS), we report, for the first time, the evolution of the surface structure and chemistry of (001)-oriented perovskite La0.8Sr0.2CoO 3-δ (LSC113) and (La0.5Sr 0.5)2CoO4+δ (LSC214)-decorated LSC113 (LSC113/214) thin films as a function of temperature. Heating the (001)-oriented LSC113 surface leads to the formation of surface LSC214-like particles, which is further confirmed by ex situ Auger electron spectroscopy (AES). In contrast, the LSC113/214 surface, with activities much higher than that of LSC 113, is stable upon heating. Combined in situ XRR and APXPS measurements support that Sr enrichment may occur at the LSC113 and LSC214 interface, which can be responsible for its markedly enhanced activities. © 2013 American Chemical Society.

In Situ Studies of the Temperature-Dependent Surface Structure and Chemistry of Single-Crystalline (001)-Oriented La 0.8 Sr 0.2 CoO 3−δ Perovskite Thin Films

KAUST Repository

Feng, Zhenxing

2013-05-02

Perovskites are used to promote the kinetics of oxygen electrocatalysis in solid oxide fuel cells and oxygen permeation membranes. Little is known about the surface structure and chemistry of perovskites at high temperatures and partial oxygen pressures. Combining in situ X-ray reflectivity (XRR) and in situ ambient pressure X-ray photoelectron spectroscopy (APXPS), we report, for the first time, the evolution of the surface structure and chemistry of (001)-oriented perovskite La0.8Sr0.2CoO 3-δ (LSC113) and (La0.5Sr 0.5)2CoO4+δ (LSC214)-decorated LSC113 (LSC113/214) thin films as a function of temperature. Heating the (001)-oriented LSC113 surface leads to the formation of surface LSC214-like particles, which is further confirmed by ex situ Auger electron spectroscopy (AES). In contrast, the LSC113/214 surface, with activities much higher than that of LSC 113, is stable upon heating. Combined in situ XRR and APXPS measurements support that Sr enrichment may occur at the LSC113 and LSC214 interface, which can be responsible for its markedly enhanced activities. © 2013 American Chemical Society.

Photocatalysis: HI-time for perovskites

DEFF Research Database (Denmark)

Vesborg, Peter Christian Kjærgaard

2017-01-01

Organolead halide perovskite solar absorbers demonstrate high photovoltaic efficiencies but they are notorious for their intolerance to water. Now, methylammonium lead iodide perovskites are used to harvest solar energy — in water — via photocatalytic generation of hydrogen from solutions...

Planar-integrated single-crystalline perovskite photodetectors

KAUST Repository

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.

Making and Breaking of Lead Halide Perovskites

KAUST Repository

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

Tunable thermodynamic activity of LaxSr1–xMnyAl1–yO3–δ (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) perovskites for solar thermochemical fuel synthesis† †Electronic supplementary information (ESI) available: Computational details, comprehensive XRD analyses, oxygen nonstoichiometry measurements and thermodynamic characterization of the perovskites. See DOI: 10.1039/c6ta06644e Click here for additional data file.

Science.gov (United States)

Ezbiri, M.; Takacs, M.; Theiler, D.; Steinfeld, A.

2017-01-01

Nonstoichiometric metal oxides with variable valence are attractive redox materials for thermochemical and electrochemical fuel processing. To guide the design of advanced redox materials for solar-driven splitting of CO2 and/or H2O to produce CO and/or H2 (syngas), we investigate the equilibrium thermodynamics of the LaxSr1–xMnyAl1–yO3–δ perovskite family (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) and La0.6Ca0.4Mn0.8Al0.2O3–δ, and compare them to those of CeO2 as the baseline. Oxygen nonstoichiometry measurements from 1573 to 1773 K and from 0.206 to 180 mbar O2 show a tunable reduction extent, increasing with increasing Sr content. Maximal nonstoichiometry of 0.32 is established with La0.2Sr0.8Mn0.8Al0.2O3–δ at 1773 K and 2.37 mbar O2. As a trend, we find that oxygen capacities are most sensitive to the A-cation composition. Partial molar enthalpy, entropy and Gibbs free energy changes for oxide reduction are extracted from the experimental data using defect models for Mn4+/Mn3+ and Mn3+/Mn2+ redox couples. We find that perovskites exhibit typically decreasing enthalpy changes with increasing nonstoichiometries. This desirable characteristic is most pronounced by La0.6Sr0.4Mn0.4Al0.6O3–δ, rendering it attractive for CO2 and H2O splitting. Generally, perovskites show lower enthalpy and entropy changes than ceria, resulting in more favorable reduction but less favorable oxidation equilibria. The energy penalties due to larger temperature swings and excess oxidants are discussed in particular. Using electronic structure theory, we conclude with a practical methodology estimating thermodynamic activity to rationally design perovskites with variable stoichiometry and valence. PMID:28580143

Parity-Forbidden Transitions and Their Impact on the Optical Absorption Properties of Lead-Free Metal Halide Perovskites and Double Perovskites.

Science.gov (United States)

Meng, Weiwei; Wang, Xiaoming; Xiao, Zewen; Wang, Jianbo; Mitzi, David B; Yan, Yanfa

2017-07-06

Using density functional theory calculations, we analyze the optical absorption properties of lead (Pb)-free metal halide perovskites (AB 2+ X 3 ) and double perovskites (A 2 B + B 3+ X 6 ) (A = Cs or monovalent organic ion, B 2+ = non-Pb divalent metal, B + = monovalent metal, B 3+ = trivalent metal, X = halogen). We show that if B 2+ is not Sn or Ge, Pb-free metal halide perovskites exhibit poor optical absorptions because of their indirect band gap nature. Among the nine possible types of Pb-free metal halide double perovskites, six have direct band gaps. Of these six types, four show inversion symmetry-induced parity-forbidden or weak transitions between band edges, making them not ideal for thin-film solar cell applications. Only one type of Pb-free double perovskite shows optical absorption and electronic properties suitable for solar cell applications, namely, those with B + = In, Tl and B 3+ = Sb, Bi. Our results provide important insights for designing new metal halide perovskites and double perovskites for optoelectronic applications.

Ionic conductivity in new perovskite type oxides: NaAZrMO6 (A = Ca or Sr; M = Nb or Ta)

International Nuclear Information System (INIS)

Rajendran, Deepthi N.; Ravindran Nair, K.; Prabhakar Rao, P.; Sibi, K.S.; Koshy, Peter; Vaidyan, V.K.

2008-01-01

New oxides of the type, NaAZrMO 6 (M = Ca or Sr; M = Nb or Ta), have been prepared by the solid-state reaction technique. Phase identification by powder X-ray diffraction (XRD) shows that NaCaZrMO 6 has orthorhombic perovskite type structure (Pnma) and NaSrZrMO 6 has cubic perovskite type structure (Pm3m). The grain morphology observation by scanning electron microscope (SEM) shows well-sintered grains. ac impedance spectra and electrical conductivity measurements in air, oxygen and nitrogen atmospheres indicate that they are probable oxide ion conductors with ionic conductivities of the order of 10 -3 S cm -1 at 750 deg. C

Symmetry mismatch-driven perpendicular magnetic anisotropy for perovskite/brownmillerite heterostructures.

Science.gov (United States)

Zhang, Jing; Zhong, Zhicheng; Guan, Xiangxiang; Shen, Xi; Zhang, Jine; Han, Furong; Zhang, Hui; Zhang, Hongrui; Yan, Xi; Zhang, Qinghua; Gu, Lin; Hu, Fengxia; Yu, Richeng; Shen, Baogen; Sun, Jirong

2018-05-15

Grouping different transition metal oxides together by interface engineering is an important route toward emergent phenomenon. While most of the previous works focused on the interface effects in perovskite/perovskite heterostructures, here we reported on a symmetry mismatch-driven spin reorientation toward perpendicular magnetic anisotropy in perovskite/brownmillerite heterostructures, which is scarcely seen in tensile perovskite/perovskite heterostructures. We show that alternately stacking perovskite La 2/3 Sr 1/3 MnO 3 and brownmillerite LaCoO 2.5 causes a strong interface reconstruction due to symmetry discontinuity at interface: neighboring MnO 6 octahedra and CoO 4 tetrahedra at the perovskite/brownmillerite interface cooperatively relax in a manner that is unavailable for perovskite/perovskite interface, leading to distinct orbital reconstructions and thus the perpendicular magnetic anisotropy. Moreover, the perpendicular magnetic anisotropy is robust, with an anisotropy constant two orders of magnitude greater than the in-plane anisotropy of the perovskite/perovskite interface. The present work demonstrates the great potential of symmetry engineering in designing artificial materials on demand.

Planar-integrated single-crystalline perovskite photodetectors

KAUST Repository

Saidaminov, Makhsud I.; Adinolfi, Valerio; Comin, Riccardo; Abdelhady, Ahmed L.; Peng, Wei; Dursun, Ibrahim; Yuan, Mingjian; Hoogland, Sjoerd; Sargent, Edward H.; Bakr, Osman

2015-01-01

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

Highly Efficient Spectrally Stable Red Perovskite Light-Emitting Diodes.

Science.gov (United States)

Tian, Yu; Zhou, Chenkun; Worku, Michael; Wang, Xi; Ling, Yichuan; Gao, Hanwei; Zhou, Yan; Miao, Yu; Guan, Jingjiao; Ma, Biwu

2018-05-01

Perovskite light-emitting diodes (LEDs) have recently attracted great research interest for their narrow emissions and solution processability. Remarkable progress has been achieved in green perovskite LEDs in recent years, but not blue or red ones. Here, highly efficient and spectrally stable red perovskite LEDs with quasi-2D perovskite/poly(ethylene oxide) (PEO) composite thin films as the light-emitting layer are reported. By controlling the molar ratios of organic salt (benzylammonium iodide) to inorganic salts (cesium iodide and lead iodide), luminescent quasi-2D perovskite thin films are obtained with tunable emission colors from red to deep red. The perovskite/polymer composite approach enables quasi-2D perovskite/PEO composite thin films to possess much higher photoluminescence quantum efficiencies and smoothness than their neat quasi-2D perovskite counterparts. Electrically driven LEDs with emissions peaked at 638, 664, 680, and 690 nm have been fabricated to exhibit high brightness and external quantum efficiencies (EQEs). For instance, the perovskite LED with an emission peaked at 680 nm exhibits a brightness of 1392 cd m -2 and an EQE of 6.23%. Moreover, exceptional electroluminescence spectral stability under continuous device operation has been achieved for these red perovskite LEDs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Water-Induced Dimensionality Reduction in Metal-Halide Perovskites

KAUST Repository

Turedi, Bekir

2018-03-30

Metal-halide perovskite materials are highly attractive materials for optoelectronic applications. However, the instability of perovskite materials caused by moisture and heat-induced degradation impairs future prospects of using these materials. Here we employ water to directly transform films of the three-dimensional (3D) perovskite CsPbBr3 to stable two-dimensional (2D) perovskite-related CsPb2Br5. A sequential dissolution-recrystallization process governs this water induced transformation under PbBr2 rich condition. We find that these post-synthesized 2D perovskite-related material films exhibit excellent stability against humidity and high photoluminescence quantum yield. We believe that our results provide a new synthetic method to generate stable 2D perovskite-related materials that could be applicable for light emitting device applications.

BMI-1 Mediates Estrogen-Deficiency-Induced Bone Loss by Inhibiting Reactive Oxygen Species Accumulation and T Cell Activation.

Science.gov (United States)

Li, Jinbo; Wang, Qian; Yang, Renlei; Zhang, Jiaqi; Li, Xing; Zhou, Xichao; Miao, Dengshun

2017-05-01

Previous studies have shown that estrogen regulates bone homeostasis through regulatory effects on oxidative stress. However, it is unclear how estrogen deficiency triggers reactive oxygen species (ROS) accumulation. Recent studies provide evidence that the B lymphoma Mo-MLV insertion region 1 (BMI-1) plays a critical role in protection against oxidative stress and that this gene is directly regulated by estrogen via estrogen receptor (ER) at the transcriptional level. In this study, ovariectomized mice were given drinking water with/without antioxidant N-acetyl-cysteine (NAC, 1 mg/mL) supplementation, and compared with each other and with sham mice. Results showed that ovariectomy resulted in bone loss with increased osteoclast surface, increased ROS levels, T cell activation, and increased TNF and RANKL levels in serum and in CD4 T cells; NAC supplementation largely prevented these alterations. BMI-1 expression levels were dramatically downregulated in CD4 T cells from ovariectomized mice. We supplemented drinking water to BMI-1-deficient mice with/without NAC and compared them with each other and with wild-type (WT) mice. We found that BMI-1 deficiency mimicked alterations observed in ovariectomy whereas NAC supplementation reversed all alterations induced by BMI-1 deficiency. Because T cells are critical in mediating ovariectomy-induced bone loss, we further assessed whether BMI-1 overexpression in lymphocytes can protect against estrogen deficiency-induced osteoclastogenesis and bone loss by inhibiting oxidative stress, T cell activation, and RANKL production. When WT and Eμ-BMI-1 transgenic mice with BMI-1 specifically overexpressed in lymphocytes were ovariectomized and compared with each other and with WT sham mice, we found that BMI-1 overexpression in lymphocytes clearly reversed all alterations induced by ovariectomy. Results from this study indicate that estrogen deficiency downregulates BMI-1 and subsequently increases ROS, T cell activation, and

Fabrication of Semiconducting Methylammonium Lead Halide Perovskite Particles by Spray Technology

Science.gov (United States)

Ahmadian-Yazdi, Mohammad-Reza; Eslamian, Morteza

2018-01-01

In this "nano idea" paper, three concepts for the preparation of methylammonium lead halide perovskite particles are proposed, discussed, and tested. The first idea is based on the wet chemistry preparation of the perovskite particles, through the addition of the perovskite precursor solution to an anti-solvent to facilitate the precipitation of the perovskite particles in the solution. The second idea is based on the milling of a blend of the perovskite precursors in the dry form, in order to allow for the conversion of the precursors to the perovskite particles. The third idea is based on the atomization of the perovskite solution by a spray nozzle, introducing the spray droplets into a hot wall reactor, so as to prepare perovskite particles, using the droplet-to-particle spray approach (spray pyrolysis). Preliminary results show that the spray technology is the most successful method for the preparation of impurity-free perovskite particles and perovskite paste to deposit perovskite thin films. As a proof of concept, a perovskite solar cell with the paste prepared by the sprayed perovskite powder was successfully fabricated.

Fabrication of Semiconducting Methylammonium Lead Halide Perovskite Particles by Spray Technology.

Science.gov (United States)

Ahmadian-Yazdi, Mohammad-Reza; Eslamian, Morteza

2018-01-10

In this "nano idea" paper, three concepts for the preparation of methylammonium lead halide perovskite particles are proposed, discussed, and tested. The first idea is based on the wet chemistry preparation of the perovskite particles, through the addition of the perovskite precursor solution to an anti-solvent to facilitate the precipitation of the perovskite particles in the solution. The second idea is based on the milling of a blend of the perovskite precursors in the dry form, in order to allow for the conversion of the precursors to the perovskite particles. The third idea is based on the atomization of the perovskite solution by a spray nozzle, introducing the spray droplets into a hot wall reactor, so as to prepare perovskite particles, using the droplet-to-particle spray approach (spray pyrolysis). Preliminary results show that the spray technology is the most successful method for the preparation of impurity-free perovskite particles and perovskite paste to deposit perovskite thin films. As a proof of concept, a perovskite solar cell with the paste prepared by the sprayed perovskite powder was successfully fabricated.

Dissolution-recrystallization method for high efficiency perovskite solar cells

Energy Technology Data Exchange (ETDEWEB)

Han, Fei; Luo, Junsheng; Wan, Zhongquan; Liu, Xingzhao; Jia, Chunyang, E-mail: cyjia@uestc.edu.cn

2017-06-30

Highlights: • Dissolution-recrystallization method can improve perovskite crystallization. • Dissolution-recrystallization method can improve TiO{sub 2}/perovskite interface. • The optimal perovskite solar cell obtains the champion PCE of 16.76%. • The optimal devices are of high reproducibility. - Abstract: In this work, a dissolution-recrystallization method (DRM) with chlorobenzene and dimethylsulfoxide treating the perovskite films during the spin-coating process is reported. This is the first time that DRM is used to control perovskite crystallization and improve the device performance. Furthermore, the DRM is good for reducing defects and grain boundaries, improving perovskite crystallization and even improving TiO{sub 2}/perovskite interface. By optimizing, the DRM2-treated perovskite solar cell (PSC) obtains the best photoelectric conversion efficiency (PCE) of 16.76% under AM 1.5 G illumination (100 mW cm{sup −2}) with enhanced J{sub sc} and V{sub oc} compared to CB-treated PSC.

Trace Element Abundances in an Unusual Hibonite-Perovskite Refractory Inclusion from Allende

Science.gov (United States)

Mane, Prajkta; Wadhwa, M.; Keller, L. P.

2013-01-01

Calcium-aluminum-rich refractory inclusions (CAIs) are thought to be the first-formed solids in the Solar protoplanetary disk and can provide information about the earliest Solar System processes (e.g., [1]). A hibonite-perovskitebearing CAI from the Allende CV3 chondrite (SHAL, [2]) contains a single of 500 micrometers hibonite grain and coarse-grained perovskite. The mineralogy and oxygen isotopic composition of this CAI shows similarities with FUN inclusions, especially HAL [2]. Here we present trace element abundances in SHAL.

Synthesis and electrocatalytic properties of La0.8Sr0.2FeO3−δ perovskite oxide for oxygen reactions

Directory of Open Access Journals (Sweden)

R.A. Silva

2017-09-01

Full Text Available Perovskites are important alternatives for precious metals as catalysts for bifunctional oxygen electrodes, involving oxygen evolution (OER and reduction (ORR reactions as is the case of regenerative fuel cells. In this work, strontium doped lanthanum ferrite La1−xSrxFeO3−δ (x = 0; 0.1; 0.2; 0.3; 0.4; 0.6 and 1.0 powders were prepared by a self-combustion route. The oxides, in the form of carbon paste electrodes, were characterised by cyclic voltammetry in alkaline solutions. Data analyses lead to the selection of La0.8Sr0.2FeO3−δ to prepare gas diffusion electrodes (GDEs. Cyclic voltammetry and steady state polarization curves were used, respectively, to assess the electrochemical behaviour of GDEs and to obtain kinetic data for both OER and ORR. It is concluded that the oxide preparation conditions/electrode configuration determine the electrode performance. The bifunctionality of the electrodes was assessed, under galvanostatic control, using a cycling protocol within the potential domains for OER and ORR. The potential window, i.e., the total combined overpotential between OER and ORR was found to be of ≈770 mV, value which compares well with that obtained under potentiostatic control. Even though the potential window keeps constant during 140 cycles, the increase in cycling time and/or current density (≥2.5 mA·cm−2 led to a gradual metallization of the GDE surface, as confirmed by Scanning Electron Microscopy and X-ray diffraction analysis.

Two-Photon Absorption in Organometallic Bromide Perovskites

KAUST Repository

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.

Two-Photon Absorption in Organometallic Bromide Perovskites

KAUST Repository

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

2015-01-01

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.

Plasma oxidation of the high T/sub c/ superconducting perovskites

International Nuclear Information System (INIS)

Bagley, B.G.; Greene, L.H.; Tarascon, J.; Hull, G.W.

1987-01-01

A near room-temperature plasma oxidation process is shown to restore superconductivity and metalliclike behavior in oxygen deficient La/sub 2-//sub x/ Sr/sub x/ CuO/sub 4-//sub y/ and YBa 2 Cu 3 O/sub 7-//sub x/ compounds. In the YBa 2 Cu 3 O/sub 7-//sub x/ compound the conversion from an oxygen deficient n-type tetragonal to the p-type orthorhombic phase with a concomitant factor of 5 x 10 5 increase in room-temperature conductivity is also accomplished. This process is of technological importance because oxygen can be restored in these materials at temperatures compatible with device processing. Of scientific interest, the process allows us to carefully control the oxidation state and thereby systematically study the 90 and 55 K superconducting transitions in YBa 2 Cu 3 O/sub 7-//sub x/

Oxygen transport in La0.6Sr0.4Co1-yFeyO3-d

NARCIS (Netherlands)

Bouwmeester, Henricus J.M.; den Otter, M.W.; Boukamp, Bernard A.

2004-01-01

The surface exchange coefficient and chemical diffusion coefficient of oxygen for the perovskites La0.6Sr0.4Co1–yFeyO3–delta (y=0.2, 0.5 and 0.8) were measured using the conductivity relaxation technique. Measurements were performed between 600 and 800 °C in an oxygen partial pressure range between

Group theoretical analysis of octahedral tilting in perovskites

International Nuclear Information System (INIS)

Howard, C.J.; Stokes, H.T.

1998-01-01

Full text: Structures of the perovskite family, ABX 3 , have interested crystallographers over many years, and continue to attract attention on account of their fascinating electrical and magnetic properties, for example the giant magnetoresistive effects exhibited by certain perovskite materials. The ideal perovskite (cubic, space group Pm -/3 m) is a particularly simple structure, but also a demanding one, since aside from the lattice parameter there are no variable parameters in the structure. Consequently, the majority of perovskite structures are distorted perovskites (hettotypes), the most common distortion being the corner-linked tilting of the practically rigid BX 6 octahedral units. In this work, group theoretical methods have been applied to the study of octahedral tilting in perovskites. The only irreducible representations of the parent group (Pm -/3 m) which produce octahedral tilting subject to corner-linking constraints are M + / 3 and R 4 ' + . A six-dimensional order parameter in the reducible representation space of M + / 3 + R + / 4 describes the different possible tilting patterns. The space groups for the different perovskites are then simply the isotropy subgroups, comprising those operations which leave the order parameter invariant. The isotropy subgroups are obtained from a computer program or tabulations. The analysis yields a list of fifteen possible space groups for perovskites derived through octahedral tilting. A connection is made to the (twenty-three) tilt systems given previously by Glazer. The group-subgroup relationships have been derived and displayed. It is interesting to note that all known perovskites based on octahedral tilting conform with the fifteen space groups on our list, with the exception of one perovskite at high temperature, the structure of which seems poorly determined

Thermochromic halide perovskite solar cells.

Science.gov (United States)

Lin, Jia; Lai, Minliang; Dou, Letian; Kley, Christopher S; Chen, Hong; Peng, Fei; Sun, Junliang; Lu, Dylan; Hawks, Steven A; Xie, Chenlu; Cui, Fan; Alivisatos, A Paul; Limmer, David T; Yang, Peidong

2018-03-01

Smart photovoltaic windows represent a promising green technology featuring tunable transparency and electrical power generation under external stimuli to control the light transmission and manage the solar energy. Here, we demonstrate a thermochromic solar cell for smart photovoltaic window applications utilizing the structural phase transitions in inorganic halide perovskite caesium lead iodide/bromide. The solar cells undergo thermally-driven, moisture-mediated reversible transitions between a transparent non-perovskite phase (81.7% visible transparency) with low power output and a deeply coloured perovskite phase (35.4% visible transparency) with high power output. The inorganic perovskites exhibit tunable colours and transparencies, a peak device efficiency above 7%, and a phase transition temperature as low as 105 °C. We demonstrate excellent device stability over repeated phase transition cycles without colour fade or performance degradation. The photovoltaic windows showing both photoactivity and thermochromic features represent key stepping-stones for integration with buildings, automobiles, information displays, and potentially many other technologies.

Thermochromic halide perovskite solar cells

Science.gov (United States)

Lin, Jia; Lai, Minliang; Dou, Letian; Kley, Christopher S.; Chen, Hong; Peng, Fei; Sun, Junliang; Lu, Dylan; Hawks, Steven A.; Xie, Chenlu; Cui, Fan; Alivisatos, A. Paul; Limmer, David T.; Yang, Peidong

2018-03-01

Smart photovoltaic windows represent a promising green technology featuring tunable transparency and electrical power generation under external stimuli to control the light transmission and manage the solar energy. Here, we demonstrate a thermochromic solar cell for smart photovoltaic window applications utilizing the structural phase transitions in inorganic halide perovskite caesium lead iodide/bromide. The solar cells undergo thermally-driven, moisture-mediated reversible transitions between a transparent non-perovskite phase (81.7% visible transparency) with low power output and a deeply coloured perovskite phase (35.4% visible transparency) with high power output. The inorganic perovskites exhibit tunable colours and transparencies, a peak device efficiency above 7%, and a phase transition temperature as low as 105 °C. We demonstrate excellent device stability over repeated phase transition cycles without colour fade or performance degradation. The photovoltaic windows showing both photoactivity and thermochromic features represent key stepping-stones for integration with buildings, automobiles, information displays, and potentially many other technologies.

NaIrO3-A pentavalent post-perovskite

International Nuclear Information System (INIS)

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

2011-01-01

Sodium iridium (V) oxide, NaIrO 3, was synthesized by a high pressure solid state method and recovered to ambient conditions. It is found to be isostructural with CaIrO 3 , the much-studied structural analog of the high-pressure post-perovskite phase of MgSiO 3 . Among the oxide post-perovskites, NaIrO 3 is the first example with a pentavalent cation. The structure consists of layers of corner- and edge-sharing IrO 6 octahedra separated by layers of NaO 8 bicapped trigonal prisms. NaIrO 3 shows no magnetic ordering and resistivity measurements show non-metallic behavior. The crystal structure, electrical and magnetic properties are discussed and compared to known post-perovskites and pentavalent perovskite metal oxides. -- Graphical abstract: Sodium iridium(V) oxide, NaIrO 3 , synthesized by a high pressure solid state method and recovered to ambient conditions is found to crystallize as the post-perovskite structure and is the first example of a pentavalent ABO 3 post-perovskite. Research highlights: → NaIrO 3 post-perovskite stabilized by pressure. → First example of a pentavalent oxide post-perovskite. → Non-metallic and non-magnetic behavior of NaIrO 3 .

Effect of the synthesis route on the microstructure and the reducibility of LaCoO3

International Nuclear Information System (INIS)

Ivanova, S.; Senyshyn, A.; Zhecheva, E.; Tenchev, K.; Nikolov, V.; Stoyanova, R.; Fuess, H.

