WorldWideScience

Sample records for perovskite stacking polytypes

  1. 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.

  2. Hexagonal perovskites with cationic vacancies. 15. Ba/sub 9/Nb/sub 6/Wvacant/sub 2/O/sub 27/ - the first perovskite stacking polytype of rhombohedral 27 L-type

    Energy Technology Data Exchange (ETDEWEB)

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

    1980-02-01

    The perovskite stacking polytype Ba/sub 9/Nb/sub 6/sup(V)Wsup(VI)vacant/sub 2/O/sub 27/ (white) is the first representative of a rhombohedral 27 L-type. The lattice parameters (trigonal setting) are: a = 5.79/sub 3/ A; c = 63.4/sub 1/ A; Z = 3 (rhosub(exp) = 6.4/sub 6/ g/cm/sup 3/; rhosub(calc) = 6.51/sub 2/ g/cm/sup 3/). The corresponding Tasup(V)-compound is isotypic; it tends to develop stacking faults.

  3. Hexagonal perovskites with cationic vacancies. 4. Ba/sub 8/Re/sub 3/Msup(V)Wvacant/sub 3/O/sub 24/ with Msup(V) = Nb, Ta - perovskite stacking polytypes of 24 L type

    Energy Technology Data Exchange (ETDEWEB)

    Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Inst. fuer Chemie

    1978-11-01

    The yellow perovskite stacking polytypes Ba/sub 8/Re/sub 3/NbWvacant/sub 3/O/sub 24/ and Ba/sub 8/Re/sub 3/TaWvacant/sub 3/O/sub 24/ have a rhombohedral layer structure of 24 L type with 3 formula units in the trigonal setting (Ba/sub 8/Re/sub 3/NbWvacant/sub 3/O/sub 24/: a = 5,82 A; c = 55.6 A; Ba/sub 8/Re/sub 3/TaWvacant/sub 3/O/sub 24/; a = 5,81 A; c = 55.6 A).

  4. Hexagonal perovskites with cationic vacancies. 11. Stacking polytype Ba/sub 6/W/sub 4/vacant/sub 2/O/sub 18/

    Energy Technology Data Exchange (ETDEWEB)

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

    1979-07-01

    The white Ba/sub 6/W/sub 4/vacant/sub 2/O/sub 18/, with a cation/vacancy ratio of 2:1 for the octahedral holes, is the first representative of a new stacking polytype for this formula type. It crystallizes in a rhombohedral six layer-structure with asub(hex) = 10.13 A; csub(hex) = 13.96 A; Z = 3 (rhosub(exp) = 7.3 g/cm/sup 3/; rhosub(calc) = 7.41 g/cm/sup 3/).

  5. Hexagonal perovskites with cationic vacancies. 5. Structure determination on H-Ba/sub 2/Lusub(2/3)vacantsub(1/3)WO/sub 6/ - a novel rhombohedral stacking polytype with 18 layers

    Energy Technology Data Exchange (ETDEWEB)

    Wischert, W; Schittenhelm, H J; Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Inst. fuer Chemie

    1979-01-01

    Compounds of type Ba/sub 2/Bsub(2/3)sup(III)vacantsub(1/3)Wsup(VI)O/sub 6/ with Bsup(III) = Gd-Lu, Y are polymorphic. They crystallize in a cubic 1:1 ordered perovskite structure and in a new rhombohedral perovskite stacking polytype of 18 L respectively. By intensity calculations out of the three possible stacking sequences (4)(2), (5)(1) and (3)1(1)1 (all space group R3m) the sequence (5)(1) can be selected. For H-Ba/sub 2/Lusub(2/3)vacant sub(1/3)WO/sub 6/ the refined R' factor is 14.1%. The structure contains groups of three octahedra connected with another by common faces which are linked with each other by three corner sharing octahedra. In the block of three face sharing octahedra the central octahedral lattice site is vacant, the two outer positions are occupied by tungsten atoms. According to this distribution a direct contact of occupied face sharing octahedra is absent.

  6. Hexagonal perovskites with cationic vacancies. 22. Polymorphism of the rhombohedral 12 L stacking polytypes in the system Sr/sub 4-x/Ba/sub x/NiRe/sub 2/vacantO/sub 12/

    Energy Technology Data Exchange (ETDEWEB)

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

    1980-10-01

    In the system Sr/sub 4-x/Ba/sub x/NiRe/sub 2/vacantO/sub 12/ two different stacking polytypes of the rhombohedral 12 L type are present. Both crystallize in the space group R-3m with the same sequence of the close packed AO/sub 3/ sheets: (3)(1) = (hhcc)/sub 3/. Accordingly the octahedral net consists of groups of three face connected octahedra which are linked by another through single corner sharing octahedra. In the strontium compound, Sr/sub 4/NiRe/sub 2/vacantO/sub 12/, the occupation of the octahedral holes is the same as in other rhombohedral 12 L perovskites of type A/sub 4/(B, M)/sub 3/vacantO/sub 12/ (The two outer octahedra are occupied by rhenium, the center is vacant and the nickel is located in the single octahedron). In the barium stacking polytype, Ba/sub 4/NiRe/sub 2/vacantO/sub 12/, the distribution is completely altered: The rhenium atoms occupy the central position in the block of three face connected octahedra and the single octahedron, the nickel atom and the vacancy are distributed statistically over the two outer positions in the block of three octahedra. Intensity calculations on powder data gave the intensity related R' value of 7.2% for Sr/sub 4/NiRe/sub 2/vacantO/sub 12/ and 6.2% for Ba/sub 4/NiRe/sub 2/vacantO/sub 12/.

  7. Hexagonal perovskites with cationic vacancies. 14. The rhombohedral 12 L-stacking polytypes Ba/sub 2/La/sub 2/Bsup(II)(W/sub 2/sup(VI)vacantO/sub 12/)

    Energy Technology Data Exchange (ETDEWEB)

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

    1980-02-01

    Rhombohedral 12 L-stacking polytypes with cationic vacancies of type Ba/sub 2/La/sub 2/Bsup(II)(W/sub 2/sup(VI)vacantO/sub 12/) are reported for Bsup(II) = Mg, Zn (white), Ni (light brown) and Co (brown). For Bsup(II) = Cu, as a consequence of the Jahn Teller effect, a triclinic distorted lattice is observed.

  8. Hexagonal perovskites with cationic vacancies. 8. Vibrational spectroscopic investigations on rhombohedral 18 L-stacking polytypes Ba/sub 6/B/sub 2/sup(III)vacantW/sub 3/sup(VI)O/sub 18/

    Energy Technology Data Exchange (ETDEWEB)

    Schittenhelm, H J; Fadini, A; Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.)

    1979-10-01

    The vibrational spectra of the 18 L stacking polytypes Ba/sub 6/B/sub 2/sup(III)vacant W/sub 3/O/sub 18/ (space group R3m; sequence (hhcccc)/sub 3/) with Bsup(III) = Lu, Y are reported. The octahedral net consists of W/sub 2/vacantO/sub 12/ and WO/sub 6/ groups, which are isolated from each other by the Ba and B ions. An assignment of the vibrational frequencies has been made with the aid of factor group analysis. For the W/sub 2/vacantO/sub 12/ block a complete force constant calculation is reported.

  9. Photoluminescence of trivalent rare earths in perovskite stacking polytypes Ba/sub 2/Lasub(2-x)REsub(x)/sup 3 +/MgW/sub 2/vacantO/sub 12/, Ba/sub 6/Ysub(2-x)REsub(x)/sup 3 +/W/sub 3/vacantO/sub 18/, and Sr/sub 8/SrGdsub(2-x)REsub(x)/sup 3 +/W/sub 4/vacantO/sub 24/

    Energy Technology Data Exchange (ETDEWEB)

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

    1981-12-01

    Rhombohedral 12 L staking polytypes Ba/sub 2/Lasub(2-x)REsub(x)/sup 3 +/MgW/sub 2/vacantO/sub 12/ show with RE/sup 3 +/ = Pr, Sm, Eu, Tb, Dy, Ho, Er, Tm; the 18 L stacking polytypes Ba/sub 6/Ysub(2-x)REsub(x)/sup 3 +/W/sub 3/vacantO/sub 18/ and the polymorphic perovskites Sr/sub 8/SrGdsub(2-x)REsub(x)/sup 3 +/W/sub 4/vacantO/sub 24/ with RE/sup 3 +/ = Sm, Eu, Dy, Ho, Er visible photoluminescence. The concentration dependence and the influence of the coordination number of the rare earth are reported.

  10. Hexagonal perovskites with cationic vacancies. 17. Structure determination on Ba/sub 9/Nb/sub 6/Wvacant/sub 2/O/sub 27/ - the first stacking polytype of a rhombohedral 27 L-type

    Energy Technology Data Exchange (ETDEWEB)

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

    1980-03-01

    The hexagonal stacking polytype of rhombohedral 27 L-type, Ba/sub 9/Nb/sub 6/Wvacant/sub 2/O/sub 27/, crystallizes in the space group R3m with the sequence (4)1(3)1 = (hhccchhcc)/sub 3/ and three formula units for the trigonal setting. The refined, intensity, related, R'-value is 9.7%. The octahedral net consists of blocks of three face connected octahedra which are linked to each other alternately through one or two octahedra connected exclusively by common vertices. The cationic vacancies are located in the centers of the groups of three octahedra. With this distribution direct contact between occupied face-sharing octahedra is avoided. The niobium and tungsten atoms are distributed statistically between the remaining octahedral holes. In the blocks of three octahedra they are displaced by approximately 0.29 A from their ideal positions in the direction of the central void. The Ba atoms neighbouring a vacancy (all in hexagonal packed BaO/sub 3/ sheets) are dislocated in the direction of the void, while the cubic packed BaO/sub 3/ sheets maintain nearly regular form.

  11. Hexagonal perovskites with cationic vacancies. 19. The rhombohedral 12 L stacking polytypes Ba/sub 3/LaBsup(III) (W/sub 2/sup(VI)vacantO/sub 12/)

    Energy Technology Data Exchange (ETDEWEB)

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

    1980-06-01

    Hexagonal perovskites are described for the new type Ba/sub 3/LaBsup(III)(W/sub 2/sup(VI)vacantO/sub 12/) with Bsup(III) = Sc, In, Lu, Yb. According to the intensity calculations for Ba/sub 3/LaIn(W/sub 2/vacantO/sub 12/) they crystallize in a rhombohedral 12 L structure with the sequence (3)(1) respectively (hhcc)/sub 3/; space group R3m. The refined, intensity related R' value is 6.7%.

  12. Hexagonal perovskites with cationic vacancies. 16. Rhombohedral 12 L-stacking polytypes Ba/sub 3/Asup(III)M/sub 3/sup(V)vacantO/sub 12/ with Msup(V) = Nb, Ta

    Energy Technology Data Exchange (ETDEWEB)

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

    1980-02-01

    The white quaternary oxides Ba/sub 3/LaM/sub 3/sup(V)vacantO/sub 12/ with Msup(V) = Nb, Ta belong to the group of hexagonal perovskites with cationic vacancies. They crystallize in a rhombohedral 12 L-structure (sequence (hhcc)/sub 3/; space group R3m) with a = 5.75 A; c = 28.1 A (Msup(V) = Nb); a = 5.74 A; c = 28.2 A (Ta) and Z = 3. Signs for the formation of isotypic compounds with Asup(III) = Pr, Nd could be obtained as well.

  13. Structure of fault stackings of molecular layers X-M-X in CdI2 polytypic crystals

    International Nuclear Information System (INIS)

    Palosz, B.; Przedmojski, J.

    1984-01-01

    The arrangements of molecular layers I-Cd-I, which may be regarded as 'faulted' for CdI 2 polytypic crystals, are analyzed. Tentative classification of faults into those which are intermediate structure between the basic polytypes 2H and 4H and faults occurring between different blocks of pure structure 4 H is proposed. The connection between some growth parameters and the structure of faults in CdI 2 crystals grown from solutions is discussed. It is shown that the geometrical classification of stacking faults used for layered inorganic crystals is not appropriate for the description of the faults existing in polytypic crystals of MX 2 type. The effect of weak external electric and magnetic fields on the polytypic structure of CdI 2 is analyzed. The experiments performed for several hundred of polytypes of CdI 2 showed that the external fields may, in some conditions, affect the organization of the polytypic structure of crystals very strongly. In particular, it was found that the external fields may change the period of polytype cells and that the relative number of hexagonal and rhombohedral polytypes differ very strongly for crystals grown in the absence and in the presence of external electric and magnetic fields. (author)

  14. Hexagonal perovskites with cationic vacancies. 13. Rhombohedral 12 L-stacking polytypes Ba/sub 4/M/sub 2/sup(V)WvacantO/sub 12/ with Msup(V) = Nb, Ta

    Energy Technology Data Exchange (ETDEWEB)

    Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.)

    1979-10-01

    The white quaternary oxides Ba/sub 4/Nb/sub 2/WvacantO/sub 12/ and Ba/sub 4/Ta/sub 2/WvacantO/sub 12/ belong to the group of hexagonal perovskites with cationic vacancies. They crystallize in the rhombohedral 12 L-type: Sequence (3)(1) = (hhcc)/sub 3/; space group R/sup -/3m (Ba/sub 4/Nb/sub 2/WvacantO/sub 12/: a = 5.77/sub 6/ A; c = 28.0/sub 55/ A; Ba/sub 4/Ta/sub 2/WvacantO/sub 12/: a = 5.77/sub 3/ A; c = 28.0/sub 75/ A; Z = 3).

  15. Hexagonal perovskites with cationic vacancies. 24. Rhombohedral 9 L stacking polytypes in the systems Ba/sub 3/Wsub(2-x)sup(VI)Msub(x)sup(V)vacantOsub(9-x/2)vacantsub(x/2) with Msup(V) = Nb, Ta

    Energy Technology Data Exchange (ETDEWEB)

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

    1980-12-01

    In the system Ba/sub 3/Wsub(2-x)sup(VI)Nbsub(x)sup(V)vacantOsub(9-x/2)vacantsub(x/2) stacking polytypes of rhombohedral 9 L type (sequence (hhc)/sub 3/; space group R-3m) can be prepared with approximately 1/3 <= x <= 2. For x = 2(Ba/sub 3/Nb/sub 2/vacantO/sub 8/vacant) two modifications are formed. In the corresponding Ta system the phase width is reduced to a smaller region with x approximately 1/3.

  16. Hexagonal perovskites with cationic vacancies. 7. Vibrational spectroscopic investigations on the rhombohedral 12 L-stacking polytypes Ba/sub 4/Bsup(II)(Re/sub 2/vacantO/sub 12/) and Ba/sub 4/Bsub(2/3)sup(III)vacantsub(1/3)(Re/sub 2/vacantO/sub 12/)

    Energy Technology Data Exchange (ETDEWEB)

    Fadini, A; Kemmler-Sack, S; Schittenhelm, H J; Rother, H J; Treiber, U [Tuebingen Univ. (Germany, F.R.). Lehrstuhl fuer Anorganische Chemie 2

    1979-07-01

    For the rhombohedral 12 L stacking polytypes Ba/sub 4/Bsup(II)(Re/sub 2/vacantO/sub 12/) and Ba/sub 4/Bsub(2/3)sup(III)vacantsub(1/3)(Re/sub 2/vacantO/sub 12/), space group R3m, sequence (3)(1), the lattice consists of groups of three face sharing octahedra with the composition Re/sub 2/vacantO/sub 12/. They are isolated from each other by the Ba and B ions. The vibrational spectra are interpreted according to the factor group analysis. For the Re/sub 2/vacantO/sub 12/ unit (symmetry Dsub(3d) the results of a complete vibrational analysis and the calculation of the force constants are reported.

  17. One dimensional model for polytypes

    International Nuclear Information System (INIS)

    Rosato, A.

    1979-01-01

    The general expression for the dispersion relation for a polyatomic one dimensional crystal obtained by the Laplace Transform Method is applied to materials with the fcc and hcp structures, both consisting of close-packed planes of atoms with the stacking sequence of plane ABC/ABC... and AB/AB... respectively. The expression is also applied to polytypes, that is materials caracterized by a stacking sequence with longer repeat unit. The effective mass is cast in a condensed form useful for further calculations. The results from this simple model are only qualitative. (Author) [pt

  18. Polytypism in CdI2: a consequence of restrictions in close-packed arrangements

    International Nuclear Information System (INIS)

    Wahab, M.A.; Kant, R.

    1986-01-01

    Based on theoretical and experimental observations, it has been established that the polytypes 2H and 4H act as basic structural units as regard to the formation of CdI 2 polytypes. As a result of this, some general rules have been formulated which help understand (i) the nature of restrictions in the close-packed arrangements and to deduce the genuine CdI 2 polytypes, and (ii) the classification of CdI 2 polytypes into various possible groups. This further helps to conclude that (i) the CdI 2 polytypes are simply a consequence of restrictions in the close-packed arrangements, (ii) the concept of stacking fault is superfluous as far as the formation of ordered polytypes are concerned, and (iii) the identification of CdI 2 polytypes on the basis of intensity data has limited implications unless some practical use of polytypes are found. (author)

  19. Modeling defects and plasticity in MgSiO3 post-perovskite: Part 1-generalized stacking faults.

    Science.gov (United States)

    Goryaeva, Alexandra M; Carrez, Philippe; Cordier, Patrick

    In this work, we examine the transferability of a pairwise potential model (derived for MgSiO 3 perovskite) to accurately compute the excess energies of the generalized stacking faults (GSF, also called γ -surfaces) in MgSiO 3 post-perovskite. All calculations have been performed at 120 GPa, a pressure relevant to the D″ layer. Taking into account an important aspect of crystal chemistry for complex materials, we consider in detail all possible locations of slip planes in the post-perovskite structure. The γ -surface calculations emphasize the easiness of glide of slip systems with the smallest shear vector [100] and of the [001](010) slip system. Our results are in agreement with previous ab initio calculations. This validates the use the chosen potential model for further full atomistic modeling of dislocations in MgSiO 3 post-perovskite.

  20. Stacking Faults and Polytypes for Layered Double Hydroxides: What Can We Learn from Simulated and Experimental X-ray Powder Diffraction Data?

    Science.gov (United States)

    Sławiński, Wojciech A; Sjåstad, Anja Olafsen; Fjellvåg, Helmer

    2016-12-19

    Layered double hydroxides (LDH) are a broad group of widely studied materials. The layered character of those materials and their high flexibility for accommodating different metals and anions make them technologically interesting. The general formula for the LDH compound is [M 1-x II M x III (OH) 2 ][A n- ] x/n ·mH 2 O, where M II is a divalent metal cation which can be substituted by M III trivalent cation, and A n- is a charge compensating anion located between positively charged layers. In this paper we present a comprehensive study on possible structural disorder in LDH. We show how X-ray powder diffraction (XRPD) can be used to reveal important features of the LDH crystal structure such as stacking faults, random interlayer shifts, anion-molecule orientation, crystal water content, distribution of interlayer distances, and also LDH slab thickness. All calculations were performed using the Discus package, which gives a better flexibility in defining stacking fault sequences, simulating and refining XRPD patterns, relative to DIFFaX, DIFFaX+, and FAULTS. Finally, we show how the modeling can be applied to two LDH samples: Ni 0.67 Cr 0.33 (OH) 2 (CO 3 ) 0.16 ·mH 2 O (3D structure) and Mg 0.67 Al 0.33 (OH) 2 (NO 3 ) 0.33 (2D layered structure).

  1. Raman Signatures of Polytypism in Molybdenum Disulfide.

    Science.gov (United States)

    Lee, Jae-Ung; Kim, Kangwon; Han, Songhee; Ryu, Gyeong Hee; Lee, Zonghoon; Cheong, Hyeonsik

    2016-02-23

    Since the stacking order sensitively affects various physical properties of layered materials, accurate determination of the stacking order is important for studying the basic properties of these materials as well as for device applications. Because 2H-molybdenum disulfide (MoS2) is most common in nature, most studies so far have focused on 2H-MoS2. However, we found that the 2H, 3R, and mixed stacking sequences exist in few-layer MoS2 exfoliated from natural molybdenite crystals. The crystal structures are confirmed by HR-TEM measurements. The Raman signatures of different polytypes are investigated by using three different excitation energies that are nonresonant and resonant with A and C excitons, respectively. The low-frequency breathing and shear modes show distinct differences for each polytype, whereas the high-frequency intralayer modes show little difference. For resonant excitations at 1.96 and 2.81 eV, distinct features are observed that enable determination of the stacking order.

  2. Anion mediated polytype selectivity among the basic salts of Co(II)

    Science.gov (United States)

    Ramesh, T. N.; Rajamathi, Michael; Vishnu Kamath, P.

    2006-08-01

    Basic salts of Co(II) crystallize in the rhombohedral structure. Two different polytypes, 3R 1 and 3R 2, with distinct stacking sequences of the metal hydroxide slabs, are possible within the rhombohedral structure. These polytypes are generated by simple translation of successive layers by (2/3, 1/3, z) or (1/3, 2/3, z). The symmetry of the anion and the mode of coordination influences polytype selection. Cobalt hydroxynitrate crystallizes in the structure of the 3R 2 polytype while the hydroxytartarate, hydroxychloride and α-cobalt hydroxide crystallize in the structure of the 3R 1 polytype. Cobalt hydroxysulfate is turbostratically disordered. The turbostratic disorder is a direct consequence of the mismatch between the crystallographically defined interlayer sites generated within the crystal and the tetrahedral symmetry of the SO 42- ions.

  3. Polytypic Functions Over Nested Datatypes

    Directory of Open Access Journals (Sweden)

    Ralf Hinze

    1999-12-01

    Full Text Available The theory and practice of polytypic programming is intimately connected with the initial algebra semantics of datatypes. This is both a blessing and a curse. It is a blessing because the underlying theory is beautiful and well developed. It is a curse because the initial algebra semantics is restricted to so-called regular datatypes. Recent work by R. Bird and L. Meertens [3] on the semantics of non-regular or nested datatypes suggests that an extension to general datatypes is not entirely straightforward. Here we propose an alternative that extends polytypism to arbitrary datatypes, including nested datatypes and mutually recursive datatypes. The central idea is to use rational trees over a suitable set of functor symbols as type arguments for polytypic functions. Besides covering a wider range of types the approach is also simpler and technically less involving than previous ones. We present several examples of polytypic functions, among others polytypic reduction and polytypic equality. The presentation assumes some background in functional and in polytypic programming. A basic knowledge of monads is required for some of the examples.

  4. Ordered perovskites with cationic vacancies. 9. Compounds of the type Sr/sub 2/Srsub(1/4)Bsub(1/2)sup(III)vacantsub(1/4)WO/sub 6/ equivalent to Sr/sub 8/SrB/sub 2/sup(III)vacantW/sub 4/O/sub 24/ (Bsup(III) = La, Pr, Nd, Sm - Tm, Y)

    Energy Technology Data Exchange (ETDEWEB)

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

    1981-08-01

    The compounds Sr/sub 2/Srsub(1/4)Bsub(1/2)sup(III)vacantsub(1/4)WO/sub 6/ equivalent to Sr/sub 8/SrB/sub 2/sup(III)vacantW/sub 4/O/sub 24/ belong to the group of perovskites with octahedral cationic vacancies (cation/vacancy ratio (CN 6) = 7:1). For the larger Bsup(III) ions (La, Pr, Nd, Sm-Dy) different ordering effects are observed. The perovskites with Bsup(III) = Sm, Eu, Gd are polymorphic too (HT modification: higher ordered cubic perovskite (Bsup(III) = Gd: a = 2 x 8.23/sub 4/ A); LT modification: hexagonal perovskite stacking polytype (Bsup(III) = Gd: a = 9.95/sub 4/ A; c = 19.0/sub 4/ A)). With the smaller Bsup(III) ions (Ho, Er, Tm and Y) a cubic, 1:1 ordered perovskite type is observed.

  5. Anion mediated polytype selectivity among the basic salts of Co(II)

    International Nuclear Information System (INIS)

    Ramesh, T.N.; Rajamathi, Michael; Vishnu Kamath, P.

    2006-01-01

    Basic salts of Co(II) crystallize in the rhombohedral structure. Two different polytypes, 3R 1 and 3R 2 , with distinct stacking sequences of the metal hydroxide slabs, are possible within the rhombohedral structure. These polytypes are generated by simple translation of successive layers by (2/3, 1/3, z) or (1/3, 2/3, z). The symmetry of the anion and the mode of coordination influences polytype selection. Cobalt hydroxynitrate crystallizes in the structure of the 3R 2 polytype while the hydroxytartarate, hydroxychloride and α-cobalt hydroxide crystallize in the structure of the 3R 1 polytype. Cobalt hydroxysulfate is turbostratically disordered. The turbostratic disorder is a direct consequence of the mismatch between the crystallographically defined interlayer sites generated within the crystal and the tetrahedral symmetry of the SO 4 2- ions. - Graphical abstract: (a) Observed PXRD pattern of cobalt hydroxytartarate compared with the DIFFaX simulated patterns of (b) 3R 1 and (c) 3R 2 polytypes, respectively

  6. Technology computer aided design of 29.5% efficient perovskite/interdigitated back contact silicon heterojunction mechanically stacked tandem solar cell for energy-efficient applications

    Science.gov (United States)

    Pandey, Rahul; Chaujar, Rishu

    2017-04-01

    A 29.5% efficient perovskite/SiC passivated interdigitated back contact silicon heterojunction (IBC-SiHJ) mechanically stacked tandem solar cell device has been designed and simulated. This is a substantial improvement of 40% and 15%, respectively, compared to the transparent perovskite solar cell (21.1%) and Si solar cell (25.6%) operated individually. The perovskite solar cell has been used as a top subcell, whereas 250- and 25-μm-thick IBC-SiHJ solar cells have been used as bottom subcells. The realistic technology computer aided design analysis has been performed to understand the physical processes in the device and to make reliable predictions of the behavior. The performance of the top subcell has been obtained for different acceptor densities and hole mobility in Spiro-MeOTAD along with the impact of counter electrode work function. To incorporate the effect of material quality, the influence of carrier lifetimes has also been studied for perovskite top and IBC-SiHJ bottom subcells. The optical and electrical behavior of the devices has been obtained for both standalone as well as tandem configuration. Results reported in this study reveal that the proposed four-terminal tandem device may open a new door for cost-effective and energy-efficient applications.

  7. Unit Cell Structure of Crystal Polytypes in InAs and InSb Nanowires

    DEFF Research Database (Denmark)

    Kriegner, Dominik; Panse, Christian; Mandl, Bernhard

    2011-01-01

    The atomic distances in hexagonal polytypes of III−V compound semiconductors differ from the values expected from simply a change of the stacking sequence of (111) lattice planes. While these changes were difficult to quantify so far, we accurately determine the lattice parameters of zinc blende......, wurtzite, and 4H polytypes for InAs and InSb nanowires, using X-ray diffraction and transmission electron microscopy. The results are compared to density functional theory calculations. Experiment and theory show that the occurrence of hexagonal bilayers tends to stretch the distances of atomic layers...

  8. Polytypism in ZnS, ZnSe, and ZnTe: First-principles study

    KAUST Repository

    Boutaiba, F.; Belabbes, Abderrezak; Ferhat, M.; Bechstedt, F.

    2014-01-01

    We report results of first-principles calculations based on the projector augmented wave (PAW) method to explore the structural, thermodynamic, and electronic properties of cubic (3C) and hexagonal (6H, 4H, and 2H) polytypes of II-VI compounds: ZnS, ZnSe, and ZnTe. We find that the different bond stacking in II-VI polytypes remarkably influences the resulting physical properties. Furthermore, the degree of hexagonality is found to be useful to understand both the ground-state properties and the electronic structure of these compounds. The resulting lattice parameters, energetic stability, and characteristic band energies are in good agreement with available experimental data. Trends with hexagonality of the polytype are investigated.

  9. Polytypism in ZnS, ZnSe, and ZnTe: First-principles study

    KAUST Repository

    Boutaiba, F.

    2014-06-23

    We report results of first-principles calculations based on the projector augmented wave (PAW) method to explore the structural, thermodynamic, and electronic properties of cubic (3C) and hexagonal (6H, 4H, and 2H) polytypes of II-VI compounds: ZnS, ZnSe, and ZnTe. We find that the different bond stacking in II-VI polytypes remarkably influences the resulting physical properties. Furthermore, the degree of hexagonality is found to be useful to understand both the ground-state properties and the electronic structure of these compounds. The resulting lattice parameters, energetic stability, and characteristic band energies are in good agreement with available experimental data. Trends with hexagonality of the polytype are investigated.

  10. An ab initio study of the polytypism in InP

    Science.gov (United States)

    Dacal, Luis C. O.; Cantarero, A.

    2016-09-01

    The existence of polytypism in semiconductor nanostructures gives rise to the appearance of stacking faults which many times can be treated as quantum wells. In some cases, despite of a careful growth, the polytypism can be hardly avoided. In this work, we perform an ab initio study of zincblende stacking faults in a wurtzite InP system, using the supercell approach and taking the limit of low density of narrow stacking faults regions. Our results confirm the type II band alignment between the phases, producing a reliable qualitative description of the band gap evolution along the growth axis. These results show an spacial asymmetry in the zincblende quantum wells, that is expected due to the fact that the wurtzite stacking sequence (ABAB) is part of the zincblende one (ABCABC), but with an unexpected asymmetry between the valence and the conduction bands. We also present results for the complex dielectric function, clearly showing the influence of the stacking on the homostructure values and surprisingly proving that the correspondent bulk results can be used to reproduce the polytypism even in the limit we considered.

  11. Crystal structure of Cr-bearing Mg3BeAl8O16, a new polytype of magnesiotaaffeite-2N′2S

    Directory of Open Access Journals (Sweden)

    Thomas Malcherek

    2016-07-01

    Full Text Available The crystal structure of a new polytype of magnesiotaaffeite-2N′2S, ideally Mg3BeAl8O16 (trimagnesium beryllium octaaluminium hexadecaoxide, is described in space-group symmetry P-3m1. It has been identified in a fragment of a mineral sample from Burma (Myanmar. The new polytype is composed of two Mg2Al4O8 (S- and two BeMgAl4O8 (N′-modules in a stacking sequence N′SSN′′ which differs from the N′SN′S-stacking sequence of the known magnesiotaaffeite-2N′2S polytype. The crystal structure can be derived from a close-packed arrangement of O atoms and is discussed with regard to its polytypism and its Cr3+ chromophore content.

  12. Polytypism of cronstedtite from Chynava, Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Hybler, Jiří; Sejkora, J.

    2017-01-01

    Roč. 62, č. 2 (2017), s. 137-146 ISSN 1802-6222 R&D Projects: GA ČR GA15-04204S Institutional support: RVO:68378271 Keywords : cronstedtite * polytypes 2H1 * 2H2 * 3T * 1T * twinning Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 0.609, year: 2016

  13. Hexagonal perovskites with cationic vacancies. 20. Ba/sub 6/Nb/sub 4/ZrvacantO/sub 18/ - a new stacking polytype with a rhombohedral 18 L structure

    Energy Technology Data Exchange (ETDEWEB)

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

    1980-06-01

    The white Ba/sub 6/Nb/sub 4/ZrvacantO/sub 18/ crystallizes in a rhombohedral 18 L structure (a = 5.82/sub 1/ A; c = 42.6/sub 3/ A; space group R3m) with three formula units for the trigonal setting (rhosub(exp) = 6.0/sub 5/ g/cm/sup 3/; rhosub(calc) = 6.27/sub 1/ g/cm/sup 3/). The corresponding Tisup(IV) and Hfsup(IV) compounds, Ba/sub 6/Nb/sub 4/TivacantO/sub 18/ and Ba/sub 6/Nb/sub 4/HfvacantO/sub 18/, are isotypic.