2009-01-01

The effect of the synthesis route on the microstructure and reducibility of lanthanum cobaltates (LaCoO 3 ) perovskites was examined. Two synthesis methods were used: thermal decomposition of freeze-dried La-Co-citrates and the Pechini method. The crystal structure, morphology and defect structure of LaCoO 3 were characterized by XRD powder diffraction, TEM and SEM analyses and electron paramagnetic resonance spectroscopy. The reducibility was tested by thermal programmed reduction with hydrogen. The intermediate stage of reduction was determined by ex situ XRD experiments. LaCoO 3 powders obtained by the Pechini method were reduced relatively easier as LaCoO 3 obtained from freeze-dried citrates. The LaCoO 3 reduction yielded Co metal and La 2 O 3 via the formation of oxygen deficient Brownmillerite-type La 3 Co 3 O 8 and La 2 Co 2 O 5 oxides. For LaCoO 3 obtained from freeze-dried citrates and annealed at higher temperatures, Co metal, in addition to oxygen deficient perovskites, was formed at the initial stage of the reduction. The different reducibility of LaCoO 3 obtained by the Pechini method and that from the freeze-dried citrates was discussed taking into account the formation of oxygen-deficient phases from the Brownmillerite and Ruddlesden-Popper series during the reduction.

Growth of MAPbBr3 perovskite crystals and its interfacial properties with Al and Ag contacts for perovskite solar cells

Science.gov (United States)

Najeeb, Mansoor Ani; Ahmad, Zubair; Shakoor, R. A.; Alashraf, Abdulla; Bhadra, Jolly; Al-Thani, N. J.; Al-Muhtaseb, Shaheen A.; Mohamed, A. M. A.

2017-11-01

In this work, the MAPbBr3 perovskite crystals were grown and the interfacial properties of the poly-crystalline MAPbBr3 with Aluminum (Al) and Silver (Ag) contacts has been investigated. MAPbBr3 crystals are turned into the poly-crystalline pellets (PCP) using compaction technique and the Al/PCP, Al/interface layer/PCP, Ag/PCP, and Ag/interface layer/PCP contacts were investigated. Scanning Electron Microscopic (SEM), Energy-dispersive X-ray spectroscopy (EDX) and current-voltage (I-V) characteristic technique were used to have an insight of the degradation mechanism happening at the Metal/perovskite interface. The Ag/PCP contact appears to be stable, whereas Al is found to be highly reactive with the MAPbBr3 perovskite crystals due to the infiltration setback of Al in to the perovskite crystals. The interface layer showed a slight effect on the penetration of Al in to the perovskite crystals however it does not seem to be an appropriate solution. It is noteworthy that the stability of the underlying metal/perovskite contact is very crucial towards the perovskite solar cells with extended device lifetime.

Improved perovskite phototransistor prepared using multi-step annealing method

Science.gov (United States)

Cao, Mingxuan; Zhang, Yating; Yu, Yu; Yao, Jianquan

2018-02-01

Organic-inorganic hybrid perovskites with good intrinsic physical properties have received substantial interest for solar cell and optoelectronic applications. However, perovskite film always suffers from a low carrier mobility due to its structural imperfection including sharp grain boundaries and pinholes, restricting their device performance and application potential. Here we demonstrate a straightforward strategy based on multi-step annealing process to improve the performance of perovskite photodetector. Annealing temperature and duration greatly affects the surface morphology and optoelectrical properties of perovskites which determines the device property of phototransistor. The perovskite films treated with multi-step annealing method tend to form highly uniform, well-crystallized and high surface coverage perovskite film, which exhibit stronger ultraviolet-visible absorption and photoluminescence spectrum compare to the perovskites prepared by conventional one-step annealing process. The field-effect mobilities of perovskite photodetector treated by one-step direct annealing method shows mobility as 0.121 (0.062) cm2V-1s-1 for holes (electrons), which increases to 1.01 (0.54) cm2V-1s-1 for that treated with muti-step slow annealing method. Moreover, the perovskite phototransistors exhibit a fast photoresponse speed of 78 μs. In general, this work focuses on the influence of annealing methods on perovskite phototransistor, instead of obtains best parameters of it. These findings prove that Multi-step annealing methods is feasible to prepared high performance based photodetector.

Fe-Mo double perovskite: From small clusters to bulk material

Energy Technology Data Exchange (ETDEWEB)

Carvajal, E., E-mail: ecarvajalq@ipn.mx [Instituto Politecnico Nacional, ESIME-Culhuacan, Av. Santa Ana 1000, C.P. 04430 Mexico, D.F. (Mexico); Oviedo-Roa, R. [Programa de Investigacion en Ingenieria Molecular, Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas Norte 152, 07730 Mexico, D.F. (Mexico); Cruz-Irisson, M. [Instituto Politecnico Nacional, ESIME-Culhuacan, Av. Santa Ana 1000, C.P. 04430 Mexico, D.F. (Mexico); Navarro, O. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, A.P. 70-360, 04510 Mexico, D.F. (Mexico)

2012-09-20

To understand the differences in behaviour between up- and down-spin electrons observed in the half-metallic Sr{sub 2}FeMoO{sub 6} double perovskite, the density of states (DOS) was studied for the (FeO{sub 6}){sup -4} and (MoO{sub 6}){sup -6} octahedral clusters using first-principles density functional theory within the generalised gradient approximation (GGA) scheme and the Perdew-Burke-Ernzerhof (PBE) functional. Our results reveal that half-metallic character is present, even starting from an isolated (FeO{sub 6}){sup -4} cluster, and is a consequence of spin decoupling of antibonding hybridisations between iron t{sub 2g} states and oxygen p states (t{sub 2g}{sup a} states), i.e., t{sub 2g}{sup a} states lie below the Highest Occupied Molecular Orbital (HOMO) in the up-spin channel, whereas they lie above the HOMO level in the down-spin channel. The spin-induced shifting between up-spin and down-spin DOS situates the HOMO in such a way that the molecular orbitals oxygen p states (p bands) are fully spin-paired by octet electrons. Thus, the down-spin channel has metallic character because the HOMO lies just at the p bands, and the up-spin channel is semiconducting because the HOMO falls within the energy gap between the t{sub 2g}{sup a} and e{sub g}{sup a} bands. Finally, the (MoO{sub 6}){sup -6} octahedron does not inhibit the perovskite half-metallic character since this cluster has a zero total spin.

Self-Assembled PbSe Nanowire:Perovskite Hybrids

KAUST Repository

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.

Self-Assembled PbSe Nanowire:Perovskite Hybrids

KAUST Repository

Yang, Zhenyu; Yassitepe, Emre; Voznyy, Oleksandr; Janmohamed, Alyf; Lan, Xinzheng; Levina, Larissa; Comin, Riccardo; Sargent, Edward H.

2015-01-01

© 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.

Systems and methods for scalable perovskite device fabrication

Science.gov (United States)

Huang, Jinsong; Dong, Qingfeng; Sao, Yuchuan

2017-02-28

Continuous processes for fabricating a perovskite device are described that include using a doctor blade for continuously forming a perovskite layer and using a conductive tape lamination process to form an anode or a cathode layer on the perovskite device.

Post-perovskite transitions in CaB4+O3 at high pressure

International Nuclear Information System (INIS)

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

2010-01-01

High-pressure phase transitions in CaRhO 3 were examined using a multianvil apparatus up to 27 GPa and 1930 o C. CaRhO 3 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. CaRhO 3 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 CaRuO 3 was measured as 15.2±3.3 kJ/mol. Combining the datum with those of CaIrO 3 , it is shown that CaIrO 3 perovskite is energetically less stable than CaRuO 3 perovskite. This is consistent with the fact that orthorhombic distortion of CaIrO 3 perovskite is larger than CaRuO 3 , as indicated with the tilt-angle of octahedral framework of perovskite structure. The transition pressure from perovskite to post-perovskite in CaBO 3 (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.

Performance and Stability Enhancement of Perovskite-Type Nanomaterials Applied for Carbon Capture Utilizing Oxyfuel Combustion

Directory of Open Access Journals (Sweden)

Qiuwan Shen

2017-02-01

Full Text Available A new series of Ba-Co-Operovskite-type oxygen carriers has been successfully synthesized by the microwave-assisted sol-gel method and further applied for producing an O2/CO2 mixture gas. The oxygen adsorption/desorption performance of synthesized samples was studied in a fixed-bed reactor system. Effects of A/B-site substitution on the oxygen desorption performance of Ba-Co-O–based perovskites are also included. Furthermore, the effects of operating conditions including the adsorption time and temperature as well as the desorption temperature on oxygen production performance were investigated in detail. The results indicated that BaCoO3-δ exhibited an excellent oxygen desorption performance among the synthesized A/B-site–substituted ACoO3-δ and BaBO3-δ samples, and that the optimal adsorption time, adsorption temperature and desorption temperatureforBaCoO3-δ were determined to be 20min, 850◦Cand850◦C, respectively, in this study.

Multifunctional optoelectronic devices based on perovskites

KAUST Repository

Saidaminov, Makhsud I.; Bakr, Osman

2017-01-01

Embodiments of the present disclosure provide methods of growing halide films (e.g., single crystal halide perovskites or multi-crystal halide perovskites) on a structure, dual-mode photodetectors, methods of use, and the like.

Multifunctional optoelectronic devices based on perovskites

KAUST Repository

Saidaminov, Makhsud I.

2017-10-19

Embodiments of the present disclosure provide methods of growing halide films (e.g., single crystal halide perovskites or multi-crystal halide perovskites) on a structure, dual-mode photodetectors, methods of use, and the like.

Halide-Dependent Electronic Structure of Organolead Perovskite Materials

KAUST Repository

Buin, Andrei; Comin, Riccardo; Xu, Jixian; Ip, Alexander H.; Sargent, Edward H.

2015-01-01

-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

Miscellaneous Lasing Actions in Organo-Lead Halide Perovskite Films.

Science.gov (United States)

Duan, Zonghui; Wang, Shuai; Yi, Ningbo; Gu, Zhiyuan; Gao, Yisheng; Song, Qinghai; Xiao, Shumin

2017-06-21

Lasing actions in organo-lead halide perovskite films have been heavily studied in the past few years. However, due to the disordered nature of synthesized perovskite films, the lasing actions are usually understood as random lasers that are formed by multiple scattering. Herein, we demonstrate the miscellaneous lasing actions in organo-lead halide perovskite films. In addition to the random lasers, we show that a single or a few perovskite microparticles can generate laser emissions with their internal resonances instead of multiple scattering among them. We experimentally observed and numerically confirmed whispering gallery (WG)-like microlasers in polygon shaped and other deformed microparticles. Meanwhile, owing to the nature of total internal reflection and the novel shape of the nanoparticle, the size of the perovskite WG laser can be significantly decreased to a few hundred nanometers. Thus, wavelength-scale lead halide perovskite lasers were realized for the first time. All of these laser behaviors are complementary to typical random lasers in perovskite film and will help the understanding of lasing actions in complex lead halide perovskite systems.

Surface oxygen vacancy and oxygen permeation flux limits of perovskite ion transport membranes

KAUST Repository

Hunt, Anton; Dimitrakopoulos, Georgios; Ghoniem, Ahmed F.

2015-01-01

© 2015 Elsevier B.V. The mechanisms and quantitative models for how oxygen is separated from air using ion transport membranes (ITMs) are not well understood, largely due to the experimental complexity for determining surface exchange reactions

Effects of Fe-Enrichment on the Equation of State and Stability of (Mg,Fe)SiO3 Perovskite and Post-Perovskite

Science.gov (United States)

Dorfman, S. M.; Holl, C. M.; Meng, Y.; Prakapenka, V.; Duffy, T. S.

2010-12-01

Fe-enrichment in the deep lower mantle has been proposed as an explanation for seismic anomalies such as large low shear velocity provinces (LLSVPs) and ultralow velocity zones (ULVZs). In order to resolve the effect of Fe on the stability and equation of state of the lower mantle’s dominant constituent, (Mg,Fe)SiO3 perovskite, we have studied Fe-rich natural orthopyroxenes, (Mg0.61Fe0.37Ca0.02)SiO3 and (Mg0.25Fe0.70Ca0.05)SiO3 (compositions determined by microprobe analysis), at lower mantle P-T conditions. Pyroxene starting materials were mixed with Au (pressure calibrant and laser absorber) and loaded with NaCl or Ne (pressure medium and thermal insulator) in a symmetric diamond anvil cell. X-ray diffraction experiments at pressures up to 122 GPa with in-situ laser heating were performed at the GSECARS (13-ID-D) and HPCAT (16-ID-B) sectors of the Advanced Photon Source. Heating samples to 2000 K produced single-phase orthorhombic GdFeO3-type perovskite at 63 GPa for the Mg# 61 composition and at 72 GPa for the Mg# 25 composition. At lower pressures (56 GPa for Mg# 61, 67 GPa for Mg# 25), heating both compositions resulted in a mixture of perovskite, SiO2 and (Mg,Fe)O. These measurements provide new constraints on the dependence of (Mg,Fe)SiO3 perovskite stability on pressure and composition. Upon further compression to 93 GPa and higher pressures with laser heating, Mg# 25 perovskite transformed to a two-phase mixture of perovskite and post-perovskite. This is consistent with previous findings that Fe substitution destabilizes (Mg,Fe)SiO3 perovskite relative to (Mg,Fe)SiO3 post-perovskite (Mao et al. 2004, Caracas and Cohen 2005). The bulk modulus at 80 GPa (K80) is ~550 GPa for both Fe-rich perovskites, comparable to values measured for MgSiO3 perovskite (Lundin et al. 2008). However, the volume of Fe-rich perovskites increases linearly with Fe-content. The (Mg0.25Fe0.70Ca0.05)SiO3 perovskite is 3% greater at 80 GPa than V80 for the Mg end

Iron-Deficiency Anemia

Medline Plus

Full Text Available ... Complications Undiagnosed or untreated iron-deficiency anemia may cause the following complications: Depression Heart problems. If you do not have enough hemoglobin-carrying red blood cells, your heart has to work harder to move oxygen-rich blood through your ...

Halide-Dependent Electronic Structure of Organolead Perovskite Materials

KAUST Repository

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.

Impact of Ultrathin C60 on Perovskite Photovoltaic Devices.

Science.gov (United States)

Liu, Dianyi; Wang, Qiong; Traverse, Christopher J; Yang, Chenchen; Young, Margaret; Kuttipillai, Padmanaban S; Lunt, Sophia Y; Hamann, Thomas W; Lunt, Richard R

2018-01-23

Halide perovskite solar cells have seen dramatic progress in performance over the past several years. Certified efficiencies of inverted structure (p-i-n) devices have now exceeded 20%. In these p-i-n devices, fullerene compounds are the most popular electron-transfer materials. However, the full function of fullerenes in perovskite solar cells is still under investigation, and the mechanism of photocurrent hysteresis suppression by fullerene remains unclear. In previous reports, thick fullerene layers (>20 nm) were necessary to fully cover the perovskite film surface to make good contact with perovskite film and avoid large leakage currents. In addition, the solution-processed fullerene layer has been broadly thought to infiltrate into the perovskite film to passivate traps on grain boundary surfaces, causing suppressed photocurrent hysteresis. In this work, we demonstrate an efficient perovskite photovoltaic device with only 1 nm C 60 deposited by vapor deposition as the electron-selective material. Utilizing a combination of fluorescence microscopy and impedance spectroscopy, we show that the ultrathin C 60 predominately acts to extract electrons from the perovskite film while concomitantly suppressing the photocurrent hysteresis by reducing space charge accumulation at the interface. This work ultimately helps to clarify the dominant role of fullerenes in perovskite solar cells while simplifying perovskite solar cell design to reduce manufacturing costs.

Two-Dimensional Perovskite Activation with an Organic Luminophore.

Science.gov (United States)

Jemli, Khaoula; Audebert, Pierre; Galmiche, Laurent; Trippé-Allard, Gaelle; Garrot, Damien; Lauret, Jean-Sébastien; Deleporte, Emmanuelle

2015-10-07

A great advantage of the hybrid organic-inorganic perovskites is the chemical flexibility and the possibility of a molecular engineering of each part of the material (the inorganic part and the organic part respectively) in order to improve or add some functionalities. An adequately chosen organic luminophore has been introduced inside a lead bromide type organic-inorganic perovskite, while respecting the two-dimensional perovskite structure. A substantial increase of the brilliance of the perovskite is obtained. This activation of the perovskite luminescence by the adequate engineering of the organic part is an original approach, and is particularly interesting in the framework of the light-emitting devices such as organic light-emitting diodes (OLEDs) or lasers.

Impact of Interfacial Layers in Perovskite Solar Cells.

Science.gov (United States)

Cho, An-Na; Park, Nam-Gyu

2017-10-09

Perovskite solar cells (PCSs) are composed of organic-inorganic lead halide perovskite as the light harvester. Since the first report on a long-term-durable, 9.7 % efficient, solid-state perovskite solar cell, organic-inorganic halide perovskites have received considerable attention because of their excellent optoelectronic properties. As a result, a power conversion efficiency (PCE) exceeding 22 % was certified. Controlling the grain size, grain boundary, morphology, and defects of the perovskite layer is important for achieving high efficiency. In addition, interfacial engineering is equally or more important to further improve the PCE through better charge collection and a reduction in charge recombination. In this Review, the type of interfacial layers and their impact on photovoltaic performance are investigated for both the normal and the inverted cell architectures. Four different interfaces of fluorine-doped tin oxide (FTO)/electron-transport layer (ETL), ETL/perovskite, perovskite/hole-transport layer (HTL), and HTL/metal are classified, and their roles are investigated. The effects of interfacial engineering with organic or inorganic materials on photovoltaic performance are described in detail. Grain-boundary engineering is also included because it is related to interfacial engineering and the grain boundary in the perovskite layer plays an important role in charge conduction, recombination, and chargecarrier life time. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sr doped BiMO{sub 3} (M = Mn, Fe, Y) perovskites: Structure correlated thermal and electrical properties

Energy Technology Data Exchange (ETDEWEB)

Thakur, Samita, E-mail: samitasthakur@gmail.com [School of Physics and Materials Science, Thapar University, Patiala 147004 (India); School of Basic Sciences, Arni University, Kathgarh (India); Singh, K.; Pandey, O.P. [School of Physics and Materials Science, Thapar University, Patiala 147004 (India)

2017-02-01

Sr{sup 2+} substituted BiMnO{sub 3−δ} (BSM), BiFeO{sub 3−δ} (BSF) and BiYO{sub 3−δ} (BSY) perovskites structured samples have been investigated for their structural, thermal and electrical properties. These samples are characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), iodometric titration, Raman spectroscopy, thermogravimetric analysis (TGA) and conductivity. Rietveld refinement confirms that BSY sample has cubic (Fm-3m) symmetry with limited solid solubility of Sr{sup 2+} as compared to tetragonal symmetry (p4mm) of BSM and BSF samples. X-ray photoelectron spectroscopy study confirms the presence of Mn{sup 4+} and Fe{sup 4+} content in BSM and BSF samples. The amount of Mn{sup 3+}, Fe{sup 4+} and oxygen vacancies in these systems are calculated by iodometric titration. The highest oxygen vacancies are found in BSF sample. The BSM system exhibit the highest conductivity followed by BSF and BSY samples due to the presence of Mn{sup 4+} content and moderate oxygen vacancies in this particular sample. - Highlights: • (BiSr)MO{sub 3} (M = Mn, Fe, Y) was synthesized by solid state reaction method. • The B-site cation highly affect the generation of defects in perovskites. • The structural and electrical properties strongly depend upon the B-site cation.

Properties and performance of BaxSr1-xCo0.8Fe0.2O3-d materials for oxygen transport membranes

NARCIS (Netherlands)

Vente, Jaap F.; McIntosh, S.; McIntosh, Steven; Haije, Wim G.; Bouwmeester, Henricus J.M.

2006-01-01

The present paper discusses the oxygen transport properties, oxygen stoichiometry, phase stability, and chemical and mechanical stability of the perovskites $${\\text{Ba}}_{{0.5}} {\\text{Sr}}_{{0.5}} {\\text{Co}}_{{0.8}} {\\text{Fe}}_{{0.2}} {\\text{O}}_{{3 - \\delta }} $$ (BSCF) and

Manganese deficiency in plants

DEFF Research Database (Denmark)

Schmidt, Sidsel Birkelund; Jensen, Poul Erik; Husted, Søren

2016-01-01

Manganese (Mn) is an essential plant micronutrient with an indispensable function as a catalyst in the oxygen-evolving complex (OEC) of photosystem II (PSII). Even so, Mn deficiency frequently occurs without visual leaf symptoms, thereby masking the distribution and dimension of the problem...... restricting crop productivity in many places of the world. Hence, timely alleviation of latent Mn deficiency is a challenge in promoting plant growth and quality. We describe here the key mechanisms of Mn deficiency in plants by focusing on the impact of Mn on PSII stability and functionality. We also address...... the mechanisms underlying the differential tolerance towards Mn deficiency observed among plant genotypes, which enable Mn-efficient plants to grow on marginal land with poor Mn availability....

Charge compensation and the incorporation of cerium in zirconolite and perovskite

International Nuclear Information System (INIS)

Begg, B.D.; Vance, E.R.; Lumpkin, G.R.

1998-01-01

charge compensating Al on the Ti site. The following three incorporation strategies were evaluated; Ce 3+ on Ca site with Al charge compensation on the Ti site - Ca 0.9 Ce 0.1 Ti 0.9 Al 0.1 O 3 , Ce 3+ on Ca site with no charge compensation - Ca 0.9 Ce 0.1 TiO 3 , and Ce 4+ on Ca site with Al charge compensation on the Ti site - Ca 0.9 Ce 0.1 Ti 0.8 Al 0.2 O 3 . The perovskite samples were similarly subjected to a range of redox conditions to examine the relative stability of the prevailing Ce valence states. The samples were characterised by scanning electron microscopy, X-ray diffraction and X-ray absorption spectroscopy (XAS). XAS was performed either at the Photon Factory, Tsukuba, Japan or at the Stanford Synchrotron Radiation Laboratory (SSRL), USA, on the Ce Lm-edge and Ti-K edge of the Ce-doped perovskites and zirconolites. Electron paramagnetic resonance (EPR) to obtain direct evidence for Ti 3+ was also performed on the Ce-perovskites and Ce-zirconolites at liquid nitrogen temperatures. Additionally, thermogravimetric analysis (TGA) was used to determine weight changes on oxidation of those samples annealed under the reducing hydrogen nitrogen environment. In contrast to the Ce-doped zirconolites, the Ce valence in most of the perovskites was dependent on the compositional design of the perovskite and not the prevailing oxygen atmosphere. Trivalent Ce was stable in all atmospheres in the perovskite containing sufficient Al on the Ti site to account for Ce 3+ . However, in a similar way to the Ce-doped zirconolites Ce was able to be incorporated into perovskite, at the 0.1 formula unit level, in the absence of any specific charge compensating additives although, unlike in the Ce-zirconolite, the Ce in the perovskite remained trivalent even when fired in air. Attempts to stabilise tetravalent Ce in perovskite resulted in ∼80% of the Ce being tetravalent in air, whilst the 3.5% H 2 /N 2 heat treatment was sufficient to fully reduce the Ce to Ce 3+ . The

Perovskite Materials for Light-Emitting Diodes and Lasers.

Science.gov (United States)

Veldhuis, Sjoerd A; Boix, Pablo P; Yantara, Natalia; Li, Mingjie; Sum, Tze Chien; Mathews, Nripan; Mhaisalkar, Subodh G

2016-08-01

Organic-inorganic hybrid perovskites have cemented their position as an exceptional class of optoelectronic materials thanks to record photovoltaic efficiencies of 22.1%, as well as promising demonstrations of light-emitting diodes, lasers, and light-emitting transistors. Perovskite materials with photoluminescence quantum yields close to 100% and perovskite light-emitting diodes with external quantum efficiencies of 8% and current efficiencies of 43 cd A(-1) have been achieved. Although perovskite light-emitting devices are yet to become industrially relevant, in merely two years these devices have achieved the brightness and efficiencies that organic light-emitting diodes accomplished in two decades. Further advances will rely decisively on the multitude of compositional, structural variants that enable the formation of lower-dimensionality layered and three-dimensional perovskites, nanostructures, charge-transport materials, and device processing with architectural innovations. Here, the rapid advancements in perovskite light-emitting devices and lasers are reviewed. The key challenges in materials development, device fabrication, operational stability are addressed, and an outlook is presented that will address market viability of perovskite light-emitting devices. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Origins of n -type doping difficulties in perovskite stannates

Science.gov (United States)

Weston, L.; Bjaalie, L.; Krishnaswamy, K.; Van de Walle, C. G.

2018-02-01

The perovskite stannates (A SnO3 ; A = Ba, Sr, Ca) are promising for oxide electronics, but control of n -type doping has proved challenging. Using first-principles hybrid density functional calculations, we investigate La dopants and explore the formation of compensating acceptor defects. We find that La on the A site always behaves as a shallow donor, but incorporation of La on the Sn site can lead to self-compensation. At low La concentrations and in O-poor conditions, oxygen vacancies form in BaSnO3. A -site cation vacancies are found to be dominant among the native compensating centers. Compared to BaSnO3, charge compensation is a larger problem for the wider-band-gap stannates, SrSnO3 and CaSnO3, a trend we can explain based on conduction-band alignments. The formation of compensating acceptor defects can be inhibited by choosing oxygen-poor (cation-rich) growth or annealing conditions, thus providing a pathway for improved n -type doping.

Patterning of Perovskite Single Crystals

KAUST Repository

Corzo, Daniel

2017-06-12

As the internet-of-things hardware integration continues to develop and the requirements for electronics keep diversifying and expanding, the necessity for specialized properties other than the classical semiconductor performance becomes apparent. The success of emerging semiconductor materials depends on the manufacturability and cost as much as on the properties and performance they offer. Solution-based semiconductors are an emerging concept that offers the advantage of being compatible with large-scale manufacturing techniques and have the potential to yield high-quality electronic devices at a lower cost than currently available solutions. In this work, patterns of high-quality MAPbBr3 perovskite single crystals in specific locations are achieved through the modification of the substrate properties and solvent engineering. The fabrication of the substrates involved modifying the surface adhesion forces through functionalization with self-assembled monolayers and patterning them by photolithography processes. Spin coating and blade coating were used to deposit the perovskite solution on the modified silicon substrates. While single crystal perovskites were obtained with the modification of substrates alone, solvent engineering helped with improving the Marangoni flows in the deposited droplets by increasing the contact angle and lowering the evaporation rate, therefore controlling and improving the shape of the grown perovskite crystals. The methodology is extended to other types of perovskites such as the transparent MAPbCl3 and the lead-free MABi2I9, demonstrating the adaptability of the process. Adapting the process to electrode arrays opened up the path towards the fabrication of optoelectronic devices including photodetectors and field-effect transistors, for which the first iterations are demonstrated. Overall, manufacturing and integration techniques permitting the fabrication of single crystalline devices, such as the method in this thesis work, are

Molecular behavior of zero-dimensional perovskites

KAUST Repository

Yin, Jun

2017-12-16

Low-dimensional perovskites offer a rare opportunity to investigate lattice dynamics and charge carrier behavior in bulk quantum-confined solids, in addition to them being the leading materials in optoelectronic applications. In particular, zero-dimensional (0D) inorganic perovskites of the Cs4PbX6 (X = Cl, Br, or I) kind have crystal structures with isolated lead halide octahedra [PbX6]4− surrounded by Cs+ cations, allowing the 0D crystals to exhibit the intrinsic properties of an individual octahedron. Using both experimental and theoretical approaches, we studied the electronic and optical properties of the prototypical 0D perovskite Cs4PbBr6. Our results underline that this 0D perovskite behaves akin to a molecule, demonstrating low electrical conductivity and mobility as well as large polaron binding energy. Density functional theory calculations and transient absorption measurements of Cs4PbBr6 perovskite films reveal the polaron band absorption and strong polaron localization features of the material. A short polaron lifetime of ~2 ps is observed in femtosecond transient absorption experiments, which can be attributed to the fast lattice relaxation of the octahedra and the weak interactions among them.

Aqueous-Containing Precursor Solutions for Efficient Perovskite Solar Cells.

Science.gov (United States)

Liu, Dianyi; Traverse, Christopher J; Chen, Pei; Elinski, Mark; Yang, Chenchen; Wang, Lili; Young, Margaret; Lunt, Richard R

2018-01-01

Perovskite semiconductors have emerged as competitive candidates for photovoltaic applications due to their exceptional optoelectronic properties. However, the impact of moisture instability on perovskite films is still a key challenge for perovskite devices. While substantial effort is focused on preventing moisture interaction during the fabrication process, it is demonstrated that low moisture sensitivity, enhanced crystallization, and high performance can actually be achieved by exposure to high water content (up to 25 vol%) during fabrication with an aqueous-containing perovskite precursor. The perovskite solar cells fabricated by this aqueous method show good reproducibility of high efficiency with average power conversion efficiency (PCE) of 18.7% and champion PCE of 20.1% under solar simulation. This study shows that water-perovskite interactions do not necessarily negatively impact the perovskite film preparation process even at the highest efficiencies and that exposure to high contents of water can actually enable humidity tolerance during fabrication in air.

Monolithic Perovskite Silicon Tandem Solar Cells with Advanced Optics

Energy Technology Data Exchange (ETDEWEB)

Goldschmidt, Jan C.; Bett, Alexander J.; Bivour, Martin; Blasi, Benedikt; Eisenlohr, Johannes; Kohlstadt, Markus; Lee, Seunghun; Mastroianni, Simone; Mundt, Laura; Mundus, Markus; Ndione, Paul; Reichel, Christian; Schubert, Martin; Schulze, Patricia S.; Tucher, Nico; Veit, Clemens; Veurman, Welmoed; Wienands, Karl; Winkler, Kristina; Wurfel, Uli; Glunz, Stefan W.; Hermle, Martin

2016-11-14

For high efficiency monolithic perovskite silicon tandem solar cells, we develop low-temperature processes for the perovskite top cell, rear-side light trapping, optimized perovskite growth, transparent contacts and adapted characterization methods.

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

International Nuclear Information System (INIS)

Kapusta, Benedicte

1990-01-01

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 MgSiO 3 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 KZnF 3 perovskite (a structural analogous of MgSiO 3 ): measurements of electric conductivity under pressure, measurements under atmospheric pressure, result discussion. The next part addresses the numerical simulation of MgSiO 3 : simulation techniques (generalities on molecular dynamics, model description), investigation of structural, elastic and thermodynamic properties, diffusion properties in quadratic phase [fr

Catalytic properties of perovskite-type mixed oxides, La/sub 1-x/Sr/sub x/CoO/sub 3/

Energy Technology Data Exchange (ETDEWEB)

Nakamura, T; Misono, M; Yoneda, Y

1982-02-01

The reactivity and related properties of oxygen both in the bulk and on the surface has been investigated for perovskite-type mixed oxides (La/sub 1-x/Sr,sub x/CoO/sub 3/), in regard to the effects of Sr/sup 2 +/-substitution and calcination temperature. The reducibility and the readiness of oxygen desorption increased with the Sr/sup 2 +/- content, x, but the reoxidation became slower with x. These results have been explained on the basis of the change in the chemical potential of lattice oxygen. The diffusivity of oxygen in the bulk and the ability to activate the oxygen molecule also increased with x. Oxygen vacancies in the bulk and on the surface, which tended to increase with x, are likely responsible for these reactions. The release of oxygen from the bulk became more difficult as the calcination temperature increased, in conformity with the trend of the catalytic activity.

Quantum-dot-in-perovskite solids

KAUST Repository

Ning, Zhijun; Gong, Xiwen; Comin, Riccardo; Walters, Grant; Fan, Fengjia; Voznyy, Oleksandr; Yassitepe, Emre; Buin, Andrei; Hoogland, Sjoerd; Sargent, Edward H.

2015-01-01

© 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.

Quantum-dot-in-perovskite solids

KAUST Repository

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.

Random lasing actions in self-assembled perovskite nanoparticles

Science.gov (United States)

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

2016-05-01

Solution-based perovskite nanoparticles have been intensively studied in the past few years due to their applications in both photovoltaic and optoelectronic devices. Here, based on the common ground between solution-based perovskite and random lasers, we have studied the mirrorless lasing actions in self-assembled perovskite nanoparticles. After synthesis from a solution, discrete lasing peaks have been observed from optically pumped perovskites without any well-defined cavity boundaries. We have demonstrated that the origin of the random lasing emissions is the scattering between the nanostructures in the perovskite microplates. The obtained quality (Q) factors and thresholds of random lasers are around 500 and 60 μJ/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 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 perovskites, two-photon pumped random lasers have also been demonstrated for the first time. We believe this research will find its potential applications in low-cost coherent light sources and biomedical detection.

Rules and mechanisms governing octahedral tilts in perovskites under pressure

Science.gov (United States)

Xiang, H. J.; Guennou, Mael; Íñiguez, Jorge; Kreisel, Jens; Bellaiche, L.

2017-08-01

The rotation of octahedra (octahedral tilting) is common in A B O3 perovskites and relevant to many physical phenomena, ranging from electronic and magnetic properties, metal-insulator transitions to improper ferroelectricity. Hydrostatic pressure is an efficient way to tune and control octahedral tiltings. However, the pressure behavior of such tiltings can dramatically differ from one material to another, with the origins of such differences remaining controversial. In this paper, we discover several new mechanisms and formulate a set of simple rules that allow us to understand how pressure affects oxygen octahedral tiltings via the use and analysis of first-principles results for a variety of compounds. Besides the known A -O interactions, we reveal that the interactions between specific B ions and oxygen ions contribute to the tilting instability. We explain the previously reported trend that the derivative of the oxygen octahedral tilting with respect to pressure (dR /dP ) usually decreases with both the tolerance factor and the ionization state of the A ion by illustrating the key role of A -O interactions and their change under pressure. Furthermore, three new mechanisms/rules are discovered, namely that (i) the octahedral rotations in A B O3 perovskites with empty low-lying d states on the B site are greatly enhanced by pressure, in order to lower the electronic kinetic energy; (ii) dR /dP is enhanced when the system possesses weak tilt instabilities, and (iii) for the most common phase exhibited by perovskites—the orthorhombic Pbnm state—the in-phase and antiphase octahedral rotations are not automatically both suppressed or both enhanced by the application of pressure because of a trilinear coupling between these two rotation types and an antipolar mode involving the A ions. We further predict that the polarization associated with the so-called hybrid improper ferroelectricity could be manipulated by hydrostatic pressure by indirectly controlling the

Scalable fabrication of perovskite solar cells

Energy Technology Data Exchange (ETDEWEB)

Li, Zhen; Klein, Talysa R.; Kim, Dong Hoe; Yang, Mengjin; Berry, Joseph J.; van Hest, Maikel F. A. M.; Zhu, Kai

2018-03-27

Perovskite materials use earth-abundant elements, have low formation energies for deposition and are compatible with roll-to-roll and other high-volume manufacturing techniques. These features make perovskite solar cells (PSCs) suitable for terawatt-scale energy production with low production costs and low capital expenditure. Demonstrations of performance comparable to that of other thin-film photovoltaics (PVs) and improvements in laboratory-scale cell stability have recently made scale up of this PV technology an intense area of research focus. Here, we review recent progress and challenges in scaling up PSCs and related efforts to enable the terawatt-scale manufacturing and deployment of this PV technology. We discuss common device and module architectures, scalable deposition methods and progress in the scalable deposition of perovskite and charge-transport layers. We also provide an overview of device and module stability, module-level characterization techniques and techno-economic analyses of perovskite PV modules.

Oxygen octahedra picker: A software tool to extract quantitative information from STEM images

Energy Technology Data Exchange (ETDEWEB)

Wang, Yi, E-mail: y.wang@fkf.mpg.de; Salzberger, Ute; Sigle, Wilfried; Eren Suyolcu, Y.; Aken, Peter A. van

2016-09-15

In perovskite oxide based materials and hetero-structures there are often strong correlations between oxygen octahedral distortions and functionality. Thus, atomistic understanding of the octahedral distortion, which requires accurate measurements of atomic column positions, will greatly help to engineer their properties. Here, we report the development of a software tool to extract quantitative information of the lattice and of BO{sub 6} octahedral distortions from STEM images. Center-of-mass and 2D Gaussian fitting methods are implemented to locate positions of individual atom columns. The precision of atomic column distance measurements is evaluated on both simulated and experimental images. The application of the software tool is demonstrated using practical examples. - Highlights: • We report a software tool for mapping atomic positions from HAADF and ABF images. • It enables quantification of both crystal lattice and oxygen octahedral distortions. • We test the measurement accuracy and precision on simulated and experimental images. • It works well for different orientations of perovskite structures and interfaces.

Recent Advances in Interface Engineering for Planar Heterojunction Perovskite Solar Cells

Directory of Open Access Journals (Sweden)

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.

Ionic conductivity in new perovskite type oxides: NaAZrMO{sub 6} (A = Ca or Sr; M = Nb or Ta)

Energy Technology Data Exchange (ETDEWEB)

Rajendran, Deepthi N.; Ravindran Nair, K. [Regional Research Laboratory (CSIR), Trivandrum 695019 (India); Prabhakar Rao, P. [Regional Research Laboratory (CSIR), Trivandrum 695019 (India)], E-mail: padala_rao@yahoo.com; Sibi, K.S.; Koshy, Peter [Regional Research Laboratory (CSIR), Trivandrum 695019 (India); Vaidyan, V.K. [Department of Physics, University of Kerala, Trivandrum 695581 (India)

2008-06-15

New oxides of the type, NaAZrMO{sub 6} (M = Ca or Sr; M = Nb or Ta), have been prepared by the solid-state reaction technique. Phase identification by powder X-ray diffraction (XRD) shows that NaCaZrMO{sub 6} has orthorhombic perovskite type structure (Pnma) and NaSrZrMO{sub 6} has cubic perovskite type structure (Pm3m). The grain morphology observation by scanning electron microscope (SEM) shows well-sintered grains. ac impedance spectra and electrical conductivity measurements in air, oxygen and nitrogen atmospheres indicate that they are probable oxide ion conductors with ionic conductivities of the order of 10{sup -3} S cm{sup -1} at 750 deg. C.

Low-Dimensional Organic-Inorganic Halide Perovskite: Structure, Properties, and Applications.

Science.gov (United States)

Misra, Ravi K; Cohen, Bat-El; Iagher, Lior; Etgar, Lioz

2017-10-09

Three-dimensional (3 D) perovskite has attracted a lot of attention owing to its success in photovoltaic (PV) solar cells. However, one of its major crucial issues lies in its stability, which has limited its commercialization. An important property of organic-inorganic perovskite is the possibility of forming a layered material by using long organic cations that do not fit into the octahedral cage. These long organic cations act as a "barrier" that "caps" 3 D perovskite to form the layered material. Controlling the number of perovskite layers could provide a confined structure with chemical and physical properties that are different from those of 3 D perovskite. This opens up a whole new batch of interesting materials with huge potential for optoelectronic applications. This Minireview presents the synthesis, properties, and structural orientation of low-dimensional perovskite. It also discusses the progress of low-dimensional perovskite in PV solar cells, which, to date, have performance comparable to that of 3 D perovskite but with enhanced stability. Finally, the use of low-dimensional perovskite in light-emitting diodes (LEDs) and photodetectors is discussed. The low-dimensional perovskites are promising candidates for LED devices, mainly because of their high radiative recombination as a result of the confined low-dimensional quantum well. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Morphology-Controlled Synthesis of Organometal Halide Perovskite Inverse Opals.

Science.gov (United States)

Chen, Kun; Tüysüz, Harun

2015-11-09

The booming development of organometal halide perovskites in recent years has prompted the exploration of morphology-control strategies to improve their performance in photovoltaic, photonic, and optoelectronic applications. However, the preparation of organometal halide perovskites with high hierarchical architecture is still highly challenging and a general morphology-control method for various organometal halide perovskites has not been achieved. A mild and scalable method to prepare organometal halide perovskites in inverse opal morphology is presented that uses a polystyrene-based artificial opal as hard template. Our method is flexible and compatible with different halides and organic ammonium compositions. Thus, the perovskite inverse opal maintains the advantage of straightforward structure and band gap engineering. Furthermore, optoelectronic investigations reveal that morphology exerted influence on the conducting nature of organometal halide perovskites. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phonon model of perovskite thermal capacity

International Nuclear Information System (INIS)

Kesler, Ya.A.; Poloznikova, M.Eh.; Petrov, K.I.

1983-01-01

A model for calculating the temperature curve of thermal capacity of perovskite family crystals on the basis of vibrational spectra is proposed. Different representatives of the perovskite family: cubic SrTiO 3 , tetragonal BaTiO 3 and orthorbombic CaTiO 3 and LaCrO 3 are considered. The total frequency set is used in thermal capacity calcUlations. Comparison of the thermal capacity values of compounds calculated on the basis of the proposed model with the experimental values shows their good agreement. The method is also recommended for other compounds with the perovskite-like structure

Evaluation of covalency of ions in lead-free perovskite-type dielectric oxides

Directory of Open Access Journals (Sweden)

Naohisa Takesue

2017-10-01

Full Text Available Electronic states of ions in lead-free perovskite-type dielectric oxides have been investigated with a first-principle cluster calculation. For this calculation a double-perovskite cluster model based upon the simple cubic ABO3 was used; A and B are both the cations, and O is the oxygen anion. Systematic variations of ionic species for A and B, and lengths of the model cube edge were given to the model. Results of charge transfers of the ions show that their magnitudes depend on the edge length; the lager length leads to the higher transfer magnitude. This tendency implies spatial tolerance of the ions to the clusters, and are expected to correlate with electric polarizability and dipole reversibility of this kind of oxides. The density of states and the overlap population indicate that the higher cation valence causes the higher covalency of the anions. Considering all results together provides us an idea to obtain lead-free high-performance ferroelectrics, as high as the lead-based solid solutions.

Relating surface chemistry and oxygen surface exchange in LnBaCo2O(5+δ) air electrodes.

Science.gov (United States)

Téllez, Helena; Druce, John; Kilner, John A; Ishihara, Tatsumi

2015-01-01

The surface and near-surface chemical composition of electroceramic materials often shows significant deviations from that of the bulk. In particular, layered materials, such as cation-ordered LnBaCo2O(5+δ) perovskites (Ln = lanthanide), undergo surface and sub-surface restructuring due to the segregation of the divalent alkaline-earth cation. These processes can take place during synthesis and processing steps (e.g. deposition, sintering or annealing), as well as at temperatures relevant for the operation of these materials as air electrodes in solid oxide fuel cells and electrolysers. Furthermore, the surface segregation in these double perovskites shows fast kinetics, starting at temperatures as low as 400 °C over short periods of time and leading to a decrease in the transition metal surface coverage exposed to the gas phase. In this work, we use a combination of stable isotope tracer labeling and surface-sensitive ion beam techniques to study the oxygen transport properties and their relationship with the surface chemistry in ordered LnBaCo2O(5+δ) perovskites. Time-of-Flight Secondary-Ion Mass Spectrometry (ToF-SIMS) combined with (18)O isotope exchange was used to determine the oxygen tracer diffusion (D*) and surface exchange (k*) coefficients. Furthermore, Low Energy Ion Scattering (LEIS) was used for the analysis of the surface and near surface chemistry as it provides information from the first mono-atomic layer of the materials. In this way, we could relate the compositional modifications (e.g. cation segregation) taking place at the electrochemically-active surface during the exchange at high temperatures and the oxygen transport properties in double perovskite electrode materials to further our understanding of the mechanism of the surface exchange process.

Novel layered perovskite GdBaCoFeO{sub 5+{delta}} as a potential cathode for proton-conducting solid oxide fuel cells

Energy Technology Data Exchange (ETDEWEB)

Ding, Hanping; Xue, Xingjian [Department of Mechanical Engineering, University of South Carolina, Columbia, SC 29208 (United States)

2010-05-15

While cobalt-containing perovskite-type cathode materials facilitate the activation of oxygen reduction, they also suffer from problems like poor chemical stability in CO{sub 2}, high thermal expansion coefficients, etc. Partial B site substitution with Fe element is expected to be able to mitigate these problems while keeping high catalyst performance. In this paper, a layered perovskite GdBaCoFeO{sub 5+{delta}} (GBCF) was developed as a cathode material for protonic ceramic membrane fuel cells (PCMFCs) based on proton-conducting electrolyte of stable BaZr{sub 0.1}Ce{sub 0.7}Y{sub 0.2}O{sub 3-{delta}} (BZCY7). The button cells of Ni-BZCY7 vertical stroke BZCY7 vertical stroke GBCF were fabricated and tested from 600 to 700 C with humidified H{sub 2} ({proportional_to}3% H{sub 2}O) as a fuel and ambient oxygen as oxidant. An open-circuit potential of 1.002 V, maximum power density of 482 mW cm{sup -2}, and a low electrode polarization resistance of 0.11 {omega}cm{sup 2} were achieved at 700 C. The experimental results indicated that the layered perovskite GBCF is a good candidate for cathode material, while the developed Ni-BZCY7 vertical stroke BZCY7 vertical stroke GBCF cell is a promising functional material system for intermediate temperature solid oxide fuel cells. (author)

Oxygen influencing the photocarriers lifetime of CH3NH3PbI3-xClx film grown by two-step interdiffusion method and its photovoltaic performance

Science.gov (United States)

Yuan, Shuai; Qiu, Zhiwen; Zhang, Hailiang; Gong, Haibo; Hao, Yufeng; Cao, Bingqiang

2016-01-01

During the growth of CH3NH3PbI3-xClx (MAPbI3-xClx) perovskite films by the two-step inter-diffusion method, the presence of a trace amount of oxygen gas is critical to their physical properties and photovoltaic performance. As the oxygen concentration increases, poor film morphologies and incomplete surface coverage are observed. Moreover, by XRD, Raman scattering, and photoluminescence measurements, we find that MAPbI3-xClx grains become more distorted and the electron-hole recombination rate dramatically increases. Higher oxygen concentration triggers a sharp decrease in the current density and the fill factor of corresponding solar cells, which degrades device performance, on average, from 14.3% to 4.4%. This work proves the importance of controlling the oxygen atmosphere in the fabrication of high-performance perovskite solar cells.

Perovskite Solar Cells for High-Efficiency Tandems

Energy Technology Data Exchange (ETDEWEB)

McGehee, Michael [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Buonassisi, Tonio [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

2017-09-30

The first monolithic perovskite/silicon tandem was made with a diffused silicon p-n junction, a tunnel junction made of n⁺⁺ hydrogenated amorphous silicon, a titania electron transport layer, a methylammonium lead iodide absorber, and a Spiro-OMeTAD hole transport layer (HTL). The power conversion efficiency (PCE) was only 13.7% due to excessive parasitic absorption of light in the HTL, limiting the matched current density to 11.5 mA/cm². Werner et al.¹⁵ raised the PCE to a record 21.2% by switching to a silicon heterojunction bottom cell and carefully tuning layer thicknesses to achieve lower optical loss and a higher current density of 15.9 mA/cm². It is clear from these reports that minimizing parasitic absorption in the window layers is crucial to achieving higher current densities and efficiencies in monolithic tandems. To this end, the window layers through which light first passes before entering the perovskite and silicon absorber materials must be highly transparent. The front electrode must also be conductive to carry current laterally across the top of the device. Indium tin oxide (ITO) is widely utilized as a transparent electrode in optoelectronic devices such as flat-panel displays, smart windows, organic light-emitting diodes, and solar cells due to its high conductivity and broadband transparency. ITO is typically deposited through magnetron sputtering; however, the high kinetic energy of sputtered particles can damage underlying layers. In perovskite solar cells, a sputter buffer layer is required to protect the perovskite and organic carrier extraction layers from damage during sputter deposition. The ideal buffer layer should also be energetically well aligned so as to act as a carrier-selective contact, have a wide bandgap to enable high optical transmission, and have no reaction with the halides in the perovskite. Additionally, this buffer layer should act as a diffusion barrier layer to prevent both

Stress-Induced Cubic-to-Hexagonal Phase Transformation in Perovskite Nanothin Films.

Science.gov (United States)

Cao, Shi-Gu; Li, Yunsong; Wu, Hong-Hui; Wang, Jie; Huang, Baoling; Zhang, Tong-Yi

2017-08-09

The strong coupling between crystal structure and mechanical deformation can stabilize low-symmetry phases from high-symmetry phases or induce novel phase transformation in oxide thin films. Stress-induced structural phase transformation in oxide thin films has drawn more and more attention due to its significant influence on the functionalities of the materials. Here, we discovered experimentally a novel stress-induced cubic-to-hexagonal phase transformation in the perovskite nanothin films of barium titanate (BaTiO 3 ) with a special thermomechanical treatment (TMT), where BaTiO 3 nanothin films under various stresses are annealed at temperature of 575 °C. Both high-resolution transmission electron microscopy and Raman spectroscopy show a higher density of hexagonal phase in the perovskite thin film under higher tensile stress. Both X-ray photoelectron spectroscopy and electron energy loss spectroscopy does not detect any change in the valence state of Ti atoms, thereby excluding the mechanism of oxygen vacancy induced cubic-to-hexagonal (c-to-h) phase transformation. First-principles calculations show that the c-to-h phase transformation can be completed by lattice shear at elevated temperature, which is consistent with the experimental observation. The applied bending plus the residual tensile stress produces shear stress in the nanothin film. The thermal energy at the elevated temperature assists the shear stress to overcome the energy barriers during the c-to-h phase transformation. The stress-induced phase transformation in perovskite nanothin films with TMT provides materials scientists and engineers a novel approach to tailor nano/microstructures and properties of ferroelectric materials.

Conducting Layered Organic-inorganic Halides Containing -Oriented Perovskite Sheets.

Science.gov (United States)

Mitzi, D B; Wang, S; Feild, C A; Chess, C A; Guloy, A M

1995-03-10

Single crystals of the layered organic-inorganic perovskites, [NH(2)C(I=NH(2)](2)(CH(3)NH(3))m SnmI3m+2, were prepared by an aqueous solution growth technique. In contrast to the recently discovered family, (C(4)H(9)NH(3))(2)(CH(3)NH(3))n-1SnnI3n+1, which consists of (100)-terminated perovskite layers, structure determination reveals an unusual structural class with sets of m -oriented CH(3)NH(3)SnI(3) perovskite sheets separated by iodoformamidinium cations. Whereas the m = 2 compound is semiconducting with a band gap of 0.33 +/- 0.05 electron volt, increasing m leads to more metallic character. The ability to control perovskite sheet orientation through the choice of organic cation demonstrates the flexibility provided by organic-inorganic perovskites and adds an important handle for tailoring and understanding lower dimensional transport in layered perovskites.

Generalized trends in the formation energies of perovskite oxides

DEFF Research Database (Denmark)

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

2013-01-01

Generalized trends in the formation energies of several families of perovskite oxides (ABO3) and plausible explanations to their existence are provided in this study through a combination of DFT calculations, solid-state physics analyses and simple physical/chemical descriptors. The studied...... elements at the A site of perovskites comprise rare-earth, alkaline-earth and alkaline metals, whereas 3d and 5d metals were studied at the B site. We also include ReO3-type compounds, which have the same crystal structure of cubic ABO3 perovskites except without A-site elements. From the observations we...... extract the following four conclusions for the perovskites studied in the present paper: for a given cation at the B site, (I) perovskites with cations of identical oxidation state at the A site possess close formation energies; and (II) perovskites with cations of different oxidation states at the A site...

Generalized trends in the formation energies of perovskite oxides.

Science.gov (United States)

Zeng, ZhenHua; Calle-Vallejo, Federico; Mogensen, Mogens B; Rossmeisl, Jan

2013-05-28

Generalized trends in the formation energies of several families of perovskite oxides (ABO3) and plausible explanations to their existence are provided in this study through a combination of DFT calculations, solid-state physics analyses and simple physical/chemical descriptors. The studied elements at the A site of perovskites comprise rare-earth, alkaline-earth and alkaline metals, whereas 3d and 5d metals were studied at the B site. We also include ReO3-type compounds, which have the same crystal structure of cubic ABO3 perovskites except without A-site elements. From the observations we extract the following four conclusions for the perovskites studied in the present paper: for a given cation at the B site, (I) perovskites with cations of identical oxidation state at the A site possess close formation energies; and (II) perovskites with cations of different oxidation states at the A site 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 contributions of their constituent oxides, the trends can be rationalized in terms of A-O and B-O interactions in the ionic crystal. These findings reveal the existence of general systematic trends in the formation energies of perovskites and provide further insight into the role of ion-ion interactions in the properties of ternary compounds.