  14. Hexagonal perovskites with cationic vacancies. 28. Structure of rhombohedral 9 L stacking polytypes Ba/sub 3/Wsub(2-x)sup(VI)Nbsub(x)sup(V)vacantOsub(9-x/2)vacantsub(x/2)

    Energy Technology Data Exchange (ETDEWEB)

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

    1981-07-01

    According to the intensity calculations for Ba/sub 3/Wsub(4/3)Nbsub(2/3)vacantOsub(26/3)vacantsub(1/3) and Ba/sub 3/Nb/sub 2/vacantO/sub 8/vacant(II) these rhombohedral 9 L compounds crystallize in the space group R-3m, sequence (hhc)/sub 3/. The refined, intensity related R' values are 6.9% (Ba/sub 3/Wsub(4/3)Nbsub(2/3)vacantOsub(26/3)vacantsub(1/3)) and 7.2% (Ba/sub 3/Nb/sub 2/vacantO/sub 8/vacant(II)). The relations between the rhombohedral 9 L structure (A/sub 3/M/sub 2/vacantO/sub 9/) and the palmierite type (A/sub 3/M/sub 2/vacantO/sub 8/vacant) are discussed.

  15. Hexagonal perovskites with cationic vacancies. 18. Structure of the rhombohedral 12 L-stacking polytypes Ba/sub 2/La/sub 2/Bsup(II)(W/sub 2/sup(VI)vacantO/sub 12/)

    Energy Technology Data Exchange (ETDEWEB)

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

    1980-04-01

    According to the intensity calcualtions for Ba/sub 2/La/sub 2/Zn(W/sub 2/vacantO/sub 12/) the compounds of this type crystallize in the space group R3m-Dsub(3d)/sup 5/ with the sequence (3)(1)equivalent (hhcc)/sub 3/. The refined, intensity related R' value is 5,8%. The octahedral net consists of blocks of three face connected octahedra which are linked to each other by corner sharing BO/sub 6/ octahedra. The cationic vacancies are located in the centers of the groups of three octahedra. The two tungsten atoms in the outer positions are displaces by about 0.13 A from their ideal positions in direction of the central void. The (Ba, La) atoms neighbouring a vacancy (all in hexagonal close packed (Ba, La)O/sub 3/ sheets) are also dislocated in direction of the void, while the (Ba, La) atoms in the cubic packed sheets maintain nearly their ideal positions. The vibrational spectra of the compounds Ba/sub 2/La/sub 2/ Bsup(II)(W/sub 2/vacantO/sub 12/) are discussed. The force constants for the W/sub 2/vacantO/sub 12/ groups (factor group and Ppoint Dsub(3d)) were calculated and compared with the correspoinding values of Re/sub 2/vacantO/sub 12/ and ReWvacantO/sub 12/ units.

  16. Hexagonal perovskites with cationic vacancies. 23. Rhombohedral 12 L stacking polytypes of type Ba/sub 3/LaBsup(II)Resup(VII)Wsup(VI)vacantO/sub 12/ with Bsup(II) = Mg, Co, Ni, Cu, Zn

    Energy Technology Data Exchange (ETDEWEB)

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

    1980-11-01

    The rhombohedral 12 L pervoskites with cationic vacancies of type Ba/sub 3/LaBsup(II)ReWvacantO/sub 12/ with Bsup(II) = Mg, Co, Ni, Cu, Zn are isotypic. According to intensity calculations on powder patterns of Ba/sub 3/LaZnReWvacantO/sub 12/ the series crystallize in the space group R-3m with the sequence (hhcc)/sub 3/; the refined, intensity related R' value is 5.7%. The octahedral net consists of blocks of three face connected octahedra with central void (ReWvacantO/sub 12/ units), which are linked via common corners through single octahedra, occupied by zinc.

  17. Polytypism of cronstedtite from Nizna Slana, Slovakia

    Czech Academy of Sciences Publication Activity Database

    Hybler, Jiří; Števko, M.; Sejkora, J.

    2017-01-01

    Roč. 29, č. 1 (2017), s. 91-99 ISSN 0935-1221 R&D Projects: GA ČR GA15-04204S Institutional support: RVO:68378271 Keywords : cronstedtite * 1:1 layer silicate * MDO polytypes 3T * 1m * 2H1 * 2H2 * twinning Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 1.362, year: 2016

  18. Strain effects in polytypical wurtzite/zinc-blend nanowhiskers

    Science.gov (United States)

    Sipahi, Guilherme; Faria, Paulo

    2012-02-01

    The recent interest on III-V nanowhiskers has led to the growth of high quality samples of systems with two different crystalline structures [1]. The crystals grown in [111]-direction for the zinc-blend (ZB) phase and [0001]-direction for the wurtzite (WZ) phase are very similar and can both be described as stacked hexagonal layers. The effect of two different structural phases coexisting in the same nanostrucure is known as polytypism and creates confinement profiles similar to a heterostructure. One can notice band offsets at the interface and the formation of electronic minibands that can be explored to design systems for device applications. Although some of the III-V compounds do not present WZ structure in bulk form, recent calculations [2] presented a theoretical prediction of their band structure. However, as they considered that ZB and WZ to have the same lattice parameters no strain effects should appear on a first approach. Our theoretical approach introduces strain effects in our previous model [3] by using group theory arguments. It allows the analysis of the biaxial strain effects for both structures in a single matrix. [1] P. Caroff et al. Nature Nanotech. 4, 50, 2009. [2] A. De and C. E. Pryor, Phys. Rev. B 81, 155210, 2010 [3] http://arxiv.org/abs/1012.022

  19. 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.

  20. Rhombohedral polytypes of the layered honeycomb delafossites with optical brilliance in the visible.

    Science.gov (United States)

    Roudebush, John H; Sahasrabudhe, Girija; Bergman, Susanna L; Cava, R J

    2015-04-06

    We report the synthesis of the Delafossite honeycomb compounds Cu3Ni2SbO6 and Cu3Co2SbO6 via a copper topotactic reaction from the layered α-NaFeO2-like precursors Na3Ni2SbO6 and Na3Co2SbO6. The low-temperature exchange reaction exclusively produces the rhombahedral 3R polytype subcell, whereas only the hexagonal 2H polytype subcell has been made by conventional synthesis. The thus-synthesized 3R variants are visually striking; they are bright lime-green (Ni variant) and terracotta-orange (Co variant), while both of the conventionally synthesized 2H variants have a burnt-red color. The new structures are characterized by powder X-ray diffraction and Rietveld analysis as well as magnetic susceptibility, X-ray photoelectron spectroscopy (XPS), and diffuse-reflectance optical spectroscopy. Using thermogravimetric analysis, we identify a second order 3R → 2H phase transition as well as a first-order structural transition associated with rearrangement of the honeycomb stacking layers. The optical absorbance spectra of the samples show discrete edges that correlate well to their visual colors. Exposing Cu3Ni2SbO6 to O2 and heat causes the sample to change color. XPS confirms the presence of Cu(2+) in these samples, which implies that the difference in color between the polytypes is due to oxygen intercalation resulting from their different synthetic routes.

  1. Raman investigation of molybdenum disulfide with different polytypes

    Science.gov (United States)

    Lee, Jae-Ung; Kim, Kangwon; Han, Songhee; Ryu, Gyeong Hee; Lee, Zonghoon; Cheong, Hyeonsik

    The Raman spectra of molybdenum disulfide (MoS2) with different polytypes are investigated. Although 2H-MoS2 is most common in nature, the 3R phase can exist due to a small difference in the formation energy. However, only a few studies are reported for the 3R phase, and most studies have focused on the 2H phase. We found the 2H, 3R and mixed phases of exfoliated few-layer MoS2 from natural molybdenite crystals. The crystal structures of 2H- and 3R-MoS2 are confirmed by the HR-TEM measurements. By using 3 different excitation energies, we compared the Raman spectra of different polytypes in detail. We show that the Raman spectroscopy can be used to identify not only the number of layers but also the polytypes of MoS2.

  2. Photoacoustic and transmission studies of SiC polytypes

    Directory of Open Access Journals (Sweden)

    A.C. de Oliveira

    2003-01-01

    Full Text Available The optical bandgap energies (OBGE of 3C, 15R, 6H and 4H-SiC have been investigate experimentally by transmission and photoacoustic spectroscopies. The measurements were performed on 470 mum thick wafers. The OBGE obtained from both spectroscopies for different polytypes show very good agreement. In order to have a better understanding of these materials calculations of eletronic band structure were performed by the full-potential linearized augmented plane wave (FPLAPW method. For the OBGE the results are compared to the measurements agreeing closely over the energies of those polytypes.

  3. Polytypism and unexpected strong interlayer coupling in two-dimensional layered ReS2

    Science.gov (United States)

    Qiao, Xiao-Fen; Wu, Jiang-Bin; Zhou, Linwei; Qiao, Jingsi; Shi, Wei; Chen, Tao; Zhang, Xin; Zhang, Jun; Ji, Wei; Tan, Ping-Heng

    2016-04-01

    Anisotropic two-dimensional (2D) van der Waals (vdW) layered materials, with both scientific interest and application potential, offer one more dimension than isotropic 2D materials to tune their physical properties. Various physical properties of 2D multi-layer materials are modulated by varying their stacking orders owing to significant interlayer vdW coupling. Multilayer rhenium disulfide (ReS2), a representative anisotropic 2D material, was expected to be randomly stacked and lack interlayer coupling. Here, we demonstrate two stable stacking orders, namely isotropic-like (IS) and anisotropic-like (AI) N layer (NL, N > 1) ReS2 are revealed by ultralow- and high-frequency Raman spectroscopy, photoluminescence and first-principles density functional theory calculation. Two interlayer shear modes are observed in AI-NL-ReS2 while only one shear mode appears in IS-NL-ReS2, suggesting anisotropic- and isotropic-like stacking orders in IS- and AI-NL-ReS2, respectively. This explicit difference in the observed frequencies identifies an unexpected strong interlayer coupling in IS- and AI-NL-ReS2. Quantitatively, the force constants of them are found to be around 55-90% of those of multilayer MoS2. The revealed strong interlayer coupling and polytypism in multi-layer ReS2 may stimulate future studies on engineering physical properties of other anisotropic 2D materials by stacking orders.Anisotropic two-dimensional (2D) van der Waals (vdW) layered materials, with both scientific interest and application potential, offer one more dimension than isotropic 2D materials to tune their physical properties. Various physical properties of 2D multi-layer materials are modulated by varying their stacking orders owing to significant interlayer vdW coupling. Multilayer rhenium disulfide (ReS2), a representative anisotropic 2D material, was expected to be randomly stacked and lack interlayer coupling. Here, we demonstrate two stable stacking orders, namely isotropic-like (IS) and

  4. Spontaneous Synthesis of Highly Crystalline TiO2 Compact/Mesoporous Stacked Films by a Low-Temperature Steam-Annealing Method for Efficient Perovskite Solar Cells.

    Science.gov (United States)

    Sanehira, Yoshitaka; Numata, Youhei; Ikegami, Masashi; Miyasaka, Tsutomu

    2018-05-23

    Highly crystalline TiO 2 nanostructured films were synthesized by a simple steam treatment of a TiCl 4 precursor film under a saturated water vapor atmosphere at 125 °C, here referred to as the steam-annealing method. In a single TiO 2 film preparation step, a bilayer structure comprising a compact bottom layer and a mesoporous surface layer was formed. The mesoporous layer was occupied by bipyramidal nanoparticles, with a composite phase of anatase and brookite crystals. Despite the low-temperature treatment process, the crystallinity of the TiO 2 film was high, comparable with that of the TiO 2 film sintered at 500 °C. The compact double-layered TiO 2 film was applied to perovskite solar cells (PSCs) as an electron-collecting layer. The PSC exhibited a maximum power conversion efficiency (PCE) of 18.9% with an open-circuit voltage ( V OC ) of 1.15 V. The PCE and V OC were higher than those of PSCs using a TiO 2 film formed by 500 °C sintering.

  5. Radiometric dating of brittle fault rocks; illite polytype age analysis and application to the Spanish Pyrenees.

    Science.gov (United States)

    van der Pluijm, B. A.; Haines, S. H.

    2008-12-01

    A variety of approaches have been available to indirectly date the timing of deformation and motion on faults, but few approaches for direct, radiometric dating of shallow crustal fault rocks were available until recently. The growing recognition of clay neomineralization at low temperatures in many fault rocks, particularly the 1Md illite polytype, allows the successful application of Ar dating to these K-bearing phases. In this presentation we will discuss our recent illite age analysis approach (sampling, treatments, analytical methods), and present new results from fault dating along the Spanish Pyrenean orogenic front as an example. X-ray quantification of polytype ratios in three or more size fractions is used to define a mixing line between (1Md illite) authigenic and (2M illite) detrital end-member phases that constrain the fault age and host rock provenance/cooling age for each fault. The common problem of recoil in clays is addressed by encapsulating samples before irradiation. Nine fault gouge ages in the south-central and south-eastern Pyrenees support several contractional pulses in the Pyrenean orogen: 1) Late Cretaceous thrusting (Boixols), 2) Latest Paleocene-Early Eocene deformation (Nogueres Zone and Freser antiformal stack), 3) Middle-Late Eocene deformation (Ripoll syncline, Vallfogona, Gavernie, Abocador and L'Escala thrusts), and 4) Middle Oligocene thrusting in the central portion of the Axial Zone (Llavorsi-Senet). The late Paleocene-Early Eocene and Middle-Late Eocene events may or may not be one single phase, due to slightly overlapping error estimates. The outboard thrusts give Hercynian ages for the detrital component of the fault rock, while the inboard thrusts, which juxtapose metamorphic units, give Cretaceous ages for the non-authigenic component, reflecting the cooling age of the adjacent wallrocks. Based on our latest work, the illite polytype dating method complements previously developed illite-smectite dating (van der Pluijm et

  6. 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.

  7. Complex (Nonstandard) Six-Layer Polytypes of Lizardite Revealed from Oblique-Texture Electron Diffraction Patterns

    International Nuclear Information System (INIS)

    Zhukhlistov, A.P.; Zinchuk, N.N.; Kotel'nikov, D.D.

    2004-01-01

    Association of simple (1T and 3R) and two complex (nonstandard) orthogonal polytypes of the serpentine mineral lizardite from the Catoca kimberlite pipe (West Africa) association is revealed from oblique-texture electron diffraction patterns. A six-layer polytype with an ordered superposition of equally oriented layers (notation 3 2 3 2 3 4 3 4 3 6 3 6 or ++ - -00) belonging to the structural group A and a three-layer (336 or I,I,II) or a six-layer (336366 or I,I,II,I,II,II) polytype with alternating oppositely oriented layers and semi-disordered structure are identified using polytype analysis

  8. Mixed valent perovskites Ba/sub 3/B/sup 3 +/Ru/sub 2/sup(4. 5+)O/sub 9/. Catalytic activity of perovskite oxides with noble metals

    Energy Technology Data Exchange (ETDEWEB)

    Treiber, U; Kemmler-Sack, S; Ehmann, A; Schaller, H U; Duerrschmidt, E; Thumm, I; Bader, H [Tuebingen Univ. (Germany, F.R.). Lehrstuhl fuer Anorganische Chemie 2

    1981-10-01

    The black compounds Ba/sub 3/B/sup 3 +/Ru/sub 2/O/sub 9/ crystallize with B/sup 3 +/ = La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y in a hexagonal BaTiO/sub 3/ structure (6L, sequence (hcc)/sub 2/) with an ordered distribution (1:2 order) of B/sup 3 +/ and ruthenium (BO/sub 6/ single octahedra; Ru/sub 2/O/sub 9/ double groups). The mean oxidation state of ruthenium is about +4.5. The properties are compared with those of other isotypic stacking polytypes Ba/sub 3/B/sup 3 +/M/sub 2/sup(4.5)O/sub 9/ (M/sub 2/ = IrRu, Ir/sub 2/, PtRu) and Ba/sub 3/B/sup 2 +/M/sub 2//sup 5 +/O/sub 9/ (M = Ru, Ir). The results of activity tests concerning the efficiency of perovskite oxides with noble metals in respect of the oxidation of CO or CHsub(x) and the reduction of NOsub(x) are reported.

  9. Kronig-Penney-like description for band gap variation in SiC polytypes

    NARCIS (Netherlands)

    Backes, W.H.; Nooij, de F.C.; Bobbert, P.A.; van Haeringen, W.

    1996-01-01

    A one-dimensional Kronig-Penney-like model for envelope wave functions is presented to explain the band gap variation of SiC polytypes. In this model the envelope functions obey discontinuous boundary conditions. The electronic band gaps of cubic and several hexagonal and rhombohedral SiC polytypes

  10. Algebraic stacks

    Indian Academy of Sciences (India)

    Deligne, Mumford and Artin [DM, Ar2]) and consider algebraic stacks, then we can cons- truct the 'moduli ... the moduli scheme and the moduli stack of vector bundles. First I will give ... 1–31. © Printed in India. 1 ...... Cultura, Spain. References.

  11. Topotactic synthesis, structure and magnetic properties of a new hexagonal polytype of silver cobaltate(III) AgCoO2+\\delta

    OpenAIRE

    Muguerra, Hervé; Colin, Claire; Anne, Michel; Julien, M. -H.; Strobel, Pierre

    2008-01-01

    International audience; A new form of delafossite-type AgCoO2+δ was prepared using ion exchange from Na0.75CoO2 in molten AgNO3-NH4NO3 at 175°C. Its structure was determined by Rietveld refinement from XRD data; it is hexagonal, space group P63/mmc, a = 2.871 and c = 12.222 Å. Its structure differs from previously reported AgCoO2 (R-3m, 3R polytype) by the stacking of Co-O layers; in the new phase the 2H stacking of the precursor Na0.75CoO2, consistent with a topotactic ion exchange of Na by ...

  12. Hexagonal perovskites with cationic vacancies. 26. Ba/sub 12/Ba/sub 2//sub 2/3/M/sub 7//sup V//sub 1/3/vacant/sub 2/O/sub 33/vacant/sub 3/ (Msup(V) =Nb, Ta) - the first stacking polytypes of a rhombohedral 36 L-type

    Energy Technology Data Exchange (ETDEWEB)

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

    1981-05-01

    In the systems BaO-M/sub 2//sup V/O/sub 5/ (M/sup V/ = Nb, Ta) for a Ba:M/sup V/ ratio of 2:1 polymorphism is observed. Here the low temperature modifications are described. They crystallize in a rhombohedral 36 L structure with three formula units Ba/sub 12/Ba/sub 2//sub 2/3/M/sub 7//sup V//sub 1/3/vacant/sub 2/O/sub 33/vacant/sub 3/ for the trigonal setting (M/sup V/ = Nb: a = 5.92/sub 2/ A; c = 93./sub 25/ A; Ta: a = 5.92/sub 2/ A; c = 93.4 A).

  13. Hexagonal perovskites with cationic vacancies. 25. Hexagonal 5 L stacking polytypes in the systems Ba/sub 5/BaWsub(3-x)sup(VI)Msub(x)sup(V)vacantOsub(15-x/2)vacantsub(x/2) with Msup(V) = Nb, Ta

    Energy Technology Data Exchange (ETDEWEB)

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

    1980-12-01

    In the systems BaO-M/sub 2/sup(V)O/sub 5/-WO/sub 3/ (Msup(V) = Nb, Ta) a new phase Ba/sub 5/BaWsub(3-x)Msub(x)sup(V)vacantOsub(15-x/2)vacantsub(x/2) with hexagonal 5 L structure (sequence hhccc; space group P-3m1) could be prepared. The range of existence is restricted to Msup(V) containing compounds. With Msup(V) = Nb the lower phase boundary is x = 3. In the Ta system it is reached between x = 2 and 3; the pure Ta pervoskite (Ba:Ta:O = 6:3:13 1/2 = 4:2:9) represents the final member of the series Ba/sub 3/Srsub(1-y)Basub(y)Ta/sub 2/O/sub 9/ with y = 1.

  14. The influence of polytypic structures on the M011-->M101 solid-solid phase transition of n-C36H74: An application of the oblique infrared transmission method

    Science.gov (United States)

    Kubota, Hideki; Kaneko, Fumitoshi; Kawaguchi, Tatsuya; Kawasaki, Masatsugu

    2004-07-01

    The molecular displacements on the M011→M101 phase transition of n-hexatriacontane (n-C36H74) have been investigated with an IR microscope designed for the oblique infrared transmission method. It has been clarified that two polytypic structures of the M011 modification, single-layered structure (Mon) and double-layered one (Orth II), both transform to the M101 modification of single-layered structure with their respective mechanisms. On the M011(Mon)→M101 transition, the inclination direction of molecular axis is changed by 90° through an intermediate state in which the molecular chain is set perpendicular to the basal plane of the single crystal. On the other hand, a polymorphic-polytypic composite structural change on the M011(Orth II)→M101 transition is accomplished through two kinds of molecular displacements occurring alternately along the stacking direction of molecular layers.

  15. Analysis of polytype stability in PVT grown silicon carbide single crystal using competitive lattice model Monte Carlo simulations

    Directory of Open Access Journals (Sweden)

    Hui-Jun Guo

    2014-09-01

    Full Text Available Polytype stability is very important for high quality SiC single crystal growth. However, the growth conditions for the 4H, 6H and 15R polytypes are similar, and the mechanism of polytype stability is not clear. The kinetics aspects, such as surface-step nucleation, are important. The kinetic Monte Carlo method is a common tool to study surface kinetics in crystal growth. However, the present lattice models for kinetic Monte Carlo simulations cannot solve the problem of the competitive growth of two or more lattice structures. In this study, a competitive lattice model was developed for kinetic Monte Carlo simulation of the competition growth of the 4H and 6H polytypes of SiC. The site positions are fixed at the perfect crystal lattice positions without any adjustment of the site positions. Surface steps on seeds and large ratios of diffusion/deposition have positive effects on the 4H polytype stability. The 3D polytype distribution in a physical vapor transport method grown SiC ingot showed that the facet preserved the 4H polytype even if the 6H polytype dominated the growth surface. The theoretical and experimental results of polytype growth in SiC suggest that retaining the step growth mode is an important factor to maintain a stable single 4H polytype during SiC growth.

  16. Is Homo sapiens polytypic? Human taxonomic diversity and its implications.

    Science.gov (United States)

    Woodley, Michael A

    2010-01-01

    The term race is a traditional synonym for subspecies, however it is frequently asserted that Homo sapiens is monotypic and that what are termed races are nothing more than biological illusions. In this manuscript a case is made for the hypothesis that H. sapiens is polytypic, and in this way is no different from other species exhibiting similar levels of genetic and morphological diversity. First it is demonstrated that the four major definitions of race/subspecies can be shown to be synonymous within the context of the framework of race as a correlation structure of traits. Next the issue of taxonomic classification is considered where it is demonstrated that H. sapiens possesses high levels morphological diversity, genetic heterozygosity and differentiation (F(ST)) compared to many species that are acknowledged to be polytypic with respect to subspecies. Racial variation is then evaluated in light of the phylogenetic species concept, where it is suggested that the least inclusive monophyletic units exist below the level of species within H. sapiens indicating the existence of a number of potential human phylogenetic species; and the biological species concept, where it is determined that racial variation is too small to represent differentiation at the level of biological species. Finally the implications of this are discussed in the context of anthropology where an accurate picture of the sequence and timing of events during the evolution of human taxa are required for a complete picture of human evolution, and medicine, where a greater appreciation of the role played by human taxonomic differences in disease susceptibility and treatment responsiveness will save lives in the future.

  17. Stability and electronic properties of oxygen-doped ZnS polytypes: DFTB study

    Science.gov (United States)

    Popov, Ilya S.; Vorokh, Andrey S.; Enyashin, Andrey N.

    2018-06-01

    Synthesis from aqueous solutions is an affordable method for fabrication of II-VI semiconductors. However, application of this method often imposes a disorder of crystal lattice, manifesting as a rich variety of polytypes arising from wurtzite and zinc blende phases. The origin of this disordering still remains debatable. Here, the influence of the most likely impurity at water environment - substitutional oxygen - on the polytypic equilibrium of zinc sulphide is studied by means of density-functional tight-binding method. According to calculations, the inclusion of such oxygen does not affect the polytypic equilibrium. Apart of thermodynamic stability, the electronic and elastic properties of ZnS polytypes are studied as the function of oxygen distribution.

  18. Identification of {2 anti 1 anti 10} and {10 anti 10} Laue patterns of hexagonal and rhombohedral silicon carbide polytypes

    International Nuclear Information System (INIS)

    Yoganathan, M.; Suttrop, W.; Devaty, R.P.; Choyke, W.J.

    1994-01-01

    The development of epitaxic and bulk-grown semiconductor SiC exhibiting uniform polytype phase homogeneity is critically dependent upon the accurate identification of crystallographic orientations corresponding to the desired polytype. In this paper, experimental transmission Laue photographs as well as computer-generated transmission Laue patterns are presented for {2 anti 1 anti 10} and {10 anti 10} faces of the 4H, 6H and 15R polytypes of silicon carbide. The transmission patterns permit easy recognition of polytypes and crystal orientations. (orig.)

  19. Stability, occurence and step morphology of polymorphs and polytypes of stearic acid. II. Mono-lamella step morphology and composite polymorphic/polytypic transformation

    Science.gov (United States)

    Inaoka, Kimio; Kobayashi, Masamichi; Okada, Masakazu; Sato, Kiyotaka

    1988-02-01

    Surface step morphology of three structural modifications of stearic acid, B(mon), B(orth II) and C(mon), was observed by replica method (TEM). The characteristic simple and interlaced patterns were observed for monoclinic and pseudo-orthorhombic polytypes, respectively. The observation on the C crystals which were transformed from B(orth II) or B(mon) enabled to detect two different modes of lattice displacement involved in composite polymorphic-polytypic transformations from B to C. B(mon) → C(mon) was found to be caused by a collective inclination of the molecules within the lamellar plane followed by the deformation of the subcell of the aliphatic chain, keeping the symmetry-axis unchanged. In contrast, B(orth II) → C(mon) occurs via an alternate rotation of the long-chain molecules in the adjacent lamellae around the c-axis of B(orth II) prototype, keeping the subcell arrangements unchanged. This means that the polytypic structure of a double-layer type was not preserved during the composite B(orth II) → C(mon) transformation. This peculiarity was discussed in terms of the interlamellar instability of a postulated double-layered polytype of the C polymorph.

  20. Hexagonal perovskites with cationic vacancies. 3. Structure determination on compounds of type Ba/sub 2/Bsub(1/3)sup(III)vacantsub(2/3)Resup(VII)O/sub 6/

    Energy Technology Data Exchange (ETDEWEB)

    Kemmler-Sack, S; Wischert, W; Treiber, U [Tuebingen Univ. (Germany, F.R.). Inst. fuer Chemie

    1978-09-01

    Compounds of type Ba/sub 2/Bsub(1/3)sup(III)vacantsub(2/3)Resup(VII)O/sub 6/ with Bsup(III) = rare earth, Y, Sc. In belong to the group of hexagonal perovskite stacking polytypes. For Bsup(III) = Gd, Y structure determinations with powder data have been performed. The refined R' factors are 9.11% for Ba/sub 2/Gdsub(1/3)vacantsub(2/3)ReO/sub 6/ and 12.07% for Ba/sub 2/Ysub(1/3)vacantsub(2/3)ReO/sub 6/. The structure represents a rhombohedral 12 L type (space group R3m) with the sequence hhcchhcchhcc. The lattice contains groups of three octahedra connected by common faces which are linked together by a single octahedron via common vertices. In the block of three face-sharing octahedra the central octahedral lattice site is vacant and the two outer positions are occupied by the rhenium atoms. According to this distribution direct contact of occupied face-sharing octahedra is absent.

  1. In situ electrical measurements of polytypic silver nanowires

    International Nuclear Information System (INIS)

    Liu Xiaohua; Zhu Jing; Jin Chuanhong; Peng Lianmao; Tang Daiming; Cheng Huiming

    2008-01-01

    Novel 4H structure silver nanowires (4H-AgNWs) have been reported to coexist with the usual face-centered cubic (FCC) ones. Here we report the electrical properties of these polytypic AgNWs for the first time. AgNWs with either 4H or FCC structures in the diameter range of 20-80 nm were measured in situ inside a transmission electron microscope (TEM). Both kinds of AgNW in the diameter range show metallic conductance. The average resistivity of the 4H-AgNWs is 19.9 μΩ cm, comparable to the 11.9 μΩ cm of the FCC-AgNWs. The failure current density can be up to ∼10 8 A cm -2 for both 4H-and FCC-AgNWs. The maximum stable current density (MSCD) is introduced to estimate the AgNWs' current-carrying ability, which shows diameter-dependence with a peak around 34 nm in diameter. It is attributed to fast annihilation of the current-induced vacancies and the enhanced surface scattering. Our investigations also suggest that the magnetic field of the electromagnetic lens may also introduce some influence on the measurements inside the TEM

  2. Soft Chemistry, Coloring and Polytypism in Filled Tetrahedral Semiconductors: Toward Enhanced Thermoelectric and Battery Materials.

    Science.gov (United States)

    White, Miles A; Medina-Gonzalez, Alan M; Vela, Javier

    2018-03-12

    Filled tetrahedral semiconductors are a rich family of compounds with tunable electronic structure, making them ideal for applications in thermoelectrics, photovoltaics, and battery anodes. Furthermore, these materials crystallize in a plethora of related structures that are very close in energy, giving rise to polytypism through the manipulation of synthetic parameters. This Minireview highlights recent advances in the solution-phase synthesis and nanostructuring of these materials. These methods enable the synthesis of metastable phases and polytypes that were previously unobtainable. Additionally, samples synthesized in solution phase have enhanced thermoelectric performance due to their decreased grain size. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Semi-transparent perovskite solar cells for tandems with silicon and CIGS

    KAUST Repository

    Bailie, Colin D.; Christoforo, M. Greyson; Mailoa, Jonathan P.; Bowring, Andrea R.; Unger, Eva L.; Nguyen, William H.; Burschka, Julian; Pellet, Norman; Lee, Jungwoo Z.; Grä tzel, Michael; Noufi, Rommel; Buonassisi, Tonio; Salleo, Alberto; McGehee, Michael D.

    2015-01-01

    solar cell. We use a transparent silver nanowire electrode on perovskite solar cells to achieve a semi-transparent device. We place the semi-transparent cell in a mechanically-stacked tandem configuration onto copper indium gallium diselenide (CIGS

  4. 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.

  5. Evidence for multiple polytypes of semiconducting boron carbide (C2B10) from electronic structure

    International Nuclear Information System (INIS)

    Lunca-Popa, Petru; Brand, J I; Balaz, Snjezana; Rosa, Luis G; Boag, N M; Bai Mengjun; Robertson, B W; Dowben, P A

    2005-01-01

    Boron carbides fabricated via plasma enhanced chemical vapour deposition from different isomeric source compounds with the same C 2 B 10 H 12 closo-icosahedral structure result in materials with very different direct (optical) band gaps. This provides compelling evidence for the existence of multiple polytypes of C 2 B 10 boron carbide and is consistent with electron diffraction results

  6. Crystallization and disorder of the polytypic α1 and α2 polymorphs of piroxicam

    DEFF Research Database (Denmark)

    Upadhyay, Pratik Pankaj; Bond, Andrew

    2015-01-01

    Polymorphism of the active pharmaceutical ingredient piroxicam, C15H13N3O4S, is investigated with an aim to clarify the identity and crystallization conditions of the α1 and α2 polymorphs. The structures are polytypic, containing identical 2-dimensional layers, with different symmetry relationships...

  7. Complex polymorphism and polytypism of potassium metaarsenate, KAsO.sub. 3./sub..

    Czech Academy of Sciences Publication Activity Database

    Stöger, B.; Dušek, Michal

    2014-01-01

    Roč. 4, č. 9 (2014), s. 4640-4657 ISSN 1528-7483 R&D Projects: GA ČR(CZ) GAP204/11/0809 Institutional support: RVO:68378271 Keywords : arsenic * phase transition * twinning * polytypism * OD theory * high temperature phase * X-ray structure analysis Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.891, year: 2014

  8. 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.

  9. Effect of an external magnetic field on polytypism of CdI2 crystals grown from solutions

    International Nuclear Information System (INIS)

    Palosz, B.; Przedmojski, J.

    1982-01-01

    The effect of growth conditions on the polytypic structure of crystals of CdI 2 was analyzed for crystallization from solutions. Three solvents were used: H 2 O, 3 H 2 O + 1 C 2 H 5 OH and 1 H 2 O + 1 C 2 H 5 OH. Crystals were grown at two temperatures: 5 and 25 0 C with low and high growth rates; an external magnetic field of about 0.25 tesla was used. The effect of the above three parameters on the formation of the basic polytypes 2H and 4H and on the ordering of faults in disordered structures and in polytype cells was studied by X-ray analysis of crystal surfaces. Some distinct relations between the polytypic structure of crystals of CdI 2 and the magnetic field were found. (author)

  10. 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 ...