Mass-specific respiration of mesozooplankton and its role in the maintenance of an oxygen-deficient ecological barrier (BEDOX) in the upwelling zone off Chile upon presence of a shallow oxygen minimum zone

Science.gov (United States)

Donoso, Katty; Escribano, Ruben

2014-01-01

A shallow oxygen minimum zone (OMZ) in the coastal upwelling zone off Chile may vertically confine most zooplankton to a narrow (oxygen consumption of the mesozooplankton community obtained in Bay of Mejillones, northern Chile (23°S) in May 2010, December 2010 and August 2011. Mass-specific respiration rates were in the range of 8.2-24.5 μmol O2 mg dry mass- 1 day- 1, at an average temperature of 12 °C. Estimates of the mesozooplankton biomass in the water column indicated that its aerobic respiration may remove daily a maximum of about 20% of oxygen available at the base of the oxycline. Since previous work indicates that zooplankton aggregate near the base of the oxycline, the impact of aerobic respiration on oxygen content might be even stronger at this depth. Mesozooplankton respiration, along with community respiration by microorganisms near the base of the oxycline and a strongly stratified condition (limiting vertical flux of O2), are suggested as being critical factors causing and maintaining a persistent subsurface oxygen-deficient ecological barrier (BEDOX) in the upwelling zone. This BEDOX layer can have a major role in affecting and regulating zooplankton distribution and their dynamics in the highly productive coastal upwelling zone of the Humboldt Current System.

Oxygen influencing the photocarriers lifetime of CH3NH3PbI3−xClx film grown by two-step interdiffusion method and its photovoltaic performance

International Nuclear Information System (INIS)

Yuan, Shuai; Qiu, Zhiwen; Zhang, Hailiang; Gong, Haibo; Cao, Bingqiang; Hao, Yufeng

2016-01-01

During the growth of CH 3 NH 3 PbI 3−x Cl x (MAPbI 3−x Cl x ) perovskite films by the two-step inter-diffusion method, the presence of a trace amount of oxygen gas is critical to their physical properties and photovoltaic performance. As the oxygen concentration increases, poor film morphologies and incomplete surface coverage are observed. Moreover, by XRD, Raman scattering, and photoluminescence measurements, we find that MAPbI 3−x Cl x grains become more distorted and the electron-hole recombination rate dramatically increases. Higher oxygen concentration triggers a sharp decrease in the current density and the fill factor of corresponding solar cells, which degrades device performance, on average, from 14.3% to 4.4%. This work proves the importance of controlling the oxygen atmosphere in the fabrication of high-performance perovskite solar cells

Band gap engineering strategy via polarization rotation in perovskite ferroelectrics

International Nuclear Information System (INIS)

Wang, Fenggong; Grinberg, Ilya; Rappe, Andrew M.

2014-01-01

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

Highly efficient light management for perovskite solar cells.

Science.gov (United States)

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

2016-01-06

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.

Synthesis under pressure and characterizations through optical spectroscopy of jahn-teller cations (LS Ni3+, is Co3+) as probes diluted in a perovskite matrix

Science.gov (United States)

Sanz-Ortiz, M. N.; Rodríguez, F.; Baranov, A.; Demazeau, G.

2008-07-01

The objective is to explore through optical spectroscopy and magnetic measurements the coordination and electronic structures of transition-metal ions introduced as impurities with unusual valence states in the oxide perovskite LaAlO3. The selected transition-metal ions Ni3+(3d7) and Co3+(3d6) are characterized by an electronic configuration likely leading to an orbital degenerate E state in Oh symmetry, and thus electron-lattice coupling due to the Jahn-Teller effect may induce low symmetry distortion around the impurity oxygen octahedron. We show that a sol-gel process followed by high oxygen pressure treatments yields stabilization of trivalent state in oxide perovskite. Information about the coordination, electronic structure and aggregation around the magnetic impurity was obtained from X-ray diffraction, FTIR and optical spectroscopy. Finally, evidence on the possible existence of intermediate spin state in Co3+ is under consideration.

Synthesis under pressure and characterizations through optical spectroscopy of jahn-teller cations (LS Ni3+, is Co3+) as probes diluted in a perovskite matrix

International Nuclear Information System (INIS)

Sanz-Ortiz, M N; RodrIguez, F; Baranov, A; Demazeau, G

2008-01-01

The objective is to explore through optical spectroscopy and magnetic measurements the coordination and electronic structures of transition-metal ions introduced as impurities with unusual valence states in the oxide perovskite LaAlO 3 . The selected transition-metal ions Ni 3+ (3d 7 ) and Co 3+ (3d 6 ) are characterized by an electronic configuration likely leading to an orbital degenerate E state in Oh symmetry, and thus electron-lattice coupling due to the Jahn-Teller effect may induce low symmetry distortion around the impurity oxygen octahedron. We show that a sol-gel process followed by high oxygen pressure treatments yields stabilization of trivalent state in oxide perovskite. Information about the coordination, electronic structure and aggregation around the magnetic impurity was obtained from X-ray diffraction, FTIR and optical spectroscopy. Finally, evidence on the possible existence of intermediate spin state in Co 3+ is under consideration

Magnetism, Spin Texture, and In-Gap States: Atomic Specialization at the Surface of Oxygen-Deficient SrTiO_{3}.

Science.gov (United States)

Altmeyer, Michaela; Jeschke, Harald O; Hijano-Cubelos, Oliver; Martins, Cyril; Lechermann, Frank; Koepernik, Klaus; Santander-Syro, Andrés F; Rozenberg, Marcelo J; Valentí, Roser; Gabay, Marc

2016-04-15

Motivated by recent spin- and angular-resolved photoemission (SARPES) measurements of the two-dimensional electronic states confined near the (001) surface of oxygen-deficient SrTiO_{3}, we explore their spin structure by means of ab initio density functional theory (DFT) calculations of slabs. Relativistic nonmagnetic DFT calculations display Rashba-like spin winding with a splitting of a few meV and when surface magnetism on the Ti ions is included, bands become spin-split with an energy difference ∼100  meV at the Γ point, consistent with SARPES findings. While magnetism tends to suppress the effects of the relativistic Rashba interaction, signatures of it are still clearly visible in terms of complex spin textures. Furthermore, we observe an atomic specialization phenomenon, namely, two types of electronic contributions: one is from Ti atoms neighboring the oxygen vacancies that acquire rather large magnetic moments and mostly create in-gap states; another comes from the partly polarized t_{2g} itinerant electrons of Ti atoms lying further away from the oxygen vacancy, which form the two-dimensional electron system and are responsible for the Rashba spin winding and the spin splitting at the Fermi surface.

Efficient perovskite light-emitting diodes featuring nanometre-sized crystallites

Science.gov (United States)

Xiao, Zhengguo; Kerner, Ross A.; Zhao, Lianfeng; Tran, Nhu L.; Lee, Kyung Min; Koh, Tae-Wook; Scholes, Gregory D.; Rand, Barry P.

2017-01-01

Organic-inorganic hybrid perovskite materials are emerging as highly attractive semiconductors for use in optoelectronics. In addition to their use in photovoltaics, perovskites are promising for realizing light-emitting diodes (LEDs) due to their high colour purity, low non-radiative recombination rates and tunable bandgap. Here, we report highly efficient perovskite LEDs enabled through the formation of self-assembled, nanometre-sized crystallites. Large-group ammonium halides added to the perovskite precursor solution act as a surfactant that dramatically constrains the growth of 3D perovskite grains during film forming, producing crystallites with dimensions as small as 10 nm and film roughness of less than 1 nm. Coating these nanometre-sized perovskite grains with longer-chain organic cations yields highly efficient emitters, resulting in LEDs that operate with external quantum efficiencies of 10.4% for the methylammonium lead iodide system and 9.3% for the methylammonium lead bromide system, with significantly improved shelf and operational stability.

Zero-Dimensional Cs4PbBr6 Perovskite Nanocrystals

KAUST Repository

Zhang, Yuhai

2017-02-09

Perovskite nanocrystals (NCs) have become leading candidates for solution-processed optoelectronics applications. While substantial work has been published on 3-D perovskite phases, the NC form of the zero-dimensional (0-D) phase of this promising class of materials remains elusive. Here we report the synthesis of a new class of colloidal semiconductor NCs based on Cs4PbBr6, the 0-D perovskite, enabled through the design of a novel low-temperature reverse microemulsion method with 85% reaction yield. These 0-D perovskite NCs exhibit high photoluminescence quantum yield (PLQY) in the colloidal form (PLQY: 65%), and, more importantly, in the form of thin film (PLQY: 54%). Notably, the latter is among the highest values reported so far for perovskite NCs in the solid form. Our work brings the 0-D phase of perovskite into the realm of colloidal NCs with appealingly high PLQY in the film form, which paves the way for their practical application in real devices.

Ceramic materials on perovskite-type structure for electronic applications

International Nuclear Information System (INIS)

Surowiak, Z.

2003-01-01

Ceramic materials exhibiting the perovskite-type structure constitute among others, resource base for many fields of widely understood electronics (i.e., piezoelectronics, accustoelectronics, optoelectronics, computer science, tele- and radioelectronics etc.). Most often they are used for fabrication of different type sensors (detectors), transducers, ferroelectric memories, limiters of the electronic current intensity, etc., and hence they are numbered among so-called intelligent materials. Prototype structure of this group of materials is the structure of the mineral called perovskite (CaTiO 3 ). By means of right choice of the chemical composition of ABO 3 and deforming the regular perovskite structure (m3m) more than 5000 different chemical compounds and solid solutions exhibiting the perovskite-type structure have been fabricated. The concept of perovskite functional ceramics among often things ferroelectric ceramics, pyroelectric ceramics, piezoelectric ceramics, electrostrictive ceramics, posistor ceramics, superconductive ceramics and ferromagnetic ceramics. New possibilities of application of the perovskite-type ceramics are opened by nanotechnology. (author)

Correlations between the Hall coefficient and the superconducting transport properties of oxygen-deficient YBa2Cu3O7-δ epitaxial thin films

International Nuclear Information System (INIS)

Jones, E.C.; Christen, D.K.; Thompson, J.R.; Feenstra, R.; Zhu, S.; Lowndes, D.H.; Phillips, J.M.; Siegal, M.P.; Budai, J.D.

1993-01-01

Strong correlations between the Hall coefficient R H , the transition temperature T c , and the critical current density J c were established in a series of epitaxial YBa 2 Cu 3 O 7-δ thin films as a function of oxygen deficiency δ. Steady increases in R H with δ suggest that deoxygenation reduces the density of states which, according to BCS theory, should lead to corresponding decreases in T c . In contrast, two well-known plateaus occurring at 90 K and 60 K were observed in T c vs δ. Others have ascribed these plateaus to either electronic phenomena or phase separations. We find that in the 90-K plateau, the critical current density J c (δ,H=0) decreases with δ and extrapolates toward zero at the edge of the plateau, while the relative-field dependence of J c (δ,H) and the flux-creep pinning energies are independent of δ. These observations suggest that the phase-separation scenario occurs on the 90-K plateau. However, electronic origins cannot be ruled out at present due to difficulties in determining the equilibrium superconducting properties of oxygen-deficient YBa 2 Cu 3 O 7-δ films

Oxygen perovskites with pentavalent ruthenium A/sub 2/sup(II)Bsup(III)Rusup(V)O/sub 6/ with Asup(II) = Ba, Sr

Energy Technology Data Exchange (ETDEWEB)

Bader, H; Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Lehrstuhl fuer Anorganische Chemie 2

1980-07-01

The perovskites Ba/sub 2/Bsup(III)Rusup(V)O/sub 6/ with Bsup(III) = La, Nd, Sm, Eu, Gd, Dy, Y are cubic (Bsup(III) = La: a = 8.54 A; Y: a = 8.33 A) with a partial order for Bsup(III) and Rusup(V). The Sc compound, Ba/sub 2/ScRuO/sub 6/, has a hexagonal 6L structure (a = 5.79 A; c = 14.22 A; sequence (hcc)/sub 2/). The lattice of the Sr perovskites, Sr/sub 2/Bsup(III)Rusup(V)O/sub 6/, with Bsup(III) = Eu, Gd, Dy, Y is rhombic distorted. The IR and FIR spectra are discussed.

Hybrid Perovskites: Prospects for Concentrator Solar Cells.

Science.gov (United States)

Lin, Qianqian; Wang, Zhiping; Snaith, Henry J; Johnston, Michael B; Herz, Laura M

2018-04-01

Perovskite solar cells have shown a meteoric rise of power conversion efficiency and a steady pace of improvements in their stability of operation. Such rapid progress has triggered research into approaches that can boost efficiencies beyond the Shockley-Queisser limit stipulated for a single-junction cell under normal solar illumination conditions. The tandem solar cell architecture is one concept here that has recently been successfully implemented. However, the approach of solar concentration has not been sufficiently explored so far for perovskite photovoltaics, despite its frequent use in the area of inorganic semiconductor solar cells. Here, the prospects of hybrid perovskites are assessed for use in concentrator solar cells. Solar cell performance parameters are theoretically predicted as a function of solar concentration levels, based on representative assumptions of charge-carrier recombination and extraction rates in the device. It is demonstrated that perovskite solar cells can fundamentally exhibit appreciably higher energy-conversion efficiencies under solar concentration, where they are able to exceed the Shockley-Queisser limit and exhibit strongly elevated open-circuit voltages. It is therefore concluded that sufficient material and device stability under increased illumination levels will be the only significant challenge to perovskite concentrator solar cell applications.

Influence of BaO in perovskite electrodes for the electrochemical reduction of NOx

DEFF Research Database (Denmark)

Simonsen, Vibe Louise Ernlund; Johnsen, M.M.; Kammer Hansen, Kent

2007-01-01

Using the point electrode method, the effect of BaO on electrochemical reduction of NO (x) was investigated using the perovskites La0.85Sr0.15MnO3 (LSM15) and La0.85Sr0.15CoO3 (LSCo15) as electrode materials. The experiments were carried out in the temperature range 400-600 degrees C in 1% NO and...... favored oxygen reduction compared to reduction of nitric oxide. The LSCO15 electrode containing BaO reacted to form a K2NiF4-structure and was not tested further....

Structures and Phase Transitions in Ordered Double Perovskites

International Nuclear Information System (INIS)

Kennedy, Brendan; Zhou, Qingdi; Cheah, Melina

2005-01-01

Full text: The basic perovskite structure is ubiquitous in the study of metal oxides, yet very few oxides actually adopt the archetypal cubic structure. The perovskite structure is based on corner sharing octahedra and in most cases cooperative rotations of successive octahedra lower the symmetry of the perovskite structure. Solid State Chemists have been fascinated by these distortions for many years, not only for their intrinsic interest but also to understand how these distortions control the electronic and magnetic properties of perovskite oxides. In this presentation we will describe the use of high-resolution powder diffraction methods to unravel the temperature and composition dependence of the structures in two series of double perovskites, Sr 1-x A x NiWO 6 (A = Ba, Ca) where there is essentially complete ordering of Ni and W cations and in Sr 1-x Ca x CrNbO 6 where there is extensive disorder of the Cr and Nb cations. (authors)

Perovskites As Electrocatalysts for Alkaline Water Electrolysis

DEFF Research Database (Denmark)

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

2014-01-01

such as X-ray diffraction, electrical conductivity, scanning electron microscopy (SEM), energy dispersive microscopy (EDX) and rotating disk electrode. The perovskites tested in this work were both produced by a ball-milling technique and by an auto-combustion synthesis, which appeared to be a fast...... and 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...

New Layered Oxide-Fluoride Perovskites: KNaNbOF5 and KNaMO2F4 (M = Mo6+, W6+

Directory of Open Access Journals (Sweden)

Rachelle Ann F. Pinlac

2011-03-01

Full Text Available KNaNbOF5 and KNaMO2F4 (M = Mo6+, W6+, three new layered oxide-fluoride perovskites with the general formula ABB’X6, form from the combination of a second-order Jahn-Teller d0 transition metal and an alkali metal (Na+ on the B-site. Alternating layers of cation vacancies and K+ cations on the A-site complete the structure. The K+ cations are found in the A-site layer where the fluoride ions are located. The A-site is vacant in the adjacent A-site layer where the axial oxides are located. This unusual layered arrangement of unoccupied A-sites and under bonded oxygen has not been observed previously although many perovskite-related structures are known.

Perovskite-Based Solar Cells: Materials, Methods, and Future Perspectives

Directory of Open Access Journals (Sweden)

Di Zhou

2018-01-01

Full Text Available A novel all-solid-state, hybrid solar cell based on organic-inorganic metal halide perovskite (CH3NH3PbX3 materials has attracted great attention from the researchers all over the world and is considered to be one of the top 10 scientific breakthroughs in 2013. The perovskite materials can be used not only as light-absorbing layer, but also as an electron/hole transport layer due to the advantages of its high extinction coefficient, high charge mobility, long carrier lifetime, and long carrier diffusion distance. The photoelectric power conversion efficiency of the perovskite solar cells has increased from 3.8% in 2009 to 22.1% in 2016, making perovskite solar cells the best potential candidate for the new generation of solar cells to replace traditional silicon solar cells in the future. In this paper, we introduce the development and mechanism of perovskite solar cells, describe the specific function of each layer, and focus on the improvement in the function of such layers and its influence on the cell performance. Next, the synthesis methods of the perovskite light-absorbing layer and the performance characteristics are discussed. Finally, the challenges and prospects for the development of perovskite solar cells are also briefly presented.

Numerical simulation of kinetic demixing and decomposition in a LaCoO3-δ oxygen membrane under an oxygen potential gradient

DEFF Research Database (Denmark)

Ta, Na; Chen, Ming; Zhang, Lijun

2018-01-01

A composition- and temperature-dependent mobility database of all ionic species in the LaCoO3-δ phase was developed and combined with a La-Co-O thermodynamic database to simulate kinetic demixing and partial decomposition in LaCoO3-δ oxygen membranes operated under a 0.0001/0.21 bar oxygen partial...... pressure difference at 1073 K for 1 year. Formation of La2O3, Co3O4 and CoO phases across the membrane is predicted. The kinetic demixing process can be divided into two stages, namely, establishment of the oxygen potential gradient (fast) and demixing of the cations (slow); the former is controlled...... by the mobility of oxygen ions, and the latter is determined by the higher mobility of Co ions as compared to the La ion in the ABO3-type perovskite. A drift motion of both oxide surfaces towards the high PO2 side occurs with the movement of cations....

Dynamic surface self-reconstruction is the key of highly active perovskite nano-electrocatalysts for water splitting

Science.gov (United States)

Fabbri, Emiliana; Nachtegaal, Maarten; Binninger, Tobias; Cheng, Xi; Kim, Bae-Jung; Durst, Julien; Bozza, Francesco; Graule, Thomas; Schäublin, Robin; Wiles, Luke; Pertoso, Morgan; Danilovic, Nemanja; Ayers, Katherine E.; Schmidt, Thomas J.

2017-09-01

The growing need to store increasing amounts of renewable energy has recently triggered substantial R&D efforts towards efficient and stable water electrolysis technologies. The oxygen evolution reaction (OER) occurring at the electrolyser anode is central to the development of a clean, reliable and emission-free hydrogen economy. The development of robust and highly active anode materials for OER is therefore a great challenge and has been the main focus of research. Among potential candidates, perovskites have emerged as promising OER electrocatalysts. In this study, by combining a scalable cutting-edge synthesis method with time-resolved X-ray absorption spectroscopy measurements, we were able to capture the dynamic local electronic and geometric structure during realistic operando conditions for highly active OER perovskite nanocatalysts. Ba0.5Sr0.5Co0.8Fe0.2O3-δ as nano-powder displays unique features that allow a dynamic self-reconstruction of the material’s surface during OER, that is, the growth of a self-assembled metal oxy(hydroxide) active layer. Therefore, besides showing outstanding performance at both the laboratory and industrial scale, we provide a fundamental understanding of the operando OER mechanism for highly active perovskite catalysts. This understanding significantly differs from design principles based on ex situ characterization techniques.

Perovskites-Based Solar Cells: A Review of Recent Progress, Materials and Processing Methods

Directory of Open Access Journals (Sweden)

Zhengqi Shi

2018-05-01

Full Text Available With the rapid increase of efficiency up to 22.1% during the past few years, hybrid organic-inorganic metal halide perovskite solar cells (PSCs have become a research “hot spot” for many solar cell researchers. The perovskite materials show various advantages such as long carrier diffusion lengths, widely-tunable band gap with great light absorption potential. The low-cost fabrication techniques together with the high efficiency makes PSCs comparable with Si-based solar cells. But the drawbacks such as device instability, J-V hysteresis and lead toxicity reduce the further improvement and the future commercialization of PSCs. This review begins with the discussion of crystal and electronic structures of perovskite based on recent research findings. An evolution of PSCs is also analyzed with a greater detail of each component, device structures, major device fabrication methods and the performance of PSCs acquired by each method. The following part of this review is the discussion of major barriers on the pathway for the commercialization of PSCs. The effects of crystal structure, fabrication temperature, moisture, oxygen and UV towards the stability of PSCs are discussed. The stability of other components in the PSCs are also discussed. The lead toxicity and updated research progress on lead replacement are reviewed to understand the sustainability issues of PSCs. The origin of J-V hysteresis is also briefly discussed. Finally, this review provides a roadmap on the current needs and future research directions to address the main issues of PSCs.

Oxygen reduction kinetics on mixed conducting SOFC model cathodes

Energy Technology Data Exchange (ETDEWEB)

Baumann, F.S.

2006-07-01

The kinetics of the oxygen reduction reaction at the surface of mixed conducting solid oxide fuel cell (SOFC) cathodes is one of the main limiting factors to the performance of these promising systems. For ''realistic'' porous electrodes, however, it is usually very difficult to separate the influence of different resistive processes. Therefore, a suitable, geometrically well-defined model system was used in this work to enable an unambiguous distinction of individual electrochemical processes by means of impedance spectroscopy. The electrochemical measurements were performed on dense thin film microelectrodes, prepared by PLD and photolithography, of mixed conducting perovskite-type materials. The first part of the thesis consists of an extensive impedance spectroscopic investigation of La0.6Sr0.4Co0.8Fe0.2O3 (LSCF) microelectrodes. An equivalent circuit was identified that describes the electrochemical properties of the model electrodes appropriately and enables an unambiguous interpretation of the measured impedance spectra. Hence, the dependencies of individual electrochemical processes such as the surface exchange reaction on a wide range of experimental parameters including temperature, dc bias and oxygen partial pressure could be studied. As a result, a comprehensive set of experimental data has been obtained, which was previously not available for a mixed conducting model system. In the course of the experiments on the dc bias dependence of the electrochemical processes a new and surprising effect was discovered: It could be shown that a short but strong dc polarisation of a LSCF microelectrode at high temperature improves its electrochemical performance with respect to the oxygen reduction reaction drastically. The electrochemical resistance associated with the oxygen surface exchange reaction, initially the dominant contribution to the total electrode resistance, can be reduced by two orders of magnitude. This &apos

Two-Dimensional Halide Perovskites for Emerging New- Generation Photodetectors

DEFF Research Database (Denmark)

Tang, Yingying; Cao, Xianyi; Chi, Qijin

2018-01-01

Compared to their conventional three-dimensional (3D) counterparts, two-dimensional (2D) halide perovskites have attracted more interests recently in a variety of areas related to optoelectronics because of their unique structural characteristics and enhanced performances. In general, there are two...... distinct types of 2D halide perovskites. One represents those perovskites with an intrinsic layered crystal structure (i.e. MX6 layers, M = metal and X = Cl, Br, I), the other defines the perovskites with a 2D nanostructured morphology such as nanoplatelets and nanosheets. Recent studies have shown that 2D...... halide perovskites hold promising potential for the development of new-generation photodetectors, mainly arising from their highly efficient photoluminescence and absorbance, color tunability in the visible-light range and relatively high stability. In this chapter, we present the summary and highlights...

Fast Postmoisture Treatment of Luminescent Perovskite Films for Efficient Light-Emitting Diodes.

Science.gov (United States)

Wang, Haoran; Li, Xiaomin; Yuan, Mingjian; Yang, Xuyong

2018-04-01

Despite the recent advances in the performance of perovskite light-emitting diodes (PeLEDs), the effects of water on the perovskite emissive layer and its electroluminescence are still unclear, even though it has been previously demonstrated that moisture has a significant impact on the quality of perovskite films in the fabrication process of perovskite solar cells and is a prerequisite for obtaining high-performance PeLEDs. Here, the effects of postmoisture on the luminescent CH 3 NH 3 PbBr 3 (MAPbBr 3 ) perovskite films are systematically investigated. It is found that postmoisture treatment can efficiently control the morphology and growth of perovskite films and only a fast moisture exposure at a 60% high relative humidity results in significantly improved crystallinity, carrier lifetime, and photoluminescence quantum yield of perovskite films. With the optimized moisture-treated perovskite films, a high-performance PeLED is fabricated, exhibiting a maximum current efficiency of 20.4 cd A -1 , which is an almost 20-fold enhancement when compared with perovskite films without moisture treatment. The results provide valuable insights into the moisture-assisted growth of luminescent perovskite films and will aid in the development of high-performance perovskite light-emitting devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface oxygen vacancy and oxygen permeation flux limits of perovskite ion transport membranes

KAUST Repository

Hunt, Anton

2015-09-01

© 2015 Elsevier B.V. The mechanisms and quantitative models for how oxygen is separated from air using ion transport membranes (ITMs) are not well understood, largely due to the experimental complexity for determining surface exchange reactions at extreme temperatures (>800°C). This is especially true when fuels are present at the permeate surface. For both inert and reactive (fuels) operations, solid-state oxygen surface vacancies (δ) are ultimately responsible for driving the oxygen flux, JO2. In the inert case, the value of δ at either surface is a function of the local PO2 and temperature, whilst the magnitude of δ dictates both the JO2 and the inherent stability of the material. In this study values of δ are presented based on experimental measurements under inert (CO2) sweep: using a permeation flux model and local PO2 measurements, collected by means of a local gas-sampling probe in our large-scale reactor, we can determine δ directly. The ITM assessed was La0.9Ca0.1FeO3-δ (LCF); the relative resistances to JO2 were quantified using the pre-defined permeation flux model and local PO2 values. Across a temperature range from 825°C to 1056°C, δ was found to vary from 0.007 to 0.029 (<1%), safely within material stability limits, whilst the permeate surface exchange resistance dominates. An inert JO2 limit was identified owing to a maximum sweep surface δ, δmaxinert. The physical presence of δmaxinert is attributed to a rate limiting step shift from desorption to associative electron transfer steps on the sweep surface as PO2 is reduced. Permeate surface exchange limitations under non-reactive conditions suggest that reactive (fuel) operation is necessary to accelerate surface chemistry for future work, to reduce flux resistance and push δpast δmaxinert in a stable manner.

Cation-Dependent Light-Induced Halide Demixing in Hybrid Organic-Inorganic Perovskites.

Science.gov (United States)

Sutter-Fella, Carolin M; Ngo, Quynh P; Cefarin, Nicola; Gardner, Kira L; Tamura, Nobumichi; Stan, Camelia V; Drisdell, Walter S; Javey, Ali; Toma, Francesca M; Sharp, Ian D

2018-06-13

Mixed cation metal halide perovskites with increased power conversion efficiency, negligible hysteresis, and improved long-term stability under illumination, moisture, and thermal stressing have emerged as promising compounds for photovoltaic and optoelectronic applications. Here, we shed light on photoinduced halide demixing using in situ photoluminescence spectroscopy and in situ synchrotron X-ray diffraction (XRD) to directly compare the evolution of composition and phase changes in CH(NH 2 ) 2 CsPb-halide (FACsPb-) and CH 3 NH 3 Pb-halide (MAPb-) perovskites upon illumination, thereby providing insights into why FACs-perovskites are less prone to halide demixing than MA-perovskites. We find that halide demixing occurs in both materials. However, the I-rich domains formed during demixing accumulate strain in FACsPb-perovskites but readily relax in MA-perovskites. The accumulated strain energy is expected to act as a stabilizing force against halide demixing and may explain the higher Br composition threshold for demixing to occur in FACsPb-halides. In addition, we find that while halide demixing leads to a quenching of the high-energy photoluminescence emission from MA-perovskites, the emission is enhanced from FACs-perovskites. This behavior points to a reduction of nonradiative recombination centers in FACs-perovskites arising from the demixing process and buildup of strain. FACsPb-halide perovskites exhibit excellent intrinsic material properties with photoluminescence quantum yields that are comparable to MA-perovskites. Because improved stability is achieved without sacrificing electronic properties, these compositions are better candidates for photovoltaic applications, especially as wide bandgap absorbers in tandem cells.

Electrodeposition of organic-inorganic tri-halide perovskites solar cell

Science.gov (United States)

Charles, U. A.; Ibrahim, M. A.; Teridi, M. A. M.

2018-02-01

Perovskite (CH3NH3PbI3) semiconductor materials are promising high-performance light energy absorber for solar cell application. However, the power conversion efficiency of perovskite solar cell is severely affected by the surface quality of the deposited thin film. Spin coating is a low-cost and widely used deposition technique for perovskite solar cell. Notably, film deposited by spin coating evolves surface hydroxide and defeats from uncontrolled precipitation and inter-diffusion reaction. Alternatively, vapor deposition (VD) method produces uniform thin film but requires precise control of complex thermodynamic parameters which makes the technique unsuitable for large scale production. Most deposition techniques for perovskite require tedious surface optimization to improve the surface quality of deposits. Optimization of perovskite surface is necessary to significantly improve device structure and electrical output. In this review, electrodeposition of perovskite solar cell is demonstrated as a scalable and reproducible technique to fabricate uniform and smooth thin film surface that circumvents the need for high vacuum environment. Electrodeposition is achieved at low temperatures, supports precise control and optimization of deposits for efficient charge transfer.

Synthesis of LaNiO{sub 3} perovskite by the modified proteic gel method and study of catalytic properties in the syngas production

Energy Technology Data Exchange (ETDEWEB)

Santos, Jose C.; Mesquita, Maria E.; Pedrosa, Anne M. Garrido, E-mail: annemgp@ufs.br, E-mail: annemgp@yahoo.com [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil). Departamento de Quimica e Engenharia Quimica; Souza, Marcelo J.B. [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil). Departamento de Engenharia Quimica; Ruiz, Juan A.C. [Centro de Tecnologias do Gas e Energias Renovaveis (CTGAS-ER), Natal, RN (Brazil). Laboratorio de Processamento do Gas; Melo, Dulce M.A. [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Centro de Ciencias Exatas e da Terra. Depaertamento de Quimica

2012-10-15

This work describes a study on the synthesis of LaNiO{sub 3} perovskites via the modified proteic gel method, varying collagen content and on the catalytic activity of LaNiO{sub 3} and LaNiO{sub 3}/Al{sub 2}O{sub 3} in the syngas (CO + H{sub 2}) production. X-ray diffraction patterns revealed the formation of perovskite structure in all samples prepared by proteic gel synthesis method, varying collagen content and after calcination at 700 deg C for 2 h. LaNiO{sub 3}/Al{sub 2}O{sub 3} catalyst prepared by the impregnation method showed diffraction peaks due to the perovskite structure and to the support (Al{sub 2}O{sub 3}). This catalyst presented: specific surface of 46.1 m{sup 2} g{sup -1}, two reduction peaks in the temperature programmed reduction (TPR) profile and 46% of methane conversion (by the partial oxidation of methane using oxygen) after 18 h of reaction. (author)

Chitosan-Assisted Crystallization and Film Forming of Perovskite Crystals through Biomineralization.

Science.gov (United States)

Yang, Yang; Sun, Chen; Yip, Hin-Lap; Sun, Runcang; Wang, Xiaohui

2016-03-18

Biomimetic mineralization is a powerful approach for the synthesis of advanced composite materials with hierarchical organization and controlled structure. Herein, chitosan was introduced into a perovskite precursor solution as a biopolymer additive to control the crystallization and to improve the morphology and film-forming properties of a perovskite film by way of biomineralization. The biopolymer additive was able to control the size and morphology of the perovskite crystals and helped to form smooth films. The mechanism of chitosan-mediated nucleation and growth of the perovskite crystals was explored. As a possible application, the chitosan-perovskite composite film was introduced into a planar heterojunction solar cell and increased power conversion efficiency relative to that observed for the pristine perovskite film was achieved. The biomimetic mineralization method proposed in this study provides an alternative way of preparing perovskite crystals with well-controlled morphology and properties and extends the applications of perovskite crystals in photoelectronic fields, including planar-heterojunction solar cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Formability of ABX3 (X=F,Cl,Br,I) halide perovskites

International Nuclear Information System (INIS)

Li Chonghea; Lu Xionggang; Ding Weizhong; Feng Liming; Gao Yonghui; Guo Ziming

2008-01-01

In this study a total of 186 complex halide systems were collected; the formabilities of ABX 3 (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-MnF 2 ) without perovskite structure and six systems (RbF-PbF 2 , CsF- BeF 2 , KCl-FeCl 2 , TlI-MnI 2 , RbI-SnI 2 , TlI-PbI 2 ) 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 ABX 3 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 ABO 3 oxide perovskite, and may be helpful to design novel halide materials with the perovskite structure. (orig.)

Oxygen Transport Membrane Reactors for Oxy-Fuel Combustion and Carbon Capture Purposes

Science.gov (United States)

Falkenstein-Smith, Ryan L.

This thesis investigates oxygen transport membrane reactors (OTMs) for the application of oxy-fuel combustion. This is done by evaluating the material properties and oxygen permeability of different OTM compositions subjected to a variety of operating conditions. The scope of this work consists of three components: (1) evaluate the oxygen permeation capabilities of perovskite-type materials for the application of oxy-fuel combustion; (2) determine the effects of dual-phase membrane compositions on the oxygen permeation performance and membrane characteristics; and (3) develop a new method for estimating the oxygen permeation performance of OTMs utilized for the application of oxy-fuel combustion. SrSc0.1Co0.9O3-delta (SSC) is selected as the primary perovskite-type material used in this research due to its reported high ionic and electronic conductive properties and chemical stability. SSC's oxygen ion diffusivity is investigated using a conductivity relaxation technique and thermogravimetric analysis. Material properties such as chemical structure, morphology, and ionic and electronic conductivity are examined by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and conductivity testing using a four-probe method, respectively. Oxygen permeation tests study the oxygen permeability OTMs under modified membrane temperatures, sweeping gas flow rates, sweeping gas compositions, membrane configurations, and membrane compositions. When utilizing a pure CO2 sweeping gas, the membrane composition was modified with the addition of Sm0.2Ce0.8O1.9-delta (SDC) at varying wt.% to improve the membranes mechanical stability. A newly developed method to evaluate the oxygen permeation performance of OTMs is also presented by fitting OTM's oxygen permeability to the methane fraction in the sweeping gas composition. The fitted data is used to estimate the overall performance and size of OTMs utilized for the application of oxy-fuel combustion. The findings from this

Meso-Molding Three-Dimensional Macroporous Perovskites: A New Approach to Generate High-Performance Nanohybrid Catalysts

DEFF Research Database (Denmark)

Arandiyan, Hamidreza; Scott, Jason; Wang, Yuan

2016-01-01

Newly designed 3D highly ordered macro/mesoporous multifunctional La1-xCexCoO3 nanohybrid frameworks with a 2D hexagonal mesostructure were fabricated via facile meso-molding in a three-dimensionally macroporous perovskite (MTMP) route. The nanohybrid framework exhibited excellent catalytic...... activity for methane combustion, which derived from the MTMP providing a larger surface area and pore volume, uniform pore sizes, higher accessible surface oxygen concentration, better low-temperature reducibility, and a unique nanovoid 3D structure....

Universal Approach toward Hysteresis-Free Perovskite Solar Cell via Defect Engineering.

Science.gov (United States)

Son, Dae-Yong; Kim, Seul-Gi; Seo, Ja-Young; Lee, Seon-Hee; Shin, Hyunjung; Lee, Donghwa; Park, Nam-Gyu

2018-01-31

Organic-inorganic halide perovskite is believed to be a potential candidate for high efficiency solar cells because power conversion efficiency (PCE) was certified to be more than 22%. Nevertheless, mismatch of PCE due to current density (J)-voltage (V) hysteresis in perovskite solar cells is an obstacle to overcome. There has been much lively debate on the origin of J-V hysteresis; however, effective methodology to solve the hysteric problem has not been developed. Here we report a universal approach for hysteresis-free perovskite solar cells via defect engineering. A severe hysteresis observed from the normal mesoscopic structure employing TiO 2 and spiro-MeOTAD is almost removed or does not exist upon doping the pure perovskites, CH 3 NH 3 PbI 3 and HC(NH 2 ) 2 PbI 3 , and the mixed cation/anion perovskites, FA 0.85 MA 0.15 PbI 2.55 Br 0.45 and FA 0.85 MA 0.1 Cs 0.05 PbI 2.7 Br 0.3 , with potassium iodide. Substantial reductions in low-frequency capacitance and bulk trap density are measured from the KI-doped perovskite, which is indicative of trap-hysteresis correlation. A series of experiments with alkali metal iodides of LiI, NaI, KI, RbI and CsI reveals that potassium ion is the right element for hysteresis-free perovskite. Theoretical studies suggest that the atomistic origin of the hysteresis of perovskite solar cells is not the migration of iodide vacancy but results from the formation of iodide Frenkel defect. Potassium ion is able to prevent the formation of Frenkel defect since K + energetically prefers the interstitial site. A complete removal of hysteresis is more pronounced at mixed perovskite system as compared to pure perovskites, which is explained by lower formation energy of K interstitial (-0.65 V for CH 3 NH 3 PbI 3 vs -1.17 V for mixed perovskite). The developed KI doping methodology is universally adapted for hysteresis-free perovskite regardless of perovskite composition and device structure.

XPS study of surface state of novel perovskite system Dy{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-δ} as cathode for solid oxide fuel cells

Energy Technology Data Exchange (ETDEWEB)

Kautkar, Pranay R.; Acharya, Smita A., E-mail: saha275@yahoo.com; Tumram, Priya V. [Depatment of Physics, Rashtrasant Tukadoji Maharaj Nagpur University Campus, Nagpur-440033 (India); Deshpande, U. P. [UGC-DAE Consortium for scientific Research, University Campus, Khandwa Road, Indore-452001, Madhya Pradesh,India (India)

2016-05-06

In the present attempt,novel perovskite oxide Dy{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3–δ} (DSCF) as cathode material has been synthesized by an Ethylene glycol-citrate combined sol-gel combustion route. Orthorhombic symmetry structure is confirmed by X-ray diffraction (XRD) and data is well fitted using Rietveld refinement by Full-Prof software suite. Chemical natureof surface of DSCF has been analyzed by using X-ray photoelectron spectroscopy (XPS). XPS result shows that Dy ions are in +3 oxidation state and Sr in +2 states. However Co2p and Fe2p spectra indicates partial change in oxidation state from Co3+/Fe3+ to Co4+/Fe4+. These attribute to develop active sites on the surface for oxygen ions. O1s XPS spectra shows two oxygen peaks relatedto lattice oxygen in perovskite and absorbed oxygen in oxygen vacancy are detected. O1s spectra demonstrate the existence of adsorbed oxygen species on the surface of DSCF oxide which is quite beneficial for intermediate temperature of Solid Oxide Fuel Cell.

Ultrasmooth Perovskite Film via Mixed Anti-Solvent Strategy with Improved Efficiency.

Science.gov (United States)

Yu, Yu; Yang, Songwang; Lei, Lei; Cao, Qipeng; Shao, Jun; Zhang, Sheng; Liu, Yan

2017-02-01

Most antisolvents employed in previous research were miscible with perovskite precursor solution. They always led to fast formation of perovskite even if the intermediate stage existed, which was not beneficial to obtain high quality perovskite films and made the formation process less controllable. In this work, a novel ethyl ether/n-hexane mixed antisolvent (MAS) was used to achieve high nucleation density and slow down the formation process of perovskite, producing films with improved orientation of grains and ultrasmooth surfaces. These high quality films exhibited efficient charge transport at the interface of perovskite/hole transport material and perovskite solar cells based on these films showed greatly improved performance with the best power conversion efficiency of 17.08%. This work also proposed a selection principle of MAS and showed that solvent engineering by designing the mixed antisolvent system can lead to the fabrication of high-performance perovskite solar cells.

Perovskite as a matrix for incorporation of long-lived radionuclides

International Nuclear Information System (INIS)

Chernyavskaya, N.E.; Ochkin, A.V.; Chizhevskaya, S.V.; Stefanovskij, S.V.

1998-01-01

SYNROC is titanate ceramics consisting mainly of zirconolite, perovskite, and hollandite, developed to immobilize high level waste. Perovskite is able to incorporate strontium, yttrium, and trivalent lanthanides and actinides. The main goal of the present work is leaching study of various radionuclides from perovskite. Samples of perovskite-rich ceramics were produced by cold pressing of oxide mixture followed by firing in resistive furnace at 1350 degC for 3 hours. For leaching tests, ceramic pellets were crushed and surface areas were measured using argon thermal desorption technique. Leach rate was measured by boiling in a Soxhlet apparatus for 5 hours. Leach rates in 0.1 M HNO 3 and NaCl solutions were measured by boiling with stirrer and reverse cooler. Leach rate was controlled with radioactive indicator technique. Density of the perovskite-rich ceramic samples prepared was about 75% of theoretical. From XRD examination, the target phase (perovskite) yield was found to be about 95 vol.%. Minor rutile (≤ 5 vol.%) was also present. Leach rate of 90 Sr from Sr-doped perovskites with specified composition Ca 1-x Sr x TiO 3 did not depend on x until certain x value. Leach rate of 90 Sr from control zirconolite sample was by one order of magnitude higher than from perovskite. Leach rates of 147 Pm, 238 Pu, and 241 Am from perovskite ceramics with nominal perovskite composition had the same order of magnitude (about 10 -4 g/(m 2 day)). Substitution of 5 at.% Ce for Ca and 5 at.% Al for Ti lowered leach rate of 238 Pu by a factor of 6. Leach rates of 90 Sr in 0.1 M HNO 3 and NaCl solutions were three and one orders of magnitude higher than in distilled water

Solid State Structure-Reactivity Studies on Bixbyites, Fluorites and Perovskites Belonging to the Vanadate, Titanate and Cerate Families

Science.gov (United States)

Shafi, Shahid P.

This thesis primarily focuses on the systematic understanding of structure-reactivity relationships in two representative systems: bixbyite and related structures as well as indium doped CeO2. Topotactic reaction routes have gained significant attention over the past two decades due to their potential to access kinetically controlled metastable materials. This has contributed substantially to the understanding of solid state reaction pathways and provided first insights into mechanisms. Contrary to the widely used ex-situ methods, in-situ techniques including powder x-ray diffraction and thermogravimetric-differential thermal analysis have been employed extensively throughout this work in order to follow the reaction pathways in real time. Detailed analysis of the AVO3 (A = In, Sc) bixbyite reactivity under oxidative conditions has been carried out and a variety of novel metastable oxygen defect phases have been identified and characterized. The novel metastable materials have oxygen deficient fluorite structures and consequently are potential ion conductors. Structural aspects of the topotactic vs. reconstructive transformations are illustrated with this model system. The structure-reactivity study of AVO3 phases was extended to AVO3 perovskite family. Based on the research methodologies and results from AVO3 bixbyite reactivity studies a generalized mechanistic oxidation pathway has been established with a non-vanadium phase, ScTiO3 bixbyite. However, there is stark contrast in terms of structural stability and features beyond this stability limit during AVO3 and ScTiO3 bixbyite reaction pathways. A series of complex reaction sequences including phase separation and phase transitions were identified during the investigation of ScTiO3 reactivity. The two-step formation pathway for the fluorite-type oxide ion conductor Ce1-xInxO2-delta (0 ≤ x ≤ 0.3) is being reported. The formation of the BaCe1-xInxO 3-delta perovskites and the subsequent CO2-capture reaction

Rational Strategies for Efficient Perovskite Solar Cells.

Science.gov (United States)

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

Phase transformation of Ca-perovskite in MORB at D" region

Science.gov (United States)

Nishitani, N.; Ohtani, E.; Sakai, T.; Kamada, S.; Miyahara, M.; Hirao, N.

2012-12-01

Seismological studies indicate the presence of seismic anomalies in the Earth's deep interior. To investigate the anomaly, the physical property of the major minerals in lower mantle such as MgSiO3-perovskite, MgSiO3 post-perovskite and MgO periclase were studied well. Other candidate, CaSiO3 perovskite (Ca-perovskite) exists in peridotitic mantle and basaltic oceanic crust (mid-ocean ridge basalt; MORB). Previous studies indicate the abundance of Ca-perovskite is up to ~9 vol.% in the pyrolite mantle and ~24 vol.% in the MORB oceanic crust. However, the pressure range of previous works are still not enough to understand the D" region. In this study, natural MORB was compressed in double sided laser heated DAC. Au was used as a pressure maker and a laser absorber. NaCl was used as the thermal insulator and pressure medium. The phase relation of Ca-perovskite in MORB was investigated from 36 to 156 GPa and 300 to 2600 K by the in situ X-ray diffraction measurements at SPring-8 (BL10XU). The transition of Ca-perovskite from a tetragonal structure to a cubic structure occurred at about 1800 K up to about 100 GPa and below 1500 K at pressures above 100 GPa. This suggests that the tetragonal-cubic transition of Ca-perovskite could occur in MORB, associating with Al2O3 contents. The present results suggest that the seismic anomaly at D" layer could be caused by the transition in Ca-perovskite.

Reconditioning perovskite films in vapor environments through repeated cation doping

Science.gov (United States)

Boonthum, Chirapa; Pinsuwan, Kusuma; Ponchai, Jitprabhat; Srikhirin, Toemsak; Kanjanaboos, Pongsakorn

2018-06-01

Perovskites have attracted considerable attention for application as high-efficiency photovoltaic devices owing to their low-cost and low-temperature fabrication. A good surface and high crystallinity are necessary for high-performance devices. We examine the negative effects of chemical ambiences on the perovskite crystal formation and morphology. The repeated cation doping (RCD) technique was developed to remedy these issues by gradually dropping methylammonium ions on top of about-to-form perovskite surfaces to cause recrystallization. RCD promotes pinhole-free, compact, and polygonal-like surfaces under various vapor conditions. Furthermore, it enhances the electronic properties and crystallization. The benefits of RCD extend beyond perovskites under vapor ambiences, as it can improve regular and wasted perovskites.

High-Performance Single-Crystalline Perovskite Thin-Film Photodetector

KAUST Repository

Yang, Zhenqian

2018-01-10

The best performing modern optoelectronic devices rely on single-crystalline thin-film (SC-TF) semiconductors grown epitaxially. The emerging halide perovskites, which can be synthesized via low-cost solution-based methods, have achieved substantial success in various optoelectronic devices including solar cells, lasers, light-emitting diodes, and photodetectors. However, to date, the performance of these perovskite devices based on polycrystalline thin-film active layers lags behind the epitaxially grown semiconductor devices. Here, a photodetector based on SC-TF perovskite active layer is reported with a record performance of a 50 million gain, 70 GHz gain-bandwidth product, and a 100-photon level detection limit at 180 Hz modulation bandwidth, which as far as we know are the highest values among all the reported perovskite photodetectors. The superior performance of the device originates from replacing polycrystalline thin film by a thickness-optimized SC-TF with much higher mobility and longer recombination time. The results indicate that high-performance perovskite devices based on SC-TF may become competitive in modern optoelectronics.

High annealing temperature induced rapid grain coarsening for efficient perovskite solar cells.

Science.gov (United States)

Cao, Xiaobing; Zhi, Lili; Jia, Yi; Li, Yahui; Cui, Xian; Zhao, Ke; Ci, Lijie; Ding, Kongxian; Wei, Jinquan

2018-08-15

Thermal annealing plays multiple roles in fabricating high quality perovskite films. Generally, it might result in large perovskite grains by elevating annealing temperature, but might also lead to decomposition of perovskite. Here, we study the effects of annealing temperature on the coarsening of perovskite grains in a temperature range from 100 to 250 °C, and find that the coarsening rate of the perovskite grain increase significantly with the annealing temperature. Compared with the perovskite films annealed at 100 °C, high quality perovskite films with large columnar grains are obtained by annealing perovskite precursor films at 250 °C for only 10 s. As a result, the power conversion efficiency of best solar cell increased from 12.35% to 16.35% due to its low recombination rate and high efficient charge transportation in solar cells. Copyright © 2018. Published by Elsevier Inc.

W-doped TiO2 photoanode for high performance perovskite solar cell

International Nuclear Information System (INIS)

Liu, Jinwang; Zhang, Jing; Yue, Guoqiang; Lu, Xingwei; Hu, Ziyang; Zhu, Yuejin

2016-01-01

Titanium dioxide (TiO 2 ) with dispersed W-doping shows its capability for efficient electron collection from perovskite to TiO 2 in perovskite solar cell. The conduction band (CB) of TiO 2 moves downward (positive shift) with increasing the tungsten (W) content, which enlarges the energy gap between the CB of TiO 2 and the perovskite. Thus, the efficiency of electron injection from perovskite to TiO 2 is increased. Due to the increased electron injection, W-doped TiO 2 (≤0.2% W content) enhances the short-circuit photocurrent (J sc ) of perovskite solar cell and improves the performance of perovskite solar cell. Perovskite solar cell with 0.1% W-doped photoanode obtains the highest power conversion efficiency (η = 10.6%), which shows enhancement by 13% in J sc and by 17% in η, as compared with the undoped TiO 2 perovskite solar cell.

Polarized emission from CsPbX3 perovskite quantum dots

Science.gov (United States)

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

Tracking the formation of methylammonium lead triiodide perovskite

International Nuclear Information System (INIS)

Liu, Lijia; McLeod, John A.; Wang, Rongbin; Shen, Pengfei; Duhm, Steffen

2015-01-01

The formation mechanism of perovskite methylammonium lead triiodide (CH 3 NH 3 PbI 3 ) was studied with in situ X-ray photoelectron spectroscopy (XPS) on successive depositions of thermally evaporated methylammonium iodide (CH 3 NH 3 I) on a lead iodide (PbI 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 3 NH 3 PbI 3 . Our most important finding is that during vapour deposition of CH 3 NH 3 I onto PbI 2 , at least two carbon species are present in the resulting material, while only one nitrogen species is present. This suggests that CH 3 NH 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 3 NH 3 substitution with CH 3 was evaluated, and electronic structure calculations show that CH 3 defects would impact the photovoltaic performance in perovskite solar cells. The possibility that not all A sites in the APbI 3 perovskite are occupied by CH 3 NH 3 is therefore an important consideration when evaluating the performance of organometallic trihalide solar cells synthesized using typical approaches

Improving the photovoltaic performance of perovskite solar cells with acetate

Science.gov (United States)

Zhao, Qian; Li, G. R.; Song, Jian; Zhao, Yulong; Qiang, Yinghuai; Gao, X. P.

2016-01-01

In an all-solid-state perovskite solar cell, methylammonium lead halide film is in charge of generating photo-excited electrons, thus its quality can directly influence the final photovoltaic performance of the solar cell. This paper accentuates a very simple chemical approach to improving the quality of a perovskite film with a suitable amount of acetic acid. With introduction of acetate ions, a homogeneous, continual and hole-free perovskite film comprised of high-crystallinity grains is obtained. UV-visible spectra, steady-state and time-resolved photoluminescence (PL) spectra reveal that the obtained perovskite film under the optimized conditions shows a higher light absorption, more efficient electron transport, and faster electron extraction to the adjoining electron transport layer. The features result in the optimized perovskite film can provide an improved short-circuit current. The corresponding solar cells with a planar configuration achieves an improved power conversion efficiency of 13.80%, and the highest power conversion efficiency in the photovoltaic measurements is up to 14.71%. The results not only provide a simple approach to optimizing perovskite films but also present a novel angle of view on fabricating high-performance perovskite solar cells. PMID:27934924

Improving the photovoltaic performance of perovskite solar cells with acetate.