  11. Topotactic synthesis, structure and magnetic properties of a new hexagonal polytype of silver cobaltate(III) AgCoO2+δ

    International Nuclear Information System (INIS)

    Muguerra, Herve; Colin, Claire; Anne, Michel; Julien, Marc-Henri; Strobel, Pierre

    2008-01-01

    A new form of delafossite-type AgCoO 2+δ was prepared using ion exchange from Na 0.75 CoO 2 in molten AgNO 3 -NH 4 NO 3 at 175 deg. C. Its structure was determined by the Rietveld refinement from X-ray powder diffraction measurements (XRD) data; it is hexagonal, space group P6 3 /mmc, a=2.871 and c=12.222 A. Its structure differs from previously reported AgCoO 2 (R3-barm, 3R polytype) by the stacking of Co-O layers; in the new phase, the 2H stacking of the precursor Na 0.75 CoO 2 is consistent with a topotactic ion exchange of Na by Ag. The new phase is found to contain a slight oxygen excess (δ=0.06). Magnetic susceptibility measurements show the absence of magnetic transition and a weak Curie term, consistent with the non-magnetic character of Co 3+ ions. - Graphical abstract: Comparison of the structures of high-temperature AgCoO 2 (left, 3R structure) and of new AgCoO 2+∂ (IE) (right, 6H structure). The latter is obtained topotactically from Na 0.7 CoO 2 by ion exchange in molten nitrates. Detailed studies showed that AgCoO 2+∂ (IE) is slightly over-stoichiometric in oxygen (∂=0.06)

  12. Topotactic synthesis, structure and magnetic properties of a new hexagonal polytype of silver cobaltate(III) AgCoO 2+δ

    Science.gov (United States)

    Muguerra, Hervé; Colin, Claire; Anne, Michel; Julien, Marc-Henri; Strobel, Pierre

    2008-11-01

    A new form of delafossite-type AgCoO 2+δ was prepared using ion exchange from Na 0.75CoO 2 in molten AgNO 3-NH 4NO 3 at 175 °C. Its structure was determined by the Rietveld refinement from X-ray powder diffraction measurements (XRD) data; it is hexagonal, space group P6 3/ mmc, a=2.871 and c=12.222 Å. Its structure differs from previously reported AgCoO 2 ( R3¯m, 3R polytype) by the stacking of Co-O layers; in the new phase, the 2H stacking of the precursor Na 0.75CoO 2 is consistent with a topotactic ion exchange of Na by Ag. The new phase is found to contain a slight oxygen excess ( δ=0.06). Magnetic susceptibility measurements show the absence of magnetic transition and a weak Curie term, consistent with the non-magnetic character of Co 3+ ions.

  13. 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.

  14. Polytypism in n-fatty acids and low-frequency Raman spectra: Stearic acid B form

    Science.gov (United States)

    Kobayashi, Masamichi; Kobayashi, Tohru; Itoh, Yuzo; Sato, Kiyotaka

    1984-03-01

    Single crystals of single-layered (mon) and double-layered (orth II) polytypes of stearic acid B form were obtained and their structures were investigated by the x-ray diffraction and vibrational spectroscopic methods. Two polytypes exhibited quite different Raman spectra in the frequency range from 65 to 2 cm-1. The Raman bands appeared as singlets in mon, while they split into doublets with different polarization in orth II through the interlamellar interactions between two successive layers contained in the unit cell. The frequencies of the phonon modes in orth II were found to be lower than the corresponding ones in mon, indicating that orth II (or mon) was the high-temperature (low-temperature) stable form.

  15. Physical vapor transport growth and properties of SiC monocrystals of 4H polytype

    Energy Technology Data Exchange (ETDEWEB)

    Augustine, G.; Hobgood, H.M.; Balakrishna, V.; Dunne, G.; Hopkins, R.H. [Northrop Grumman Corp., Pittsburgh, PA (United States). Electron. Sensors and Syst. Div.

    1997-07-01

    The physical vapor transport technique can be employed to fabricate large diameter silicon carbide crystals (up to 50 mm diameter) exhibiting uniform 4H-polytype over the full crystal volume. Crystal growth rate is controlled to first order by temperature conditions and ambient pressure. 4H-polytype uniformity is controlled by polarity of the seed crystal and the growth temperature. 4H-SiC crystals exhibit crystalline defects mainly in the form of dislocations with densities in the 10{sup 4} cm{sup -2} range and micropipe defects, the latter having densities as low as 10 cm{sup -2} in best crystals. Electrical conductivity in 4H-SiC bulk crystals ranges from <10{sup -2} {Omega} cm, n-type, to insulating (>10{sup 15} {Omega} cm) at room temperature. (orig.) 33 refs.

  16. 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.

  17. Anisotropic formation and distribution of stacking faults in II-VI semiconductor nanorods.

    Science.gov (United States)

    Hughes, Steven M; Alivisatos, A Paul

    2013-01-09

    Nanocrystals of cadmium selenide exhibit a form of polytypism with stable forms in both the wurtzite and zinc blende crystal structures. As a result, wurtzite nanorods of cadmium selenide tend to form stacking faults of zinc blende along the c-axis. These faults were found to preferentially form during the growth of the (001) face, which accounts for 40% of the rod's total length. Since II-VI semiconductor nanorods lack inversion symmetry along the c-axis of the particle, the two ends of the nanorod may be identified by this anisotropic distribution of faults.

  18. A combined optical, SEM and STM study of growth spirals on the polytypic cadmium iodide crystals

    Science.gov (United States)

    Singh, Rajendra; Samanta, S. B.; Narlikar, A. V.; Trigunayat, G. C.

    2000-05-01

    Some novel results of a combined sequential study of growth spirals on the basal surface of the richly polytypic CdI 2 crystals by optical microscopy, scanning electron microscopy (SEM) and scanning tunneling microscopy (STM) are presented and discussed. Under the high resolution and magnification achieved in the scanning electron microscope, the growth steps of large heights seen in the optical micrographs are found to have a large number of additional steps of smaller heights existing between any two adjacent large height growth steps. When further seen by a scanning tunneling microscope, which provides still higher resolution, sequences of unit substeps, each of height equal to the unit cell height of the underlying polytype, are revealed to exist on the surface. Several large steps also lie between the unit steps, with heights equal to an integral multiple of either the unit cell height of the underlying polytype or the thickness of a molecular sheet I-Cd-I. It is suggested that initially a giant screw dislocation may form by brittle fracture of the crystal platelet, which may gradually decompose into numerous unit dislocations during subsequent crystal growth.

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. Inelastic neutron scattering study on the polytypism of even-numbered n-alkanes

    Science.gov (United States)

    Kubota, Hideki; Kaneko, Fumitoshi; Kawaguchi, Tatsuya

    2005-02-01

    The thermodynamic properties of the two polytypes of n-hexatriacontane ( n- C36H74), single-layered structure Mon and double-layered structure Orth II, have been studied with incoherent inelastic neutron scattering and solubility measurements. The solubility measurements show that Orth II is more stable than Mon, because of its larger entropy. The neutron scattering measurements reveal that the vibrational modes of Orth II shift to the lower frequencies compared with those of Mon in the frequency region below 120 cm-1. The vibrational modes in this region make a dominant contribution to the vibrational entropy of a system, and the advantage of Orth II in vibrational entropy due to the low-frequency shifts is estimated to be 7.8 J K-1 mol-1 at 288 K under the harmonic approximation, which is in good agreement with the entropy difference between Mon and Orth II determined by solubility measurements. These results suggest that the relative stability of polytypic structures of long-chain compounds is mainly determined by the vibrational entropy of the low-frequency modes.

  4. Stability, occurrence and step morphology of polymorphs and polytypes of stearic acid. I. Stability and occurrence

    Science.gov (United States)

    Sato, Kiyotaka; Kobayashi, Masamichi; Morishita, Hirofumi

    1988-02-01

    The thermodynamical stability and occurrence of three different structural modifications: monoclinic and pseudo-orthorhombic polytypes of the B polymorph, called B(mon) and B(orth II) respectively, and monoclinic C polymorph, C(mon), of stearic acid have been examined. The solubility measurements, overgrowth and isothermal crystallization proved that B(orth II) and C(mon) are most stable below and above 32°C, respectively, whereas B(mon) is always metastable, turning to be more stable than C(mon) below between 23 and 24°C. It was confirmed by micro-probe Raman spectroscopy that the polytypic structure of the newly-overgrown crystal on the (001) faces of the seed crystal of B(mon) changed from the original monoclinic to pseudo-orthorhombic, B(orth II), at very small supersaturations above 23°C. This conversion was caused by the solubility difference. The occurrence experiment indicated a slight tendency that B(mon) crystallized more than B(orth II) at lower temperatures.

  5. Diversification within glacial refugia: tempo and mode of evolution of the polytypic fish Barbus sclateri.

    Science.gov (United States)

    Gante, Hugo F; Micael, Joana; Oliva-Paterna, Francisco J; Doadrio, Ignacio; Dowling, Thomas E; Alves, Maria Judite

    2009-08-01

    A diversity of evolutionary processes can be responsible for generating and maintaining biodiversity. Molecular markers were used to investigate the influence of Plio-Pleistocene climatic oscillations on the evolutionary history of taxa restricted to the freshwaters of a classical glacial refugium. Population genetic, phylogenetic and phylogeographical methods allowed the inference of temporal dynamics of cladogenesis and processes shaping present-day genetic constitution of Barbus sclateri, a polytypic taxon found in several independent river drainages in southern Iberian Peninsula. Results from different analyses consistently indicate several range expansions, high levels of allopatric fragmentation, and admixture following secondary contacts throughout its evolutionary history. Using a Bayesian demographical coalescent model on mitochondrial DNA sequences calibrated with fossil evidence, all cladogenetic events within B. sclateri are inferred to have occurred during the Pleistocene and were probably driven by environmental factors. Our results suggest that glaciation cycles did not inhibit cladogenesis and probably interacted with regional geomorphology to promote diversification. We conclude that this polytypic taxon is a species complex that recently diversified in allopatry, and that Pleistocene glaciation-deglaciation cycles probably contributed to the generation of biological diversity in a classical glacial refugium with high endemicity.

  6. Ellipsometry investigation of perovskite/pyrochlore PZT thin film stacks

    Czech Academy of Sciences Publication Activity Database

    Deineka, Alexander; Glinchuk, M. D.; Jastrabík, Lubomír; Suchaneck, G.; Gerlach, G.

    2001-01-01

    Roč. 258, - (2001), s. 271-276 ISSN 0015-0193 R&D Projects: GA MŠk LN00A015; GA ČR GA202/00/1425 Institutional research plan: CEZ:AV0Z1010914 Keywords : ferroelectric film * depth profile * interface Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.471, year: 2001

  7. OpenStack essentials

    CERN Document Server

    Radez, Dan

    2015-01-01

    If you need to get started with OpenStack or want to learn more, then this book is your perfect companion. If you're comfortable with the Linux command line, you'll gain confidence in using OpenStack.

  8. Stack gas treatment

    Science.gov (United States)

    Reeves, Adam A.

    1977-04-12

    Hot stack gases transfer contained heat to a gravity flow of pebbles treated with a catalyst, cooled stacked gases and a sulfuric acid mist is withdrawn from the unit, and heat picked up by the pebbles is transferred to air for combustion or other process. The sulfuric acid (or sulfur, depending on the catalyst) is withdrawn in a recovery unit.

  9. Mastering OpenStack

    CERN Document Server

    Khedher, Omar

    2015-01-01

    This book is intended for system administrators, cloud engineers, and system architects who want to deploy a cloud based on OpenStack in a mid- to large-sized IT infrastructure. If you have a fundamental understanding of cloud computing and OpenStack and want to expand your knowledge, then this book is an excellent checkpoint to move forward.

  10. Stacking with stochastic cooling

    Energy Technology Data Exchange (ETDEWEB)

    Caspers, Fritz E-mail: Fritz.Caspers@cern.ch; Moehl, Dieter

    2004-10-11

    Accumulation of large stacks of antiprotons or ions with the aid of stochastic cooling is more delicate than cooling a constant intensity beam. Basically the difficulty stems from the fact that the optimized gain and the cooling rate are inversely proportional to the number of particles 'seen' by the cooling system. Therefore, to maintain fast stacking, the newly injected batch has to be strongly 'protected' from the Schottky noise of the stack. Vice versa the stack has to be efficiently 'shielded' against the high gain cooling system for the injected beam. In the antiproton accumulators with stacking ratios up to 10{sup 5} the problem is solved by radial separation of the injection and the stack orbits in a region of large dispersion. An array of several tapered cooling systems with a matched gain profile provides a continuous particle flux towards the high-density stack core. Shielding of the different systems from each other is obtained both through the spatial separation and via the revolution frequencies (filters). In the 'old AA', where the antiproton collection and stacking was done in one single ring, the injected beam was further shielded during cooling by means of a movable shutter. The complexity of these systems is very high. For more modest stacking ratios, one might use azimuthal rather than radial separation of stack and injected beam. Schematically half of the circumference would be used to accept and cool new beam and the remainder to house the stack. Fast gating is then required between the high gain cooling of the injected beam and the low gain stack cooling. RF-gymnastics are used to merge the pre-cooled batch with the stack, to re-create free space for the next injection, and to capture the new batch. This scheme is less demanding for the storage ring lattice, but at the expense of some reduction in stacking rate. The talk reviews the 'radial' separation schemes and also gives some

  11. Random geometry capability in RMC code for explicit analysis of polytype particle/pebble and applications to HTR-10 benchmark

    International Nuclear Information System (INIS)

    Liu, Shichang; Li, Zeguang; Wang, Kan; Cheng, Quan; She, Ding

    2018-01-01

    Highlights: •A new random geometry was developed in RMC for mixed and polytype particle/pebble. •This capability was applied to the full core calculations of HTR-10 benchmark. •Reactivity, temperature coefficient and control rod worth of HTR-10 were compared. •This method can explicitly model different packing fraction of different pebbles. •Monte Carlo code with this method can simulate polytype particle/pebble type reactor. -- Abstract: With the increasing demands of high fidelity neutronics analysis and the development of computer technology, Monte Carlo method is becoming more and more attractive in accurate simulation of pebble bed High Temperature gas-cooled Reactor (HTR), owing to its advantages of the flexible geometry modeling and the use of continuous-energy nuclear cross sections. For the double-heterogeneous geometry of pebble bed, traditional Monte Carlo codes can treat it by explicit geometry description. However, packing methods such as Random Sequential Addition (RSA) can only produce a sphere packing up to 38% volume packing fraction, while Discrete Element Method (DEM) is troublesome and also time consuming. Moreover, traditional Monte Carlo codes are difficult and inconvenient to simulate the mixed and polytype particles or pebbles. A new random geometry method was developed in Monte Carlo code RMC to simulate the particle transport in polytype particle/pebble in double heterogeneous geometry systems. This method was verified by some test cases, and applied to the full core calculations of HTR-10 benchmark. The reactivity, temperature coefficient and control rod worth of HTR-10 were compared for full core and initial core in helium and air atmosphere respectively, and the results agree well with the benchmark results and experimental results. This work would provide an efficient tool for the innovative design of pebble bed, prism HTRs and molten salt reactors with polytype particles or pebbles using Monte Carlo method.

  12. Ferroelectric ultrathin perovskite films

    Science.gov (United States)

    Rappe, Andrew M; Kolpak, Alexie Michelle

    2013-12-10

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

  13. Entropy in halide perovskites

    Science.gov (United States)

    Katan, Claudine; Mohite, Aditya D.; Even, Jacky

    2018-05-01

    Claudine Katan, Aditya D. Mohite and Jacky Even discuss the possible impact of various entropy contributions (stochastic structural fluctuations, anharmonicity and lattice softness) on the optoelectronic properties of halide perovskite materials and devices.

  14. Perovskites keep on giving

    Science.gov (United States)

    2018-05-01

    Whether you like exploring the mysteries of light-matter interactions, playing with a versatile chemical platform, or developing the most efficient devices, metal halide perovskites could be the materials for you.

  15. Polytypic Programming

    NARCIS (Netherlands)

    Jeuring, J.T.; Jansson, P.

    1996-01-01

    Many functions have to be written over and over again for different datatypes, either because datatypes change during the development of programs, or because functions with similar functionality are needed on different datatypes. Examples of such functions are pretty printers, debuggers, equality

  16. Polytypic transformations during the thermal decomposition of cobalt hydroxide and cobalt hydroxynitrate

    International Nuclear Information System (INIS)

    Ramesh, Thimmasandra Narayan

    2010-01-01

    The isothermal decomposition of cobalt hydroxide and cobalt hydroxynitrate at different intervals of temperature leads to the formation of Co 3 O 4 . The phase evolution during the decomposition process was monitored using powder X-ray diffraction. The transformation of cobalt hydroxide to cobalt oxide occurs via three phase mixture while cobalt hydroxynitrate to cobalt oxide occurs through a two phase mixture. The nature of the sample and its preparation method controls the decomposition mechanism. The comparison of topotactical relationship between the precursors to the decomposed product has been reported in relation to polytypism. - Graphical abstract: Isothermal thermal decomposition studies of cobalt hydroxide and cobalt hydroxynitrate at different intervals of temperature show the metastable phase formed prior to Co 3 O 4 phase.

  17. Electrons, holes, and excitons in GaAs polytype quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Climente, Juan I.; Segarra, Carlos; Rajadell, Fernando; Planelles, Josep, E-mail: josep.planelles@uji.es [Departament de Química Física i Analítica, Universitat Jaume I, E-12080 Castelló (Spain)

    2016-03-28

    Single and multi-band k⋅p Hamiltonians for GaAs crystal phase quantum dots are used to assess ongoing experimental activity on the role of such factors as quantum confinement, spontaneous polarization, valence band mixing, and exciton Coulomb interaction. Spontaneous polarization is found to be a dominating term. Together with the control of dot thickness [Vainorius et al., Nano Lett. 15, 2652 (2015)], it enables wide exciton wavelength and lifetime tunability. Several new phenomena are predicted for small diameter dots [Loitsch et al., Adv. Mater. 27, 2195 (2015)], including non-heavy hole ground state, strong hole spin admixture, and a type-II to type-I exciton transition, which can be used to improve the absorption strength and reduce the radiative lifetime of GaAs polytypes.

  18. Structure and magnetic properties of Ba5Ce1.25Mn3.75O15, a new 10H-polytype in the Ba–Ce–Mn–O system

    International Nuclear Information System (INIS)

    Macías, Mario A.; Mentré, Olivier; Colis, Silviu; Cuello, Gabriel J.; Gauthier, Gilles H.

    2013-01-01

    Based on the peculiar magnetic properties that are observed in pseudo one-dimensional manganites, we decided to synthesize the new Ba 5 Ce 1.25 Mn 3.75 O 15 compound. The preparation was performed by solid state reaction in air at about 1350 °C, for which we found that the compound crystallizes in a hexagonal symmetry with space group P6 3 /mmc (No-194) and cell parameters a=b=5.7861(2) Å and c=23.902(1) Å. The structural description was correlated with neutron diffraction and bond valence calculations, confirming the presence of Ce 4+ and Mn 4+ segregated in the different crystallographic positions. Ba 5 Ce 1.25 Mn 3.75 O 15 displays evidence for strong AFM couplings already set at room temperature. The main arrangement of Mn 4+ in magnetically isolated tetramers of face-sharing octahedra is responsible for a metamagnetic-like transition around 50 K. - Graphical abstract: The new Ba 5 Ce 1.25 Mn 3.75 O 15 polytype shows strong AFM couplings in magnetically isolated [Ce 0.25 Mn 3.75 O 15 ] tetramers of face-sharing octahedral, resulting in a metamagnetic-like transition around 50 K. Highlights: ► Ba 5 Ce 1.25 Mn 3.75 O 15 , a new 10H polytype, has been prepared in the Ba–Ce–Mn–O system. ► The compound crystallizes in the P6 3 /mmc space group with (cchhh) 2 stacking sequence. ► [Ce 0.25 Mn 3.75 O 15 ] tetramers are separated by [CeO 6 ] octahedra in the structure. ► Instead of robust AFM ordering, a metamagnetic-like transition is found around 50 K.

  19. Stacking the Equiangular Spiral

    OpenAIRE

    Agrawal, A.; Azabi, Y. O.; Rahman, B. M.

    2013-01-01

    We present an algorithm that adapts the mature Stack and Draw (SaD) methodology for fabricating the exotic Equiangular Spiral Photonic Crystal Fiber. (ES-PCF) The principle of Steiner chains and circle packing is exploited to obtain a non-hexagonal design using a stacking procedure based on Hexagonal Close Packing. The optical properties of the proposed structure are promising for SuperContinuum Generation. This approach could make accessible not only the equiangular spiral but also other qua...

  20. Short-Range Stacking Disorder in Mixed-Layer Compounds: A HAADF STEM Study of Bastnäsite-Parisite Intergrowths

    Directory of Open Access Journals (Sweden)

    Cristiana L. Ciobanu

    2017-11-01

    Full Text Available Atomic-scale high angle annular dark field scanning transmission electron microscopy (HAADF STEM imaging and electron diffractions are used to address the complexity of lattice-scale intergrowths of REE-fluorocarbonates from an occurrence adjacent to the Olympic Dam deposit, South Australia. The aims are to define the species present within the intergrowths and also assess the value of the HAADF STEM technique in resolving stacking sequences within mixed-layer compounds. Results provide insights into the definition of species and crystal-structural modularity. Lattice-scale intergrowths account for the compositional range between bastnäsite and parasite, as measured by electron probe microanalysis (at the µm-scale throughout the entire area of the intergrowths. These comprise rhythmic intervals of parisite and bastnäsite, or stacking sequences with gradational changes in the slab stacking between B, BBS and BS types (B—bastnäsite, S—synchysite. An additional occurrence of an unnamed B2S phase [CaCe3(CO34F3], up to 11 unit cells in width, is identified among sequences of parisite and bastnäsite within the studied lamellar intergrowths. Both B2S and associated parisite show hexagonal lattices, interpreted as 2H polytypes with c = 28 and 38 Å, respectively. 2H parisite is a new, short hexagonal polytype that can be added to the 14 previously reported polytypes (both hexagonal and rhombohedral for this mineral. The correlation between satellite reflections and the number of layers along the stacking direction (c* can be written empirically as: Nsat = [(m × 2 + (n × 4] − 1 for all BmSn compounds with S ≠ 0. The present study shows intergrowths characterised by short-range stacking disorder and coherent changes in stacking along perpendicular directions. Knowing that the same compositional range can be expressed as long-period stacking compounds in the group, the present intergrowths are interpreted as being related to disequilibrium

  1. Multilayer Transparent Top Electrode for Solution Processed Perovskite/Cu(In,Ga)(Se,S)2 Four Terminal Tandem Solar Cells.

    Science.gov (United States)

    Yang, Yang Michael; Chen, Qi; Hsieh, Yao-Tsung; Song, Tze-Bin; Marco, Nicholas De; Zhou, Huanping; Yang, Yang

    2015-07-28

    Halide perovskites (PVSK) have attracted much attention in recent years due to their high potential as a next generation solar cell material. To further improve perovskites progress toward a state-of-the-art technology, it is desirable to create a tandem structure in which perovskite may be stacked with a current prevailing solar cell such as silicon (Si) or Cu(In,Ga)(Se,S)2 (CIGS). The transparent top electrode is one of the key components as well as challenges to realize such tandem structure. Herein, we develop a multilayer transparent top electrode for perovskite photovoltaic devices delivering an 11.5% efficiency in top illumination mode. The transparent electrode is based on a dielectric/metal/dielectric structure, featuring an ultrathin gold seeded silver layer. A four terminal tandem solar cell employing solution processed CIGS and perovskite cells is also demonstrated with over 15% efficiency.

  2. Compositionally Graded Absorber for Efficient and Stable Near-Infrared-Transparent Perovskite Solar Cells.

    Science.gov (United States)

    Fu, Fan; Pisoni, Stefano; Weiss, Thomas P; Feurer, Thomas; Wäckerlin, Aneliia; Fuchs, Peter; Nishiwaki, Shiro; Zortea, Lukas; Tiwari, Ayodhya N; Buecheler, Stephan

    2018-03-01

    Compositional grading has been widely exploited in highly efficient Cu(In,Ga)Se 2 , CdTe, GaAs, quantum dot solar cells, and this strategy has the potential to improve the performance of emerging perovskite solar cells. However, realizing and maintaining compositionally graded perovskite absorber from solution processing is challenging. Moreover, the operational stability of graded perovskite solar cells under long-term heat/light soaking has not been demonstrated. In this study, a facile partial ion-exchange approach is reported to achieve compositionally graded perovskite absorber layers. Incorporating compositional grading improves charge collection and suppresses interface recombination, enabling to fabricate near-infrared-transparent perovskite solar cells with power conversion efficiency of 16.8% in substrate configuration, and demonstrate 22.7% tandem efficiency with 3.3% absolute gain when mechanically stacked on a Cu(In,Ga)Se 2 bottom cell. Non-encapsulated graded perovskite device retains over 93% of its initial efficiency after 1000 h operation at maximum power point at 60 °C under equivalent 1 sun illumination. The results open an avenue in exploring partial ion-exchange to design graded perovskite solar cells with improved efficiency and stability.

  3. Compositionally Graded Absorber for Efficient and Stable Near‐Infrared‐Transparent Perovskite Solar Cells

    Science.gov (United States)

    Pisoni, Stefano; Weiss, Thomas P.; Feurer, Thomas; Wäckerlin, Aneliia; Fuchs, Peter; Nishiwaki, Shiro; Zortea, Lukas; Tiwari, Ayodhya N.

    2018-01-01

    Abstract Compositional grading has been widely exploited in highly efficient Cu(In,Ga)Se2, CdTe, GaAs, quantum dot solar cells, and this strategy has the potential to improve the performance of emerging perovskite solar cells. However, realizing and maintaining compositionally graded perovskite absorber from solution processing is challenging. Moreover, the operational stability of graded perovskite solar cells under long‐term heat/light soaking has not been demonstrated. In this study, a facile partial ion‐exchange approach is reported to achieve compositionally graded perovskite absorber layers. Incorporating compositional grading improves charge collection and suppresses interface recombination, enabling to fabricate near‐infrared‐transparent perovskite solar cells with power conversion efficiency of 16.8% in substrate configuration, and demonstrate 22.7% tandem efficiency with 3.3% absolute gain when mechanically stacked on a Cu(In,Ga)Se2 bottom cell. Non‐encapsulated graded perovskite device retains over 93% of its initial efficiency after 1000 h operation at maximum power point at 60 °C under equivalent 1 sun illumination. The results open an avenue in exploring partial ion‐exchange to design graded perovskite solar cells with improved efficiency and stability. PMID:29593970

  4. Towards stacked zone plates

    International Nuclear Information System (INIS)

    Werner, S; Rehbein, S; Guttman, P; Heim, S; Schneider, G

    2009-01-01

    Fresnel zone plates are the key optical elements for soft and hard x-ray microscopy. For short exposure times and minimum radiation load of the specimen the diffraction efficiency of the zone plate objectives has to be maximized. As the efficiency strongly depends on the height of the diffracting zone structures the achievable aspect ratio of the nanostructures determines these limits. To reach aspect ratios ≥ 20:1 for high efficient optics we propose to superimpose zone plates on top of each other. With this multiplication approach the final aspect ratio is only limited by the number of stacked zone plate layers. For the stack process several nanostructuring process steps have to be developed and/or improved. Our results show for the first time two layers of zone plates stacked on top of each other.

  5. Stochastic stacking without filters

    International Nuclear Information System (INIS)

    Johnson, R.P.; Marriner, J.

    1982-12-01

    The rate of accumulation of antiprotons is a critical factor in the design of p anti p colliders. A design of a system to accumulate higher anti p fluxes is presented here which is an alternative to the schemes used at the CERN AA and in the Fermilab Tevatron I design. Contrary to these stacking schemes, which use a system of notch filters to protect the dense core of antiprotons from the high power of the stack tail stochastic cooling, an eddy current shutter is used to protect the core in the region of the stack tail cooling kicker. Without filters one can have larger cooling bandwidths, better mixing for stochastic cooling, and easier operational criteria for the power amplifiers. In the case considered here a flux of 1.4 x 10 8 per sec is achieved with a 4 to 8 GHz bandwidth

  6. Stack filter classifiers

    Energy Technology Data Exchange (ETDEWEB)

    Porter, Reid B [Los Alamos National Laboratory; Hush, Don [Los Alamos National Laboratory

    2009-01-01

    Just as linear models generalize the sample mean and weighted average, weighted order statistic models generalize the sample median and weighted median. This analogy can be continued informally to generalized additive modeels in the case of the mean, and Stack Filters in the case of the median. Both of these model classes have been extensively studied for signal and image processing but it is surprising to find that for pattern classification, their treatment has been significantly one sided. Generalized additive models are now a major tool in pattern classification and many different learning algorithms have been developed to fit model parameters to finite data. However Stack Filters remain largely confined to signal and image processing and learning algorithms for classification are yet to be seen. This paper is a step towards Stack Filter Classifiers and it shows that the approach is interesting from both a theoretical and a practical perspective.

  7. Infrared spectroscopic study on polytypic transformation of growing single crystal of n-hexatriacontane ( n-C 36H 74)

    Science.gov (United States)

    Kubota, Hideki; Kaneko, Fumitoshi; Kawaguchi, Tatsuya; Kawasaki, Masatsugu

    2005-02-01

    There are two polytypic structures, single-layered structure Mon and double-layered structure Orth II for the M 011 modification of n-hexatriacontane ( n-C 36H 74). The solution crystal growth of the two polytypes under controlled supersaturation was investigated by the oblique IR transmission method. As to the supersaturation dependence of growth behavior, there was a significant difference between the two polytypes. While the overgrowth of Orth II took place on the (0 0 1) face of the Mon crystal at moderate supersaturations, the overgrowth of Mon on the Orth II crystals was not confirmed at any supersaturations below 0.30. The growth rate of Mon showed about a second-order dependence on supersaturation, whereas that of Orth II showed a first-order dependence. The growth mechanism of the M 011 modification and the cause for the one-way overgrowth were deduced on the basis of the thermodynamical stabilities and the supersaturation dependence of the growth rates.

  8. Atomic and electronic structure of trilayer graphene/SiC(0001): Evidence of Strong Dependence on Stacking Sequence and charge transfer.

    Science.gov (United States)

    Pierucci, Debora; Brumme, Thomas; Girard, Jean-Christophe; Calandra, Matteo; Silly, Mathieu G; Sirotti, Fausto; Barbier, Antoine; Mauri, Francesco; Ouerghi, Abdelkarim

    2016-09-15

    The transport properties of few-layer graphene are the directly result of a peculiar band structure near the Dirac point. Here, for epitaxial graphene grown on SiC, we determine the effect of charge transfer from the SiC substrate on the local density of states (LDOS) of trilayer graphene using scaning tunneling microscopy/spectroscopy and angle resolved photoemission spectroscopy (ARPES). Different spectra are observed and are attributed to the existence of two stable polytypes of trilayer: Bernal (ABA) and rhomboedreal (ABC) staking. Their electronic properties strongly depend on the charge transfer from the substrate. We show that the LDOS of ABC stacking shows an additional peak located above the Dirac point in comparison with the LDOS of ABA stacking. The observed LDOS features, reflecting the underlying symmetry of the two polytypes, were reproduced by explicit calculations within density functional theory (DFT) including the charge transfer from the substrate. These findings demonstrate the pronounced effect of stacking order and charge transfer on the electronic structure of trilayer or few layer graphene. Our approach represents a significant step toward understand the electronic properties of graphene layer under electrical field.

  9. Laser pulse stacking method

    Science.gov (United States)

    Moses, E.I.