Science.gov (United States)

Zhao, Qian; Li, G R; Song, Jian; Zhao, Yulong; Qiang, Yinghuai; Gao, X P

2016-12-09

In an all-solid-state perovskite solar cell, methylammonium lead halide film is in charge of generating photo-excited electrons, thus its quality can directly influence the final photovoltaic performance of the solar cell. This paper accentuates a very simple chemical approach to improving the quality of a perovskite film with a suitable amount of acetic acid. With introduction of acetate ions, a homogeneous, continual and hole-free perovskite film comprised of high-crystallinity grains is obtained. UV-visible spectra, steady-state and time-resolved photoluminescence (PL) spectra reveal that the obtained perovskite film under the optimized conditions shows a higher light absorption, more efficient electron transport, and faster electron extraction to the adjoining electron transport layer. The features result in the optimized perovskite film can provide an improved short-circuit current. The corresponding solar cells with a planar configuration achieves an improved power conversion efficiency of 13.80%, and the highest power conversion efficiency in the photovoltaic measurements is up to 14.71%. The results not only provide a simple approach to optimizing perovskite films but also present a novel angle of view on fabricating high-performance perovskite solar cells.

Toward Increasing Micropore Volume between Hybrid Layered Perovskites with Silsesquioxane Interlayers.

Science.gov (United States)

Kataoka, Sho; Kamimura, Yoshihiro; Endo, Akira

2018-04-10

Hybrid organic-inorganic layered perovskites are typically nonporous solids. However, the incorporation of silsesquioxanes with a cubic cage structure as interlayer materials creates micropores between the perovskite layers. In this study, we increase in the micropore volume in layered perovskites by replacing a portion of the silsesquioxane interlayers with organic amines. In the proposed method, approximately 20% of the silsesquioxane interlayers can be replaced without changing the layer distance owing to the size of the silsesquioxane. When small amines (e.g., ethylamine) are used in this manner, the micropore volume of the obtained hybrid layered perovskites increases by as much as 44%; when large amines (e.g., phenethylamine) are used, their micropore volume decreases by as much as 43%. Through the variation of amine fraction, the micropore volume can be adjusted in the range. Finally, the magnetic moment measurements reveal that the layered perovskites with mixed interlayers exhibit ferromagnetic ordering at temperature below 20 K, thus indicating that the obtained perovskites maintain their functions as layered perovskites.

Research progress on organic-inorganic halide perovskite materials and solar cells

Science.gov (United States)

Ono, Luis K.; Qi, Yabing

2018-03-01

Owing to the intensive research efforts across the world since 2009, perovskite solar cell power conversion efficiencies (PCEs) are now comparable or even better than several other photovoltaic (PV) technologies. In this topical review article, we review recent progress in the field of organic-inorganic halide perovskite materials and solar cells. We associate these achievements with the fundamental knowledge gained in the perovskite research. The major recent advances in the fundamental perovskite material and solar cell research are highlighted, including the current efforts in visualizing the dynamical processes (in operando) taking place within a perovskite solar cell under operating conditions. We also discuss the existing technological challenges. Based on a survey of recently published works, we point out that to move the perovskite PV technology forward towards the next step of commercialization, what perovskite PV technology need the most in the coming next few years is not only further PCE enhancements, but also up-scaling, stability, and lead-toxicity.

Fabrication of single phase 2D homologous perovskite microplates by mechanical exfoliation

Science.gov (United States)

Li, Junze; Wang, Jun; Zhang, Yingjun; Wang, Haizhen; Lin, Gaoming; Xiong, Xuan; Zhou, Weihang; Luo, Hongmei; Li, Dehui

2018-04-01

The two-dimensional (2D) Ruddlesden-Popper type perovskites have attracted intensive interest for their great environmental stability and various potential optoelectronic applications. Fundamental understanding of the photophysical and electronic properties of the 2D perovskites with pure single phase is essential for improving the performance of the optoelectronic devices and designing devices with new architectures. Investigating the optical and electronic properties of these materials with pure single phase is required to obtain pure single phase 2D perovskites. Here, we report on an alternative approach to fabricate (C4H9NH3)2(CH3NH3) n-1Pb n I3n+1 microplates with pure single n-number perovskite phase for n  >  2 by mechanical exfoliation. Micro-photoluminescence and absorption spectroscopy studies reveal that the as-synthesized 2D perovskite plates for n  >  2 are comprised by dominant n-number phase and small inclusions of hybrid perovskite phases with different n values, which is supported by excitation power dependent photoluminescence. By mechanical exfoliation method, 2D perovskite microplates with the thickness of around 20 nm are obtained, which surprisingly have single n-number perovskite phase for n  =  2-5. In addition, we have demonstrated that the exfoliated 2D perovskite microplates can be integrated with other 2D layered materials such as boron nitride, and are able to be transferred to prefabricated electrodes for photodetections. Our studies not only provide a strategy to prepare 2D perovskites with a single n-number perovskite phase allowing us to extract the basic optical and electronic parameters of pure phase perovskites, but also demonstrate the possibility to integrate the 2D perovskites with other 2D layered materials to extend the device’s functionalities.

Full coverage of perovskite layer onto ZnO nanorods via a modified sequential two-step deposition method for efficiency enhancement in perovskite solar cells

Science.gov (United States)

Ruankham, Pipat; Wongratanaphisan, Duangmanee; Gardchareon, Atcharawon; Phadungdhitidhada, Surachet; Choopun, Supab; Sagawa, Takashi

2017-07-01

Full coverage of perovskite layer onto ZnO nanorod substrates with less pinholes is crucial for achieving high-efficiency perovskite solar cells. In this work, a two-step sequential deposition method is modified to achieve an appropriate property of perovskite (MAPbI3) film. Surface treatment of perovskite layer and its precursor have been systematically performed and their morphologies have been investigated. By pre-wetting of lead iodide (PbI2) and letting it dry before reacting with methylammonium iodide (MAI) provide better coverage of perovskite film onto ZnO nanorod substrate than one without any treatment. An additional MAI deposition followed with toluene drop-casting technique on the perovskite film is also found to increase the coverage and enhance the transformation of PbI2 to MAPbI3. These lead to longer charge carrier lifetime, resulting in an enhanced power conversion efficiency (PCE) from 1.21% to 3.05%. The modified method could been applied to a complex ZnO nanorods/TiO2 nanoparticles substrate. The enhancement in PCE to 3.41% is observed. These imply that our introduced method provides a simple way to obtain the full coverage and better transformation to MAPbI3 phase for enhancement in performances of perovskite solar cells.

Effect of atmosphere on the formation of perovskite phase in 0.90Pb(Zn{sub 1/3}Nb{sub 2/3})O{sub 3}-0.10PbTiO{sub 3} (PZN-10PT) powders

Energy Technology Data Exchange (ETDEWEB)

Raigoza, C.F.V., E-mail: claudiafercha@gmail.com [Universidad del Cauca, Dpto. de Física, Grupo de Ciencia y Tecnología de Materiales Cerámicos, Popayán (Colombia); Kiminami, R.H.G.A. [Federal University of São Carlos, Department of Materials Engineering, São Carlos, SP, 13565-905 (Brazil); Eiras, J.A.; Garcia, D. [Federal University of São Carlos, Department of Physics, São Carlos, SP, 13565-905 (Brazil)

2017-04-01

Lead zinc niobate (PZN) and lead titanate (PT) solid solutions close to the morphotropic phase boundary (MPB) exhibit unusually large dielectric and piezoelectric constants. PZN-PT ceramics with a composition close to the MPB processed by the conventional route yield ceramics with a pyrochlore structure. In the last few decades, attempts to synthesize PZN-PT powders with perovskite structure via traditional ceramic methods and novel chemical processing routes have failed. In the present research, an analysis was made of the effect of the calcination atmosphere on the formation of perovskite phase in PZN-10PT powders. To this end, thermal analyses were carried out in four different atmospheres: oxygen, air, argon and nitrogen. The powders were calcined at the temperatures at which the DTA curves presented peaks, and the resulting phases were identified by X-ray diffraction. - Highlights: • PZN-PT ceramics powders. • Air, oxygen, argon and nitrogen as synthesis atmospheres. • Zinc as essential element in the formation and stabilization of the perovskite phase. • Nitrogen as inhibitor of the decomposition the zinc oxide.

Understanding perovskite formation through the intramolecular exchange method in ambient conditions

Science.gov (United States)

Szostak, Rodrigo; Castro, Jhon A. P.; Marques, Adriano S.; Nogueira, Ana F.

2017-04-01

Among the methods to prepare hybrid organic-inorganic perovskite films, the intramolecular exchange method was the first one that made possible to prepare perovskite solar cells with efficiencies higher than 20%. However, perovskite formation by this method is not completely understood, especially in ambient conditions. In this work, perovskite films were prepared by the intramolecular exchange method in ambient conditions. The spin coating speed and the frequency of the MAI solution dripping onto PbI2(DMSO) were varied during the deposition steps. With the combination of these two parameters, a rigid control of the solvent drying was possible. Thus, depending on the chosen conditions, the intermediate MAPb3I8·2DMSO was formed with residual PbI2. Otherwise, direct formation of perovskite film was attained. A mechanism for the direct formation of bulk perovskite was proposed. We also investigated how the posterior thermal annealing affects the crystallinity and defects in perovskite films. With prolonged thermal annealing, the excess of MAI can be avoided, increasing the efficiency and decreasing the hysteresis of the solar cells. The best perovskite solar cell achieved a stabilized power output of 12.9%. The findings of this work pave the way for realizing the fabrication of efficient perovskite solar cells in ambient atmosphere, a very desirable condition for cost-efficient large scale manufacturing of this technology.

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

Science.gov (United States)

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.

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

Science.gov (United States)

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 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.

High pressure Moessbauer spectroscopy of perovskite iron oxide

International Nuclear Information System (INIS)

Nasu, Saburo; Suenaga, Tomoya; Morimoto, Shotaro; Kawakami, Takateru; Kuzushita, Kaori; Takano, Mikio

2003-01-01

High-pressure 57 Fe Moessbauer spectroscopy using a diamond anvil cell has been performed for perovskite iron oxides SrFeO 3 , CaFeO 3 and La 1/3 Sr 2/3 O 3 . The charge states and the magnetic dependency to pressure were determined. Pressure magnetic phase diagrams of these perovskite iron oxides are determined up to about 70 GPa. To be clear the magnetic ordered state, they are measured up to 7.8 T external magnetic fields at 4.5K. The phase transition of these perovskite oxides to ferromagnetisms with high magnetic ordered temperature is observed. In higher pressure, high spin-low spin transition of oxides besides CaFeO 3 is generated. The feature of Moessbauer spectroscopy, perovskite iron oxide and Moessbauer spectroscopy under high pressure are explained. (S.Y.)

Performance of planar heterojunction perovskite solar cells under light concentration

Directory of Open Access Journals (Sweden)

Aaesha Alnuaimi

2016-11-01

Full Text Available In this work, we present 2D simulation of planar heterojunction perovskite solar cells under high concentration using physics-based TCAD. The performance of planar perovskite heterojunction solar cells is examined up to 1000 suns. We analyze the effect of HTM mobility and band structure, surface recombination velocities at interfaces and the effect of series resistance under concentrated light. The simulation results revealed that the low mobility of HTM material limits the improvement in power conversation efficiency of perovskite solar cells under concentration. In addition, large band offset at perovskite/HTM interface contributes to the high series resistance. Moreover, losses due to high surface recombination at interfaces and the high series resistance deteriorate significantly the performance of perovskite solar cells under concentration.

Antiferroelectric Nature of CH3NH3PbI3-xClx Perovskite and Its Implication for Charge Separation in Perovskite Solar Cells

Science.gov (United States)

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.

Sensing properties of perovskite oxide La0.5SR0.5Co0-3-d obtained by using pulsed laser deposition

NARCIS (Netherlands)

Dam, T.V.A.; Olthuis, Wouter; Bergveld, Piet

2004-01-01

La1−xSrxCoO3−δ belongs to the group of perovskite oxides of the ABO3 structure, with a trivalent rare earth in the A position (La) and a trivalent metal ion in the B position (Co). Doping with divalent Sr-ions at the trivalent La-positions creates oxygen vacancies which give the oxide catalytic

Quantum confinement effect and exciton binding energy of layered perovskite nanoplatelets

Directory of Open Access Journals (Sweden)

Qiang Wang

2018-02-01

Full Text Available We report the preparation of monolayer (n = 1, few-layer (n = 2–5 and 3D (n = ∞ organic lead bromide perovskite nanoplatelets (NPLs by tuning the molar ratio of methylammonium bromide (MABr and hexadecammonium bromide (HABr. The absorption spectrum of the monolayer (HA2PbBr4 perovskite NPLs shows about 138 nm blue shift from that of 3D MAPbBr3 perovskites, which is attributed to strong quantum confinement effect. We further investigate the two-photon photoluminescence (PL of the NPLs and measure the exciton binding energy of monolayer perovskite NPLs using linear absorption and two-photon PL excitation spectroscopy. The exciton binding energy of monolayer perovskite NPLs is about 218 meV, which is far larger than tens of meV in 3D lead halide perovskites.

Ab-initio study of the dielectric response of high-permittivity perovskites for energy storage

International Nuclear Information System (INIS)

Do-Amaral-De-Andrade-Sophia, Gustavo

2014-01-01

Many of materials based on transition metals have a wide range of applications, such as the storage of energy, due to their peculiar properties (high-dielectric constants, ferro-electricity,...). The knowledge of their bulk properties is essential in designing targeted devices with high performance. For instance, ABO 3 perovskites are peculiarly interesting for their atomic structural flexibility, allowing high number of atoms substitution and giving them specific chemical and electrical properties compared to the pure compounds. In this context, first principles calculations can be useful to understand the structural and electronic properties of these materials. The pressure-induced giant dielectric anomaly of ABO 3 perovskites has been investigated at the ab initio level. Its mechanism has been analyzed in terms of thermodynamic phase stability, structural and phonon contributions and Born effective charges. It is shown that the IR-active soft phonon is responsible for the anomaly. This mode always involves a displacement and a deformation of the oxygen octahedra, while the roles of A and B ions vary among the materials and between high- and low-pressure phase transitions. A sharp increase in the phonon amplitude near the phase transition gives rise to the dielectric anomaly. The use of hybrid functionals is required for agreement with experimental data. The calculations show that the dielectric anomaly in the pressure-induced phase transitions of these perovskites is a property of the bulk material. (author)

Extended x-ray absorption fine structure study of phase transitions in the piezoelectric perovskite K0.5Na0.5NbO3

Science.gov (United States)

Kodre, A.; Tellier, J.; Arčon, I.; Malič, B.; Kosec, M.

2009-06-01

Following an x-ray diffraction study of phase transitions of the piezoelectric perovskite K0.5Na0.5NbO3 the structural changes of the material are studied using extended x-ray absorption fine structure analysis, whereby the neighborhood of Nb atom is determined in the temperature range of monoclinic, tetragonal, and cubic phases. Within the entire range Nb atom is displaced from the center of the octahedron of its immediate oxygen neighbors, as witnessed by the splitting of Nb-O distance. The model shows high prevalence of the displacement in the (111) crystallographic direction of the simple perovskite cell. The corresponding splitting of the Nb-Nb distance is negligible. There is no observable disalignment of the linear Nb-O-Nb bonds from the ideal cubic arrangement, judging from the intensity of the focusing of the photoelectron wave on the Nb-Nb scattering path by the interposed oxygen atom. As a general result, the phase transitions are found as an effect of the long-range order, while the placement of the atoms in the immediate vicinity remains largely unaffected.

Calculated optical absorption of different perovskite phases

DEFF Research Database (Denmark)

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...... of perovskites the solar light absorption efficiency varies greatly depending not only on bandgap size and character (direct/indirect) but also on the dipole matrix elements. The oxides exhibit generally a fairly weak absorption efficiency due to indirect bandgaps while the most efficient absorbers are found...... in the classes of oxynitride and organometal halide perovskites with strong direct transitions....

Theoretical calculations on layered perovskites: implications for photocatalysis

Directory of Open Access Journals (Sweden)

Xiang Liu

2014-12-01

Full Text Available The application of first-principles calculations to the study of layered perovskites is reviewed here, with an emphasis on properties relevant to the use of these materials in photocatalysis. First, the accuracies of the theoretical methods in common use for the study of layered perovskites are compared. The main body of the article then reviews studies of the bulk atomic and electronic structures of pure and doped perovskites; first-principles thermodynamics studies; studies of surfaces and studies of adsorption on surfaces.

Photoluminescence of Se-related oxygen deficient center in ion-implanted silica films

International Nuclear Information System (INIS)

Zatsepin, A.F.; Buntov, E.A.; Pustovarov, V.A.; Fitting, H.-J.

2013-01-01

The results of low-temperature time-resolved photoluminescence (PL) investigation of thin SiO 2 films implanted with Se + ions are presented. The films demonstrate an intensive PL band in the violet spectral region, which is attributed to the triplet luminescence of a new variant of selenium-related oxygen deficient center (ODC). The main peculiarity of the defect energy structure is the inefficient direct optical excitation. Comparison with spectral characteristics of isoelectronic Si-, Ge- and SnODCs show that the difference in electronic properties of the new center is related to ion size factor. It was established that the dominating triplet PL excitation under VUV light irradiation is related to the energy transfer from SiO 2 excitons. A possible model of Se-related ODC is considered. -- Highlights: • The low-temperature photoluminescence of thin SiO 2 films implanted with Se + ions was studied. • The 3.4 eV PL band was attributed to triplet luminescence of Se-related ODC. • The peculiarity of SeODC electronic properties is related to ion size factor. • The dominating VUV excitation of triplet PL is related to energy transfer from SiO 2 excitons. • A possible model of Se-related ODC is considered

Novel Mg-Doped SrMoO3 Perovskites Designed as Anode Materials for Solid Oxide Fuel Cells

Directory of Open Access Journals (Sweden)

Vanessa Cascos

2016-07-01

Full Text Available SrMo1−xMxO3−δ (M = Fe and Cr, x = 0.1 and 0.2 oxides have been recently described as excellent anode materials for solid oxide fuel cells at intermediate temperatures (IT-SOFC with LSGM as the electrolyte. In this work, we have improved their properties by doping with aliovalent Mg ions at the B-site of the parent SrMoO3 perovskite. SrMo1−xMgxO3−δ (x = 0.1, 0.2 oxides have been prepared, characterized and tested as anode materials in single solid-oxide fuel cells, yielding output powers near 900 mW/cm−2 at 850 °C using pure H2 as fuel. We have studied its crystal structure with an “in situ” neutron power diffraction (NPD experiment at temperatures as high as 800 °C, emulating the working conditions of an SOFC. Adequately high oxygen deficiencies, observed by NPD, together with elevated disk-shaped anisotropic displacement factors suggest a high ionic conductivity at the working temperatures. Furthermore, thermal expansion measurements, chemical compatibility with the LSGM electrolyte, electronic conductivity and reversibility upon cycling in oxidizing-reducing atmospheres have been carried out to find out the correlation between the excellent performance as an anode and the structural features.

Understanding and Tailoring Grain Growth of Lead-Halide Perovskite for Solar Cell Application.

Science.gov (United States)

Ma, Yongchao; Liu, Yanliang; Shin, Insoo; Hwang, In-Wook; Jung, Yun Kyung; Jeong, Jung Hyun; Park, Sung Heum; Kim, Kwang Ho

2017-10-04

The fundamental mechanism of grain growth evolution in the fabrication process from the precursor phase to the perovskite phase is not fully understood despite its importance in achieving high-quality grains in organic-inorganic hybrid perovskites, which are strongly affected by processing parameters. In this work, we investigate the fundamental conversion mechanism from the precursor phase of perovskite to the complete perovskite phase and how the intermediate phase promotes growth of the perovskite grains during the fabrication process. By monitoring the morphological evolution of the perovskite during the film fabrication process, we observed a clear rod-shaped intermediate phase in the highly crystalline perovskite and investigated the role of the nanorod intermediate phase on the growth of the grains of the perovskite film. Furthermore, on the basis of these findings, we developed a simple and effective method to tailor grain properties including the crystallinity, size, and number of grain boundaries, and then utilized the film with the tailored grains to develop perovskite solar cells.

A Direct Bandgap Copper-Antimony Halide Perovskite.

Science.gov (United States)

Vargas, Brenda; Ramos, Estrella; Pérez-Gutiérrez, Enrique; Alonso, Juan Carlos; Solis-Ibarra, Diego

2017-07-12

Since the establishment of perovskite solar cells (PSCs), there has been an intense search for alternative materials to replace lead and improve their stability toward moisture and light. As single-metal perovskite structures have yielded unsatisfactory performances, an alternative is the use of double perovskites that incorporate a combination of metals. To this day, only a handful of these compounds have been synthesized, but most of them have indirect bandgaps and/or do not have bandgaps energies well-suited for photovoltaic applications. Here we report the synthesis and characterization of a unique mixed metal ⟨111⟩-oriented layered perovskite, Cs 4 CuSb 2 Cl 12 (1), that incorporates Cu 2+ and Sb 3+ into layers that are three octahedra thick (n = 3). In addition to being made of abundant and nontoxic elements, we show that this material behaves as a semiconductor with a direct bandgap of 1.0 eV and its conductivity is 1 order of magnitude greater than that of MAPbI 3 (MA = methylammonium). Furthermore, 1 has high photo- and thermal-stability and is tolerant to humidity. We conclude that 1 is a promising material for photovoltaic applications and represents a new type of layered perovskite structure that incorporates metals in 2+ and 3+ oxidation states, thus significantly widening the possible combinations of metals to replace lead in PSCs.

Perovskite-fullerene hybrid materials suppress hysteresis in planar diodes

Science.gov (United States)

Xu, Jixian; Buin, Andrei; Ip, Alexander H.; Li, Wei; Voznyy, Oleksandr; Comin, Riccardo; Yuan, Mingjian; Jeon, Seokmin; Ning, Zhijun; McDowell, Jeffrey J.; Kanjanaboos, Pongsakorn; Sun, Jon-Paul; Lan, Xinzheng; Quan, Li Na; Kim, Dong Ha; Hill, Ian G.; Maksymovych, Peter; Sargent, Edward H.

2015-05-01

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.

Perovskite-fullerene hybrid materials suppress hysteresis in planar diodes.

KAUST Repository

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.

Tracking the formation of methylammonium lead triiodide perovskite

Energy Technology Data Exchange (ETDEWEB)

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.

Investigating the Effect of Pyridine Vapor Treatment on Perovskite Solar Cells

Energy Technology Data Exchange (ETDEWEB)

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.

Exciton Dynamics of 2D Hybrid Perovskite Nanocrystal

Science.gov (United States)

Guo, Rui; Zhu, Zhuan; Boulesbaa, Abdelaziz; Venkatesan, Swaminathan; Xiao, Kai; Bao, Jiming; Yao, Yan; Li, Wenzhi

Organic-inorganic hybrid perovskites have emerged as promising materials for applications in photovoltaic and optoelectronic devices. Among the perovskites, two dimensional (2D) perovskites are of great interests due to their remarkable optical and electrical properties as well as the flexibility of material selection for the organic and inorganic moieties. In this study, we demonstrate the solution-phase growth of large square-shaped single-crystalline 2D hybrid perovskites of (C6H5C2H4 NH3) 2 PbBr4 with a few unit cells thickness. Compared to the bulk crystal, a band gap shift and new photoluminescence (PL) peak are observed from the hybrid perovskite sheets. Color of the 2D crystals can be tuned by adjusting the sheet thickness. Pump-probe spectroscopy is used to investigate the exciton dynamics and exhibits a biexponential decay with an amplitude-weighted lifetime of 16.7 ps. Such high-quality (C6H5C2H4 NH3) 2 PbBr4 sheets are expected to have high PL quantum efficiency which can be adopted for light-emitting devices. National Science Foundation (Grant No. CMMI-1334417 and DMR-1506640).

Junction Propagation in Organometal Halide Perovskite-Polymer Composite Thin Films.

Science.gov (United States)

Shan, Xin; Li, Junqiang; Chen, Mingming; Geske, Thomas; Bade, Sri Ganesh R; Yu, Zhibin

2017-06-01

With the emergence of organometal halide perovskite semiconductors, it has been discovered that a p-i-n junction can be formed in situ due to the migration of ionic species in the perovskite when a bias is applied. In this work, we investigated the junction formation dynamics in methylammonium lead tribromide (MAPbBr 3 )/polymer composite thin films. It was concluded that the p- and n- doped regions propagated into the intrinsic region with an increasing bias, leading to a reduced intrinsic perovskite layer thickness and the formation of an effective light-emitting junction regardless of perovskite layer thicknesses (300 nm to 30 μm). The junction propagation also played a major role in deteriorating the LED operation lifetime. Stable perovskite LEDs can be achieved by restricting the junction propagation after its formation.

Development of thin film oxygen transport membranes on metallic supports

Energy Technology Data Exchange (ETDEWEB)

Xing, Ye

2012-04-25

Asymmetric membrane structure has an attractive potential in the application of O{sub 2}/N{sub 2} gas separation membrane for the future membrane-based fossil fuel power plant using oxyfuel technology, which will reduce the carbon dioxide emission. The aim of this study is the development of a metal supported multi-layer membrane structure with a thin film top membrane layer and porous ceramic interlayers. Four perovskite materials were studied as candidate membrane materials. Material properties of these perovskite materials were investigated and compared. La{sub 0.58}Sr{sub 0.4}Co{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} (LSCF58428) showed sufficient oxygen permeability, an acceptable thermal expansion coefficient and a moderate sintering temperature. Alternatively, Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} (BSCF5582) is considered obtaining very high oxygen permeability but a higher thermal expansion and a lower thermal stability than LSCF58428. Four different Ni-based alloys were studied as candidate substrate materials in the asymmetric membrane structure. The chromia-scale alloys (Hastelloy X, Inconel 600 and Haynes 214) caused Cr poisoning of the membrane layer material LSCF58428 during high-temperature co-firing in air. NiCoCrAlY with a high Al content (12.7 wt%) was found to be the most promising substrate material. It showed a good chemical compatibility with perovskite materials at high temperatures. In order to bridge the highly porous substrate and the thin top membrane layer interlayers were developed. Two interlayers were coated by screen printing on the porous NiCoCrAlY substrate which was sintered at 1225 C in flowing H{sub 2} atmosphere. Screen printing pastes were optimized by investigating various solvent and binder combinations and various ceramic powder contents. The first interlayer significantly improved the surface quality and the surface pore size has been reduced from 30-50{mu}m on the substrate to few {mu}m on the first

Lung transplantation and survival outcomes in patients with oxygen-dependent COPD with regard to their alpha-1 antitrypsin deficiency status

Directory of Open Access Journals (Sweden)

Ekström M

2017-11-01

Full Text Available Magnus Ekström, Hanan Tanash Department of Respiratory Medicine and Allergology, Skåne University Hospital, Lund University, Lund, Sweden Background: Individuals with severe alpha-1 antitrypsin deficiency (AATD have an increased risk of developing COPD. However, outcomes during long-term oxygen therapy (LTOT in patients with severe AATD and hypoxemia are unknown.Patients and methods: This was a prospective, population-based, consecutive cohort study of patients on LTOT due to COPD in the period from January 1, 1987, to June 30, 2015, in the Swedish National Registry for Respiratory Failure (Swedevox. Severe AATD was identified using the Swedish AATD registry and confirmed by isoelectric focusing. Data on lung transplantation (LTx were obtained from the two lung transplantation centers in Sweden. Mortality and causes of death were assessed based on the National Causes of Death Registry and analyzed using multivariable Cox regression.Results: A total of 14,644 patients who started LTOT due to COPD were included in this study. No patient was lost to follow up. Patients with AATD were younger, included more males and more never smokers, and had fewer comorbidities. During a median follow-up of 1.6 years (interquartile range [IQR], 2.7 on LTOT, patients without severe AATD had a higher mortality, hazard ratio [HR] 1.53 (95% CI, 1.24–1.88, adjusting for age, sex, smoking status, body mass index, performance status, level of hypoxemia, and comorbidities. Cardiovascular deaths were increased. A higher proportion of AATD patients underwent LTx, 53 (19% vs 118 (1%. Survival after LTx was similar for AATD and non-AATD patients and was predicted by age.Conclusion: In oxygen-dependent COPD, patients with severe AATD have a longer survival time on LTOT, but they have a similar prognosis after lung transplantation compared with patients without AATD. Keywords: COPD, long-term oxygen therapy, lung transplantation, severe alpha-1 antitrypsin deficiency

Metallic substrate materials for thin film oxygen transport membranes for application in a fossil power plant

Energy Technology Data Exchange (ETDEWEB)

Xing, Y.; Baumann, S.; Sebold, D.; Meulenberg, W.A.; Stoever, D. [Forschungszentrum Juelich GmbH (DE). Inst. fuer Energieforschung (IEF) - IEF-1 Materials Synthesis and Processing

2010-07-01

La{sub 0.58}Sr{sub 0.4}CO{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} (LSCF58428) and Ba{sub 0.5}Sr{sub 0.5}CO{sub 0.8}Fe{sub 3-{delta}} (BSCF5582) exhibit high oxygen permeability due to their high ionic and electronic conductivity. For this reason they are under discussion for application in oxygen transport membranes (OTMs) in zero-emission power plants using oxyfuel technology. A thin film membrane which can increase the oxygen flux is beneficial and a structural substrate is required. Two types of Ni-base alloys were studied as substrate material candidates with a number of advantages, such as high strength, high temperature stability, easy joining and similar thermal expansion coefficient to the selected perovskite materials. Chemical compositions and thermal expansion coefficients of Ni-base alloys were measured in this study. LSCF58428 and BSCF5582 layers were screen printed on Ni-based alloys and co-fired at high temperature in air. The microstructure and element analysis of samples were characterized by scanning electron microscopy (SEM and EDX). A Ni-base alloy, MCrAlY, with a high Al content was the most suitable substrate material, and showed better chemical compatibility with perovskite materials at high temperature than Hastelloy X, which is a chromia-forming Ni-base alloy. A reaction occurred between Sr in the perovskite and the alumina surface layers on MCr-AlY. However, the reaction zone did not increase in thickness during medium-term annealing at 800 C in air. Hence, it is expected that this reaction will not prevent the application of MCr-AlY as a substrate material. (orig.)

Hybrid solar cells composed of perovskite and polymer photovoltaic structures

Science.gov (United States)

Phaometvarithorn, Apatsanan; Chuangchote, Surawut; Kumnorkaew, Pisist; Wootthikanokkhan, Jatuphorn

2018-06-01

Organic/inorganic lead halide perovskite solar cells have recently attracted much attention in photovoltaic research, due to the devices show promising ways to achieve high efficiencies. The perovskite devices with high efficiencies, however, are typically fabricated in tandem solar cell which is complicated. In this research work, we introduce a solar cell device with the combination of CH3NH3PbI3-xClx perovskite and bulk heterojunction PCDTBT:PC70BM polymer without any tandem structure. The new integrated perovskite/polymer hybrid structure of ITO/PEDOT:PSS/perovskite/PCDTBT:PC70BM/PC70BM/TiOx/Al provides higher power conversion efficiency (PCE) of devices compared with conventional perovskite cell structure. With the optimized PCDTBT:PC70BM thickness of ∼70 nm, the highest PCE of 11.67% is achieved. Variation of conducting donor polymers in this new structure is also preliminary demonstrated. This study provides an attractively innovative structure and a promising design for further development of the new-generation solar cells.

Conducting tin halides with a layered organic-based perovskite structure

Science.gov (United States)

Mitzi, D. B.; Feild, C. A.; Harrison, W. T. A.; Guloy, A. M.

1994-06-01

THE discovery1 of high-temperature superconductivity in layered copper oxide perovskites has generated considerable fundamental and technological interest in this class of materials. Only a few other examples of conducting layered perovskites are known; these are also oxides such as (La1-xSrx)n+1 MnnO3n+1 (ref. 2), Lan+1NinO3n+1 (ref. 3) and Ban+1PbnO3n+1 (ref. 4), all of which exhibit a trend from semiconducting to metallic behaviour with increasing number of perovskite layers (n). We report here the synthesis of a family of organic-based layered halide perovskites, (C4H9NH3)2(CH3NH3)n-1Snnl3n+1 which show a similar transition from semiconducting to metallic behaviour with increasing n. The incorporation of an organic modulation layer between the conducting tin iodide sheets potentially provides greater flexibility for tuning the electrical properties of the perovskite sheets, and we suggest that such an approach will prove valuable for exploring the range of transport properties possible with layered perovskites.

Crystallization of perovskite film using ambient moisture and water as co-solvent for efficient planar perovskite solar cell (Conference Presentation)

Science.gov (United States)

Dubey, Ashish; Reza, Khan M.; Gaml, Eman; Adhikari, Nirmal; Qiao, Qiquan

2016-09-01

Smooth, compact and defect free morphology of perovskite is highly desired for enhanced device performance. Several routes such as thermal annealing, use of solvent mixtures, growth under controlled humidity has been adopted to obtain crystalline, smooth and defect free perovskite film. Herein we showed direct use of water (H2O) as co-solvent in precursor solution and have optimized the water content required to obtain smooth and dense film. Varying concentration of water was used in precursor solution of CH3NH3I and PbI2 mixed in γ-butyrolactone (GBL) and dimethylsulfoxide (DMSO). Perovskite films were crystallized using toluene assisted solvent engineering method using GBL:DMSO:H2O as solvent mixture. The amount of water was varied from 1% to 25%, which resulted in change in film morphology and perovskite crystallinity. It was concluded that an appropriate amount of water is required to assist the crystallization process to obtain smooth pin-hole free morphology. The change in morphology led to improved fill factor in the device, with highest efficiency 14%, which was significantly higher than devices made from perovskite film without adding water. We also showed that addition of up to 25% by volume of water does not significantly change the device performance.

Light-Responsive Ion-Redistribution-Induced Resistive Switching in Hybrid Perovskite Schottky Junctions

KAUST Repository

Guan, Xinwei

2017-11-23

Hybrid Perovskites have emerged as a class of highly versatile functional materials with applications in solar cells, photodetectors, transistors, and lasers. Recently, there have also been reports on perovskite-based resistive switching (RS) memories, but there remain open questions regarding device stability and switching mechanism. Here, an RS memory based on a high-quality capacitor structure made of an MAPbBr3 (CH3NH3PbBr3) perovskite layer sandwiched between Au and indium tin oxide (ITO) electrodes is reported. Such perovskite devices exhibit reliable RS with an ON/OFF ratio greater than 103, endurance over 103 cycles, and a retention time of 104 s. The analysis suggests that the RS operation hinges on the migration of charged ions, most likely MA vacancies, which reversibly modifies the perovskite bulk transport and the Schottky barrier at the MAPbBr3/ITO interface. Such perovskite memory devices can also be fabricated on flexible polyethylene terephthalate substrates with high bendability and reliability. Furthermore, it is found that reference devices made of another hybrid perovskite MAPbI3 consistently exhibit filament-type switching behavior. This work elucidates the important role of processing-dependent defects in the charge transport of hybrid perovskites and provides insights on the ion-redistribution-based RS in perovskite memory devices.

Bandgap calculations and trends of organometal halide perovskites

DEFF Research Database (Denmark)

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...

Distribution and Magnitude of Dinitrogen Fixation in the Eastern Tropical North Pacific Oxygen Deficient Zone.

Science.gov (United States)

Selden, C.; Mulholland, M. R.; Widner, B.; Bernhardt, P. W.; Macías Tapia, A.; Jayakumar, A.

2016-12-01

The Eastern Tropical North Pacific Ocean (ETNP) hosts one of the world's three major open ocean oxygen deficient zones (ODZs). Hotspots for fixed nitrogen (N) loss processes, ODZs have classically been discounted as areas of significant dinitrogen (N2) fixation, the microbe-mediated reduction of N2 to ammonium (NH4+), which has historically been ascribed primarily to euphotic, nutrient-deplete tropical waters. Challenging this paradigm, active expression of nifH (the dinitrogen reductase structural gene) has recently been documented in the ETNP, Eastern Tropical South Pacific, and Arabian Sea ODZs, implying a closer coupling of fixed nitrogen input and loss processes than previously thought. Here, we report rates of N­2 fixation measured in the ETNP ODZ along vertical gradients of oxygen, light, and dissolved N concentrations. Detailed vertical profiles of N2 fixation rates and dissolved N concentrations made within the ODZ were compared with similar profiles from oxic waters outside the ODZ. In addition, different organic carbon sources were investigated as potential rate-limiting factors for N2 fixation in sub-euphotic waters. By establishing the magnitude and distribution of N­2 fixation in the ETNP ODZ, this study contributes to current understanding of N cycling in anoxic and aphotic waters, and serves to elucidate nuances in the global N budget, enabling more accurate biogeochemical modeling. Understanding these processes in present day ODZs is crucial for predicting how ongoing anthropogenic intensification of coastal ODZs will alter biogeochemical cycles in the future.

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

DEFF Research Database (Denmark)

Kammer Hansen, K.

2006-01-01

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...

Application of carbon nanotubes in perovskite solar cells: A review

Science.gov (United States)

Oo, Thet Tin; Debnath, Sujan

2017-11-01

Solar power, as alternative renewable energy source, has gained momentum in global energy generation in recent time. Solar photovoltaics (PV) systems now fulfill a significant portion of electricity demand and the capacity of solar PV capacity is growing every year. PV cells efficiency has improved significantly following decades of research, evolving into third generations of PV cells. These third generation PV cells are set out to provide low-cost and efficient PV systems, further improving the commercial competitiveness of solar energy generation. Among these latest generations of PV cells, perovskite solar cells have gained attraction due to the simple manufacturing process and the immense growth in PV efficiency in a short period of research and development. Despite these advantages, perovskite solar cells are known for the weak stability and decomposition in exposure to humidity and high temperature, hindering the possibility of commercialization. This paper will discuss the role of carbon nanotubes (CNTs) in improving the efficiency and stability of perovskite solar cells, in various components such as perovskite layer and hole transport layer, as well as the application of CNTs in unique aspects. These includes the use of CNTs fiber in making the perovskite solar cells flexible, as well as simplification of perovskite PV production by using CNT flash evaporation printing process. Despite these advances, challenges remain in incorporation CNTs into perovskite such as lower conversion efficiency compared to rare earth metals and improvements need to be made. Thus, the paper will be also highlighting the CNTs materials suggested for further research and improvement of perovskite solar cells.

Autothermal reforming catalyst having perovskite structure

Science.gov (United States)

Krumpel, Michael [Naperville, IL; Liu, Di-Jia [Naperville, IL

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.

Fundamental and excited states of F-type centres in MgSiO3 perovskite

International Nuclear Information System (INIS)

Stashans, Arvids; Piedra, Lorena; Briceno, Tamara

2010-01-01

Quantum-chemical modelling based on the Hartree-Fock methodology and a periodic supercell model is done to study oxygen vacancy and F-type centres in the perovskite-type MgSiO 3 crystal. The equilibrium geometry of defects is obtained, confirming the importance of electrostatic interaction in determination of atomic shifts. The calculated relaxation energies due to the defect formation are between 8 and 10 eV, thus evidencing favourability in the occurrence of such defects. The wave functions describing both F + and F centres are rather diffuse and the point defects are not well localised within the oxygen vacancy region. The Δ SCF computed absorption energies due to the F-type centres fall well within the ultraviolet spectrum, between 136 and 254 nm for the F + centre and between 163 and 248 nm for the F centre.

Water-Induced Dimensionality Reduction in Metal-Halide Perovskites

KAUST Repository

Turedi, Bekir; Lee, Kwangjae; Dursun, Ibrahim; Alamer, Badriah Jaber; Wu, Zhennan; Alarousu, Erkki; Mohammed, Omar F.; Cho, Namchul; Bakr, Osman

2018-01-01

. Here we employ water to directly transform films of the three-dimensional (3D) perovskite CsPbBr3 to stable two-dimensional (2D) perovskite-related CsPb2Br5. A sequential dissolution-recrystallization process governs this water induced transformation

Wavelength-tunable waveguides based on polycrystalline organic-inorganic perovskite microwires

Science.gov (United States)

Wang, Ziyu; Liu, Jingying; Xu, Zai-Quan; Xue, Yunzhou; Jiang, Liangcong; Song, Jingchao; Huang, Fuzhi; Wang, Yusheng; Zhong, Yu Lin; Zhang, Yupeng; Cheng, Yi-Bing; Bao, Qiaoliang

2016-03-01

Hybrid organic-inorganic perovskites have emerged as new photovoltaic materials with impressively high power conversion efficiency due to their high optical absorption coefficient and long charge carrier diffusion length. In addition to high photoluminescence quantum efficiency and chemical tunability, hybrid organic-inorganic perovskites also show intriguing potential for diverse photonic applications. In this work, we demonstrate that polycrystalline organic-inorganic perovskite microwires can function as active optical waveguides with small propagation loss. The successful production of high quality perovskite microwires with different halogen elements enables the guiding of light with different colours. Furthermore, it is interesting to find that out-coupled light intensity from the microwire can be effectively modulated by an external electric field, which behaves as an electro-optical modulator. This finding suggests the promising applications of perovskite microwires as effective building blocks in micro/nano scale photonic circuits.

High pressure Moessbauer spectroscopy of perovskite iron oxide

CERN Document Server

Nasu, S; Morimoto, S; Kawakami, T; Kuzushita, K; Takano, M

2003-01-01

High-pressure sup 5 sup 7 Fe Moessbauer spectroscopy using a diamond anvil cell has been performed for perovskite iron oxides SrFeO sub 3 , CaFeO sub 3 and La sub 1 sub / sub 3 Sr sub 2 sub / sub 3 O sub 3. The charge states and the magnetic dependency to pressure were determined. Pressure magnetic phase diagrams of these perovskite iron oxides are determined up to about 70 GPa. To be clear the magnetic ordered state, they are measured up to 7.8 T external magnetic fields at 4.5K. The phase transition of these perovskite oxides to ferromagnetisms with high magnetic ordered temperature is observed. In higher pressure, high spin-low spin transition of oxides besides CaFeO sub 3 is generated. The feature of Moessbauer spectroscopy, perovskite iron oxide and Moessbauer spectroscopy under high pressure are explained. (S.Y.)

Toward enhanced hydrogen generation from water using oxygen permeating LCF membranes

KAUST Repository

Wu, Xiao-Yu

2015-01-01

© the Owner Societies. Hydrogen production from water thermolysis can be enhanced by the use of perovskite-type mixed ionic and electronic conducting (MIEC) membranes, through which oxygen permeation is driven by a chemical potential gradient. In this work, water thermolysis experiments were performed using 0.9 mm thick La0.9Ca0.1FeO3-δ (LCF-91) perovskite membranes at 990 °C in a lab-scale button-cell reactor. We examined the effects of the operating conditions such as the gas species concentrations and flow rates on the feed and sweep sides on the water thermolysis rate and oxygen flux. A single step reaction mechanism is proposed for surface reactions, and three-resistance permeation models are derived. Results show that water thermolysis is facilitated by the LCF-91 membrane especially when a fuel is added to the sweep gas. Increasing the gas flow rate and water concentration on the feed side or the hydrogen concentration on the sweep side enhances the hydrogen production rate. In this work, hydrogen is used as the fuel by construction, so that a single-step surface reaction mechanism can be developed and water thermolysis rate parameters can be derived. Both surface reaction rate parameters for oxygen incorporation/dissociation and hydrogen-oxygen reactions are fitted at 990 °C. We compare the oxygen fluxes in water thermolysis and air separation experiments, and identify different limiting steps in the processes involving various oxygen sources and sweep gases for this 0.9 mm thick LCF-91 membrane. In the air feed-inert sweep case, the bulk diffusion and sweep side surface reaction are the two limiting steps. In the water feed-inert sweep case, surface reaction on the feed side dominates the oxygen permeation process. Yet in the water feed-fuel sweep case, surface reactions on both the feed and sweep sides are rate determining when hydrogen concentration in the sweep side is in the range of 1-5 vol%. Furthermore, long term studies show that the surface

CO2 Plasma-Treated TiO2 Film as an Effective Electron Transport Layer for High-Performance Planar Perovskite Solar Cells.

Science.gov (United States)

Wang, Kang; Zhao, Wenjing; Liu, Jia; Niu, Jinzhi; Liu, Yucheng; Ren, Xiaodong; Feng, Jiangshan; Liu, Zhike; Sun, Jie; Wang, Dapeng; Liu, Shengzhong Frank

2017-10-04

Perovskite solar cells (PSCs) have received great attention because of their excellent photovoltaic properties especially for the comparable efficiency to silicon solar cells. The electron transport layer (ETL) is regarded as a crucial medium in transporting electrons and blocking holes for PSCs. In this study, CO 2 plasma generated by plasma-enhanced chemical vapor deposition (PECVD) was introduced to modify the TiO 2 ETL. The results indicated that the CO 2 plasma-treated compact TiO 2 layer exhibited better surface hydrophilicity, higher conductivity, and lower bulk defect state density in comparison with the pristine TiO 2 film. The quality of the stoichiometric TiO 2 structure was improved, and the concentration of oxygen-deficiency-induced defect sites was reduced significantly after CO 2 plasma treatment for 90 s. The PSCs with the TiO 2 film treated by CO 2 plasma for 90 s exhibited simultaneously improved short-circuit current (J SC ) and fill factor. As a result, the PSC-based TiO 2 ETL with CO 2 plasma treatment affords a power conversion efficiency of 15.39%, outperforming that based on pristine TiO 2 (13.54%). These results indicate that the plasma treatment by the PECVD method is an effective approach to modify the ETL for high-performance planar PSCs.

The modulation of oxygen vacancies by the combined current effect and temperature cycling in La0.7Sr0.3CoO3 film

Science.gov (United States)

Li, J.; Wang, J.; Kuang, H.; Zhao, Y. Y.; Qiao, K. M.; Liu, Y.; Hu, F. X.; Sun, J. R.; Shen, B. G.

2018-05-01

Modulating the oxygen defect concentration has been accepted as an effective method to obtain high catalytic activity in perovskite cobaltites. However, controllably modifying the oxygen vacancy is still a challenge in this type of materials, which strongly obstructs their application. Here, we report a successful oxygen vacancies modulation in the La0.7Sr0.3CoO3 (LSCO) film by using combined current effect and temperature cycling. The temperature dependent transport properties of the LSCO/LAO film were investigated. The results revealed that the resistance of the film keeps increasing under the repeated measurements. It was found that the accumulation of the oxygen vacancy by current effect transforms the Co4+ ion into Co3+ ion, which results in the enhancement of the resistance and thus the transport switching behavior. Moreover, the resistance in the cooling process was found to be much higher than that in previous cooling and heating processes, which indicates that the oxygen escapes more quickly in the high temperature region. On the other hand, our analysis indicates that the CoO6 distortion may contribute to the switching of transport behaviors in the low temperature region. Our work provides an effective and controllable way to modulate oxygen defect in the perovskite-type oxides.

Development of novel CO{sub 2}-stable oxygen permeable dual phase membranes for CO{sub 2} capture in an oxy-fuel process

Energy Technology Data Exchange (ETDEWEB)

Luo, Huixia

2012-07-19

The combustion of fossil fuels in power stations with pure oxygen following the oxy-fuel process allows the Sequestration of CO{sub 2}. The pure oxygen needed can be separated from air by oxygen transporting ceramics like single phase perovskites. However, most of the so far developed single phase perovskites have stability problems in a CO{sub 2} containing atmosphere. Dual phase membranes are micro-scale mixtures of an electron conducting phase and an oxygen ion conducting phase and their compositions can be tailored according to practical requirements, which are considered to be promising substitutes for the single phase perovskite materials. In my thesis the issues of phase stability for perovskite-type material with the common composition Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 3-{delta}} (BSCF) as weil as the development of a series of novel CO{sub 2}-stable dual phase membranes were studied. In Chapter 2, the phase stability and permeation behavior of a dead-end BSCF tube membrane in high-purity oxygen at temperatures below 750 C, were elucidated using powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), high-angle annular dark-field (HAADF) and scanning transmission electron microscopy (STEM). lt was found that parts of the cubic perovskite BSCF transformed into a hexagonal perovskite Ba{sub 0.5{+-}x}Sr{sub 0.5{+-}x}CoO{sub 3-{delta}} (x {approx} 0.1) and a trigonal mixed oxide Ba{sub 1-x}Sr{sub x}CO{sub 2-y}Fe{sub y}O{sub 5{+-}{delta}} (x {approx} 0.15, y {approx} 0.25) in high-purity oxygen at 750 C. On the other hand, it was found that the partial degradation of cubic BSCF perovskite at 750 C was more pronounced under the strongly oxidizing conditions on the oxygen supply (feed) side than on the oxygen release (permeate) side of the membrane. The structural instability of BSCF is attributed to an oxidation of cobalt from Co{sup 2+} to Co{sup 3+} and Co{sup 4+}, which exhibits an ionic radius that is too small to be tolerated by

Advancement on Lead-Free Organic-Inorganic Halide Perovskite Solar Cells: A Review.

Science.gov (United States)

Sani, Faruk; Shafie, Suhaidi; Lim, Hong Ngee; Musa, Abubakar Ohinoyi

2018-06-14

Remarkable attention has been committed to the recently discovered cost effective and solution processable lead-free organic-inorganic halide perovskite solar cells. Recent studies have reported that, within five years, the reported efficiency has reached 9.0%, which makes them an extremely promising and fast developing candidate to compete with conventional lead-based perovskite solar cells. The major challenge associated with the conventional perovskite solar cells is the toxic nature of lead (Pb) used in the active layer of perovskite material. If lead continues to be used in fabricating solar cells, negative health impacts will result in the environment due to the toxicity of lead. Alternatively, lead free perovskite solar cells could give a safe way by substituting low-cost, abundant and non toxic material. This review focuses on formability of lead-free organic-inorganic halide perovskite, alternative metal cations candidates to replace lead (Pb), and possible substitutions of organic cations, as well as halide anions in the lead-free organic-inorganic halide perovskite architecture. Furthermore, the review gives highlights on the impact of organic cations, metal cations and inorganic anions on stability and the overall performance of lead free perovskite solar cells.

Interspace modification of titania-nanorod arrays for efficient mesoscopic perovskite solar cells

International Nuclear Information System (INIS)

Chen, Peng; Jin, Zhixin; Wang, Yinglin; Wang, Meiqi; Chen, Shixin; Zhang, Yang; Wang, Lingling; Zhang, Xintong; Liu, Yichun

2017-01-01

Highlights: • The fabrication of perovskite solar cells utilizing TiO_2 NR arrays. • Investigation of the interspace effect of TiO_2 NR on perovskite layer. • Understanding of the balance between perovskite capping layer and pore filling. - Abstract: Morphology of electron transport layers (ETLs) has an important influence on the device architecture and electronic processes of mesostructured solar cells. In this work, we thoroughly investigated the effect of the interspace of TiO_2 nanorod (NR) arrays on the photovoltaic performance of the perovskite solar cells (PSCs). Along with the interspace in TiO_2-NR arrays increasing, the thickness as well as the crystal size of perovskite capping layer are reduced accordingly, and the filling of perovskite in the channel becomes incomplete. Electrochemical impedance spectroscopy measurements reveal that this variation of perovskite absorber layer, induced by interspace of TiO_2 NR arrays, causes the change of charge recombination process at the TiO_2/perovskite interface, suggesting that a balance between capping layer and the perovskite filling is critical to obtain high charge collection efficiency of PSCs. A power conversion efficiency of 10.3% could be achieved through careful optimization of interspace in TiO_2-NR arrays. Our research will shed light on the morphology control of ETLs with 1D structure for heterojunction solar cells fabricated by solution-deposited method.

Doping Lanthanide into Perovskite Nanocrystals: Highly Improved and Expanded Optical Properties.

Science.gov (United States)

Pan, Gencai; Bai, Xue; Yang, Dongwen; Chen, Xu; Jing, Pengtao; Qu, Songnan; Zhang, Lijun; Zhou, Donglei; Zhu, Jinyang; Xu, Wen; Dong, Biao; Song, Hongwei

2017-12-13

Cesium lead halide (CsPbX 3 ) perovskite nanocrystals (NCs) have demonstrated extremely excellent optical properties and great application potentials in various optoelectronic devices. However, because of the anion exchange, it is difficult to achieve white-light and multicolor emission for practical applications. Herein, we present the successful doping of various lanthanide ions (Ce 3+ , Sm 3+ , Eu 3+ , Tb 3+ , Dy 3+ , Er 3+ , and Yb 3+ ) into the lattices of CsPbCl 3 perovskite NCs through a modified hot-injection method. For the lanthanide ions doped perovskite NCs, high photoluminescence quantum yield (QY) and stable and widely tunable multicolor emissions spanning from visible to near-infrared (NIR) regions are successfully obtained. This work indicates that the doped perovskite NCs will inherit most of the unique optical properties of lanthanide ions and deliver them to the perovskite NC host, thus endowing the family of perovskite materials with excellent optical, electric, or magnetic properties.