    1992-12-01

    A laser pulse stacking method is disclosed. A problem with the prior art has been the generation of a series of laser beam pulses where the outer and inner regions of the beams are generated so as to form radially non-synchronous pulses. Such pulses thus have a non-uniform cross-sectional area with respect to the outer and inner edges of the pulses. The present invention provides a solution by combining the temporally non-uniform pulses in a stacking effect to thus provide a more uniform temporal synchronism over the beam diameter. 2 figs.

  10. Learning SaltStack

    CERN Document Server

    Myers, Colton

    2015-01-01

    If you are a system administrator who manages multiple servers, then you know how difficult it is to keep your infrastructure in line. If you've been searching for an easier way, this book is for you. No prior experience with SaltStack is required.

  11. Textured perovskite cells

    NARCIS (Netherlands)

    Deelen, J. van; Tezsevin, Y.; Barink, M.

    2017-01-01

    Most research of texturization of solar cells has been devoted to Si based cells. For perovskites, it was assumed that texturization would not have much of an impact because of the relatively low refractive indexes lead to relatively low reflection as compared to the Si based cells. However, our

  12. Weathering of natural uranyl oxide hydrates: Schoepite polytypes and dehydration effects

    International Nuclear Information System (INIS)

    Finch, R.J.; Miller, M.L.; Ewing, R.C.

    1992-01-01

    Partial dehydration of schoepite, UO 3 x2H 2 O, is reported to produce three discrete schoepite polytypes with characteristic unit cell parameters, but this has not been confirmed. The loss of structural water from the schoepite interlayer results in progressive modification to the structure; expansion parallel to schoepite cleavage planes, and extensive fracturing. Dehydration of schoepite commences at grain boundaries and progresses inward until the entire grain is converted to dehydrated schoepite, UO 3 x0.8H 2 O. The volume decrease associated with dehydration results in expanded grain boundaries. These gaps can provide pathways for the access of groundwater, and uranyl silicates and uranyl carbonates have precipitated within these gaps, replacing both schoepite and dehydrated schoepite. Schoepite, however, is not observed to re-precipitate where in contact with dehydrated schoepite. Thus, while the formation of schoepite early during the corrosion of uraninite may be favored, schoepite is not a long-term solubility limiting phase for oxidized uranium in natural ground waters containing dissolved silica or carbonate. (orig.)

  13. OpenStack cloud security

    CERN Document Server

    Locati, Fabio Alessandro

    2015-01-01

    If you are an OpenStack administrator or developer, or wish to build solutions to protect your OpenStack environment, then this book is for you. Experience of Linux administration and familiarity with different OpenStack components is assumed.

  14. Stacked magnet superconducting bearing

    International Nuclear Information System (INIS)

    Rigney, T.K. II; Saville, M.P.

    1993-01-01

    A superconducting bearing is described, comprising: a plurality of permanent magnets magnetized end-to-end and stacked side-by-side in alternating polarity, such that flux lines flow between ends of adjacent magnets; isolating means, disposed between said adjacent magnets, for reducing flux leakage between opposing sides of said adjacent magnets; and a member made of superconducting material having at least one surface in communication with said flux lines

  15. Iridium Interfacial Stack (IRIS)

    Science.gov (United States)

    Spry, David James (Inventor)

    2015-01-01

    An iridium interfacial stack ("IrIS") and a method for producing the same are provided. The IrIS may include ordered layers of TaSi.sub.2, platinum, iridium, and platinum, and may be placed on top of a titanium layer and a silicon carbide layer. The IrIS may prevent, reduce, or mitigate against diffusion of elements such as oxygen, platinum, and gold through at least some of its layers.

  16. Four-Terminal All-Perovskite Tandem Solar Cells Achieving Power Conversion Efficiencies Exceeding 23%

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Kai [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Zhao, Dewei [University of Toledo; Wang, Changlei [University of Toledo; Wuhan University; Song, Zhaoning [University of Toledo; Yu, Yue [University of Toledo; Chen, Cong [University of Toledo; Zhao, Xingzhong [Wuhan University; Yan, Yanfa [University of Toledo

    2018-02-09

    We report on fabrication of 4-terminal all-perovskite tandem solar cells with power conversion efficiencies exceeding 23% by mechanically stacking semitransparent 1.75 eV wide-bandgap FA0.8Cs0.2Pb(I0.7Br0.3)3 perovskite top cells with 1.25 eV low-bandgap (FASnI3)0.6(MAPbI3)0.4 bottom cells. The top cells use MoOx/ITO transparent electrodes and achieve transmittance up to 70% beyond 700 nm.

  17. MEAN STACK WEB DEVELOPMENT

    OpenAIRE

    Le Thanh, Nghi

    2017-01-01

    The aim of the thesis is to provide a universal website using JavaScript as the main programming language. It also shows the basic parts anyone need to create a web application. The thesis creates a simple CMS using MEAN stack. MEAN is a collection of JavaScript based technologies used to develop web application. It is an acronym for MongoDB, Express, AngularJS and Node.js. It also allows non-technical users to easily update and manage a website’s content. But the application also lets o...

  18. Die-stacking architecture

    CERN Document Server

    Xie, Yuan

    2015-01-01

    The emerging three-dimensional (3D) chip architectures, with their intrinsic capability of reducing the wire length, promise attractive solutions to reduce the delay of interconnects in future microprocessors. 3D memory stacking enables much higher memory bandwidth for future chip-multiprocessor design, mitigating the ""memory wall"" problem. In addition, heterogenous integration enabled by 3D technology can also result in innovative designs for future microprocessors. This book first provides a brief introduction to this emerging technology, and then presents a variety of approaches to design

  19. Local Conduction in MoxW1–xSe2: The Role of Stacking Faults, Defects, and Alloying

    Science.gov (United States)

    2018-01-01

    Here, we report on the surface conductivity of WSe2 and MoxW1–xSe2 (0 ≤ x ≤ 1) crystals investigated with conductive atomic force microscopy. We found that stacking faults, defects, and chemical heterogeneities form distinct two-dimensional and one-dimensional conduction paths on the transition metal dichalcogenide surface. In the case of WSe2, in addition to step edges, we find a significant amount of stacking faults (formed during the cleaving process) that strongly influence the surface conductivity. These regions are attributed to the alternation of the 2H and 3R polytypism. The stacking faults form regular 2D patterns by alternation of the underlying stacking order, with a periodicity that varies significantly between different regions and samples. In the case of MoxW1–xSe2, its conductivity has a localized nature, which depends on the underlying chemical composition and the Mo/W ratio. Segregation to W-rich and Mo-rich regions during the growth process leads to nonuniform conduction paths on the surface of the alloy. We found a gradual change of the conductivity moving from one region to the other, reminiscent of lateral band bending. Our results demonstrate the use of C-AFM as a nanoscopic tool to probe the electrical properties of largely inhomogeneous samples and show the complicated nature of the surface conductivity of TMDC alloys. PMID:29578328

  20. Local Conduction in Mo xW1- xSe2: The Role of Stacking Faults, Defects, and Alloying.

    Science.gov (United States)

    Bampoulis, Pantelis; Sotthewes, Kai; Siekman, Martin H; Zandvliet, Harold J W

    2018-04-18

    Here, we report on the surface conductivity of WSe 2 and Mo x W 1- x Se 2 (0 ≤ x ≤ 1) crystals investigated with conductive atomic force microscopy. We found that stacking faults, defects, and chemical heterogeneities form distinct two-dimensional and one-dimensional conduction paths on the transition metal dichalcogenide surface. In the case of WSe 2 , in addition to step edges, we find a significant amount of stacking faults (formed during the cleaving process) that strongly influence the surface conductivity. These regions are attributed to the alternation of the 2H and 3R polytypism. The stacking faults form regular 2D patterns by alternation of the underlying stacking order, with a periodicity that varies significantly between different regions and samples. In the case of Mo x W 1- x Se 2 , its conductivity has a localized nature, which depends on the underlying chemical composition and the Mo/W ratio. Segregation to W-rich and Mo-rich regions during the growth process leads to nonuniform conduction paths on the surface of the alloy. We found a gradual change of the conductivity moving from one region to the other, reminiscent of lateral band bending. Our results demonstrate the use of C-AFM as a nanoscopic tool to probe the electrical properties of largely inhomogeneous samples and show the complicated nature of the surface conductivity of TMDC alloys.

  1. Asymmetric Flexible Supercapacitor Stack

    Directory of Open Access Journals (Sweden)

    Leela Mohana Reddy A

    2008-01-01

    Full Text Available AbstractElectrical double layer supercapacitor is very significant in the field of electrical energy storage which can be the solution for the current revolution in the electronic devices like mobile phones, camera flashes which needs flexible and miniaturized energy storage device with all non-aqueous components. The multiwalled carbon nanotubes (MWNTs have been synthesized by catalytic chemical vapor deposition technique over hydrogen decrepitated Mischmetal (Mm based AB3alloy hydride. The polymer dispersed MWNTs have been obtained by insitu polymerization and the metal oxide/MWNTs were synthesized by sol-gel method. Morphological characterizations of polymer dispersed MWNTs have been carried out using scanning electron microscopy (SEM, transmission electron microscopy (TEM and HRTEM. An assymetric double supercapacitor stack has been fabricated using polymer/MWNTs and metal oxide/MWNTs coated over flexible carbon fabric as electrodes and nafion®membrane as a solid electrolyte. Electrochemical performance of the supercapacitor stack has been investigated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy.

  2. Structure and magnetic properties of Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15}, a new 10H-polytype in the Ba-Ce-Mn-O system

    Energy Technology Data Exchange (ETDEWEB)

    Macias, Mario A. [Grupo de Investigacion en Quimica Estructural (GIQUE), Universidad Industrial de Santander, A.A. 678, Carrera 27, Calle 9, Ciudad Universitaria, Bucaramanga (Colombia); Mentre, Olivier [Universite Lille Nord de France, Unite de Catalyse et de Chimie du Solide, Equipe Chimie du Solide, Avenue Dimitri Mendeleieev, Batiment C7, ENSCL/UST Lille 1, BP 90108, 59652 Villeneuve d' Ascq Cedex (France); Colis, Silviu [Institut de Physique et Chimie des Materiaux de Strasbourg (IPCMS), UMR 7504 UDS-CNRS (UDS-ECPM), 23 rue du Loess, BP 43, F-67034 Strasbourg Cedex 2 (France); Cuello, Gabriel J. [Institut Laue Langevin, 6 rue Jules Horowitz BP 156, F-38042 Grenoble cedex 9 (France); Gauthier, Gilles H., E-mail: gilgau@uis.edu.co [Grupo de Investigacion en Quimica Estructural (GIQUE), Universidad Industrial de Santander, A.A. 678, Carrera 27, Calle 9, Ciudad Universitaria, Bucaramanga (Colombia); CEA, LITEN, Laboratoire d' Innovation Technologique et des Energies Nouvelles, 17 rue des Martyrs, 38054 Grenoble (France)

    2013-02-15

    Based on the peculiar magnetic properties that are observed in pseudo one-dimensional manganites, we decided to synthesize the new Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15} compound. The preparation was performed by solid state reaction in air at about 1350 Degree-Sign C, for which we found that the compound crystallizes in a hexagonal symmetry with space group P6{sub 3}/mmc (No-194) and cell parameters a=b=5.7861(2) A and c=23.902(1) A. The structural description was correlated with neutron diffraction and bond valence calculations, confirming the presence of Ce{sup 4+} and Mn{sup 4+} segregated in the different crystallographic positions. Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15} displays evidence for strong AFM couplings already set at room temperature. The main arrangement of Mn{sup 4+} in magnetically isolated tetramers of face-sharing octahedra is responsible for a metamagnetic-like transition around 50 K. - Graphical abstract: The new Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15} polytype shows strong AFM couplings in magnetically isolated [Ce{sub 0.25}Mn{sub 3.75}O{sub 15}] tetramers of face-sharing octahedral, resulting in a metamagnetic-like transition around 50 K. Highlights: Black-Right-Pointing-Pointer Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15}, a new 10H polytype, has been prepared in the Ba-Ce-Mn-O system. Black-Right-Pointing-Pointer The compound crystallizes in the P6{sub 3}/mmc space group with (cchhh){sub 2} stacking sequence. Black-Right-Pointing-Pointer [Ce{sub 0.25}Mn{sub 3.75}O{sub 15}] tetramers are separated by [CeO{sub 6}] octahedra in the structure. Black-Right-Pointing-Pointer Instead of robust AFM ordering, a metamagnetic-like transition is found around 50 K.

  3. Anharmonicity and Disorder in the Black Phases of Cesium Lead Iodide Used for Stable Inorganic Perovskite Solar Cells.

    Science.gov (United States)

    Marronnier, Arthur; Roma, Guido; Boyer-Richard, Soline; Pedesseau, Laurent; Jancu, Jean-Marc; Bonnassieux, Yvan; Katan, Claudine; Stoumpos, Constantinos C; Kanatzidis, Mercouri G; Even, Jacky

    2018-04-24

    Hybrid organic-inorganic perovskites emerged as a new generation of absorber materials for high-efficiency low-cost solar cells in 2009. Very recently, fully inorganic perovskite quantum dots also led to promising efficiencies, making them a potentially stable and efficient alternative to their hybrid cousins. Currently, the record efficiency is obtained with CsPbI 3 , whose crystallographical characterization is still limited. Here, we show through high-resolution in situ synchrotron XRD measurements that CsPbI 3 can be undercooled below its transition temperature and temporarily maintained in its perovskite structure down to room temperature, stabilizing a metastable perovskite polytype (black γ-phase) crucial for photovoltaic applications. Our analysis of the structural phase transitions reveals a highly anisotropic evolution of the individual lattice parameters versus temperature. Structural, vibrational, and electronic properties of all the experimentally observed black phases are further inspected based on several theoretical approaches. Whereas the black γ-phase is shown to behave harmonically around equilibrium, for the tetragonal phase, density functional theory reveals the same anharmonic behavior, with a Brillouin zone-centered double-well instability, as for the cubic phase. Using total energy and vibrational entropy calculations, we highlight the competition between all the low-temperature phases of CsPbI 3 (γ, δ, β) and show that avoiding the order-disorder entropy term arising from double-well instabilities is key to preventing the formation of the yellow perovskitoid phase. A symmetry-based tight-binding model, validated by self-consistent GW calculations including spin-orbit coupling, affords further insight into their electronic properties, with evidence of Rashba effect for both cubic and tetragonal phases when using the symmetry-breaking structures obtained through frozen phonon calculations.

  4. Instant BlueStacks

    CERN Document Server

    Judge, Gary

    2013-01-01

    Get to grips with a new technology, understand what it is and what it can do for you, and then get to work with the most important features and tasks. A fast-paced, example-based approach guide for learning BlueStacks.This book is for anyone with a Mac or PC who wants to run Android apps on their computer. Whether you want to play games that are freely available for Android but not your computer, or you want to try apps before you install them on a physical device or use it as a development tool, this book will show you how. No previous experience is needed as this is written in plain English

  5. Synthesis, structure and phase separation of a new 12R-type perovskite-related oxide Ba3NdMn2O9

    International Nuclear Information System (INIS)

    Yang, H.; Tang, Y.K.; Yao, L.D.; Zhang, W.; Li, Q.A.; Li, F.Y.; Jin, C.Q.; Yu, R.C.

    2007-01-01

    A new 12R-type perovskite-related oxide, Ba 3 NdMn 2 O 9 , has been prepared by traditional solid-state reaction method and the presence of chemical phase separation phenomenon has been revealed by transmission electron microscopy. The perfect grains of the compound have an average chemical composition of Ba 4 NdMn 3 O 12 (mainly for cationic ratio) according to the characterization by TEM-EDX. In this perfect 12R-type structure with composition Ba 4 NdMn 3 O 12 , the Nd cations are located in the corner-sharing octahedra, whereas the Mn cations are located in the face-sharing octahedra, leading to a remarkable cation ordering. Superstructure modulation was found to be a common phenomenon in the 12R polytype and the modulated areas were revealed by both EDX and EELS to be Nd rich compared to the perfect areas. This result together with the previous work [A.F. Fuentes, K. Boulahya, U. Amador, J. Solid State Chem. 177 (2004) 714] has shown that, for the rare-earth-containing Ba-RE-Mn-O systems (RE being rare-earth elements), the composition Ba 4 REMn 3 O 12 (mainly for cationic ratio) is required for the formation of perfect 12R polytype

  6. Assessing Elementary Algebra with STACK

    Science.gov (United States)

    Sangwin, Christopher J.

    2007-01-01

    This paper concerns computer aided assessment (CAA) of mathematics in which a computer algebra system (CAS) is used to help assess students' responses to elementary algebra questions. Using a methodology of documentary analysis, we examine what is taught in elementary algebra. The STACK CAA system, http://www.stack.bham.ac.uk/, which uses the CAS…

  7. Spherical Torus Center Stack Design

    International Nuclear Information System (INIS)

    C. Neumeyer; P. Heitzenroeder; C. Kessel; M. Ono; M. Peng; J. Schmidt; R. Woolley; I. Zatz

    2002-01-01

    The low aspect ratio spherical torus (ST) configuration requires that the center stack design be optimized within a limited available space, using materials within their established allowables. This paper presents center stack design methods developed by the National Spherical Torus Experiment (NSTX) Project Team during the initial design of NSTX, and more recently for studies of a possible next-step ST (NSST) device

  8. Structural Properties of Ferroelectric Perovskites

    National Research Council Canada - National Science Library

    Vanderbilt, David

    1998-01-01

    Under this research grant, we carried out realistic first-principles computer calculations of the ground-state and finite-temperature structural and dielectric properties of cubic perovskite materials...

  9. Modeling fuel cell stack systems

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J H [Los Alamos National Lab., Los Alamos, NM (United States); Lalk, T R [Dept. of Mech. Eng., Texas A and M Univ., College Station, TX (United States)

    1998-06-15

    A technique for modeling fuel cell stacks is presented along with the results from an investigation designed to test the validity of the technique. The technique was specifically designed so that models developed using it can be used to determine the fundamental thermal-physical behavior of a fuel cell stack for any operating and design configuration. Such models would be useful tools for investigating fuel cell power system parameters. The modeling technique can be applied to any type of fuel cell stack for which performance data is available for a laboratory scale single cell. Use of the technique is demonstrated by generating sample results for a model of a Proton Exchange Membrane Fuel Cell (PEMFC) stack consisting of 125 cells each with an active area of 150 cm{sup 2}. A PEMFC stack was also used in the verification investigation. This stack consisted of four cells, each with an active area of 50 cm{sup 2}. Results from the verification investigation indicate that models developed using the technique are capable of accurately predicting fuel cell stack performance. (orig.)

  10. Structure of the mixed-metal carbonate KAgCO₃ revisited: order-disorder (OD) polytypism and allotwinning.

    Science.gov (United States)

    Hans, Philipp; Stöger, Berthold; Weil, Matthias; Zobetz, Erich

    2015-04-01

    Crystals of KAgCO3 belong to an order-disorder (OD) family of structures composed of layers of two kinds. There are two polytypes with a maximum degree of order [MDO1: Pccb; MDO2: Ibca, doubled a-axis compared with MDO1], which are both realised to a different extent in two crystals under investigation [volume fraction MDO1:MDO2 in crystal (I): 0.0216:0.9784 (3) and in crystal (II): 0.9657:0.0343 (3)]. Sharp diffraction spots and the absence of diffuse scattering indicate highly ordered macroscopic domains. The structure of KAgCO3 was refined concurrently against all reflections using an allotwin model (addition of the intensities of both domains). It is shown that a disorder model refined against reflections of only one domain can lead to a significant overestimation of the volume fraction of this domain.

  11. Environmental assessment of phosphogypsum stacks

    International Nuclear Information System (INIS)

    Odat, M.; Al-Attar, L.; Raja, G.; Abdul Ghany, B.

    2009-01-01

    Phosphogypsum is one of the most important by-products of phosphate fertilizer industry. It is kept in large stacks to the west of Homs city. Storing Phosphogypsum as open stacks exposed to various environmental effects, wind and rain, may cause pollution of the surrounding ecosystem (soil, plant, water and air). This study was carried out in order to assess the environmental impact of Phosphogypsum stacks on the surrounding ecosystem. The obtained results show that Phosphogypsum stacks did not increase the concentration of radionuclides, i.e. Radon-222 and Radium-226, the external exposed dose of gamma rays, as well as the concentration of heavy metals in the components of the ecosystem, soil, plant, water and air, as their concentrations did not exceed the permissible limits. However, the concentration of fluorine in the upper layer of soil, located to the east of the Phosphogypsum stacks, increased sufficiently, especially in the dry period of the year. Also, the concentration of fluoride in plants growing up near-by the Phosphogypsum stacks was too high, exceeded the permissible levels. This was reflected in poising plants and animals, feeding on the plants. Consequently, increasing the concentration of fluoride in soil and plants is the main impact of Phosphogypsum stacks on the surrounding ecosystem. Minimising this effect could be achieved by establishing a 50 meter wide protection zone surrounding the Phosphogypsum stacks, which has to be planted with non palatable trees, such as pine and cypress, forming wind barriers. Increasing the concentrations of heavy metals and fluoride in infiltrated water around the stacks was high; hence cautions must be taken to prevent its usage in any application or disposal in adjacent rivers and leaks.(author)

  12. Environmental assessment of phosphogypsum stacks

    International Nuclear Information System (INIS)

    Odat, M.; Al-Attar, L.; Raja, G.; Abdul Ghany, B.

    2008-03-01

    Phosphogypsum is one of the most important by-products of phosphate fertilizer industry. It is kept in large stacks to the west of Homs city. Storing Phosphogypsum as open stacks exposed to various environmental effects, wind and rain, may cause pollution of the surrounding ecosystem (soil, plant, water and air). This study was carried out in order to assess the environmental impact of Phosphogypsum stacks on the surrounding ecosystem. The obtained results show that Phosphogypsum stacks did not increase the concentration of radionuclides, i.e. Radon-222 and Radium-226, the external exposed dose of gamma rays, as well as the concentration of heavy metals in the components of the ecosystem, soil, plant, water and air, as their concentrations did not exceed the permissible limits. However, the concentration of fluorine in the upper layer of soil, located to the east of the Phosphogypsum stacks, increased sufficiently, especially in the dry period of the year. Also, the concentration of fluoride in plants growing up near-by the Phosphogypsum stacks was too high, exceeded the permissible levels. This was reflected in poising plants and animals, feeding on the plants. Consequently, increasing the concentration of fluoride in soil and plants is the main impact of Phosphogypsum stacks on the surrounding ecosystem. Minimising this effect could be achieved by establishing a 50 meter wide protection zone surrounding the Phosphogypsum stacks, which has to be planted with non palatable trees, such as pine and cypress, forming wind barriers. Increasing the concentrations of heavy metals and fluoride in infiltrated water around the stacks was high; hence cautions must be taken to prevent its usage in any application or disposal in adjacent rivers and leaks.(author)

  13. 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.

  14. 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...

  15. 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.

  16. Infrared spectroscopic study of polytypic effects on the crystal-growth mechanism of n-hexatriacontane (n-C36H74)

    Science.gov (United States)

    Kubota, Hideki; Kaneko, Fumitoshi; Kawaguchi, Tatsuya; Kawasaki, Masatsugu

    2005-10-01

    The solution-crystallization mechanism was investigated for two polytypes in the M011 modification of n-hexatriacontane (n-C36H74), single-layered structure Mon, and double-layered one Orth II. The crystal growth under controlled supersaturation was followed with a micro- Fourier-transform-infrared spectrometer equipped with an optical system for oblique transmission measurements. Supersaturation dependence of growth behavior was significantly different between Mon and Orth II. Although the Mon crystal continued growing at a supersaturation of 0.27, the overgrowth of Orth II on the (001) face of the Mon crystal was confirmed at supersaturations below 0.21. Such a polytypic transformation was not observed for the Orth II crystal at any supersaturation below 0.30. The growth rate of Mon showed a quadratic dependence on supersaturation, while that of Orth II was approximately linear, suggesting spiral growth and two-dimensional-nucleation mechanisms for Mon and Orth II, respectively.

  17. Warning signal brightness variation: sexual selection may work under the radar of natural selection in populations of a polytypic poison frog.

    Science.gov (United States)

    Crothers, Laura R; Cummings, Molly E

    2013-05-01

    Though theory predicts consistency of warning signals in aposematic species to facilitate predator learning, variation in these signals often occurs in nature. The strawberry poison frog Dendrobates pumilio is an exceptionally polytypic (populations are phenotypically distinct) aposematic frog exhibiting variation in warning color and brightness. In the Solarte population, males and females both respond differentially to male brightness variation. Here, we demonstrate through spectrophotometry and visual modeling that aposematic brightness variation within this population is likely visible to two putative predators (crabs, snakes) and conspecifics but not to the presumed major predator (birds). This study thus suggests that signal brightness within D. pumilio populations can be shaped by sexual selection, with limited opportunity for natural selection to influence this trait due to predator sensory constraints. Because signal brightness changes can ultimately lead to changes in hue, our findings at the within-population level can provide insights into understanding this polytypism at across-population scales.

  18. 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.

  19. 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.

  20. 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

  1. Glassy carbon based supercapacitor stacks

    Energy Technology Data Exchange (ETDEWEB)

    Baertsch, M; Braun, A; Koetz, R; Haas, O [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    Considerable effort is being made to develop electrochemical double layer capacitors (EDLC) that store relatively large quantities of electrical energy and possess at the same time a high power density. Our previous work has shown that glassy carbon is suitable as a material for capacitor electrodes concerning low resistance and high capacity requirements. We present the development of bipolar electrochemical glassy carbon capacitor stacks of up to 3 V. Bipolar stacks are an efficient way to meet the high voltage and high power density requirements for traction applications. Impedance and cyclic voltammogram measurements are reported here and show the frequency response of a 1, 2, and 3 V stack. (author) 3 figs., 1 ref..

  2. Time-predictable Stack Caching

    DEFF Research Database (Denmark)

    Abbaspourseyedi, Sahar

    completely. Thus, in systems with hard deadlines the worst-case execution time (WCET) of the real-time software running on them needs to be bounded. Modern architectures use features such as pipelining and caches for improving the average performance. These features, however, make the WCET analysis more...... addresses, provides an opportunity to predict and tighten the WCET of accesses to data in caches. In this thesis, we introduce the time-predictable stack cache design and implementation within a time-predictable processor. We introduce several optimizations to our design for tightening the WCET while...... keeping the timepredictability of the design intact. Moreover, we provide a solution for reducing the cost of context switching in a system using the stack cache. In design of these caches, we use custom hardware and compiler support for delivering time-predictable stack data accesses. Furthermore...

  3. 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.

  4. The structure of denisovite, a fibrous nanocrystalline polytypic disordered `very complex' silicate, studied by a synergistic multi-disciplinary approach employing methods of electron crystallography and X-ray powder diffraction

    Directory of Open Access Journals (Sweden)

    Ira V. Rozhdestvenskaya

    2017-05-01

    either Δz = c/4 or −c/4. Such behaviour is typical for polytypic sequences and leads to disorder along [100]. In fact, the diffraction pattern does not show any sharp reflections with l odd, but continuous diffuse streaks parallel to a* instead. Only reflections with l even are sharp. The diffuse scattering is caused by (100 nanolamellae separated by stacking faults and twin boundaries. The structure can be described according to the order–disorder (OD theory as a stacking of layers parallel to (100.

  5. 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.

  6. 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.

  7. Magnetoresistance stories of double perovskites

    Indian Academy of Sciences (India)

    grain surfaces have also been proposed to act as tunnel barriers in Sr2FeMoO6. ... these double perovskites, a gradual decrease in the low-field MR and saturation ... simultaneously, and therefore serious material engineering was needed.

  8. Vibrational spectra of ordered perovskites

    NARCIS (Netherlands)

    Corsmit, A.F.; Hoefdraad, H.E.; Blasse, G.

    1972-01-01

    The vibrational spectra of the molecular M6+O6 (M = Mo, Te, W) group in ordered perovskites of the type Ba2M2+M6+O6 are reported. These groups have symmetry Oh, whereas their site symmetry is also Oh. An assignment of the internal vibrations is presented.

  9. 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.

  10. 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.

  11. Magnetoresistance stories of double perovskites

    Indian Academy of Sciences (India)

    2015-05-28

    May 28, 2015 ... Tunnelling magnetoresistance (TMR) in polycrystalline double perovskites has been an important research topic for more than a decade now, where the nature of the insulating tunnel barrier is the core issue of debate. Other than the nonmagnetic grain boundaries as conventional tunnel barriers, intragrain ...

  12. Perovskite catalysts for oxidative coupling

    Science.gov (United States)

    Campbell, Kenneth D.

    1991-01-01

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

  13. 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

  14. Stack semantics of type theory

    DEFF Research Database (Denmark)

    Coquand, Thierry; Mannaa, Bassel; Ruch, Fabian

    2017-01-01

    We give a model of dependent type theory with one univalent universe and propositional truncation interpreting a type as a stack, generalizing the groupoid model of type theory. As an application, we show that countable choice cannot be proved in dependent type theory with one univalent universe...

  15. Multilayer Piezoelectric Stack Actuator Characterization

    Science.gov (United States)

    Sherrit, Stewart; Jones, Christopher M.; Aldrich, Jack B.; Blodget, Chad; Bao, Xioaqi; Badescu, Mircea; Bar-Cohen, Yoseph

    2008-01-01

    Future NASA missions are increasingly seeking to use actuators for precision positioning to accuracies of the order of fractions of a nanometer. For this purpose, multilayer piezoelectric stacks are being considered as actuators for driving these precision mechanisms. In this study, sets of commercial PZT stacks were tested in various AC and DC conditions at both nominal and extreme temperatures and voltages. AC signal testing included impedance, capacitance and dielectric loss factor of each actuator as a function of the small-signal driving sinusoidal frequency, and the ambient temperature. DC signal testing includes leakage current and displacement as a function of the applied DC voltage. The applied DC voltage was increased to over eight times the manufacturers' specifications to investigate the correlation between leakage current and breakdown voltage. Resonance characterization as a function of temperature was done over a temperature range of -180C to +200C which generally exceeded the manufacturers' specifications. In order to study the lifetime performance of these stacks, five actuators from one manufacturer were driven by a 60volt, 2 kHz sine-wave for ten billion cycles. The tests were performed using a Lab-View controlled automated data acquisition system that monitored the waveform of the stack electrical current and voltage. The measurements included the displacement, impedance, capacitance and leakage current and the analysis of the experimental results will be presented.

  16. V-stack piezoelectric actuator

    Science.gov (United States)

    Ardelean, Emil V.; Clark, Robert L.

    2001-07-01

    Aeroelastic control of wings by means of a distributed, trailing-edge control surface is of interest with regards to maneuvers, gust alleviation, and flutter suppression. The use of high energy density, piezoelectric materials as motors provides an appealing solution to this problem. A comparative analysis of the state of the art actuators is currently being conducted. A new piezoelectric actuator design is presented. This actuator meets the requirements for trailing edge flap actuation in both stroke and force. It is compact, simple, sturdy, and leverages stroke geometrically with minimum force penalties while displaying linearity over a wide range of stroke. The V-Stack Piezoelectric Actuator, consists of a base, a lever, two piezoelectric stacks, and a pre-tensioning element. The work is performed alternately by the two stacks, placed on both sides of the lever. Pre-tensioning can be readily applied using a torque wrench, obviating the need for elastic elements and this is for the benefit of the stiffness of the actuator. The characteristics of the actuator are easily modified by changing the base or the stacks. A prototype was constructed and tested experimentally to validate the theoretical model.

  17. Open stack thermal battery tests

    Energy Technology Data Exchange (ETDEWEB)

    Long, Kevin N. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Roberts, Christine C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Grillet, Anne M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Headley, Alexander J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Fenton, Kyle [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Wong, Dennis [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ingersoll, David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-04-17

    We present selected results from a series of Open Stack thermal battery tests performed in FY14 and FY15 and discuss our findings. These tests were meant to provide validation data for the comprehensive thermal battery simulation tools currently under development in Sierra/Aria under known conditions compared with as-manufactured batteries. We are able to satisfy this original objective in the present study for some test conditions. Measurements from each test include: nominal stack pressure (axial stress) vs. time in the cold state and during battery ignition, battery voltage vs. time against a prescribed current draw with periodic pulses, and images transverse to the battery axis from which cell displacements are computed. Six battery configurations were evaluated: 3, 5, and 10 cell stacks sandwiched between 4 layers of the materials used for axial thermal insulation, either Fiberfrax Board or MinK. In addition to the results from 3, 5, and 10 cell stacks with either in-line Fiberfrax Board or MinK insulation, a series of cell-free “control” tests were performed that show the inherent settling and stress relaxation based on the interaction between the insulation and heat pellets alone.

  18. Adding large EM stack support

    KAUST Repository

    Holst, Glendon

    2016-12-01

    Serial section electron microscopy (SSEM) image stacks generated using high throughput microscopy techniques are an integral tool for investigating brain connectivity and cell morphology. FIB or 3View scanning electron microscopes easily generate gigabytes of data. In order to produce analyzable 3D dataset from the imaged volumes, efficient and reliable image segmentation is crucial. Classical manual approaches to segmentation are time consuming and labour intensive. Semiautomatic seeded watershed segmentation algorithms, such as those implemented by ilastik image processing software, are a very powerful alternative, substantially speeding up segmentation times. We have used ilastik effectively for small EM stacks – on a laptop, no less; however, ilastik was unable to carve the large EM stacks we needed to segment because its memory requirements grew too large – even for the biggest workstations we had available. For this reason, we refactored the carving module of ilastik to scale it up to large EM stacks on large workstations, and tested its efficiency. We modified the carving module, building on existing blockwise processing functionality to process data in manageable chunks that can fit within RAM (main memory). We review this refactoring work, highlighting the software architecture, design choices, modifications, and issues encountered.

  19. Efficient Semitransparent Perovskite Solar Cells Using a Transparent Silver Electrode and Four-Terminal Perovskite/Silicon Tandem Device Exploration

    Directory of Open Access Journals (Sweden)

    Dazheng Chen

    2018-01-01

    Full Text Available Four-terminal tandem solar cells employing a perovskite top cell and crystalline silicon (Si bottom cell offer a simpler pathway to surpass the efficiency limit of market-leading single-junction silicon solar cells. To obtain cost-effective top cells, it is crucial to develop transparent conductive electrodes with low parasitic absorption and manufacturing cost. The commonly used indium tin oxide (ITO shows some drawbacks, like the increasing prices and high-energy magnetron sputtering process. Transparent metal electrodes are promising candidates owing to the simple evaporation process, facile process conditions, and high conductivity, and the cheaper silver (Ag electrode with lower parasitic absorption than gold may be the better choice. In this work, efficient semitransparent perovskite solar cells (PSCs were firstly developed by adopting the composite cathode of an ultrathin Ag electrode at its percolation threshold thickness (11 nm, a molybdenum oxide optical coupling layer, and a bathocuproine interfacial layer. The resulting power conversion efficiency (PCE is 13.38% when the PSC is illuminated from the ITO side and the PCE is 8.34% from the Ag side, and no obvious current hysteresis can be observed. Furthermore, by stacking an industrial Si bottom cell (PCE = 14.2% to build a four-terminal architecture, the overall PCEs of 17.03% (ITO side and 11.60% (Ag side can be obtained, which are 27% and 39% higher, respectively, than those of the perovskite top cell. Also, the PCE of the tandem cell has exceeded that of the reference Si solar cell by about 20%. This work provides an outlook to fabricate high-performance solar cells via the cost-effective pathway.

  20. 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.

  1. 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.

  2. 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.

  3. Semi-transparent perovskite solar cells for tandems with silicon and CIGS

    KAUST Repository

    Bailie, Colin D.

    2015-01-01

    © 2015 The Royal Society of Chemistry. A promising approach for upgrading the performance of an established low-bandgap solar technology without adding much cost is to deposit a high bandgap polycrystalline semiconductor on top to make a tandem solar cell. We use a transparent silver nanowire electrode on perovskite solar cells to achieve a semi-transparent device. We place the semi-transparent cell in a mechanically-stacked tandem configuration onto copper indium gallium diselenide (CIGS) and low-quality multicrystalline silicon (Si) to achieve solid-state polycrystalline tandem solar cells with a net improvement in efficiency over the bottom cell alone. This work paves the way for integrating perovskites into a low-cost and high-efficiency (>25%) tandem cell.

  4. Vertical melting of a stack of membranes

    Science.gov (United States)

    Borelli, M. E. S.; Kleinert, H.; Schakel, A. M. J.

    2001-02-01

    A stack of tensionless membranes with nonlinear curvature energy and vertical harmonic interaction is studied. At low temperatures, the system forms a lamellar phase. At a critical temperature, the stack disorders vertically in a melting-like transition.

  5. Helping Students Design HyperCard Stacks.

    Science.gov (United States)

    Dunham, Ken

    1995-01-01

    Discusses how to teach students to design HyperCard stacks. Highlights include introducing HyperCard, developing storyboards, introducing design concepts and scripts, presenting stacks, evaluating storyboards, and continuing projects. A sidebar presents a HyperCard stack evaluation form. (AEF)

  6. PRECISION COSMOGRAPHY WITH STACKED VOIDS

    International Nuclear Information System (INIS)

    Lavaux, Guilhem; Wandelt, Benjamin D.

    2012-01-01

    We present a purely geometrical method for probing the expansion history of the universe from the observation of the shape of stacked voids in spectroscopic redshift surveys. Our method is an Alcock-Paczyński (AP) test based on the average sphericity of voids posited on the local isotropy of the universe. It works by comparing the temporal extent of cosmic voids along the line of sight with their angular, spatial extent. We describe the algorithm that we use to detect and stack voids in redshift shells on the light cone and test it on mock light cones produced from N-body simulations. We establish a robust statistical model for estimating the average stretching of voids in redshift space and quantify the contamination by peculiar velocities. Finally, assuming that the void statistics that we derive from N-body simulations is preserved when considering galaxy surveys, we assess the capability of this approach to constrain dark energy parameters. We report this assessment in terms of the figure of merit (FoM) of the dark energy task force and in particular of the proposed Euclid mission which is particularly suited for this technique since it is a spectroscopic survey. The FoM due to stacked voids from the Euclid wide survey may double that of all other dark energy probes derived from Euclid data alone (combined with Planck priors). In particular, voids seem to outperform baryon acoustic oscillations by an order of magnitude. This result is consistent with simple estimates based on mode counting. The AP test based on stacked voids may be a significant addition to the portfolio of major dark energy probes and its potentialities must be studied in detail.

  7. Docker on OpenStack

    OpenAIRE

    Agarwal, Nitin; Moreira, Belmiro

    2014-01-01

    Project Specification CERN is establishing a large scale private cloud based on OpenStack as part of the expansion of the computing infrastructure for storing the data coming out of the Large Hadron Collider (LHC) experiments. As the data coming out of the detectors is increasing continuously that needs to be stored in the data center, we need more physical resources (more money) and since Virtual machines takes lot of CPU and memory overhead and minutes for creating the images, booting u...

  8. Hexagonal perovskites with cationic vacancies. 12. Structure determination on Ba/sub 6/W/sub 4/vacant/sub 2/O/sub 18/

    Energy Technology Data Exchange (ETDEWEB)

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

    1979-08-01

    The stacking polytype Ba/sub 6/W/sub 4/vacant/sub 2/O/sub 18/ is the first oxide variant of the Cs/sub 3/Tl/sub 2/Cl/sub 9/-type. The structure determination gave for the space group R3c with the sequence (h)/sub 6/, Z = 3, the refined, intensity related R' value of 6.8%. The octahedral net consists of groups of two face sharing WO/sub 6/ octahedra (W/sub 2/ Osub(6/2)O/sub 6/), which are in the (110) plane displaced against each other. In the double octahedra the tungsten atoms are shifted away from their ideal central position (W-W:2.32/sub 7/ A) with the result, that the W-W distance has increased to 2.90/sub 5/ A.

  9. Perovskites synthesis to SOFC anodes

    International Nuclear Information System (INIS)

    Wendler, L.P.; Chinelatto, A.L.; Chinelatto, A.S.A.; Ramos, K.

    2012-01-01

    Perovskite structure materials containing lanthanum have been widely applied as solid oxide fuel cells (SOFCs) electrodes, due to its electrical properties. Was investigated the obtain of the perovskite structure LaCr 0,5 Ni 0,5 O 3 , by Pechini method, and its suitability as SOFC anode. The choice of this composition was based on the stability provided by chromium and the catalytic properties of nickel. After preparing the resins, the samples were calcined at 300 deg C, 600 deg C, 700 deg C and 850 deg C. The resulting powders were characterized by X-ray diffraction to determine the existing phases. Furthermore, were performed other analysis, like X-ray fluorescence, He pycnometry, specific surface area by BET isotherm and scanning electronic microscopy (author)

  10. Stack Monitor Operating Experience Review

    International Nuclear Information System (INIS)

    Cadwallader, L.C.; Bruyere, S.A.

    2009-01-01

    Stack monitors are used to sense radioactive particulates and gases in effluent air being vented from rooms of nuclear facilities. These monitors record the levels and types of effluents to the environment. This paper presents the results of a stack monitor operating experience review of the U.S. Department of Energy (DOE) Occurrence Reporting and Processing System (ORPS) database records from the past 18 years. Regulations regarding these monitors are briefly described. Operating experiences reported by the U.S. DOE and in engineering literature sources were reviewed to determine the strengths and weaknesses of these monitors. Electrical faults, radiation instrumentation faults, and human errors are the three leading causes of failures. A representative 'all modes' failure rate is 1E-04/hr. Repair time estimates vary from an average repair time of 17.5 hours (with spare parts on hand) to 160 hours (without spare parts on hand). These data should support the use of stack monitors in any nuclear facility, including the National Ignition Facility and the international ITER project.

  11. Composition control of low-volatile solids through chemical vapor transport reactions. III. The example of gallium monoselenide: Control of the polytypic structure, non-stoichiometry and properties

    International Nuclear Information System (INIS)

    Zavrazhnov, A.; Naumov, A.; Sidey, V.; Pervov, V.

    2012-01-01

    Highlights: ► This work is devoted to the composition control of solids with selective CVT method. ► Phase identity and non-stoichiometry of solids (GaSe, etc.) depend on CVT-temperatures. ► The interrelation between the properties of GaSe and CVT conditions is also found. ► For iodide transporting system the diagram of phase stability of solids is adjusted. ► High temperatures and Se-rich non-stoichiometry are necessary for γ-GaSe stability. - Abstract: By means of particular examples, the present work demonstrates the possibility of directed delicate non-destructive control of structure, composition and properties of inorganic solids using the method of selective chemical vapor transport (SCVT). Gallium monoselenide GaSe is the main model object. Additional, though less detailed, explanation is given by the example of gallium monosulfide GaS. Experimental evidences on the possibility of the control of polytypic structure, non-stoichiometry and properties of gallium monoselenide were obtained in non-isothermal variant of selective chemical vapor transport which has non-destructive character. Diagnostics of the phase (polytypic) composition and non-stoichiometry of GaSe was performed with the use of X-ray diffractometry as well as with the use of cathode luminescence spectra. It was experimentally found that there exists a connection of non-stoichiometry and the properties of gallium selenides with the determining conditions of selective chemical vapor transport: temperature of controlled sample (T 2 ) and the difference of temperatures between the hot and cold zones (ΔT). It is shown that the phase diagram of Ga–Se system needs to be partially revised near the composition of Ga 1 Se 1 . The reason for such revision is the fact that two polytypes (ε-GaSe and γ-GaSe) exist on this phase diagram as independent phases.

  12. The nitrogen acceptor in 2H-Polytype synthetic MoS2. Frequency and temperature dependent ESR analysis

    International Nuclear Information System (INIS)

    Schoenaers, Ben; Stesmans, Andre; Afanas'ev, Valery V.

    2017-01-01

    In extending on recent electron spin resonance (ESR) work which has revealed the N acceptor (N substituting for S site) in 2H-polytype bulk synthetic MoS 2 , the dopant is extensively analyzed in terms of its frequency, temperature (T), and magnetic field B angular dependent ESR spectral characteristics. For B parallel c-axis, the multi-frequency analysis confirms the ESR spectrum as being composed of a 14 N hyperfine (hf) triplet with hf splitting constant A parallel = 14.7 ± 0.2 G (B parallel c-axis) and making up ∼74% of the total spectrum intensity, superimposed on a central line centered at about equal g-value [g parallel = 2.032(2)]. The presence of the latter signal, points to some non-uniformity in dopant distribution, that is, clustering, with about ∼26% of the total N response not originating from N incorporated in the preferred ''isolated'' dopant configuration. Angular dependent measurements reveal distinct anisotropy of the hf matrix, whereas ESR probing over a wide T-range exposes drastic signal broadening with increasing T above ∼150 K. Detailed study of the N acceptor signal intensity versus T at Q-band reveals an activation energy E a = 50 ± 10 meV, herewith consolidating the value reported initially. Besides unveiling the S-site substitutional N impurity as an appropriate p-type dopant for MoS 2 , the total of the ESR work establishes a basic frame of the N acceptor ESR characteristics, giving way for further in-depth theoretical perusal. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Properties of point defects either native or induced by irradiation in the 3C and 6H polytypes of silicon carbide determined by positron annihilation and EPR

    International Nuclear Information System (INIS)

    Kerbiriou, X.

    2006-02-01

    Potential applications of silicon carbide (SiC) in micro-electronics have justified many studies on point defects, which play an important role in the electrical compensation. Moreover, this material has many assets to take part in the fissile materials confining in the gas cooled reactors of the future (4. generation). In this thesis, we have used Electronic Paramagnetic Resonance and Positron Annihilation Spectroscopy to study the properties of point defects (nature, size, charge state, migration and agglomeration during annealing), either native or induced by irradiation with various particles (H + , e - , carbon ions), in the 3C and 6H polytypes of SiC. The positron annihilation study of native defects in 6H-SiC has shown the presence of a strong concentration of non-vacancy traps of acceptor type, which are not present in the 3C-SiC crystals. The nature of the defects detected after irradiation with low energy electrons (190 keV) depends on the polytype. Indeed, while silicon Frenkel pairs and carbon mono-vacancies are detected in the 6H crystals, only carbon mono-vacancies are detected in the 3C crystals. We propose that these differences concerning the populations of detected point defects result from different values of the silicon displacement threshold energy for the two polytypes (approximately 20 eV for 6H and 25 V for 3C). In addition, the irradiations with 12 MeV protons and 132 MeV carbon ions have created silicon mono-vacancies as well as VSi-VC di-vacancies. Neither the particle (protons or ions carbon), nor the polytype (3C or 6H) influence the nature of the generated defects. Finally the study of the annealing of 6H-SiC monocrystals irradiated with 12 MeV protons have revealed several successive processes. The most original result is the agglomeration of the silicon mono-vacancies with the VSi-VC di-vacancies which leads to the formation of VSi-VC-VSi tri-vacancies. (author)

  14. Lightweight Stacks of Direct Methanol Fuel Cells

    Science.gov (United States)

    Narayanan, Sekharipuram; Valdez, Thomas

    2004-01-01

    An improved design concept for direct methanol fuel cells makes it possible to construct fuel-cell stacks that can weigh as little as one-third as much as do conventional bipolar fuel-cell stacks of equal power. The structural-support components of the improved cells and stacks can be made of relatively inexpensive plastics. Moreover, in comparison with conventional bipolar fuel-cell stacks, the improved fuel-cell stacks can be assembled, disassembled, and diagnosed for malfunctions more easily. These improvements are expected to bring portable direct methanol fuel cells and stacks closer to commercialization. In a conventional bipolar fuel-cell stack, the cells are interspersed with bipolar plates (also called biplates), which are structural components that serve to interconnect the cells and distribute the reactants (methanol and air). The cells and biplates are sandwiched between metal end plates. Usually, the stack is held together under pressure by tie rods that clamp the end plates. The bipolar stack configuration offers the advantage of very low internal electrical resistance. However, when the power output of a stack is only a few watts, the very low internal resistance of a bipolar stack is not absolutely necessary for keeping the internal power loss acceptably low.

  15. Solid Oxide Fuel Cell Stack Diagnostics

    DEFF Research Database (Denmark)

    Mosbæk, Rasmus Rode; Barfod, Rasmus Gottrup

    As SOFC technology is moving closer to a commercial break through, methods to measure the “state-of-health” of operating stacks are becoming of increasing interest. This requires application of advanced methods for detailed electrical and electrochemical characterization during operation....... An operating stack is subject to compositional gradients in the gaseous reactant streams, and temperature gradients across each cell and across the stack, which complicates detailed analysis. Several experimental stacks from Topsoe Fuel Cell A/S were characterized using Electrochemical Impedance Spectroscopy...... in the hydrogen fuel gas supplied to the stack. EIS was used to examine the long-term behavior and monitor the evolution of the impedance of each of the repeating units and the whole stack. The observed impedance was analyzed in detail for one of the repeating units and the whole stack and the losses reported...

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Study of thermodynamic stabilities of polytypes of n-C36H74 by solubility measurements and incoherent inelastic neutron scattering

    Science.gov (United States)

    Kubota, Hideki; Kaneko, Fumitoshi; Kawaguchi, Tatsuya

    2005-01-01

    The thermodynamic properties of the two polytypes of n-hexatriacontane (n-C36H74), single-layered structure Mon and double-layered structure Orth II have been investigated by means of solubility measurements and incoherent inelastic neutron scattering. The solubility measurements reveal that Orth II is more stable than Mon by 1.2 kJ/mol because of the advantage of larger entropy. The neutron scattering measurements show that the vibrational modes of Orth II shift to the lower frequencies compared with those of Mon in the frequency region below 120 cm-1. The advantage of Orth II in vibrational entropy due to the low-frequency shifts is estimated to be 9.6 J K-1/mol at 288 K under the harmonic approximation, which nearly agrees with the entropy difference of 6.8 J K-1/mol between Mon and Orth II determined by solubility measurements. These results suggest that the difference in vibrational entropy due to low-frequency modes mainly contributes to the relative thermodynamic stabilities of polytypic structures of long-chain compounds. From the frequency of methyl torsional mode, it is suggested that the cohesive force at the lamellar interface is stronger in Mon than in Orth II.

  2. First principles examination of electronic structure and optical features of 4H-GaN1-xPx polytype alloys

    Science.gov (United States)

    Laref, A.; Hussain, Z.; Laref, S.; Yang, J. T.; Xiong, Y. C.; Luo, S. J.

    2018-04-01

    By using first-principles calculations, we compute the electronic band structures and typical aspects of the optical spectra of hexagonally structured GaN1-xPx alloys. Although a type III-V semiconductor, GaP commonly possesses a zinc-blende structure with an indirect band gap; as such, it may additionally form hexagonal polytypes under specific growth conditions. The electronic structures and optical properties are calculated by combining a non-nitride III-V semiconductor and a nitride III-V semiconductor, as GaP and GaN crystallizing in a 4H polytype, with the N composition ranging between x = 0-1. For all studied materials, the energy gap is found to be direct. The optical properties of the hexagonal materials may illustrate the strong polarization dependence owing to the crystalline anisotropy. This investigation for GaN1-xPx alloys is anticipated to supply paramount information for applications in the visible/ultraviolet spectral regions. At a specific concentration, x, these alloys would be exclusively appealing candidates for solar-cell applications.

  3. Vertically stacked nanocellulose tactile sensor.

    Science.gov (United States)

    Jung, Minhyun; Kim, Kyungkwan; Kim, Bumjin; Lee, Kwang-Jae; Kang, Jae-Wook; Jeon, Sanghun

    2017-11-16

    Paper-based electronic devices are attracting considerable attention, because the paper platform has unique attributes such as flexibility and eco-friendliness. Here we report on what is claimed to be the firstly fully integrated vertically-stacked nanocellulose-based tactile sensor, which is capable of simultaneously sensing temperature and pressure. The pressure and temperature sensors are operated using different principles and are stacked vertically, thereby minimizing the interference effect. For the pressure sensor, which utilizes the piezoresistance principle under pressure, the conducting electrode was inkjet printed on the TEMPO-oxidized-nanocellulose patterned with micro-sized pyramids, and the counter electrode was placed on the nanocellulose film. The pressure sensor has a high sensitivity over a wide range (500 Pa-3 kPa) and a high durability of 10 4 loading/unloading cycles. The temperature sensor combines various materials such as poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), silver nanoparticles (AgNPs) and carbon nanotubes (CNTs) to form a thermocouple on the upper nanocellulose layer. The thermoelectric-based temperature sensors generate a thermoelectric voltage output of 1.7 mV for a temperature difference of 125 K. Our 5 × 5 tactile sensor arrays show a fast response, negligible interference, and durable sensing performance.

  4. 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.

  5. Oxygen permeation modelling of perovskites

    NARCIS (Netherlands)

    van Hassel, Bart A.; van Hassel, B.A.; Kawada, Tatsuya; Sakai, Natsuko; Yokokawa, Harumi; Dokiya, Masayuki; Bouwmeester, Henricus J.M.

    1993-01-01

    A point defect model was used to describe the oxygen nonstoichiometry of the perovskites La0.75Sr0.25CrO3, La0.9Sr0.1FeO3, La0.9Sr0.1CoO3 and La0.8Sr0.2MnO3 as a function of the oxygen partial pressure. Form the oxygen vacancy concentration predicte by the point defect model, the ionic conductivity

  6. The untyped stack calculus and Bohm's theorem

    Directory of Open Access Journals (Sweden)

    Alberto Carraro

    2013-03-01

    Full Text Available The stack calculus is a functional language in which is in a Curry-Howard correspondence with classical logic. It enjoys confluence but, as well as Parigot's lambda-mu, does not admit the Bohm Theorem, typical of the lambda-calculus. We present a simple extension of stack calculus which is for the stack calculus what Saurin's Lambda-mu is for lambda-mu.

  7. Flexural characteristics of a stack leg

    International Nuclear Information System (INIS)

    Cook, J.

    1979-06-01

    A 30 MV tandem Van de Graaff accelerator is at present under construction at Daresbury Laboratory. The insulating stack of the machine is of modular construction, each module being 860 mm in length. Each live section stack module contains 8 insulating legs mounted between bulkhead rings. The design, fabrication (from glass discs bonded to stainless steel discs using an epoxy film adhesive) and testing of the stack legs is described. (U.K.)

  8. Interface engineering of perovskite solar cells with multifunctional polymer interlayer toward improved performance and stability

    Science.gov (United States)

    Huang, Li-Bo; Su, Pei-Yang; Liu, Jun-Min; Huang, Jian-Feng; Chen, Yi-Fan; Qin, Su; Guo, Jing; Xu, Yao-Wei; Su, Cheng-Yong

    2018-02-01

    This work proposes a new perovskite solar cell structure by inserting a polymer interlayer between perovskite and hole transporting material (HTM) to minimize the interface losses via interface engineering. The multifunctional interlayers improve the photovoltaic efficiency and device stability by shielding perovskite from moisture, suppressing charge combination, and promoting hole transport. The five different polymer layers are utilized to investigate the relationships of polymer structure, layer morphology and cell performance systematically. It is found that a reliable power conversion efficiency exceeding 19.0% is realized based on P3HT/spiro-OMeTAD composite structure, surpassing that of pure spiro-OMeTAD (15.0%). Moreover, the device with P3HT interlayer shows more brilliant long-term stability than that without interlayer when exposed into moisture. The enhanced device performance based on P3HT interlayer compared with the other polymers can be ascribed to the long hydrophobic alkyl chains and the small molecule monomers of P3HT, which contribute to self-assembly of the polymers into insulating layers and formation of the efficient π-π stacking in polymer/spiro-OMeTAD interface simultaneously. This study provides a practical route for the integration of a new class of easily-accessible, solution-processed interfacial polymer materials for high-performance and long-time stable PSC.

  9. 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

  10. 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....

  11. ooi: OpenStack OCCI interface

    Directory of Open Access Journals (Sweden)

    Álvaro López García

    2016-01-01

    Full Text Available In this document we present an implementation of the Open Grid Forum’s Open Cloud Computing Interface (OCCI for OpenStack, namely ooi (Openstack occi interface, 2015  [1]. OCCI is an open standard for management tasks over cloud resources, focused on interoperability, portability and integration. ooi aims to implement this open interface for the OpenStack cloud middleware, promoting interoperability with other OCCI-enabled cloud management frameworks and infrastructures. ooi focuses on being non-invasive with a vanilla OpenStack installation, not tied to a particular OpenStack release version.

  12. ooi: OpenStack OCCI interface

    Science.gov (United States)

    López García, Álvaro; Fernández del Castillo, Enol; Orviz Fernández, Pablo

    In this document we present an implementation of the Open Grid Forum's Open Cloud Computing Interface (OCCI) for OpenStack, namely ooi (Openstack occi interface, 2015) [1]. OCCI is an open standard for management tasks over cloud resources, focused on interoperability, portability and integration. ooi aims to implement this open interface for the OpenStack cloud middleware, promoting interoperability with other OCCI-enabled cloud management frameworks and infrastructures. ooi focuses on being non-invasive with a vanilla OpenStack installation, not tied to a particular OpenStack release version.

  13. Ab initio determination of the novel perovskite-related structure of La7Mo7O30 from powder diffraction

    International Nuclear Information System (INIS)

    Goutenoire, F.; Retoux, R.; Lacorre, P.

    1999-01-01

    A new mixed valence molybdate, La 7 Mo 7 O 30 , first prepared by high energy ball milling, has been successfully synthesized by controlled hydrogen reduction of La 2 Mo 2 O 9 . Its original crystal structure was determined from X-ray and neutron powder diffraction (space group R 3 ; a = b = 17.0051(2) angstrom, c = 6.8607(1) angstrom; Z = 3; reliability factors: R p = 0.081, R wp = 0.091, χ 2 = 3.1, R Bragg = 0.049, R F = 0.033). It consists in the hexagonal stacking of individual cylinders of perovskite-type arrangement. These cylinders are built up from perovskite cages sharing corners in trans-position along their diagonal axis. Two different mixed-valence molybdenum sites coexist, with more (Mo +5.75 ) or less (Mo +4.5 ) distorted octahedral environments. Lanthanum atoms are located within the perovskite cages and around them, very close to their regular positions in the perovskite structure. Lanthanum and molybdenum atoms thus form two rows of almost perfect cubes, shifted from each other by c/2. An electron microscopy study revealed the defect-free cationic and octahedral arrangements in the (a,b) plane

  14. Strongly correlated perovskite fuel cells

    Science.gov (United States)

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

    2016-06-01

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

  15. Stacks of SPS Dipole Magnets

    CERN Multimedia

    1974-01-01

    Stacks of SPS Dipole Magnets ready for installation in the tunnel. The SPS uses a separated function lattice with dipoles for bending and quadrupoles for focusing. The 6.2 m long normal conducting dipoles are of H-type with coils that are bent-up at the ends. There are two types, B1 (total of 360) and B2 (384). Both are for a maximum field of 1.8 Tesla and have the same outer dimensions (450x800 mm2 vxh) but with different gaps (B1: 39x129 mm2, B2: 52x92 mm2) tailored to the beam size. The yoke, made of 1.5 mm thick laminations, consists of an upper and a lower half joined together in the median plane once the coils have been inserted.

  16. California dreaming?[PEM stacks

    Energy Technology Data Exchange (ETDEWEB)

    Crosse, J.

    2002-06-01

    Hyundai's Santa Fe FCEV will be on sale by the end of 2002. Hyundai uses PEM stacks that are manufactured by International Fuel Cells (IFC), a division of United Technologies. Santa Fe is equipped with a 65 kW electric powertrain of Enova systems and Shell's new gasoline reformer called Hydrogen Source. Eugene Jang, Senior Engineer - Fuel Cell and Materials at Hyundai stated that the compressor related losses on IFC system are below 3%. The maximum speed offered by the vehicle is estimated as 123km/hr while the petrol equivalent fuel consumption is quoted between 5.6L/100 km and 4.8L/100 km. Santa Fe is a compact vehicle offering better steering response and a pleasant drive. (author)

  17. Neutral Color Semitransparent Microstructured Perovskite Solar Cells

    KAUST Repository

    Eperon, Giles E.; Burlakov, Victor M.; Goriely, Alain; Snaith, Henry J.

    2014-01-01

    Neutral-colored semitransparent solar cells are commercially desired to integrate solar cells into the windows and cladding of buildings and automotive applications. Here, we report the use of morphological control of perovskite thin films to form

  18. Ambipolar solution-processed hybrid perovskite phototransistors

    KAUST Repository

    Li, Feng; Ma, Chun; Wang, Hong; Hu, Weijin; Yu, Weili; Sheikh, Arif D.; Wu, Tao

    2015-01-01

    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

  19. 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...

  20. Making and Breaking of Lead Halide Perovskites

    KAUST Repository

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

    2016-01-01

    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

  1. 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.

  2. Perovskite Thin Films via Atomic Layer Deposition

    KAUST Repository

    Sutherland, Brandon R.; Hoogland, Sjoerd; Adachi, Michael M.; Kanjanaboos, Pongsakorn; Wong, Chris T. O.; McDowell, Jeffrey J.; Xu, Jixian; Voznyy, Oleksandr; Ning, Zhijun; Houtepen, Arjan J.; Sargent, Edward H.

    2014-01-01

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

  3. 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.

  4. Perovskite Thin Films via Atomic Layer Deposition

    KAUST Repository

    Sutherland, Brandon R.

    2014-10-30

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

  5. Vector Fields and Flows on Differentiable Stacks

    DEFF Research Database (Denmark)

    A. Hepworth, Richard

    2009-01-01

    This paper introduces the notions of vector field and flow on a general differentiable stack. Our main theorem states that the flow of a vector field on a compact proper differentiable stack exists and is unique up to a uniquely determined 2-cell. This extends the usual result on the existence...... of vector fields....

  6. Project W-420 stack monitoring system upgrades

    International Nuclear Information System (INIS)

    CARPENTER, K.E.

    1999-01-01

    This project will execute the design, procurement, construction, startup, and turnover activities for upgrades to the stack monitoring system on selected Tank Waste Remediation System (TWRS) ventilation systems. In this plan, the technical, schedule, and cost baselines are identified, and the roles and responsibilities of project participants are defined for managing the Stack Monitoring System Upgrades, Project W-420

  7. 40 CFR 61.44 - Stack sampling.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 8 2010-07-01 2010-07-01 false Stack sampling. 61.44 Section 61.44 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL... Firing § 61.44 Stack sampling. (a) Sources subject to § 61.42(b) shall be continuously sampled, during...

  8. On the "stacking fault" in copper

    NARCIS (Netherlands)

    Fransens, J.R.; Pleiter, F

    2003-01-01

    The results of a perturbed gamma-gamma angular correlations experiment on In-111 implanted into a properly cut single crystal of copper show that the defect known in the literature as "stacking fault" is not a planar faulted loop but a stacking fault tetrahedron with a size of 10-50 Angstrom.

  9. Learning OpenStack networking (Neutron)

    CERN Document Server

    Denton, James

    2014-01-01

    If you are an OpenStack-based cloud operator with experience in OpenStack Compute and nova-network but are new to Neutron networking, then this book is for you. Some networking experience is recommended, and a physical network infrastructure is required to provide connectivity to instances and other network resources configured in the book.

  10. 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.

  11. Status of MCFC stack technology at IHI

    Energy Technology Data Exchange (ETDEWEB)

    Hosaka, M.; Morita, T.; Matsuyama, T.; Otsubo, M. [Ishikawajima-Harima Heavy Industries Co., Ltd., Tokyo (Japan)

    1996-12-31

    The molten carbonate fuel cell (MCFC) is a promising option for highly efficient power generation possible to enlarge. IHI has been studying parallel flow MCFC stacks with internal manifolds that have a large electrode area of 1m{sup 2}. IHI will make two 250 kW stacks for MW plant, and has begun to make cell components for the plant. To improve the stability of stack, soft corrugated plate used in the separator has been developed, and a way of gathering current from stacks has been studied. The DC output potential of the plant being very high, the design of electric insulation will be very important. A 20 kW short stack test was conducted in 1995 FY to certificate some of the improvements and components of the MW plant. These activities are presented below.