Influence of coating steps of perovskite on low-temperature amorphous compact TiO x upon the morphology, crystallinity, and photovoltaic property correlation in planar perovskite solar cells

Science.gov (United States)

Shahiduzzaman, Md.; Furumoto, Yoshikazu; Yamamoto, Kohei; Yonezawa, Kyosuke; Azuma, Yosuke; Kitamura, Michinori; Matsuzaki, Hiroyuki; Karakawa, Makoto; Kuwabara, Takayuki; Takahashi, Kohshin; Taima, Tetsuya

2018-03-01

The fabrication of high-efficiency solution-processable perovskite solar cells has been achieved using mesostructured films and compact titanium dioxide (TiO2) layers in a process that involves high temperatures and cost. Here, we present an efficient approach for fabricating chemical-bath-deposited, low-temperature, and low-cost amorphous compact TiO x -based planar heterojunction perovskite solar cells by one-step and two-step coatings of the perovskite layer. We also investigate the effect of the number of perovskite coating steps on the compact TiO x layer. The grazing incidence wide-angle X-ray scattering technique is used to clarify the relationship between morphology, crystallinity, and photovoltaic properties of the resulting devices. Analysis of the films revealed that one-step spin-coating of perovskite exhibited an enhancement of film quality and crystallization that correlates to photovoltaic performance 1.5 times higher than that of a two-step-coated device. Our findings show that the resulting morphology, crystallinity, and device performances are strongly dependent on the number of coating steps of the perovskite thin layer on the compact TiO x layer. This result is useful knowledge for the low-cost production of planar perovskite solar cells.

Organohalide Perovskites for Solar Energy Conversion.

Science.gov (United States)

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

The effect of strontium and barium doping on perovskite-structured energy materials for photovoltaic applications

Science.gov (United States)

Wu, Ming-Chung; Chen, Wei-Cheng; Chan, Shun-Hsiang; Su, Wei-Fang

2018-01-01

Perovskite solar cell is a novel photovoltaic technology with the superior progress in efficiency and the simple solution processes. Develop lead-free or lead-reduced perovskite materials is a significant concern for high-performance perovskite solar cell. Among the alkaline earth metals, the Sr2+ and Ba2+ are suitable for Pb2+ replacement in perovskite film due to fitting Goldschmidt's tolerance factor. In this study, we adopted Ba-doped and Sr-doped perovskite structured materials with different doping levels, including 1.0, 5.0, and 10.0 mol%, to prepare perovskite solar cells. Both Ba-doped and Sr-doped perovskite structured materials have a related tendency in absorption behavior and surface morphology. At 10.0 mol% doping level, the power conversion efficiency (PCE) of Sr-doped perovskite solar cells is only ∼0.5%, but the PCE of Ba-doped perovskite solar cells can be achieved to ∼9.7%. Ba-doped perovskite solar cells showed the acceptable photovoltaic characteristics than Sr-doped perovskite solar cells. Ba dopant can partially replace the amount of lead in the perovskite solar cells, and it could be a potential candidate in the field of lead-free or lead-reduced perovskite energy materials.

OXYGEN TRANSPORT CERAMIC MEMBRANES

Energy Technology Data Exchange (ETDEWEB)

Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

2000-10-01

This is the third quarterly report on oxygen Transport Ceramic Membranes. In the following, the report describes the progress made by our university partners in Tasks 1 through 6, experimental apparatus that was designed and built for various tasks of this project, thermodynamic calculations, where applicable and work planned for the future. (Task 1) Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. (Task 2) Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. (Task 3) Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. (Task 4) Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. (Task 5) Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. (Task 6) Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

Computational study on oxynitride perovskites for CO_2 photoreduction

International Nuclear Information System (INIS)

Hafez, Ahmed M.; Zedan, Abdallah F.; AlQaradawi, Siham Y.; Salem, Noha M.; Allam, Nageh K.

2016-01-01

Highlights: • Oxynitride perovskites are investigated for photoelectrochemical CO_2 reduction. • They have small electron and hole effective masses, rendering higher mobility. • The effect of cation size on the band gap is investigated and discussed. • W-doping allowed the selection of specific CO_2 reduction products. - Abstract: The photocatalytic conversion of CO_2 into chemical fuels is an attractive route for recycling this greenhouse gas. However, the large scale application of such approach is limited by the low selectivity and activity of the currently used photocatalysts. Using first principles calculations, we report on the selection of optimum oxynitride perovskites as photocatalysts for photoelectrochemical CO_2 reduction. The results revealed six perovskites that perfectly straddle the carbon dioxide redox potential; namely, BaTaO_2N, SrTaO_2N, CaTaO_2N, LaTiO_2N, BaNbO_2N, and SrNbO_2N. The electronic structure and the effective mass of the selected candidates are discussed in details, the partial and total density of states illustrated the orbital hybridization and the contribution of each element in the valence and conduction band minima. The effect of cation size in the ABO_2N perovskites on the band gap is investigated and discussed. The optical properties of the selected perovskites are calculated to account for their photoactivity. Moreover, the effect of W doping on improving the selectivity of perovskites toward specific hydrocarbon product (methane) is discussed in details. This study reveals the promising optical and structural properties of oxynitride perovskite candidates for CO_2 photoreduction.

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

Directory of Open Access Journals (Sweden)

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.

Simulation design of P–I–N-type all-perovskite solar cells with high efficiency

International Nuclear Information System (INIS)

Du Hui-Jing; Wang Wei-Chao; Gu Yi-Fan

2017-01-01

According to the good charge transporting property of perovskite, we design and simulate a p–i–n-type all-perovskite solar cell by using one-dimensional device simulator. The perovskite charge transporting layers and the perovskite absorber constitute the all-perovskite cell. By modulating the cell parameters, such as layer thickness values, doping concentrations and energy bands of n-, i-, and p-type perovskite layers, the all-perovskite solar cell obtains a high power conversion efficiency of 25.84%. The band matched cell shows appreciably improved performance with widen absorption spectrum and lowered recombination rate, so weobtain a high J sc of 32.47 mA/cm 2 . The small series resistance of the all-perovskite solar cell also benefits the high J sc . The simulation provides a novel thought of designing perovskite solar cells with simple producing process, low production cost and high efficient structure to solve the energy problem. (paper)

Oxygen influencing the photocarriers lifetime of CH{sub 3}NH{sub 3}PbI{sub 3−x}Cl{sub x} film grown by two-step interdiffusion method and its photovoltaic performance

Energy Technology Data Exchange (ETDEWEB)

Yuan, Shuai; Qiu, Zhiwen; Zhang, Hailiang; Gong, Haibo; Cao, Bingqiang, E-mail: mse-caobq@ujn.edu.cn [Laboratory of Inorganic Energy and Environment Materials, School of Material Science and Engineering, University of Jinan, Jinan 250022, Shandong (China); Hao, Yufeng [Department of Mechanical Engineering, Columbia University, New York, New York 10027 (United States)

2016-01-18

During the growth of CH{sub 3}NH{sub 3}PbI{sub 3−x}Cl{sub x} (MAPbI{sub 3−x}Cl{sub x}) perovskite films by the two-step inter-diffusion method, the presence of a trace amount of oxygen gas is critical to their physical properties and photovoltaic performance. As the oxygen concentration increases, poor film morphologies and incomplete surface coverage are observed. Moreover, by XRD, Raman scattering, and photoluminescence measurements, we find that MAPbI{sub 3−x}Cl{sub x} grains become more distorted and the electron-hole recombination rate dramatically increases. Higher oxygen concentration triggers a sharp decrease in the current density and the fill factor of corresponding solar cells, which degrades device performance, on average, from 14.3% to 4.4%. This work proves the importance of controlling the oxygen atmosphere in the fabrication of high-performance perovskite solar cells.

Method for single crystal growth of photovoltaic perovskite material and devices

Science.gov (United States)

Huang, Jinsong; Dong, Qingfeng

2017-11-07

Systems and methods for perovskite single crystal growth include using a low temperature solution process that employs a temperature gradient in a perovskite solution in a container, also including at least one small perovskite single crystal, and a substrate in the solution upon which substrate a perovskite crystal nucleates and grows, in part due to the temperature gradient in the solution and in part due to a temperature gradient in the substrate. For example, a top portion of the substrate external to the solution may be cooled.

Determining the energetics of vicinal perovskite oxide surfaces

NARCIS (Netherlands)

Wessels, W.A.; Bollmann, Tjeerd Rogier Johannes; Koster, Gertjan; Zandvliet, Henricus J.W.; Rijnders, Augustinus J.H.M.

2017-01-01

The energetics of vicinal SrTiO3(001) and DyScO3(110), prototypical perovskite vicinal surfaces, has been studied using topographic atomic force microscopy imaging. The kink formation and strain relaxation energies are extracted from a statistical analysis of the step meandering. Both perovskite

Multifunctional MgO Layer in Perovskite Solar Cells.

Science.gov (United States)

Guo, Xudong; Dong, Haopeng; Li, Wenzhe; Li, Nan; Wang, Liduo

2015-06-08

A multifunctional magnesium oxide (MgO) layer was successfully introduced into perovskite solar cells (PSCs) to enhance their performance. MgO was coated onto the surface of mesoporous TiO(2) by the decomposition of magnesium acetate and, therefore, could block contact between the perovskite and TiO(2). X-ray photoelectron spectroscopy and infrared spectroscopy showed that the amount of H(2)O/hydroxyl absorbed on the TiO(2) decreased after MgO modification. The UV/Vis absorption spectra of the perovskite with MgO modification revealed an enhanced photoelectric performance compared with that of unmodified perovskite after UV illumination. In addition to the photocurrent, the photovoltage and fill factor also showed an enhancement after modification, which resulted in an increase in the overall efficiency of the cell from 9.6 to 13.9 %. Electrochemical impedance spectroscopy (EIS) confirmed that MgO acts as an insulating layer to reduce charge recombination. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Field-emission from quantum-dot-in-perovskite solids.

Science.gov (United States)

García de Arquer, F Pelayo; Gong, Xiwen; Sabatini, Randy P; Liu, Min; Kim, Gi-Hwan; Sutherland, Brandon R; Voznyy, Oleksandr; Xu, Jixian; Pang, Yuangjie; Hoogland, Sjoerd; Sinton, David; Sargent, Edward

2017-03-24

Quantum dot and well architectures are attractive for infrared optoelectronics, and have led to the realization of compelling light sensors. However, they require well-defined passivated interfaces and rapid charge transport, and this has restricted their efficient implementation to costly vacuum-epitaxially grown semiconductors. Here we report solution-processed, sensitive infrared field-emission photodetectors. Using quantum-dots-in-perovskite, we demonstrate the extraction of photocarriers via field emission, followed by the recirculation of photogenerated carriers. We use in operando ultrafast transient spectroscopy to sense bias-dependent photoemission and recapture in field-emission devices. The resultant photodiodes exploit the superior electronic transport properties of organometal halide perovskites, the quantum-size-tuned absorption of the colloidal quantum dots and their matched interface. These field-emission quantum-dot-in-perovskite photodiodes extend the perovskite response into the short-wavelength infrared and achieve measured specific detectivities that exceed 10 12 Jones. The results pave the way towards novel functional photonic devices with applications in photovoltaics and light emission.

Quantum Dots in Two-Dimensional Perovskite Matrices for Efficient Near-Infrared Light Emission

KAUST Repository

Yang, Zhenyu

2017-03-13

Quantum-dot-in-perovskite solids are excellent candidates for infrared light-emitting applications. The first generation of dot-in-perovskite light-emitting diodes (LEDs) has shown bright infrared electroluminescence with tunable emission wavelength; however, their performance has been limited by degradation of the active layer at practical operating voltages. This arises from the instability of the three-dimensional (3D) organolead halide perovskite matrix. Herein we report the first dot-in-perovskite solids that employ two-dimensional (2D) perovskites as the matrix. 2D perovskite passivation is achieved via an in situ alkylammonium/alkylamine substitution carried out during the quantum dot (QD) ligand exchange process. This single-step film preparation process enables deposition of the QD/perovskite active layers with thicknesses of 40 nm, over seven times thinner than the first-generation dot-in-perovskite thin films that relied on a multistep synthesis. The dot-in-perovskite film roughness improved from 31 nm for the first-generation films to 3 nm for films as a result of this new approach. The best devices exhibit external quantum efficiency peaks exceeding 2% and radiances of ∼1 W sr–1 m–2, with an improved breakdown voltage up to 7.5 V. Compared to first-generation dot-in-perovskites, this new process reduces materials consumptions 10-fold and represents a promising step toward manufacturable devices.

Quantum Dots in Two-Dimensional Perovskite Matrices for Efficient Near-Infrared Light Emission

KAUST Repository

Yang, Zhenyu; Voznyy, Oleksandr; Walters, Grant; Fan, James Z.; Liu, Min; Kinge, Sachin; Hoogland, Sjoerd; Sargent, Edward H.

2017-01-01

Quantum-dot-in-perovskite solids are excellent candidates for infrared light-emitting applications. The first generation of dot-in-perovskite light-emitting diodes (LEDs) has shown bright infrared electroluminescence with tunable emission wavelength; however, their performance has been limited by degradation of the active layer at practical operating voltages. This arises from the instability of the three-dimensional (3D) organolead halide perovskite matrix. Herein we report the first dot-in-perovskite solids that employ two-dimensional (2D) perovskites as the matrix. 2D perovskite passivation is achieved via an in situ alkylammonium/alkylamine substitution carried out during the quantum dot (QD) ligand exchange process. This single-step film preparation process enables deposition of the QD/perovskite active layers with thicknesses of 40 nm, over seven times thinner than the first-generation dot-in-perovskite thin films that relied on a multistep synthesis. The dot-in-perovskite film roughness improved from 31 nm for the first-generation films to 3 nm for films as a result of this new approach. The best devices exhibit external quantum efficiency peaks exceeding 2% and radiances of ∼1 W sr–1 m–2, with an improved breakdown voltage up to 7.5 V. Compared to first-generation dot-in-perovskites, this new process reduces materials consumptions 10-fold and represents a promising step toward manufacturable devices.

Hydrogen Bonding and Stability of Hybrid Organic-Inorganic Perovskites

KAUST Repository

El-Mellouhi, Fedwa

2016-09-08

In the past few years, the efficiency of solar cells based on hybrid organic–inorganic perovskites has exceeded the level needed for commercialization. However, existing perovskites solar cells (PSCs) suffer from several intrinsic instabilities, which prevent them from reaching industrial maturity, and stabilizing PSCs has become a critically important problem. Here we propose to stabilize PSCs chemically by strengthening the interactions between the organic cation and inorganic anion of the perovskite framework. In particular, we show that replacing the methylammonium cation with alternative protonated cations allows an increase in the stability of the perovskite by forming strong hydrogen bonds with the halide anions. This interaction also provides opportunities for tuning the electronic states near the bandgap. These mechanisms should have a universal character in different hybrid organic–inorganic framework materials that are widely used.

Hydrogen Bonding and Stability of Hybrid Organic-Inorganic Perovskites

KAUST Repository

El-Mellouhi, Fedwa; Marzouk, Asma; Bentria, El Tayeb; Rashkeev, Sergey N.; Kais, Sabre; Alharbi, Fahhad H.

2016-01-01

In the past few years, the efficiency of solar cells based on hybrid organic–inorganic perovskites has exceeded the level needed for commercialization. However, existing perovskites solar cells (PSCs) suffer from several intrinsic instabilities, which prevent them from reaching industrial maturity, and stabilizing PSCs has become a critically important problem. Here we propose to stabilize PSCs chemically by strengthening the interactions between the organic cation and inorganic anion of the perovskite framework. In particular, we show that replacing the methylammonium cation with alternative protonated cations allows an increase in the stability of the perovskite by forming strong hydrogen bonds with the halide anions. This interaction also provides opportunities for tuning the electronic states near the bandgap. These mechanisms should have a universal character in different hybrid organic–inorganic framework materials that are widely used.

Perovskite Solar Cells—Towards Commercialization

International Nuclear Information System (INIS)

Ono, Luis K.; Park, Nam-Gyu; Zhu, Kai; Huang, Wei; Qi, Yabing

2017-01-01

The Symposium ES1, Perovskite Solar Cells - Towards Commercialization, held at the 2017 Materials Research Society (MRS) Spring Meeting in Phoenix, Arizona (April 17-21, 2017) received ~200 abstracts. The 23 invited talks and 72 contributed oral presentations as well as 3 poster presentation sessions were organized into 13 principal themes according to the contents of the received abstracts. This Energy Focus article provides a concise summary of the opinions from the scientists and engineers who participated in this symposium regarding the recent progresses, challenges, and future directions for perovskite solar cells as well as other optoelectronic devices.

Role of thermal analysis in the study of superconductor YBa2Cu3O7-δ

International Nuclear Information System (INIS)

Virkar, A.N.

1993-01-01

The interstitial oxygen atoms along the b-axis of the orthorhombic unit cell of superconducting phase of YBa 2 Cu 3 O 7 form a chain of Cu-O-Cu-O located in the perovskite basal plane and these chains are interpreted to be responsible for superconductivity. Superconductivity can be strongly suppressed by introducing oxygen defects into the chain sites. The characteristic chain structure disappears in the non-superconducting tetragonal phase. Thus orthorhombic to tetragonal transformation takes place by an order-disorder transition between filled and vacant oxygen sites in the basal plane which results in the loss of superconductivity in oxygen deficient YBa 2 Cu 3 O 7-δ phase. (author). 12 refs., 8 figs

Phase transition in metastable perovskite Pb(AlNb)0,5O3

International Nuclear Information System (INIS)

Zhabko, T.E.; Olekhnovich, N.M.; Shilin, A.D.

1987-01-01

Dielectric properties of metastable perovskite Pb(AlNb) 0.5 O 3 and X-ray temperature investigations of both perovskite and pyrochlore modifications of the given compound are studied. Samples with the perovskite structure are prepared from the pyrochlorephase at 4-5 GPa pressure and 1170-1270 K. Ferroelectric phase transition is shown to occur in the metastable perovskite phase Pb(AlNb) 0.5 O 3 at 170 K

Efficient Planar Structured Perovskite Solar Cells with Enhanced Open-Circuit Voltage and Suppressed Charge Recombination Based on a Slow Grown Perovskite Layer from Lead Acetate Precursor.

Science.gov (United States)

Li, Cong; Guo, Qiang; Wang, Zhibin; Bai, Yiming; Liu, Lin; Wang, Fuzhi; Zhou, Erjun; Hayat, Tasawar; Alsaedi, Ahmed; Tan, Zhan'ao

2017-12-06

For planar structured organic-inorganic hybrid perovskite solar cells (PerSCs) with the poly(3,4-ethylenedioxythiophene:polystyrene sulfonate) (PEDOT:PSS) hole transport layer, the open-circuit voltage (V oc ) of the device is limited to be about 1.0 V, resulting in inferior performance in comparison with TiO 2 -based planar counterparts. Therefore, increasing V oc of the PEDOT:PSS-based planar device is an important way to enhance the efficiency of the PerSCs. Herein, we demonstrate a novel approach for perovskite film formation and the film is formed by slow growth from lead acetate precursor via a one-step spin-coating process without the thermal annealing (TA) process. Because the perovskite layer grows slowly and naturally, high-quality perovskite film can be achieved with larger crystalline particles, less defects, and smoother surface morphology. Ultraviolet absorption, X-ray diffraction, scanning electron microscopy, steady-state fluorescence spectroscopy (photoluminescence), and time-resolved fluorescence spectroscopy are used to clarify the crystallinity, morphology, and internal defects of perovskite thin films. The power conversion efficiency of p-i-n PerSCs based on slow-grown film (16.33%) shows greatly enhanced performance compared to that of the control device based on traditional thermally annealed perovskite film (14.33%). Furthermore, the V oc of the slow-growing device reaches 1.12 V, which is 0.1 V higher than that of the TA device. These findings indicate that slow growth of the perovskite layer from lead acetate precursor is a promising approach to achieve high-quality perovskite film for high-performance PerSCs.

A New Generation of Luminescent Materials Based on Low-Dimensional Perovskites

KAUST Repository

Pan, Jun

2017-06-02

Low-dimensional perovskites with high luminescence properties are promising materials for optoelectronic applications. In this article, properties of two emerging types of low-dimensional perovskites are discussed, including perovskite quantum dots CsPbX3 (X = Cl, Br or I) and zero-dimensional perovskite Cs4PbBr6. Moreover, their application for light down conversion in LCD backlighting systems and in visible light communication are also presented. With their superior optical properties, we believe that further development of these materials will potentially open more prospective applications, especially for optoelectronics devices.

Interspace modification of titania-nanorod arrays for efficient mesoscopic perovskite solar cells

Energy Technology Data Exchange (ETDEWEB)

Chen, Peng; Jin, Zhixin; Wang, Yinglin, E-mail: wangyl100@nenu.edu.cn; Wang, Meiqi; Chen, Shixin; Zhang, Yang; Wang, Lingling; Zhang, Xintong, E-mail: xtzhang@nenu.edu.cn; Liu, Yichun, E-mail: ycliu@nenu.edu.cn

2017-04-30

Highlights: • The fabrication of perovskite solar cells utilizing TiO{sub 2} NR arrays. • Investigation of the interspace effect of TiO{sub 2} NR on perovskite layer. • Understanding of the balance between perovskite capping layer and pore filling. - Abstract: Morphology of electron transport layers (ETLs) has an important influence on the device architecture and electronic processes of mesostructured solar cells. In this work, we thoroughly investigated the effect of the interspace of TiO{sub 2} nanorod (NR) arrays on the photovoltaic performance of the perovskite solar cells (PSCs). Along with the interspace in TiO{sub 2}-NR arrays increasing, the thickness as well as the crystal size of perovskite capping layer are reduced accordingly, and the filling of perovskite in the channel becomes incomplete. Electrochemical impedance spectroscopy measurements reveal that this variation of perovskite absorber layer, induced by interspace of TiO{sub 2} NR arrays, causes the change of charge recombination process at the TiO{sub 2}/perovskite interface, suggesting that a balance between capping layer and the perovskite filling is critical to obtain high charge collection efficiency of PSCs. A power conversion efficiency of 10.3% could be achieved through careful optimization of interspace in TiO{sub 2}-NR arrays. Our research will shed light on the morphology control of ETLs with 1D structure for heterojunction solar cells fabricated by solution-deposited method.

Stable Graphene-Two-Dimensional Multiphase Perovskite Heterostructure Phototransistors with High Gain.

Science.gov (United States)

Shao, Yuchuan; Liu, Ye; Chen, Xiaolong; Chen, Chen; Sarpkaya, Ibrahim; Chen, Zhaolai; Fang, Yanjun; Kong, Jaemin; Watanabe, Kenji; Taniguchi, Takashi; Taylor, André; Huang, Jinsong; Xia, Fengnian

2017-12-13

Recently, two-dimensional (2D) organic-inorganic perovskites emerged as an alternative material for their three-dimensional (3D) counterparts in photovoltaic applications with improved moisture resistance. Here, we report a stable, high-gain phototransistor consisting of a monolayer graphene on hexagonal boron nitride (hBN) covered by a 2D multiphase perovskite heterostructure, which was realized using a newly developed two-step ligand exchange method. In this phototransistor, the multiple phases with varying bandgap in 2D perovskite thin films are aligned for the efficient electron-hole pair separation, leading to a high responsivity of ∼10 5 A W -1 at 532 nm. Moreover, the designed phase alignment method aggregates more hydrophobic butylammonium cations close to the upper surface of the 2D perovskite thin film, preventing the permeation of moisture and enhancing the device stability dramatically. In addition, faster photoresponse and smaller 1/f noise observed in the 2D perovskite phototransistors indicate a smaller density of deep hole traps in the 2D perovskite thin film compared with their 3D counterparts. These desirable properties not only improve the performance of the phototransistor, but also provide a new direction for the future enhancement of the efficiency of 2D perovskite photovoltaics.

Large polarons in lead halide perovskites

OpenAIRE

Miyata, Kiyoshi; Meggiolaro, Daniele; Trinh, M. Tuan; Joshi, Prakriti P.; Mosconi, Edoardo; Jones, Skyler C.; De Angelis, Filippo; Zhu, X.-Y.

2017-01-01

Lead halide perovskites show marked defect tolerance responsible for their excellent optoelectronic properties. These properties might be explained by the formation of large polarons, but how they are formed and whether organic cations are essential remain open questions. We provide a direct time domain view of large polaron formation in single-crystal lead bromide perovskites CH3NH3PbBr3 and CsPbBr3. We found that large polaron forms predominantly from the deformation of the PbBr3 ? framewor...

Maximizing and stabilizing luminescence from halide perovskites with potassium passivation

Science.gov (United States)

Abdi-Jalebi, Mojtaba; Andaji-Garmaroudi, Zahra; Cacovich, Stefania; Stavrakas, Camille; Philippe, Bertrand; Richter, Johannes M.; Alsari, Mejd; Booker, Edward P.; Hutter, Eline M.; Pearson, Andrew J.; Lilliu, Samuele; Savenije, Tom J.; Rensmo, Håkan; Divitini, Giorgio; Ducati, Caterina; Friend, Richard H.; Stranks, Samuel D.

2018-03-01

Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield—a quantity that must be maximized to obtain high efficiency—remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can

Thermodynamic stability and kinetics of perovskite dissolution

Energy Technology Data Exchange (ETDEWEB)

Nesbitt, H W; Bancroft, G M; Fyfe, W S; Karkhanis, S N; Nishijima, A [Western Ontario Univ., London (Canada); Shin, S [National Chemical Lab. for Industry, Tsukuba (Japan)

1981-01-29

Perovskite, a SYNROC host mineral for nuclear wastes, is thermodynamically unstable in natural waters and in association with common minerals. Leach experiments demonstrate that CaTiO/sub 3/ (perovskite), SrTiO/sub 3/ and BaTiO/sub 3/ are as reactive as some silicate glasses below 100/sup 0/C, but leach much more slowly than glasses above 100/sup 0/C.