  12. Modular fuel-cell stack assembly

    Science.gov (United States)

    Patel, Pinakin

    2010-07-13

    A fuel cell assembly having a plurality of fuel cells arranged in a stack. An end plate assembly abuts the fuel cell at an end of said stack. The end plate assembly has an inlet area adapted to receive an exhaust gas from the stack, an outlet area and a passage connecting the inlet area and outlet area and adapted to carry the exhaust gas received at the inlet area from the inlet area to the outlet area. A further end plate assembly abuts the fuel cell at a further opposing end of the stack. The further end plate assembly has a further inlet area adapted to receive a further exhaust gas from the stack, a further outlet area and a further passage connecting the further inlet area and further outlet area and adapted to carry the further exhaust gas received at the further inlet area from the further inlet area to the further outlet area.

  13. Properties of point defects either native or induced by irradiation in the 3C and 6H polytypes of silicon carbide determined by positron annihilation and EPR; Proprietes des defauts ponctuels natifs et induits par irradiation dans les polytypes 3C et 6H du carbure de silicium determinees par annihilation de positons et RPE

    Energy Technology Data Exchange (ETDEWEB)

    Kerbiriou, X

    2006-02-15

    Potential applications of silicon carbide (SiC) in micro-electronics have justified many studies on point defects, which play an important role in the electrical compensation. Moreover, this material has many assets to take part in the fissile materials confining in the gas cooled reactors of the future (4. generation). In this thesis, we have used Electronic Paramagnetic Resonance and Positron Annihilation Spectroscopy to study the properties of point defects (nature, size, charge state, migration and agglomeration during annealing), either native or induced by irradiation with various particles (H{sup +}, e{sup -}, carbon ions), in the 3C and 6H polytypes of SiC. The positron annihilation study of native defects in 6H-SiC has shown the presence of a strong concentration of non-vacancy traps of acceptor type, which are not present in the 3C-SiC crystals. The nature of the defects detected after irradiation with low energy electrons (190 keV) depends on the polytype. Indeed, while silicon Frenkel pairs and carbon mono-vacancies are detected in the 6H crystals, only carbon mono-vacancies are detected in the 3C crystals. We propose that these differences concerning the populations of detected point defects result from different values of the silicon displacement threshold energy for the two polytypes (approximately 20 eV for 6H and 25 V for 3C). In addition, the irradiations with 12 MeV protons and 132 MeV carbon ions have created silicon mono-vacancies as well as VSi-VC di-vacancies. Neither the particle (protons or ions carbon), nor the polytype (3C or 6H) influence the nature of the generated defects. Finally the study of the annealing of 6H-SiC monocrystals irradiated with 12 MeV protons have revealed several successive processes. The most original result is the agglomeration of the silicon mono-vacancies with the VSi-VC di-vacancies which leads to the formation of VSi-VC-VSi tri-vacancies. (author)

  14. Polytypic pattern matching

    NARCIS (Netherlands)

    Jeuring, J.T.

    1995-01-01

    The pattern matching problem can be informally specified as follows: given a pattern and a text, find all occurrences of the pattern in the text. The pattern and the text may both be lists, or they may both be trees, or they may both be multi-dimensional arrays, etc. This paper describes a general

  15. Functional Pearls : Polytypic Unification

    NARCIS (Netherlands)

    Jansson, P.; Jeuring, J.T.

    1998-01-01

    Unification, or two-way pattern matching, is the process of solving an equation involving two first-order terms with variables. Unification is used in type inference in many programming languages and in the execution of logic programs. This means that unification algorithms have to be written over

  16. 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.

  17. 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.

  18. Probing Temperature Inside Planar SOFC Short Stack, Modules, and Stack Series

    Science.gov (United States)

    Yu, Rong; Guan, Wanbing; Zhou, Xiao-Dong

    2017-02-01

    Probing temperature inside a solid oxide fuel cell (SOFC) stack lies at the heart of the development of high-performance and stable SOFC systems. In this article, we report our recent work on the direct measurements of the temperature in three types of SOFC systems: a 5-cell short stack, a 30-cell stack module, and a stack series consisting of two 30-cell stack modules. The dependence of temperature on the gas flow rate and current density was studied under a current sweep or steady-state operation. During the current sweep, the temperature inside the 5-cell stack decreased with increasing current, while it increased significantly at the bottom and top of the 30-cell stack. During a steady-state operation, the temperature of the 5-cell stack was stable while it was increased in the 30-cell stack. In the stack series, the maximum temperature gradient reached 190°C when the gas was not preheated. If the gas was preheated and the temperature gradient was reduced to 23°C in the stack series with the presence of a preheating gas and segmented temperature control, this resulted in a low degradation rate.

  19. The impact of stack geometry and mean pressure on cold end temperature of stack in thermoacoustic refrigeration systems

    Science.gov (United States)

    Wantha, Channarong

    2018-02-01

    This paper reports on the experimental and simulation studies of the influence of stack geometries and different mean pressures on the cold end temperature of the stack in the thermoacoustic refrigeration system. The stack geometry was tested, including spiral stack, circular pore stack and pin array stack. The results of this study show that the mean pressure of the gas in the system has a significant impact on the cold end temperature of the stack. The mean pressure of the gas in the system corresponds to thermal penetration depth, which results in a better cold end temperature of the stack. The results also show that the cold end temperature of the pin array stack decreases more than that of the spiral stack and circular pore stack geometry by approximately 63% and 70%, respectively. In addition, the thermal area and viscous area of the stack are analyzed to explain the results of such temperatures of thermoacoustic stacks.

  20. 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%.

  1. Ordered meso- and macroporous perovskite oxide catalysts for emerging applications

    DEFF Research Database (Denmark)

    Arandiyan, Hamidreza; Wang, Yuan; Sun, Hongyu

    2018-01-01

    This feature article summarizes the recent progress in porous perovskite oxides as advanced catalysts for both energy conversion applications and various heterogeneous reactions. Recently, research has been focused on specifically designing porous perovskite materials so that large surface areas ...

  2. Polytypism and band alignment in ZnSe nanowires revealed by photoluminescence spectroscopy of embedded (Zn,Cd)Se quantum dots

    Science.gov (United States)

    Bieker, S.; Pfeuffer, R.; Kiessling, T.; Tarakina, N.; Schumacher, C.; Ossau, W.; Molenkamp, L. W.; Karczewski, G.

    2015-03-01

    We report on the optical characterization of single (Zn,Cd)Se quantum dots (QDs) embedded in vapor-liquid-solid-grown ZnSe nanowires (NWs). The temperature dependent quenching of the QD luminescence demonstrates that their electronic structure is comparable to that of self-assembled (Zn,Cd)Se QDs in ZnSe matrices. The photoluminescence excitation (PLE) spectrum of single nanowire QDs reveals the presence of both zinc blende (ZB) and wurtzite (WZ) crystal modifications of ZnSe in the NW shafts. PLE provides, therefore, a complementary technique to transmission electron microscopy imaging to reveal polytypism in ZnSe NWs. A transient quenching of the PL emission suggests a type II staggered band alignment at the ZB/WZ interface in our ZnSe NWs.

  3. In situ doping of catalyst-free InAs nanowires with Si: Growth, polytypism, and local vibrational modes of Si

    Energy Technology Data Exchange (ETDEWEB)

    Dimakis, Emmanouil; Ramsteiner, Manfred; Huang, Chang-Ning; Trampert, Achim; Riechert, Henning; Geelhaar, Lutz [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Davydok, Anton; Biermanns, Andreas; Pietsch, Ullrich [Festkörperphysik, Universität Siegen, Walter-Flex-Str. 3, 57072 Siegen (Germany)

    2013-09-30

    Growth and structural aspects of the in situ doping of InAs nanowires with Si have been investigated. The nanowires were grown catalyst-free on Si(111) substrates by molecular beam epitaxy. The supply of Si influenced the growth kinetics, affecting the nanowire dimensions, but not the degree of structural polytypism, which was always pronounced. As determined by Raman spectroscopy, Si was incorporated as substitutional impurity exclusively on In sites, which makes it a donor. Previously unknown Si-related Raman peaks at 355 and 360 cm{sup −1} were identified, based on their symmetry properties in polarization-dependent measurements, as the two local vibrational modes of an isolated Si impurity on In site along and perpendicular, respectively, to the c-axis of the wurtzite InAs crystal.

  4. Five stacks over the Danube

    International Nuclear Information System (INIS)

    Anon.

    1998-01-01

    Following the departure of Communism, Hungary adopted the most ambitious privatisation programme of all the eastern European countries. Within a year the state electricity company, MVM, and the oil and gas company, MOL, were prepared for sale and a consequent injection of foreign capital. Control of prices by central government inhibited investment initially but a new legal framework put in place in 1995 introduced a pricing regime more attractive to external investors. Particular interest was shown in the 2,200MW mixed heavy oil and natural gas power plant at Dunamenti on the Danube, characterised by its five stacks of varying height which reflect the changing technology employed at the plant. The bid was won by Tractabel of Belgium who have been highly successful in improving plant efficiency. However, the impact of privatisation is now being felt in uncertainty over fuel supply. Removing such uncertainty in order to maintain existing investment and provide the additional 4000MW of generating capacity needed to keep pace with demand, is a major problem which the incoming government faces. (UK)

  5. 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.

  6. 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

  7. Density of oxidation-induced stacking faults in damaged silicon

    NARCIS (Netherlands)

    Kuper, F.G.; Hosson, J.Th.M. De; Verwey, J.F.

    1986-01-01

    A model for the relation between density and length of oxidation-induced stacking faults on damaged silicon surfaces is proposed, based on interactions of stacking faults with dislocations and neighboring stacking faults. The model agrees with experiments.

  8. 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

  9. Dynamical stability of slip-stacking particles

    Energy Technology Data Exchange (ETDEWEB)

    Eldred, Jeffrey; Zwaska, Robert

    2014-09-01

    We study the stability of particles in slip-stacking configuration, used to nearly double proton beam intensity at Fermilab. We introduce universal area factors to calculate the available phase space area for any set of beam parameters without individual simulation. We find perturbative solutions for stable particle trajectories. We establish Booster beam quality requirements to achieve 97% slip-stacking efficiency. We show that slip-stacking dynamics directly correspond to the driven pendulum and to the system of two standing-wave traps moving with respect to each other.

  10. Text-Filled Stacked Area Graphs

    DEFF Research Database (Denmark)

    Kraus, Martin

    2011-01-01

    -filled stacked area graphs; i.e., graphs that feature stacked areas that are filled with small-typed text. Since these graphs allow for computing the text layout automatically, it is possible to include large amounts of textual detail with very little effort. We discuss the most important challenges and some...... solutions for the design of text-filled stacked area graphs with the help of an exemplary visualization of the genres, publication years, and titles of a database of several thousand PC games....

  11. Tunable electro-optic filter stack

    Science.gov (United States)

    Fontecchio, Adam K.; Shriyan, Sameet K.; Bellingham, Alyssa

    2017-09-05

    A holographic polymer dispersed liquid crystal (HPDLC) tunable filter exhibits switching times of no more than 20 microseconds. The HPDLC tunable filter can be utilized in a variety of applications. An HPDLC tunable filter stack can be utilized in a hyperspectral imaging system capable of spectrally multiplexing hyperspectral imaging data acquired while the hyperspectral imaging system is airborne. HPDLC tunable filter stacks can be utilized in high speed switchable optical shielding systems, for example as a coating for a visor or an aircraft canopy. These HPDLC tunable filter stacks can be fabricated using a spin coating apparatus and associated fabrication methods.

  12. 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

  13. Characterization of Piezoelectric Stacks for Space Applications

    Science.gov (United States)

    Sherrit, Stewart; Jones, Christopher; Aldrich, Jack; Blodget, Chad; Bao, Xiaoqi; Badescu, Mircea; Bar-Cohen, Yoseph

    2008-01-01

    Future NASA missions are increasingly seeking to actuate mechanisms to precision levels in the nanometer range and below. Co-fired multilayer piezoelectric stacks offer the required actuation precision that is needed for such mechanisms. To obtain performance statistics and determine reliability for extended use, sets of commercial PZT stacks were tested in various AC and DC conditions at both nominal and high temperatures and voltages. In order to study the lifetime performance of these stacks, five actuators were driven sinusoidally for up to ten billion cycles. An automated data acquisition system was developed and implemented to monitor each stack's electrical current and voltage waveforms over the life of the test. As part of the monitoring tests, the displacement, impedance, capacitance and leakage current were measured to assess the operation degradation. This paper presents some of the results of this effort.

  14. The stack on software and sovereignty

    CERN Document Server

    Bratton, Benjamin H

    2016-01-01

    A comprehensive political and design theory of planetary-scale computation proposing that The Stack -- an accidental megastructure -- is both a technological apparatus and a model for a new geopolitical architecture.

  15. Development of Auto-Stacking Warehouse Truck

    Directory of Open Access Journals (Sweden)

    Kuo-Hsien Hsia

    2018-03-01

    Full Text Available Warehouse automation is a very important issue for the promotion of traditional industries. For the production of larger and stackable products, it is usually necessary to operate a fork-lifter for the stacking and storage of the products by a skilled person. The general autonomous warehouse-truck does not have the ability of stacking objects. In this paper, we develop a prototype of auto-stacking warehouse-truck that can work without direct operation by a skill person. With command made by an RFID card, the stacker truck can take the packaged product to the warehouse on the prior-planned route and store it in a stacking way in the designated storage area, or deliver the product to the shipping area or into the container from the storage area. It can significantly reduce the manpower requirements of the skilled-person of forklift technician and improve the safety of the warehousing area.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Exploring online evolution of network stacks

    OpenAIRE

    Imai, Pierre

    2013-01-01

    Network stacks today follow a one-size-fits-all philosophy. They are mostly kept unmodified due to often prohibitive costs of engineering, deploying and administrating customisation of the networking software, with the Internet stack architecture still largely being based on designs and assumptions made for the ARPANET 40 years ago. We venture that heterogeneous and rapidly changing networks of the future require, in order to be successful, run-time self-adaptation mechanisms at different tim...

  1. New Type of 2D Perovskites with Alternating Cations in the Interlayer Space, (C(NH 2 ) 3 )(CH 3 NH 3 ) n Pb n I 3n+1 : Structure, Properties, and Photovoltaic Performance

    Energy Technology Data Exchange (ETDEWEB)

    Soe, Chan Myae Myae; Stoumpos, Constantinos C.; Kepenekian, Mikaël; Traoré, Boubacar; Tsai, Hsinhan; Nie, Wanyi; Wang, Binghao; Katan, Claudine; Seshadri, Ram; Mohite, Aditya D.; Even, Jacky; Marks, Tobin J.; Kanatzidis, Mercouri G. (UCSB); (NWU); (LANL); (CNRS-UMR)

    2017-11-01

    We present the new homologous series (C(NH2)3)(CH3NH3)nPbnI3n+1 (n = 1, 2, 3) of layered 2D perovskites. Structural characterization by single-crystal X-ray diffraction reveals that these compounds adopt an unprecedented structure type, which is stabilized by the alternating ordering of the guanidinium and methylammonium cations in the interlayer space (ACI). Compared to the more common Ruddlesden–Popper (RP) 2D perovskites, the ACI perovskites have a different stacking motif and adopt a higher crystal symmetry. The higher symmetry of the ACI perovskites is expressed in their physical properties, which show a characteristic decrease of the bandgap with respect to their RP perovskite counterparts with the same perovskite layer thickness (n). The compounds show a monotonic decrease in the optical gap as n increases: Eg = 2.27 eV for n = 1 to Eg = 1.99 eV for n = 2 and Eg = 1.73 eV for n = 3, which show slightly narrower gaps compared to the corresponding RP perovskites. First-principles theoretical electronic structure calculations confirm the experimental optical gap trends suggesting that the ACI perovskites are direct bandgap semiconductors with wide valence and conduction bandwidths. To assess the potential of the ACI perovskites toward solar cell applications, we studied the (C(NH2)3)(CH3NH3)3Pb3I10 (n = 3) compound. Compact thin films from the (C(NH2)3)(CH3NH3)3Pb3I10 compound with excellent surface coverage can be obtained from the antisolvent dripping method. Planar photovoltaic devices from optimized ACI perovskite films yield a power-conversion-efficiency of 7.26% with a high open-circuit voltage of ~1 V and a striking fill factor of ~80%.

  2. A Time-predictable Stack Cache

    DEFF Research Database (Denmark)

    Abbaspour, Sahar; Brandner, Florian; Schoeberl, Martin

    2013-01-01

    Real-time systems need time-predictable architectures to support static worst-case execution time (WCET) analysis. One architectural feature, the data cache, is hard to analyze when different data areas (e.g., heap allocated and stack allocated data) share the same cache. This sharing leads to le...... of a cache for stack allocated data. Our port of the LLVM C++ compiler supports the management of the stack cache. The combination of stack cache instructions and the hardware implementation of the stack cache is a further step towards timepredictable architectures.......Real-time systems need time-predictable architectures to support static worst-case execution time (WCET) analysis. One architectural feature, the data cache, is hard to analyze when different data areas (e.g., heap allocated and stack allocated data) share the same cache. This sharing leads to less...... precise results of the cache analysis part of the WCET analysis. Splitting the data cache for different data areas enables composable data cache analysis. The WCET analysis tool can analyze the accesses to these different data areas independently. In this paper we present the design and implementation...

  3. StackGAN++: Realistic Image Synthesis with Stacked Generative Adversarial Networks

    OpenAIRE

    Zhang, Han; Xu, Tao; Li, Hongsheng; Zhang, Shaoting; Wang, Xiaogang; Huang, Xiaolei; Metaxas, Dimitris

    2017-01-01

    Although Generative Adversarial Networks (GANs) have shown remarkable success in various tasks, they still face challenges in generating high quality images. In this paper, we propose Stacked Generative Adversarial Networks (StackGAN) aiming at generating high-resolution photo-realistic images. First, we propose a two-stage generative adversarial network architecture, StackGAN-v1, for text-to-image synthesis. The Stage-I GAN sketches the primitive shape and colors of the object based on given...

  4. Defect-induced polytype transformations in LPE grown SiC epilayers on (1 1 1) 3C-SiC seeds grown by VLS on 6H-SiC

    International Nuclear Information System (INIS)

    Marinova, Maya; Zoulis, Georgios; Robert, Teddy; Mercier, Frederic; Mantzari, Alkioni; Galben, Irina; Kim-Hak, Olivier; Lorenzzi, Jean; Juillaguet, Sandrine; Chaussende, Didier; Ferro, Gabriel; Camassel, Jean; Polychroniadis, Efstathios K.

    2009-01-01

    The results of transmission electron microscopy (TEM) with low-temperature photoluminescence (LTPL) and Raman studies of liquid phase grown epilayers on top of a vapor liquid solid (VLS) grown 3C-SiC buffer layer are compared. While the 6H-SiC substrate was completely covered by the 3C-SiC seed after the first VLS process, degradation occurred during the early stage of the liquid phase epitaxy process. This resulted in polytype instabilities, such that several rhombohedral forms stabilized one after the other. These (21R-SiC, 57R-SiC) eventually led after few microns to a final transition back to 6H-SiC. This interplay of polytypes resulted in a complex optical signature, with specific LTPL and Raman features.

  5. 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.

  6. 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.

  7. 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.

  8. Research Update: Luminescence in lead halide perovskites

    Directory of Open Access Journals (Sweden)

    Ajay Ram Srimath Kandada

    2016-09-01

    Full Text Available Efficiency and dynamics of radiative recombination of carriers are crucial figures of merit for optoelectronic materials. Following the recent success of lead halide perovskites in efficient photovoltaic and light emitting technologies, here we review some of the noted literature on the luminescence of this emerging class of materials. After outlining the theoretical formalism that is currently used to explain the carrier recombination dynamics, we review a few significant works which use photoluminescence as a tool to understand and optimize the operation of perovskite based optoelectronic devices.

  9. Partial oxidation of 2-propanol on perovskites

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-12-31

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

  10. 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...

  11. 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

  12. 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.

  13. Thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap semiconductors SiC, GaN, and ZnO

    Directory of Open Access Journals (Sweden)

    Zheng Huang

    2015-09-01

    Full Text Available We have investigated the thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap(n-type semiconductors SiC, GaN, and ZnO based on first-principles calculations and Boltzmann transport theory. Our results show that the thermoelectric performance increases from 3C to 6H, 4H, and 2H structures with an increase of hexagonality for SiC. However, for GaN and ZnO, their power factors show a very weak dependence on the polytype. Detailed analysis of the thermoelectric properties with respect to temperature and carrier concentration of 4H-SiC, 2H-GaN, and 2H-ZnO shows that the figure of merit of these three compounds increases with temperature, indicating the promising potential applications of these thermoelectric materials at high temperature. The significant difference of the polytype-dependent thermoelectric properties among SiC, GaN, and ZnO might be related to the competition between covalency and ionicity in these semiconductors. Our calculations may provide a new way to enhance the thermoelectric properties of wide-band-gap semiconductors through atomic structure design, especially hexagonality design for SiC.

  14. Start-Stop Test Procedures on the PEMFC Stack Level

    DEFF Research Database (Denmark)

    Mitzel, Jens; Nygaard, Frederik; Veltzé, Sune

    The test is addressed to investigate the influence on stack durability of a long stop followed by a restart of a stack. Long stop should be defined as a stop in which the anodic compartment is fully filled by air due to stack leakages. In systems, leakage level of the stack is low and time to fil...

  15. Principles for Instructional Stack Development in HyperCard.

    Science.gov (United States)

    McEneaney, John E.

    The purpose of this paper is to provide information about obtaining and using HyperCard stacks that introduce users to principles of stack development. The HyperCard stacks described are available for downloading free of charge from a server at Indiana University South Bend. Specific directions are given for stack use, with advice for beginners. A…

  16. 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.

  17. 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.

  18. EmuStack: An OpenStack-Based DTN Network Emulation Platform (Extended Version

    Directory of Open Access Journals (Sweden)

    Haifeng Li

    2016-01-01

    Full Text Available With the advancement of computing and network virtualization technology, the networking research community shows great interest in network emulation. Compared with network simulation, network emulation can provide more relevant and comprehensive details. In this paper, EmuStack, a large-scale real-time emulation platform for Delay Tolerant Network (DTN, is proposed. EmuStack aims at empowering network emulation to become as simple as network simulation. Based on OpenStack, distributed synchronous emulation modules are developed to enable EmuStack to implement synchronous and dynamic, precise, and real-time network emulation. Meanwhile, the lightweight approach of using Docker container technology and network namespaces allows EmuStack to support a (up to hundreds of nodes large-scale topology with only several physical nodes. In addition, EmuStack integrates the Linux Traffic Control (TC tools with OpenStack for managing and emulating the virtual link characteristics which include variable bandwidth, delay, loss, jitter, reordering, and duplication. Finally, experiences with our initial implementation suggest the ability to run and debug experimental network protocol in real time. EmuStack environment would bring qualitative change in network research works.

  19. Forced Air-Breathing PEMFC Stacks

    Directory of Open Access Journals (Sweden)

    K. S. Dhathathreyan

    2012-01-01

    Full Text Available Air-breathing fuel cells have a great potential as power sources for various electronic devices. They differ from conventional fuel cells in which the cells take up oxygen from ambient air by active or passive methods. The air flow occurs through the channels due to concentration and temperature gradient between the cell and the ambient conditions. However developing a stack is very difficult as the individual cell performance may not be uniform. In order to make such a system more realistic, an open-cathode forced air-breathing stacks were developed by making appropriate channel dimensions for the air flow for uniform performance in a stack. At CFCT-ARCI (Centre for Fuel Cell Technology-ARC International we have developed forced air-breathing fuel cell stacks with varying capacity ranging from 50 watts to 1500 watts. The performance of the stack was analysed based on the air flow, humidity, stability, and so forth, The major advantage of the system is the reduced number of bipolar plates and thereby reduction in volume and weight. However, the thermal management is a challenge due to the non-availability of sufficient air flow to remove the heat from the system during continuous operation. These results will be discussed in this paper.

  20. Levitation characteristics of HTS tape stacks

    Energy Technology Data Exchange (ETDEWEB)

    Pokrovskiy, S. V.; Ermolaev, Y. S.; Rudnev, I. A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation)

    2015-03-15

    Due to the considerable development of the technology of second generation high-temperature superconductors and a significant improvement in their mechanical and transport properties in the last few years it is possible to use HTS tapes in the magnetic levitation systems. The advantages of tapes on a metal substrate as compared with bulk YBCO material primarily in the strength, and the possibility of optimizing the convenience of manufacturing elements of levitation systems. In the present report presents the results of the magnetic levitation force measurements between the stack of HTS tapes containing of tapes and NdFeB permanent magnet in the FC and ZFC regimes. It was found a non- linear dependence of the levitation force from the height of the array of stack in both modes: linear growth at small thickness gives way to flattening and constant at large number of tapes in the stack. Established that the levitation force of stacks comparable to that of bulk samples. The numerical calculations using finite element method showed that without the screening of the applied field the levitation force of the bulk superconductor and the layered superconductor stack with a critical current of tapes increased by the filling factor is exactly the same, and taking into account the screening force slightly different.

  1. Synthesis of Freestanding Single-crystal Perovskite Films and Heterostructures by Etching of Sacrificial Water-soluble Layers

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Di; Baek, David J.; Hong, Seung Sae; Kourkoutis, Lena F.; Hikita, Yasuyuki; Hwang, Harold Y.

    2016-08-22

    The ability to create and manipulate materials in two-dimensional (2D) form has repeatedly had transformative impact on science and technology. In parallel with the exfoliation and stacking of intrinsically layered crystals, atomic-scale thin film growth of complex materials has enabled the creation of artificial 2D heterostructures with novel functionality and emergent phenomena, as seen in perovskite heterostructures. However, separation of these layers from the growth substrate has proven challenging, limiting the manipulation capabilities of these heterostructures with respect to exfoliated materials. Here we present a general method to create freestanding perovskite membranes. The key is the epitaxial growth of water-soluble Sr3Al2O6 on perovskite substrates, followed by in situ growth of films and heterostructures. Millimetre-size single-crystalline membranes are produced by etching the Sr3Al2O6 layer in water, providing the opportunity to transfer them to arbitrary substrates and integrate them with heterostructures of semiconductors and layered compounds.

  2. 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.

  3. 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.

  4. Molecular behavior of zero-dimensional perovskites

    KAUST Repository

    Yin, Jun; Maity, Partha; de Bastiani, Michele; Dursun, Ibrahim; Bakr, Osman; Bredas, Jean-Luc; Mohammed, Omar F.

    2017-01-01

    -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

  5. Elastic softness of hybrid lead halide perovskites

    KAUST Repository

    Ferreira, A. C.; Lé toublon, A.; Paofai, S.; Raymond, S.; Ecolivet, C.; Rufflé , B.; Cordier, S.; Katan, C.; Saidaminov, Makhsud I.; Zhumekenov, A. A.; Bakr, Osman; Even, J.; Bourges, Ph.

    2018-01-01

    scattering, low frequency acoustic phonons in four different hybrid perovskite single crystals: MAPbBr3, FAPbBr3, MAPbI3 and α-FAPbI3 (MA: methylammonium, FA: formamidinium). We report a complete set of elastic constants caracterized by a very soft shear

  6. Combustion synthesis and characterization of porous perovskite ...

    Indian Academy of Sciences (India)

    TECS

    But those perovskite-structural complex oxides produced via ... and cobalt nitrates in a desired molar ratio were dis- solved in a ... At pH 6-7 (ammonia adjustor), ... areas were measured by nitrogen adsorption-desorp- .... The obtained oxide.

  7. High performance magnetocaloric perovskites for magnetic refrigeration

    DEFF Research Database (Denmark)

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

    2012-01-01

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

  8. 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

  9. Hybrid solar cells : Perovskites under the Sun

    NARCIS (Netherlands)

    Loi, Maria Antonietta; Hummelen, Jan C.

    2013-01-01

    Mixed-halide organic–inorganic hybrid perovskites are reported to display electron–hole diffusion lengths over 1 μm. This observation provides important insight into the charge-carrier dynamics of this class of semiconductors and increases the expectations for highly efficient and cheap solar cells.

  10. Calculated optical absorption of different perovskite phases

    Energy Technology Data Exchange (ETDEWEB)

    Castelli, Ivano E. [Center for Atomic-scale Materials Design; Department of Physics; Technical University of Denmark; DK 2800, Kongens Lyngby; Denmark; Thygesen, Kristian S. [Center for Atomic-scale Materials Design; Department of Physics; Technical University of Denmark; DK 2800, Kongens Lyngby; Denmark; Jacobsen, Karsten W. [Center for Atomic-scale Materials Design; Department of Physics; Technical University of Denmark; DK 2800, Kongens Lyngby; Denmark

    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.

  11. Small polarons in 2D perovskites

    KAUST Repository

    Cortecchia, Daniele

    2017-11-02

    We demonstrate that white light luminescence in two-dimensional (2D) perovskites stems from photoinduced formation of small polarons confined at specific sites of the inorganic framework in the form of self-trapped electrons and holes. We discuss their application in white light emitting devices and X-ray scintillators.

  12. Small polarons in 2D perovskites

    KAUST Repository

    Cortecchia, Daniele; Yin, Jun; Birowosuto, Muhammad D.; Lo, Shu-Zee A.; Gurzadyan, Gagik G.; Bruno, Annalisa; Bredas, Jean-Luc; Soci, Cesare

    2017-01-01

    We demonstrate that white light luminescence in two-dimensional (2D) perovskites stems from photoinduced formation of small polarons confined at specific sites of the inorganic framework in the form of self-trapped electrons and holes. We discuss their application in white light emitting devices and X-ray scintillators.

  13. Spontaneous emission enhancement of colloidal perovskite nanocrystals

    Science.gov (United States)

    Yang, Zhili; Waks, Edo

    Halide perovskite semiconductors have emerged as prominent photovoltaic materials since their high conversion efficiency and promising light emitting materials in optoelectronics. In particular, easy-to-fabricated colloidal perovskite nanocrystals based on CsPbX3 quantum dots has been intensively investigated recently. Their luminescent wavelength could be tuned precisely by their chemical composition and size of growth. This opens new applications including light-emitting diodes, optical amplifiers and lasing since their promising performance as emitters. However, this potentially high-efficient emitter and gain material has not been fully investigated and realized in integrated photonic structures. Here we demonstrate Purcell enhancement effect of CsPbBr3 perovskite nanocrystals by coupling to an optimized photonic crystal nanobeam cavity as a first crucial step towards realization of integrated on-chip coherent light source with low energy consumption. We show clearly highly-enhanced photoluminescent spectrum and an averaged Purcell enhancement factor of 2.9 is achieved when they are coupled to nanobeam photonic crystal cavities compared to the ones on unpatterned surface in our lifetime measurement. Our success in enhancement of emission from CsPbX3 perovskite nanocrystals paves the way towards the realization of efficient light sources for integrated optoelectronic devices with low energy consumption.

  14. Monocrystalline halide perovskite nanostructures for optoelectronic applications

    NARCIS (Netherlands)

    Khoram, P.

    2018-01-01

    Halide perovskites are a promising class of materials for incorporation in optoelectronics with higher efficiency and lower cost. The solution processability of these materials provides unique opportunities for simple nanostructure fabrication. In the first half of the thesis (chapter 2 and 3) we

  15. Progress of MCFC stack technology at Toshiba

    Energy Technology Data Exchange (ETDEWEB)

    Hori, M.; Hayashi, T.; Shimizu, Y. [Toshiba Corp., Tokyo (Japan)

    1996-12-31

    Toshiba is working on the development of MCFC stack technology; improvement of cell characteristics, and establishment of separator technology. For the cell technology, Toshiba has concentrated on both the restraints of NiO cathode dissolution and electrolyte loss from cells, which are the critical issues to extend cell life in MCFC, and great progress has been made. On the other hand, recognizing that the separator is one of key elements in accomplishing reliable and cost-competitive MCFC stacks, Toshiba has been accelerating the technology establishment and verification of an advanced type separator. A sub-scale stack with such a separator was provided for an electric generating test, and has been operated for more than 10,000 hours. This paper presents several topics obtained through the technical activities in the MCFC field at Toshiba.

  16. Development of an Integrated Polymer Microfluidic Stack

    International Nuclear Information System (INIS)

    Datta, Proyag; Hammacher, Jens; Pease, Mark; Gurung, Sitanshu; Goettert, Jost

    2006-01-01

    Microfluidic is a field of considerable interest. While significant research has been carried out to develop microfluidic components, very little has been done to integrate the components into a complete working system. We present a flexible modular system platform that addresses the requirements of a complete microfluidic system. A microfluidic stack system is demonstrated with the layers of the stack being modular for specific functions. The stack and accompanying infrastructure provides an attractive platform for users to transition their design concepts into a working microfluidic system quickly with very little effort. The concept is demonstrated by using the system to carry out a chemilumiscence experiment. Details regarding the fabrication, assembly and experimental methods are presented

  17. Detailed Electrochemical Characterisation of Large SOFC Stacks

    DEFF Research Database (Denmark)

    Mosbæk, Rasmus Rode; Hjelm, Johan; Barfod, R.

    2012-01-01

    application of advanced methods for detailed electrochemical characterisation during operation. An operating stack is subject to steep compositional gradients in the gaseous reactant streams, and significant temperature gradients across each cell and across the stack, which makes it a complex system...... Fuel Cell A/S was characterised in detail using electrochemical impedance spectroscopy. An investigation of the optimal geometrical placement of the current probes and voltage probes was carried out in order to minimise measurement errors caused by stray impedances. Unwanted stray impedances...... are particularly problematic at high frequencies. Stray impedances may be caused by mutual inductance and stray capacitance in the geometrical set-up and do not describe the fuel cell. Three different stack geometries were investigated by electrochemical impedance spectroscopy. Impedance measurements were carried...

  18. High power, repetitive stacked Blumlein pulse generators

    Energy Technology Data Exchange (ETDEWEB)

    Davanloo, F; Borovina, D L; Korioth, J L; Krause, R K; Collins, C B [Univ. of Texas at Dallas, Richardson, TX (United States). Center for Quantum Electronics; Agee, F J [US Air Force Phillips Lab., Kirtland AFB, NM (United States); Kingsley, L E [US Army CECOM, Ft. Monmouth, NJ (United States)

    1997-12-31

    The repetitive stacked Blumlein pulse power generators developed at the University of Texas at Dallas consist of several triaxial Blumleins stacked in series at one end. The lines are charged in parallel and synchronously commuted with a single switch at the other end. In this way, relatively low charging voltages are multiplied to give a high discharge voltage across an arbitrary load. Extensive characterization of these novel pulsers have been performed over the past few years. Results indicate that they are capable of producing high power waveforms with rise times and repetition rates in the range of 0.5-50 ns and 1-300 Hz, respectively, using a conventional thyratron, spark gap, or photoconductive switch. The progress in the development and use of stacked Blumlein pulse generators is reviewed. The technology and the characteristics of these novel pulsers driving flash x-ray diodes are discussed. (author). 4 figs., 5 refs.

  19. Calculation of tritium release from reactor's stack

    International Nuclear Information System (INIS)

    Akhadi, M.

    1996-01-01

    Method for calculation of tritium release from nuclear to environment has been discussed. Part of gas effluent contain tritium in form of HTO vapor released from reactor's stack was sampled using silica-gel. The silica-gel was put in the water to withdraw HTO vapor absorbed by silica-gel. Tritium concentration in the water was measured by liquid scintillation counter of Aloka LSC-703. Tritium concentration in the gas effluent and total release of tritium from reactor's stack during certain interval time were calculated using simple mathematic formula. This method has examined for calculation of tritium release from JRR-3M's stack of JAERI, Japan. From the calculation it was obtained the value of tritium release as much as 4.63 x 10 11 Bq during one month. (author)

  20. Nonlinearly stacked low noise turbofan stator

    Science.gov (United States)

    Schuster, William B. (Inventor); Nolcheff, Nick A. (Inventor); Gunaraj, John A. (Inventor); Kontos, Karen B. (Inventor); Weir, Donald S. (Inventor)

    2009-01-01

    A nonlinearly stacked low noise turbofan stator vane having a characteristic curve that is characterized by a nonlinear sweep and a nonlinear lean is provided. The stator is in an axial fan or compressor turbomachinery stage that is comprised of a collection of vanes whose highly three-dimensional shape is selected to reduce rotor-stator and rotor-strut interaction noise while maintaining the aerodynamic and mechanical performance of the vane. The nonlinearly stacked low noise turbofan stator vane reduces noise associated with the fan stage of turbomachinery to improve environmental compatibility.

  1. Stack Monitoring System At PUSPATI TRIGA Reactor

    International Nuclear Information System (INIS)

    Zamrul Faizad Omar; Mohd Sabri Minhat; Zareen Khan Abdul Jalil Khan; Ridzuan Abdul Mutalib; Khairulezwan Abdul Manan; Nurfarhana Ayuni Joha; Izhar Abu Hussin

    2014-01-01

    This paper describes the current Stack Monitoring System at PUSPATI TRIGA Reactor (RTP) building. A stack monitoring system is a continuous air monitor placed at the reactor top for monitoring the presence of radioactive gaseous in the effluent air from the RTP building. The system consists of four detectors that provide the reading for background, particulate, Iodine and Noble gas. There is a plan to replace the current system due to frequent fault of the system, thus thorough understanding of the current system is required. Overview of the whole system will be explained in this paper. Some current results would be displayed and moving forward brief plan would be mentioned. (author)

  2. Polar-solvent-free colloidal synthesis of highly luminescent alkylammonium lead halide perovskite nanocrystals

    Science.gov (United States)

    Vybornyi, Oleh; Yakunin, Sergii; Kovalenko, Maksym V.

    2016-03-01

    A novel synthesis of hybrid organic-inorganic lead halide perovskite nanocrystals (CH3NH3PbX3, X = Br or I) that does not involve the use of dimethylformamide or other polar solvents is presented. The reaction between methylamine and PbX2 salts is conducted in a high-boiling nonpolar solvent (1-octadecene) in the presence of oleylamine and oleic acid as coordinating ligands. The resulting nanocrystals are characterized by high photoluminescence quantum efficiencies of 15-50%, outstanding phase purity and tunable shapes (nanocubes, nanowires, and nanoplatelets). Nanoplatelets spontaneously assemble into micrometer-length wires by face-to-face stacking. In addition, we demonstrate amplified spontaneous emission from thin films of green-emitting CH3NH3PbBr3 nanowires with low pumping thresholds of 3 μJ cm-2.A novel synthesis of hybrid organic-inorganic lead halide perovskite nanocrystals (CH3NH3PbX3, X = Br or I) that does not involve the use of dimethylformamide or other polar solvents is presented. The reaction between methylamine and PbX2 salts is conducted in a high-boiling nonpolar solvent (1-octadecene) in the presence of oleylamine and oleic acid as coordinating ligands. The resulting nanocrystals are characterized by high photoluminescence quantum efficiencies of 15-50%, outstanding phase purity and tunable shapes (nanocubes, nanowires, and nanoplatelets). Nanoplatelets spontaneously assemble into micrometer-length wires by face-to-face stacking. In addition, we demonstrate amplified spontaneous emission from thin films of green-emitting CH3NH3PbBr3 nanowires with low pumping thresholds of 3 μJ cm-2. Electronic supplementary information (ESI) available: Materials and methods, additional figures. See DOI: 10.1039/c5nr06890h

  3. 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.

  4. 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.

  5. 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.

  6. 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...

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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)

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

    Directory of Open Access Journals (Sweden)

    Viktor Fruth

    2010-09-01

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

  13. Stacked spheres and lower bound theorem

    Indian Academy of Sciences (India)

    BASUDEB DATTA

    2011-11-20

    Nov 20, 2011 ... Preliminaries. Lower bound theorem. On going work. Definitions. An n-simplex is a convex hull of n + 1 affinely independent points. (called vertices) in some Euclidean space R. N . Stacked spheres and lower bound theorem. Basudeb Datta. Indian Institute of Science. 2 / 27 ...

  14. Contemporary sample stacking in analytical electrophoresis

    Czech Academy of Sciences Publication Activity Database

    Šlampová, Andrea; Malá, Zdeňka; Pantůčková, Pavla; Gebauer, Petr; Boček, Petr

    2013-01-01

    Roč. 34, č. 1 (2013), s. 3-18 ISSN 0173-0835 R&D Projects: GA ČR GAP206/10/1219 Institutional support: RVO:68081715 Keywords : biological samples * stacking * trace analysis * zone electrophoresis Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.161, year: 2013

  15. SRS reactor stack plume marking tests

    International Nuclear Information System (INIS)

    Petry, S.F.

    1992-03-01

    Tests performed in 105-K in 1987 and 1988 demonstrated that the stack plume can successfully be made visible (i.e., marked) by introducing smoke into the stack breech. The ultimate objective of these tests is to provide a means during an emergency evacuation so that an evacuee can readily identify the stack plume and evacuate in the opposite direction, thus minimizing the potential of severe radiation exposure. The EPA has also requested DOE to arrange for more tests to settle a technical question involving the correct calculation of stack downwash. New test canisters were received in 1988 designed to produce more smoke per unit time; however, these canisters have not been evaluated, because normal ventilation conditions have not been reestablished in K Area. Meanwhile, both the authorization and procedure to conduct the tests have expired. The tests can be performed during normal reactor operation. It is recommended that appropriate authorization and procedure approval be obtained to resume testing after K Area restart

  16. Scaling the CERN OpenStack cloud

    Science.gov (United States)

    Bell, T.; Bompastor, B.; Bukowiec, S.; Castro Leon, J.; Denis, M. K.; van Eldik, J.; Fermin Lobo, M.; Fernandez Alvarez, L.; Fernandez Rodriguez, D.; Marino, A.; Moreira, B.; Noel, B.; Oulevey, T.; Takase, W.; Wiebalck, A.; Zilli, S.

    2015-12-01

    CERN has been running a production OpenStack cloud since July 2013 to support physics computing and infrastructure services for the site. In the past year, CERN Cloud Infrastructure has seen a constant increase in nodes, virtual machines, users and projects. This paper will present what has been done in order to make the CERN cloud infrastructure scale out.

  17. Stacking non-BPS D-branes

    International Nuclear Information System (INIS)

    Alberghi, Gian Luigi; Caceres, Elena; Goldstein, Kevin; Lowe, David A. . lowe@het.brown.edu

    2001-08-01

    We present a candidate supergravity solution for a stacked configuration of stable non-BPS D-branes in Type II string theory compactified on T 4 /Z 2 . This gives a supergravity description of nonabelian tachyon condensation on the brane woldvolume. (author)

  18. Trace interpolation by slant-stack migration

    International Nuclear Information System (INIS)

    Novotny, M.

    1990-01-01

    The slant-stack migration formula based on the radon transform is studied with respect to the depth steep Δz of wavefield extrapolation. It can be viewed as a generalized trace-interpolation procedure including wave extrapolation with an arbitrary step Δz. For Δz > 0 the formula yields the familiar plane-wave decomposition, while for Δz > 0 it provides a robust tool for migration transformation of spatially under sampled wavefields. Using the stationary phase method, it is shown that the slant-stack migration formula degenerates into the Rayleigh-Sommerfeld integral in the far-field approximation. Consequently, even a narrow slant-stack gather applied before the diffraction stack can significantly improve the representation of noisy data in the wavefield extrapolation process. The theory is applied to synthetic and field data to perform trace interpolation and dip reject filtration. The data examples presented prove that the radon interpolator works well in the dip range, including waves with mutual stepouts smaller than half the dominant period

  19. Contemporary sample stacking in analytical electrophoresis

    Czech Academy of Sciences Publication Activity Database

    Malá, Zdeňka; Šlampová, Andrea; Křivánková, Ludmila; Gebauer, Petr; Boček, Petr

    2015-01-01

    Roč. 36, č. 1 (2015), s. 15-35 ISSN 0173-0835 R&D Projects: GA ČR(CZ) GA13-05762S Institutional support: RVO:68081715 Keywords : biological samples * stacking * trace analysis * zone electrophoresis Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 2.482, year: 2015

  20. 40 CFR 61.53 - Stack sampling.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 8 2010-07-01 2010-07-01 false Stack sampling. 61.53 Section 61.53 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL... sampling. (a) Mercury ore processing facility. (1) Unless a waiver of emission testing is obtained under...

  1. 40 CFR 61.33 - Stack sampling.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 8 2010-07-01 2010-07-01 false Stack sampling. 61.33 Section 61.33 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL... sampling. (a) Unless a waiver of emission testing is obtained under § 61.13, each owner or operator...

  2. OpenStack cloud computing cookbook

    CERN Document Server

    Jackson, Kevin

    2013-01-01

    A Cookbook full of practical and applicable recipes that will enable you to use the full capabilities of OpenStack like never before.This book is aimed at system administrators and technical architects moving from a virtualized environment to cloud environments with familiarity of cloud computing platforms. Knowledge of virtualization and managing linux environments is expected.

  3. Toward advising SME's on stacked funding

    NARCIS (Netherlands)

    Rauwerda, Kirsten; van Teeffelen, Lex; de Graaf, Frank Jan

    2017-01-01

    This paper addresses new funding issues faced by SMEs. Over a period of nine months, the authors conducted a preliminary study into the problems surrounding stacked funding faced by SMEs and their financial advisers. The study includes a short literature review, the outcomes of three round table

  4. Photoswitchable Intramolecular H-Stacking of Perylenebisimide

    NARCIS (Netherlands)

    Wang, Jiaobing; Kulago, Artem; Browne, Wesley R.; Feringa, Ben L.

    2010-01-01

    Dynamic control over the formation of H- or J-type aggregates of chromophores is of fundamental importance for developing responsive organic optoelectronic materials. In this study, the first example of photoswitching between a nonstacked and an intramolecularly H-stacked arrangement of

  5. Optoelectronic interconnects for 3D wafer stacks

    Science.gov (United States)

    Ludwig, David; Carson, John C.; Lome, Louis S.

    1996-01-01

    Wafer and chip stacking are envisioned as means of providing increased processing power within the small confines of a three-dimensional structure. Optoelectronic devices can play an important role in these dense 3-D processing electronic packages in two ways. In pure electronic processing, optoelectronics can provide a method for increasing the number of input/output communication channels within the layers of the 3-D chip stack. Non-free space communication links allow the density of highly parallel input/output ports to increase dramatically over typical edge bus connections. In hybrid processors, where electronics and optics play a role in defining the computational algorithm, free space communication links are typically utilized for, among other reasons, the increased network link complexity which can be achieved. Free space optical interconnections provide bandwidths and interconnection complexity unobtainable in pure electrical interconnections. Stacked 3-D architectures can provide the electronics real estate and structure to deal with the increased bandwidth and global information provided by free space optical communications. This paper will provide definitions and examples of 3-D stacked architectures in optoelectronics processors. The benefits and issues of these technologies will be discussed.

  6. OpenStack Object Storage (Swift) essentials

    CERN Document Server

    Kapadia, Amar; Varma, Sreedhar

    2015-01-01

    If you are an IT administrator and you want to enter the world of cloud storage using OpenStack Swift, then this book is ideal for you. Basic knowledge of Linux and server technology is beneficial to get the most out of the book.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. Hexagonal perovskites with cationic vacancies. 32. Photoluminescence of trivalent rare earth in the systems Ba/sub 2-y/Sr/sub y/La/sub 2-x/RE/sub x/MgW/sub 2/vacantO/sub 12/

    Energy Technology Data Exchange (ETDEWEB)

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

    1982-06-01

    In the series Ba/sub 2-y/Sr/sub y/La/sub 2-x/RE/sub x/MgW/sub 2/vacantO/sub 12/ the Ba/sup 2 +/ can be completely substituted by Sr/sup 2 +/. All compounds crystallize in the rhombohedral 12 L-type (space group R-3m; sequence (hhcc)/sub 3/). By doping the stacking polytypes with some of the trivalent rare earths efficient visible photoluminescence is obtained. The simultaneous incorporation of two different rare earth ions leads to two-color-phosphors, which, according to the excitation energy used, emit either mainly the typical spectrum from one or the other activator; the corresponding luminescence mechanism are discussed.

  13. 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.

  14. Elastic softness of hybrid lead halide perovskites

    KAUST Repository

    Ferreira, A. C.

    2018-01-26

    Much recent attention has been devoted towards unravelling the microscopic optoelectronic properties of hybrid organic-inorganic perovskites (HOP). Here we investigate by coherent inelastic neutron scattering spectroscopy and Brillouin light scattering, low frequency acoustic phonons in four different hybrid perovskite single crystals: MAPbBr3, FAPbBr3, MAPbI3 and α-FAPbI3 (MA: methylammonium, FA: formamidinium). We report a complete set of elastic constants caracterized by a very soft shear modulus C44. Further, a tendency towards an incipient ferroelastic transition is observed in FAPbBr3. We observe a systematic lower sound group velocity in the technologically important iodide-based compounds compared to the bromide-based ones. The findings suggest that low thermal conductivity and hot phonon bottleneck phenomena are expected to be enhanced by low elastic stiffness, particularly in the case of the ultrasoft α-FAPbI3.

  15. Perovskite Materials: Solar Cell and Optoelectronic Applications

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Bin [ORNL; Geohegan, David B [ORNL; Xiao, Kai [ORNL

    2017-01-01

    Hybrid organometallic trihalide perovskites are promising candidates in the applications for next-generation, high-performance, low-cost optoelectronic devices, including photovoltaics, light emitting diodes, and photodetectors. Particularly, the solar cells based on this type of materials have reached 22% lab scale power conversion efficiency in only about seven years, comparable to the other thin film photovoltaic technologies. Hybrid perovskite materials not only exhibit superior optoelectronic properties, but also show many interesting physical properties such as ion migration and defect physics, which may allow the exploration of more device functionalities. In this article, the fundamental understanding of the interrelationships between crystal structure, electronic structure, and material properties is discussed. Various chemical synthesis and processing methods for superior device performance in solar cells and optoelectronic devices are reviewed.

  16. Project W-420 Stack Monitoring system upgrades conceptual design report

    International Nuclear Information System (INIS)

    TUCK, J.A.

    1998-01-01

    This document describes the scope, justification, conceptual design, and performance of Project W-420 stack monitoring system upgrades on six NESHAP-designated, Hanford Tank Farms ventilation exhaust stacks

  17. Project W-420 Stack Monitoring system upgrades conceptual design report

    Energy Technology Data Exchange (ETDEWEB)

    TUCK, J.A.

    1998-11-06

    This document describes the scope, justification, conceptual design, and performance of Project W-420 stack monitoring system upgrades on six NESHAP-designated, Hanford Tank Farms ventilation exhaust stacks.

  18. 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.

  19. Dynamics of photoinduced degradation of perovskite photovoltaics

    DEFF Research Database (Denmark)

    Khenkin, M. V.; Anoop, K. M.; Visoly-Fischer, I.

    2018-01-01

    The operational stability of perovskite solar cells (PSCs) remains a limiting factor in their commercial implementation. We studied the long-term outdoor stability of ITO/SnO2/Cs0.05((CH3NH3)0.15(CH(NH2)2)0.85)0.95PbI2.55Br0.45/spiro-OMeTAD/Au cells, as well as the dynamics of their degradation...

  20. Spatial Atmospheric Pressure Atomic Layer Deposition of Tin Oxide as an Impermeable Electron Extraction Layer for Perovskite Solar Cells with Enhanced Thermal Stability.

    Science.gov (United States)

    Hoffmann, Lukas; Brinkmann, Kai O; Malerczyk, Jessica; Rogalla, Detlef; Becker, Tim; Theirich, Detlef; Shutsko, Ivan; Görrn, Patrick; Riedl, Thomas

    2018-02-14

    Despite the notable success of hybrid halide perovskite-based solar cells, their long-term stability is still a key-issue. Aside from optimizing the photoactive perovskite, the cell design states a powerful lever to improve stability under various stress conditions. Dedicated electrically conductive diffusion barriers inside the cell stack, that counteract the ingress of moisture and prevent the migration of corrosive halogen species, can substantially improve ambient and thermal stability. Although atomic layer deposition (ALD) is excellently suited to prepare such functional layers, ALD suffers from the requirement of vacuum and only allows for a very limited throughput. Here, we demonstrate for the first time spatial ALD-grown SnO x at atmospheric pressure as impermeable electron extraction layers for perovskite solar cells. We achieve optical transmittance and electrical conductivity similar to those in SnO x grown by conventional vacuum-based ALD. A low deposition temperature of 80 °C and a high substrate speed of 2.4 m min -1 yield SnO x layers with a low water vapor transmission rate of ∼10 -4 gm -2 day -1 (at 60 °C/60% RH). Thereby, in perovskite solar cells, dense hybrid Al:ZnO/SnO x electron extraction layers are created that are the key for stable cell characteristics beyond 1000 h in ambient air and over 3000 h at 60 °C. Most notably, our work of introducing spatial ALD at atmospheric pressure paves the way to the future roll-to-roll manufacturing of stable perovskite solar cells.

  1. Magnetotransport in doped manganate perovskites (invited) (abstract)

    International Nuclear Information System (INIS)

    Sun, J.Z.; Krusin-Elbaum, L.; Gupta, A.; Xiao, G.; Duncombe, P.R.; Gallagher, W.J.; Parkin, S.S.

    1997-01-01

    Recent progress in oxide perovskite thin-film technology has led to the discovery of a large negative magnetoresistance at room temperature in the doped manganate perovskite thin films. For applications such as magnetic-field sensing, the saturation magnetic field for large magnetoresistance has to be significantly lowered. The magnetic and transport properties of the doped manganates involve a curious magnetic-field scale, on the order of 1 endash 10 T. Upon the application of a field on this scale, the magnetoresistance saturates, and a significant broadening of the temperature-dependent magnetization is seen. An understanding of the materials physics that underlie such behavior can point to new ways of lowering the saturation field in this class of materials. We argue that this characteristic field is suggestive of an inhomogeneous magnetic state in the system. We will discuss the basic phenomena and physics of magnetotransport in this class of materials. We will also report the successful fabrication of a trilayer thin-film pillar structure made using the doped manganate perovskites in which a magnetoresistance change by about a factor of 2 was observed at temperatures below 100 K in a field less than 200 Oe, proving that large magnetoresistance in low field can be obtained in these materials. copyright 1997 American Institute of Physics

  2. Modified titanate perovskites in photocatalytic water splitting

    Energy Technology Data Exchange (ETDEWEB)

    Wlodarczak, M.; Ludwiczak, M.; Laniecki, M. [A. Mickiewicz Univ. (Poland)

    2010-07-01

    Received materials have structure of perovskite, what was shown by XRD diffraction patterns. Perovskite structure is present in all samples with strontium, barium and one sample with calcium. Moreover, received barium and strontium titanate are very similar to pattern materials. XRD results show, that temperature 500 C is too low to create perovskite structure in CaTiO{sub 3}. However, it is high enough in case of SrTiO{sub 3} and BaTiO{sub 3}. One regularity is obvious, surface area increases for samples calcined in lower temperature. There is a connection between surface area and dispersion of platinum. Both of them reach the greatest value to the calcium titanate. Catalytic activity was shown by all of received samples. Measurable values were received to samples calcined in 700 C. Calcium titanate had the best catalytic activity, both an amount of hydrogen and a ratio of hydrogen to platinum. There is one regularity to all samples, the ration of hydrogen to platinum increase when amount of platinum decrease. (orig.)

  3. PbBr3 Perovskite Crystals

    KAUST Repository

    Wei, Tzu-Chiao

    2018-01-31

    Researchers have recently revealed that hybrid lead halide perovskites exhibit ferroelectricity, which is often associated with other physical characteristics, such as a large nonlinear optical response. In this work, the nonlinear optical properties of single crystal inorganic–organic hybrid perovskite CH3NH3PbBr3 are studied. By exciting the material with a 1044 nm laser, strong two-photon absorption-induced photoluminescence in the green spectral region is observed. Using the transmission open-aperture Z-scan technique, the values of the two-photon absorption coefficient are observed to be 8.5 cm GW−1, which is much higher than that of standard two-photon absorbing materials that are industrially used in nonlinear optical applications, such as lithium niobate (LiNbO3), LiTaO3, KTiOPO4, and KH2PO4. Such a strong two-photon absorption effect in CH3NH3PbBr3 can be used to modulate the spectral and spatial profiles of laser pulses, as well as to reduce noise, and can be used to strongly control the intensity of incident light. In this study, the superior optical limiting, pulse reshaping, and stabilization properties of CH3NH3PbBr3 are demonstrated, opening new applications for perovskites in nonlinear optics.

  4. Light-trapping in perovskite solar cells

    Directory of Open Access Journals (Sweden)

    Qing Guo Du

    2016-06-01

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

  5. 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

  6. Magnetic field effects in hybrid perovskite devices

    Science.gov (United States)

    Zhang, C.; Sun, D.; Sheng, C.-X.; Zhai, Y. X.; Mielczarek, K.; Zakhidov, A.; Vardeny, Z. V.

    2015-05-01

    Magnetic field effects have been a successful tool for studying carrier dynamics in organic semiconductors as the weak spin-orbit coupling in these materials gives rise to long spin relaxation times. As the spin-orbit coupling is strong in organic-inorganic hybrid perovskites, which are promising materials for photovoltaic and light-emitting applications, magnetic field effects are expected to be negligible in these optoelectronic devices. We measured significant magneto-photocurrent, magneto-electroluminescence and magneto-photoluminescence responses in hybrid perovskite devices and thin films, where the amplitude and shape are correlated to each other through the electron-hole lifetime, which depends on the perovskite film morphology. We attribute these responses to magnetic-field-induced spin-mixing of the photogenerated electron-hole pairs with different g-factors--the Δg model. We validate this model by measuring large Δg (~ 0.65) using field-induced circularly polarized photoluminescence, and electron-hole pair lifetime using picosecond pump-probe spectroscopy.

  7. Surface Restructuring of Hybrid Perovskite Crystals

    KAUST Repository

    Banavoth, Murali

    2016-11-07

    Hybrid perovskite crystals have emerged as an important class of semiconductors because of their remarkable performance in optoelectronics devices. The interface structure and chemistry of these crystals are key determinants of the device\\'s performance. Unfortunately, little is known about the intrinsic properties of the surfaces of perovskite materials because extrinsic effects, such as complex microstructures, processing conditions, and hydration under ambient conditions, are thought to cause resistive losses and high leakage current in solar cells. We reveal the intrinsic structural and optoelectronic properties of both pristinely cleaved and aged surfaces of single crystals. We identify surface restructuring on the aged surfaces (visualized on the atomic-scale by scanning tunneling microscopy) that lead to compositional and optical bandgap changes as well as degradation of carrier dynamics, photocurrent, and solar cell device performance. The insights reported herein clarify the key variables involved in the performance of perovskite-based solar cells and fabrication of high-quality surface single crystals, thus paving the way toward their future exploitation in highly efficient solar cells.

  8. Light-trapping in perovskite solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Du, Qing Guo, E-mail: duqi0001@e.ntu.edu.sg [Department of Physics, University of Toronto, 60 ST. George St., Toronto, Ontario, M5S 1A7 (Canada); Institute of High Performance Computing, A* STAR, Singapore, 138632 (Singapore); Shen, Guansheng [Department of Physics, University of Toronto, 60 ST. George St., Toronto, Ontario, M5S 1A7 (Canada); School of Information and Communication Engineering, Beijing University of Posts and Telecommunications, Beijing 100876 (China); John, Sajeev [Department of Physics, University of Toronto, 60 ST. George St., Toronto, Ontario, M5S 1A7 (Canada); Department of Physics, Soochow University, Suzhou (China)

    2016-06-15

    We numerically demonstrate enhanced light harvesting efficiency in both CH{sub 3}NH{sub 3}PbI{sub 3} and CH(NH{sub 2}){sub 2}PbI{sub 3}-based perovskite solar cells using inverted vertical-cone photonic-crystal nanostructures. For CH{sub 3}NH{sub 3}PbI{sub 3} perovskite solar cells, the maximum achievable photocurrent density (MAPD) reaches 25.1 mA/cm{sup 2}, corresponding to 92% of the total available photocurrent in the absorption range of 300 nm to 800 nm. Our cell shows 6% absorption enhancement compared to the Lambertian limit (23.7 mA/cm{sup 2}) and has a projected power conversion efficiency of 12.9%. Excellent solar absorption is numerically demonstrated over a broad angular range from 0 to 60 degree for both S- and P- polarizations. For the corresponding CH(NH{sub 2}){sub 2}PbI{sub 3} based perovskite solar cell, with absorption range of 300 nm to 850 nm, we find a MAPD of 29.1 mA/cm{sup 2}, corresponding to 95.4% of the total available photocurrent. The projected power conversion efficiency of the CH(NH{sub 2}){sub 2}PbI{sub 3} based photonic crystal solar cell is 23.4%, well above the current world record efficiency of 20.1%.

  9. Large polarons in lead halide perovskites

    Science.gov (United States)

    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− frameworks, irrespective of the cation type. The difference lies in the polaron formation time, which, in CH3NH3PbBr3 (0.3 ps), is less than half of that in CsPbBr3 (0.7 ps). First-principles calculations confirm large polaron formation, identify the Pb-Br-Pb deformation modes as responsible, and explain quantitatively the rate difference between CH3NH3PbBr3 and CsPbBr3. The findings reveal the general advantage of the soft [PbX3]− sublattice in charge carrier protection and suggest that there is likely no mechanistic limitations in using all-inorganic or mixed-cation lead halide perovskites to overcome instability problems and to tune the balance between charge carrier protection and mobility. PMID:28819647

  10. Lattice effects on ferromagnetism in perovskite ruthenates

    Science.gov (United States)

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

    2013-01-01

    Ferromagnetism and its evolution in the orthorhombic perovskite system Sr1–xCaxRuO3 have been widely believed to correlate with structural distortion. The recent development of high-pressure synthesis of the Ba-substituted Sr1–yBayRuO3 makes it possible to study ferromagnetism over a broader phase diagram, which includes the orthorhombic Imma and the cubic phases. However, the chemical substitutions introduce the A-site disorder effect on Tc, which complicates determination of the relationship between ferromagnetism and structural distortion. By clarifying the site disorder effect on Tc in several unique series of ruthenates in which the average bond length 〈A–O〉 remains the same but the bond-length variance varies, we are able to demonstrate a parabolic curve of Tc versus mean bond length 〈A–O〉. A much higher Tc ∼ 177 K than that found in orthorhombic SrRuO3 can be obtained from the curve at a bond length 〈A–O〉, which makes the geometric factor t = 〈A–O〉/(√2〈Ru–O〉) ∼ 1. This result reveals not only that the ferromagnetism in the ruthenates is extremely sensitive to the lattice strain, but also that it has an important implication for exploring the structure–property relationship in a broad range of oxides with perovskite or a perovskite-related structure. PMID:23904477

  11. Multistage Force Amplification of Piezoelectric Stacks

    Science.gov (United States)

    Xu, Tian-Bing (Inventor); Siochi, Emilie J. (Inventor); Zuo, Lei (Inventor); Jiang, Xiaoning (Inventor); Kang, Jin Ho (Inventor)

    2015-01-01

    Embodiments of the disclosure include an apparatus and methods for using a piezoelectric device, that includes an outer flextensional casing, a first cell and a last cell serially coupled to each other and coupled to the outer flextensional casing such that each cell having a flextensional cell structure and each cell receives an input force and provides an output force that is amplified based on the input force. The apparatus further includes a piezoelectric stack coupled to each cell such that the piezoelectric stack of each cell provides piezoelectric energy based on the output force for each cell. Further, the last cell receives an input force that is the output force from the first cell and the last cell provides an output apparatus force In addition, the piezoelectric energy harvested is based on the output apparatus force. Moreover, the apparatus provides displacement based on the output apparatus force.

  12. Radiation-Tolerant Intelligent Memory Stack - RTIMS

    Science.gov (United States)

    Ng, Tak-kwong; Herath, Jeffrey A.

    2011-01-01

    This innovation provides reconfigurable circuitry and 2-Gb of error-corrected or 1-Gb of triple-redundant digital memory in a small package. RTIMS uses circuit stacking of heterogeneous components and radiation shielding technologies. A reprogrammable field-programmable gate array (FPGA), six synchronous dynamic random access memories, linear regulator, and the radiation mitigation circuits are stacked into a module of 42.7 42.7 13 mm. Triple module redundancy, current limiting, configuration scrubbing, and single- event function interrupt detection are employed to mitigate radiation effects. The novel self-scrubbing and single event functional interrupt (SEFI) detection allows a relatively soft FPGA to become radiation tolerant without external scrubbing and monitoring hardware

  13. Development of on-site PAFC stacks

    Energy Technology Data Exchange (ETDEWEB)

    Hotta, K.; Matsumoto, Y. [Kansai Electric Power Co., Amagasaki (Japan); Horiuchi, H.; Ohtani, T. [Mitsubishi Electric Corp., Kobe (Japan)

    1996-12-31

    PAFC (Phosphoric Acid Fuel Cell) has been researched for commercial use and demonstration plants have been installed in various sites. However, PAFC don`t have a enough stability yet, so more research and development must be required in the future. Especially, cell stack needs a proper state of three phases (liquid, gas and solid) interface. It is very difficult technology to keep this condition for a long time. In the small size cell with the electrode area of 100 cm{sup 2}, gas flow and temperature distributions show uniformity. But in the large size cell with the electrode area of 4000 cm{sup 2}, the temperature distributions show non-uniformity. These distributions would cause to be shorten the cell life. Because these distributions make hot-spot and gas poverty in limited parts. So we inserted thermocouples in short-stack for measuring three-dimensional temperature distributions and observed effects of current density and gas utilization on temperature.

  14. System for inspection of stacked cargo containers

    Science.gov (United States)

    Derenzo, Stephen [Pinole, CA

    2011-08-16

    The present invention relates to a system for inspection of stacked cargo containers. One embodiment of the invention generally comprises a plurality of stacked cargo containers arranged in rows or tiers, each container having a top, a bottom a first side, a second side, a front end, and a back end; a plurality of spacers arranged in rows or tiers; one or more mobile inspection devices for inspecting the cargo containers, wherein the one or more inspection devices are removeably disposed within the spacers, the inspection means configured to move through the spacers to detect radiation within the containers. The invented system can also be configured to inspect the cargo containers for a variety of other potentially hazardous materials including but not limited to explosive and chemical threats.

  15. Industrial stacks design; Diseno de chimeneas industriales

    Energy Technology Data Exchange (ETDEWEB)

    Cacheux, Luis [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1987-12-31

    The Instituto de Investigaciones Electricas (IIE) though its Civil Works Department, develops, under contract with CFE`s Gerencia de Proyectos Termoelectricos (Management of Fossil Power Plant Projects), a series of methods for the design of stacks, which pretends to solve the a present day problem: the stack design of the fossil power plants that will go into operation during the next coming years in the country. [Espanol] El Instituto de Investigaciones Electricas (IIE), a traves del Departamento de Ingenieria Civil, desarrolla, bajo contrato con la Gerencia de Proyectos Termoelectricos, de la Comision Federal de Electricidad (CFE), un conjunto de metodos para el diseno de chimeneas, con el que se pretende resolver un problema inmediato: el diseno de las chimeneas de las centrales termoelectricas que entraran en operacion durante los proximos anos, en el pais.

  16. Absorption spectra of AA-stacked graphite

    International Nuclear Information System (INIS)

    Chiu, C W; Lee, S H; Chen, S C; Lin, M F; Shyu, F L

    2010-01-01

    AA-stacked graphite shows strong anisotropy in geometric structures and velocity matrix elements. However, the absorption spectra are isotropic for the polarization vector on the graphene plane. The spectra exhibit one prominent plateau at middle energy and one shoulder structure at lower energy. These structures directly reflect the unique geometric and band structures and provide sufficient information for experimental fitting of the intralayer and interlayer atomic interactions. On the other hand, monolayer graphene shows a sharp absorption peak but no shoulder structure; AA-stacked bilayer graphene has two absorption peaks at middle energy and abruptly vanishes at lower energy. Furthermore, the isotropic features are expected to exist in other graphene-related systems. The calculated results and the predicted atomic interactions could be verified by optical measurements.

  17. Industrial stacks design; Diseno de chimeneas industriales

    Energy Technology Data Exchange (ETDEWEB)

    Cacheux, Luis [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1986-12-31

    The Instituto de Investigaciones Electricas (IIE) though its Civil Works Department, develops, under contract with CFE`s Gerencia de Proyectos Termoelectricos (Management of Fossil Power Plant Projects), a series of methods for the design of stacks, which pretends to solve the a present day problem: the stack design of the fossil power plants that will go into operation during the next coming years in the country. [Espanol] El Instituto de Investigaciones Electricas (IIE), a traves del Departamento de Ingenieria Civil, desarrolla, bajo contrato con la Gerencia de Proyectos Termoelectricos, de la Comision Federal de Electricidad (CFE), un conjunto de metodos para el diseno de chimeneas, con el que se pretende resolver un problema inmediato: el diseno de las chimeneas de las centrales termoelectricas que entraran en operacion durante los proximos anos, en el pais.

  18. 400 W High Temperature PEM Fuel Cell Stack Test

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen

    2006-01-01

    This work demonstrates the operation of a 30 cell high temperature PEM (HTPEM) fuel cell stack. This prototype stack has been developed at the Institute of Energy Technology, Aalborg University, as a proof-of-concept for a low pressure cathode air cooled HTPEM stack. The membranes used are Celtec...

  19. Role of stacking disorder in ice nucleation.

    Science.gov (United States)

    Lupi, Laura; Hudait, Arpa; Peters, Baron; Grünwald, Michael; Gotchy Mullen, Ryan; Nguyen, Andrew H; Molinero, Valeria

    2017-11-08

    The freezing of water affects the processes that determine Earth's climate. Therefore, accurate weather and climate forecasts hinge on good predictions of ice nucleation rates. Such rate predictions are based on extrapolations using classical nucleation theory, which assumes that the structure of nanometre-sized ice crystallites corresponds to that of hexagonal ice, the thermodynamically stable form of bulk ice. However, simulations with various water models find that ice nucleated and grown under atmospheric temperatures is at all sizes stacking-disordered, consisting of random sequences of cubic and hexagonal ice layers. This implies that stacking-disordered ice crystallites either are more stable than hexagonal ice crystallites or form because of non-equilibrium dynamical effects. Both scenarios challenge central tenets of classical nucleation theory. Here we use rare-event sampling and free energy calculations with the mW water model to show that the entropy of mixing cubic and hexagonal layers makes stacking-disordered ice the stable phase for crystallites up to a size of at least 100,000 molecules. We find that stacking-disordered critical crystallites at 230 kelvin are about 14 kilojoules per mole of crystallite more stable than hexagonal crystallites, making their ice nucleation rates more than three orders of magnitude higher than predicted by classical nucleation theory. This effect on nucleation rates is temperature dependent, being the most pronounced at the warmest conditions, and should affect the modelling of cloud formation and ice particle numbers, which are very sensitive to the temperature dependence of ice nucleation rates. We conclude that classical nucleation theory needs to be corrected to include the dependence of the crystallization driving force on the size of the ice crystallite when interpreting and extrapolating ice nucleation rates from experimental laboratory conditions to the temperatures that occur in clouds.

  20. A Late Pleistocene sea level stack

    OpenAIRE

    Spratt Rachel M; Lisiecki Lorraine E

    2016-01-01

    Late Pleistocene sea level has been reconstructed from ocean sediment core data using a wide variety of proxies and models. However, the accuracy of individual reconstructions is limited by measurement error, local variations in salinity and temperature, and assumptions particular to each technique. Here we present a sea level stack (average) which increases the signal-to-noise ratio of individual reconstructions. Specifically, we perform principal componen...

  1. CAM and stack air sampler design guide

    International Nuclear Information System (INIS)

    Phillips, T.D.

    1994-01-01

    About 128 air samplers and CAMs presently in service to detect and document potential radioactive release from 'H' and 'F' area tank farm ventilation stacks are scheduled for replacement and/or upgrade by Projects S-5764, S-2081, S-3603, and S-4516. The seven CAMs scheduled to be upgraded by Project S-4516 during 1995 are expected to provide valuable experience for the three remaining projects. The attached document provides design guidance for the standardized High Level Waste air sampling system

  2. Extended Life PZT Stack Test Fixture

    Science.gov (United States)

    Badescu, Mircea; Sherrit, S.; Bao, X.; Aldrich, J.; Bar-Cohen, Y.; Jones, C.

    2009-01-01

    Piezoelectric stacks are being sought to be used as actuators for precision positioning and deployment of mechanisms in future planetary missions. Beside the requirement for very high operation reliability, these actuators are required for operation at space environments that are considered harsh compared to normal terrestrial conditions.These environmental conditions include low and high temperatures and vacuum or high pressure. Additionally, the stacks are subjected to high stress and in some applications need to operate with a very long lifetime durability.Many of these requirements are beyond the current industry design margins for nominal terrestrial applications. In order to investigate some of the properties that will indicate the durability of such actuators and their limitations we have developed a new type of test fixture that can be easily integrated in various test chambers for simulating environmental conditions, can provide access for multiple measurements while being exposed to adjustable stress levels. We designed and built two test fixtures and these fixtures were made to be adjustable for testing stacks with different dimensions and can be easily used in small or large numbers. The properties that were measured using these fixtures include impedance, capacitance, dielectric loss factor, leakage current, displacement, breakdown voltage, and lifetime performance. The fixtures characteristics and the test capabilities are presented in this paper.

  3. Electrochemical Detection in Stacked Paper Networks.

    Science.gov (United States)

    Liu, Xiyuan; Lillehoj, Peter B

    2015-08-01

    Paper-based electrochemical biosensors are a promising technology that enables rapid, quantitative measurements on an inexpensive platform. However, the control of liquids in paper networks is generally limited to a single sample delivery step. Here, we propose a simple method to automate the loading and delivery of liquid samples to sensing electrodes on paper networks by stacking multiple layers of paper. Using these stacked paper devices (SPDs), we demonstrate a unique strategy to fully immerse planar electrodes by aqueous liquids via capillary flow. Amperometric measurements of xanthine oxidase revealed that electrochemical sensors on four-layer SPDs generated detection signals up to 75% higher compared with those on single-layer paper devices. Furthermore, measurements could be performed with minimal user involvement and completed within 30 min. Due to its simplicity, enhanced automation, and capability for quantitative measurements, stacked paper electrochemical biosensors can be useful tools for point-of-care testing in resource-limited settings. © 2015 Society for Laboratory Automation and Screening.

  4. 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

  5. Progress, challenges and perspectives in flexible perovskite solar cells

    NARCIS (Netherlands)

    Di Giacomo, F.; Fakharuddin, A.; Jose, R.; Brown, T.M.

    2016-01-01

    Perovskite solar cells have attracted enormous interest since their discovery only a few years ago because they are able to combine the benefits of high efficiency and remarkable ease of processing over large areas. Whereas most of research has been carried out on glass, perovskite deposition and

  6. On the luminescence of perovskite type rare earth gallates

    International Nuclear Information System (INIS)

    Jianmei, Y.; Qingyuan, W.; Shuzhen, L.; Lianren, S.; Mingyu, C.

    1985-01-01

    It has been reported that perovskite type lanthanum gallates may be a good host material for laser and luminescence, but in the rare earth gallates studied, the numbers of perovskite type are less than that of the garnet type and there is less report on their spectroscopic properties in the literature. In this paper synthesis and spectroscopic properties of these compounds are studied

  7. 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...

  8. Temperature Dependent Charge Carrier Dynamics in Formamidinium Lead Iodide Perovskite

    NARCIS (Netherlands)

    Gelvez Rueda, M.C.; Renaud, N.; Grozema, F.C.

    2017-01-01

    The fundamental opto-electronic properties of organic-inorganic hybrid perovskites are strongly affected by their structural parameters. These parameters are particularly critical in formamidinium lead iodide (FAPbI3), in which its large structural disorder leads to a non-perovskite

  9. NREL Research Pushes Perovskites Closer to Market | News | NREL

    Science.gov (United States)

    even get close-to the above-20% efficiencies dominated by silicon solar panels. NREL researcher Kai Zhu ; Perovskites have a couple of major benefits over silicon solar panels. The silicon technology requires a high as excellent semiconductors. This means perovskite panels are more flexible than rigid silicon panels

  10. 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.

  11. 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 .

  12. 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.

  13. 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.

  14. 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

  15. Guanine base stacking in G-quadruplex nucleic acids

    Science.gov (United States)

    Lech, Christopher Jacques; Heddi, Brahim; Phan, Anh Tuân

    2013-01-01

    G-quadruplexes constitute a class of nucleic acid structures defined by stacked guanine tetrads (or G-tetrads) with guanine bases from neighboring tetrads stacking with one another within the G-tetrad core. Individual G-quadruplexes can also stack with one another at their G-tetrad interface leading to higher-order structures as observed in telomeric repeat-containing DNA and RNA. In this study, we investigate how guanine base stacking influences the stability of G-quadruplexes and their stacked higher-order structures. A structural survey of the Protein Data Bank is conducted to characterize experimentally observed guanine base stacking geometries within the core of G-quadruplexes and at the interface between stacked G-quadruplex structures. We couple this survey with a systematic computational examination of stacked G-tetrad energy landscapes using quantum mechanical computations. Energy calculations of stacked G-tetrads reveal large energy differences of up to 12 kcal/mol between experimentally observed geometries at the interface of stacked G-quadruplexes. Energy landscapes are also computed using an AMBER molecular mechanics description of stacking energy and are shown to agree quite well with quantum mechanical calculated landscapes. Molecular dynamics simulations provide a structural explanation for the experimentally observed preference of parallel G-quadruplexes to stack in a 5′–5′ manner based on different accessible tetrad stacking modes at the stacking interfaces of 5′–5′ and 3′–3′ stacked G-quadruplexes. PMID:23268444

  16. 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)

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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...

  6. 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. [...

  7. 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.

  8. 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

  9. 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.

  10. Dynamic Model of High Temperature PEM Fuel Cell Stack Temperature

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen

    2007-01-01

    cathode air cooled 30 cell HTPEM fuel cell stack developed at the Institute of Energy Technology at Aalborg University. This fuel cell stack uses PEMEAS Celtec P-1000 membranes, runs on pure hydrogen in a dead end anode configuration with a purge valve. The cooling of the stack is managed by running......The present work involves the development of a model for predicting the dynamic temperature of a high temperature PEM (HTPEM) fuel cell stack. The model is developed to test different thermal control strategies before implementing them in the actual system. The test system consists of a prototype...... the stack at a high stoichiometric air flow. This is possible because of the PBI fuel cell membranes used, and the very low pressure drop in the stack. The model consists of a discrete thermal model dividing the stack into three parts: inlet, middle and end and predicting the temperatures in these three...

  11. 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.

  12. NSF tandem stack support structure deflection characteristics

    International Nuclear Information System (INIS)

    Cook, J.

    1979-12-01

    Results are reported of load tests carried out on the glass legs of the insulating stack of the 30 MV tandem Van de Graaff accelerator now under construction at Daresbury Laboratory. The tests to investigate the vulnerability of the legs when subjected to tensile stresses were designed to; establish the angle of rotation of the pads from which the stresses in the glass legs may be calculated, proof-test the structure and at the same time reveal any asymmetry in pad rotations or deflections, and to confirm the validity of the computer design analysis. (UK)

  13. Compliant Glass Seals for SOFC Stacks

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Yeong -Shyung [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Choi, Jung-Pyung [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Xu, Wei [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Stephens, Elizabeth V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Koeppel, Brian J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Stevenson, Jeffry W. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lara-Curzio, Edgar [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2014-04-30

    This report summarizes results from experimental and modeling studies performed by participants in the Solid-State Energy Conversion Alliance (SECA) Core Technology Program, which indicate that compliant glass-based seals offer a number of potential advantages over conventional seals based on de-vitrifying glasses, including reduced stresses during stack operation and thermal cycling, and the ability to heal micro-damage induced during thermal cycling. The properties and composition of glasses developed and/or investigated in these studies are reported, along with results from long-term (up to 5,800h) evaluations of seals based on a compliant glass containing ceramic particles or ceramic fibers.

  14. Improved Direct Methanol Fuel Cell Stack

    Science.gov (United States)

    Wilson, Mahlon S.; Ramsey, John C.

    2005-03-08

    A stack of direct methanol fuel cells exhibiting a circular footprint. A cathode and anode manifold, tie-bolt penetrations and tie-bolts are located within the circular footprint. Each fuel cell uses two graphite-based plates. One plate includes a cathode active area that is defined by serpentine channels connecting the inlet and outlet cathode manifold. The other plate includes an anode active area defined by serpentine channels connecting the inlet and outlet of the anode manifold, where the serpentine channels of the anode are orthogonal to the serpentine channels of the cathode. Located between the two plates is the fuel cell active region.

  15. Displacive phase transformations and generalized stacking faults

    Czech Academy of Sciences Publication Activity Database

    Paidar, Václav; Ostapovets, Andriy; Duparc, O. H.; Khalfallah, O.

    2012-01-01

    Roč. 122, č. 3 (2012), s. 490-492 ISSN 0587-4246. [International Symposium on Physics of Materials, ISPMA /12./. Praha, 04.09.2011-08.09.2011] R&D Projects: GA AV ČR IAA100100920 Institutional research plan: CEZ:AV0Z10100520 Keywords : ab-initio calculations * close-packed structures * generalized stacking faults * homogeneous deformation * lattice deformation * many-body potentials Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.531, year: 2012

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Properties of perovskites and other oxides

    CERN Document Server

    Müller, K Alex

    2010-01-01

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

  2. Superconductivity in multilayer perovskite. Weak coupling analysis

    International Nuclear Information System (INIS)

    Koikegami, Shigeru; Yanagisawa, Takashi

    2006-01-01

    We investigate the superconductivity of a three-dimensional d-p model with a multilayer perovskite structure on the basis of the second-order perturbation theory within the weak coupling framework. Our model has been designed with multilayer high-T c superconducting cuprates in mind. In our model, multiple Fermi surfaces appear, and the component of a superconducting gap function develops on each band. We have found that the multilayer structure can stabilize the superconductivity in a wide doping range. (author)

  3. 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.

  4. 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)

  5. Computerized plutonium laboratory-stack monitoring system

    International Nuclear Information System (INIS)

    Stafford, R.G.; DeVore, R.K.

    1977-01-01

    The Los Alamos Scientific Laboratory has recently designed and constructed a Plutonium Research and Development Facility to meet design criteria imposed by the United States Energy Research and Development Administration. A primary objective of the design criteria is to assure environmental protection and to reliably monitor plutonium effluent via the ventilation exhaust systems. A state-of-the-art facility exhaust air monitoring system is described which establishes near ideal conditions for evaluating plutonium activity in the stack effluent. Total and static pressure sensing manifolds are incorporated to measure average velocity and integrated total discharge air volume. These data are logged at a computer which receives instrument data through a multiplex scanning system. A multipoint isokinetic sampling assembly with associated instrumentation is described. Continuous air monitors have been designed to sample from the isokinetic sampling assembly and transmit both instantaneous and integrated stack effluent concentration data to the computer and various cathode ray tube displays. The continuous air monitors also serve as room air monitors in the plutonium facility with the primary objective of timely evacuation of personnel if an above tolerance airborne plutonium concentration is detected. Several continuous air monitors are incorporated in the ventilation system to assist in identification of release problem areas

  6. Control of heteroepitaxial stacking by substrate miscut

    International Nuclear Information System (INIS)

    Bonham, S.W.; Flynn, C.P.

    1998-01-01

    We report studies of fcc epitaxial crystals, grown on Nb(110), in which the Nb surface offers a template for selection between the two alternative stackings, ABCA hor-ellipsis and ACBA hor-ellipsis of the fcc close-packed planes. The Nb templates were grown epitaxially about 500 Angstrom thick on sapphire (11 bar 20), and the fcc material studied was Cu 3 Au. From symmetry it is not possible for the perfect bcc (110) surface to cause any such selection, which is here attributed instead to vicinal miscut: the logarithm of the stacking ratio must be even in miscut along [001] and odd in miscut along [1 bar 10]. We find that the measured selectivity is small for miscuts less than about 0.5 degree, but approaches a factor 10 3 for miscuts along [1 bar 10] greater than about 1 degree. A mechanism for the selection process is discussed in terms of fingered mesostructures that grow on Nb(110) in this regime, as observed first by Zhou, Bonham, and Flynn. copyright 1998 The American Physical Society

  7. Generalized stacking fault energies of alloys.

    Science.gov (United States)

    Li, Wei; Lu, Song; Hu, Qing-Miao; Kwon, Se Kyun; Johansson, Börje; Vitos, Levente

    2014-07-02

    The generalized stacking fault energy (γ surface) provides fundamental physics for understanding the plastic deformation mechanisms. Using the ab initio exact muffin-tin orbitals method in combination with the coherent potential approximation, we calculate the γ surface for the disordered Cu-Al, Cu-Zn, Cu-Ga, Cu-Ni, Pd-Ag and Pd-Au alloys. Studying the effect of segregation of the solute to the stacking fault planes shows that only the local chemical composition affects the γ surface. The calculated alloying trends are discussed using the electronic band structure of the base and distorted alloys.Based on our γ surface results, we demonstrate that the previous revealed 'universal scaling law' between the intrinsic energy barriers (IEBs) is well obeyed in random solid solutions. This greatly simplifies the calculations of the twinning measure parameters or the critical twinning stress. Adopting two twinnability measure parameters derived from the IEBs, we find that in binary Cu alloys, Al, Zn and Ga increase the twinnability, while Ni decreases it. Aluminum and gallium yield similar effects on the twinnability.

  8. 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.

  9. Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain.

    Science.gov (United States)

    Zhang, Wenrui; Li, Mingtao; Chen, Aiping; Li, Leigang; Zhu, Yuanyuan; Xia, Zhenhai; Lu, Ping; Boullay, Philippe; Wu, Lijun; Zhu, Yimei; MacManus-Driscoll, Judith L; Jia, Quanxi; Zhou, Honghui; Narayan, Jagdish; Zhang, Xinghang; Wang, Haiyan

    2016-07-06

    Study of layered complex oxides emerge as one of leading topics in fundamental materials science because of the strong interplay among intrinsic charge, spin, orbital, and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials that exhibit new phenomena beyond their conventional forms. Here, we report a strain-driven self-assembly of bismuth-based supercell (SC) with a two-dimensional (2D) layered structure. With combined experimental analysis and first-principles calculations, we investigated the full SC structure and elucidated the fundamental growth mechanism achieved by the strain-enabled self-assembled atomic layer stacking. The unique SC structure exhibits room-temperature ferroelectricity, enhanced magnetic responses, and a distinct optical bandgap from the conventional double perovskite structure. This study reveals the important role of interfacial strain modulation and atomic rearrangement in self-assembling a layered singe-phase multiferroic thin film, which opens up a promising avenue in the search for and design of novel 2D layered complex oxides with enormous promise.

  10. CH(3)NH(3)PbI(3) perovskite / silicon tandem solar cells: characterization based optical simulations.

    Science.gov (United States)

    Filipič, Miha; Löper, Philipp; Niesen, Bjoern; De Wolf, Stefaan; Krč, Janez; Ballif, Christophe; Topič, Marko

    2015-04-06

    In this study we analyze and discuss the optical properties of various tandem architectures: mechanically stacked (four-terminal) and monolithically integrated (two-terminal) tandem devices, consisting of a methyl ammonium lead triiodide (CH(3)NH(3)PbI(3)) perovskite top solar cell and a crystalline silicon bottom solar cell. We provide layer thickness optimization guidelines and give estimates of the maximum tandem efficiencies based on state-of-the-art sub cells. We use experimental complex refractive index spectra for all involved materials as input data for an in-house developed optical simulator CROWM. Our characterization based simulations forecast that with optimized layer thicknesses the four-terminal configuration enables efficiencies over 30%, well above the current single-junction crystalline silicon cell record of 25.6%. Efficiencies over 30% can also be achieved with a two-terminal monolithic integration of the sub-cells, combined with proper selection of layer thicknesses.

  11. Shear response of Fe-bearing MgSiO3 post-perovskite at lower mantle pressures

    Science.gov (United States)

    METSUE, Arnaud; TSUCHIYA, Taku

    2013-01-01

    We investigate the shear response of possible slip systems activated in pure and Fe-bearing MgSiO3 post-perovskite (PPv) through ab initio generalized stacking fault (GSF) energy calculations. Here we show that the [100](001) slip system has the easiest response to plastic shear among ten possible slip systems investigated. Incorporation of Fe2+ decreases the strength of all slip systems but does not change the plastic anisotropy style. Therefore, pure and Fe-bearing MgSiO3 PPv should demonstrate similar LPO patterns with a strong signature of the [100](001) slip system. An aggregate with this deformation texture is expected to produce a VSH > VSV type polarization anisotropy, being consistent with seismological observations. PMID:23318681

  12. Up-scaling perovskite solar cell manufacturing from sheet-to-sheet to roll-to-roll: challenges and solutions

    Science.gov (United States)

    Di Giacomo, Francesco; Galagan, Yulia; Shanmugam, Santhosh; Gorter, Harrie; van den Bruele, Fieke; Kirchner, Gerwin; de Vries, Ike; Fledderus, Henri; Lifka, Herbert; Veenstra, Sjoerd; Aernouts, Tom; Groen, Pim; Andrissen, Ronn

    2017-08-01

    Organometallic halide perovskite solar cells (PSCs) are extremely promising novel materials for thin-film photovoltaics, exhibiting efficiencies over 22% on glass and over 17% on foil 1, 2 . First, a sheet-to-sheet (S2S) production of PSCs and modules on 152x152 mm2 substrates was established, using a combination of sputtering, e-beam evaporation, slot die coating and thermal evaporation (average PCE of 14.6 +/- 1.3 % over 64 devices, more than 10% initial PCE on modules). Later the steps towards a roll-to-roll production will be investigated, starting from the optimization of the stack to make it compatible with a faster production at low temperature. A water based SnOx nanoparticles dispersion was used as solution processable ETL, and the deposition process was scaled-up from spin coating to R2R slot die coating on a 300 mm wide roll of PET/ITO. R2R production is often carried out in ambient atmosphere and involve the use of large volumes of materials, thus a first point is the development of a green solvent and precursor system for the perovskite layer to prevent the emission of toxic compound in the environment. The first results on device fabrication are encouraging, which allow partial R2R manufacturing of flexible PSC (R2R coating of SnOx and perovskite, S2S for Spiro-OMeTAD and gold) with stabilized PCE of 12.6%, a remarkable value for these novel devices. This result can be considered an important milestone towards the production of efficient, low cost, lightweight, flexible PSC on large area.

  13. Amorphous Tin Oxide as a Low-Temperature-Processed Electron-Transport Layer for Organic and Hybrid Perovskite Solar Cells

    KAUST Repository

    Barbe, Jeremy

    2017-02-08

    Chemical bath deposition (CBD) of tin oxide (SnO) thin films as an electron-transport layer (ETL) in a planar-heterojunction n-i-p organohalide lead perovskite and organic bulk-heterojunction (BHJ) solar cells is reported. The amorphous SnO (a-SnO) films are grown from a nontoxic aqueous bath of tin chloride at a very low temperature (55 °C) and do not require postannealing treatment to work very effectively as an ETL in a planar-heterojunction n-i-p organohalide lead perovskite or organic BHJ solar cells, in lieu of the commonly used ETL materials titanium oxide (TiO) and zinc oxide (ZnO), respectively. Ultraviolet photoelectron spectroscopy measurements on the glass/indium-tin oxide (ITO)/SnO/methylammonium lead iodide (MAPbI)/2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene device stack indicate that extraction of photogenerated electrons is facilitated by a perfect alignment of the conduction bands at the SnO/MAPbI interface, while the deep valence band of SnO ensures strong hole-blocking properties. Despite exhibiting very low electron mobility, the excellent interfacial energetics combined with high transparency (E > 4 eV) and uniform substrate coverage make the a-SnO ETL prepared by CBD an excellent candidate for the potentially low-cost and large-scale fabrication of organohalide lead perovskite and organic photovoltaics.

  14. Description of gasket failure in a 7 cell PEMFC stack

    Energy Technology Data Exchange (ETDEWEB)

    Husar, Attila; Serra, Maria [Institut de Robotica i Informatica Industrial, Parc Tecnologic de Barcelona, Edifici U, C. Llorens i Artigas, 4-6, 2a Planta, 08028 Barcelona (Spain); Kunusch, Cristian [Laboratorio de Electronica Industrial Control e Instrumentacion, Facultad de Ingenieria, UNLP (Argentina)

    2007-06-10

    This article presents the data and the description of a fuel cell stack that failed due to gasket degradation. The fuel cell under study is a 7 cell stack. The unexpected change in several variables such as temperature, pressure and voltage indicated the possible failure of the stack. The stack was monitored over a 6 h period in which data was collected and consequently analyzed to conclude that the fuel cell stack failed due to a crossover leak on the anode inlet port located on the cathode side gasket of cell 2. This stack failure analysis revealed a series of indicators that could be used by a super visional controller in order to initiate a shutdown procedure. (author)

  15. Simple Stacking Methods for Silicon Micro Fuel Cells

    Directory of Open Access Journals (Sweden)

    Gianmario Scotti

    2014-08-01

    Full Text Available We present two simple methods, with parallel and serial gas flows, for the stacking of microfabricated silicon fuel cells with integrated current collectors, flow fields and gas diffusion layers. The gas diffusion layer is implemented using black silicon. In the two stacking methods proposed in this work, the fluidic apertures and gas flow topology are rotationally symmetric and enable us to stack fuel cells without an increase in the number of electrical or fluidic ports or interconnects. Thanks to this simplicity and the structural compactness of each cell, the obtained stacks are very thin (~1.6 mm for a two-cell stack. We have fabricated two-cell stacks with two different gas flow topologies and obtained an open-circuit voltage (OCV of 1.6 V and a power density of 63 mW·cm−2, proving the viability of the design.

  16. Neutral Color Semitransparent Microstructured Perovskite Solar Cells

    KAUST Repository

    Eperon, Giles E.

    2014-01-28

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

  17. Electrically Anisotropic Layered Perovskite Single Crystal

    KAUST Repository

    Li, Ting-You

    2016-04-01

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

  18. Finding New Perovskite Halides via Machine learning

    Directory of Open Access Journals (Sweden)

    Ghanshyam ePilania

    2016-04-01

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

  19. Magnetic and Electric Properties of , ( Layered Perovskites

    Directory of Open Access Journals (Sweden)

    A. I. Ali

    2013-01-01

    Full Text Available The electric and magnetic properties of layered perovskites have been investigated systematically over the doping range . It was found that both Sr1.5Y0.5CoO4 and Sr1.4Y0.6CoO4 undergo ferromagnetic (FM transition around 145 K and 120 K, respectively. On the other hand, Sr1.3Y0.7CoO4 and Sr1.2Y0.8CoO4 compounds showed paramagnetic behavior over a wide range of temperatures. In addition, spin-glass transition ( was observed at 10 K for Sr1.3Y0.7CoO4. All investigated samples are semiconducting-like within the temperature range of 10–300 K. The temperature dependence of the electrical resistivity, , was described by two-dimensional variable range hopping (2D-VRH model at 50 K < ≤ 300 K. Comparison with other layered perovskites was discussed in this work.

  20. Finding New Perovskite Halides via Machine learning

    Science.gov (United States)

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

    2016-04-01

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

  1. Local polar fluctuations in lead halide perovskites

    Science.gov (United States)

    Tan, Liang; Yaffe, Omer; Guo, Yinsheng; Brus, Louis; Rappe, Andrew; Egger, David; Kronik, Leeor

    The lead halide perovskites have recently attracted much attention because of their large and growing photovoltaic power conversion efficiencies. However, questions remain regarding the temporal and spatial correlations of the structural fluctuations, their atomistic nature, and how they affect electronic and photovoltaic properties. To address these questions, we have performed a combined ab initio molecular dynamics (MD) and density functional theory (DFT) study on CsPbBr3. We have observed prevalent anharmonic motion in our MD trajectories, with local polar fluctuations involving head-to-head motion of A-site Cs cations coupled with Br window opening. We calculate Raman spectra from the polarizability auto-correlation functions obtained from these trajectories and show that anharmonic A-site cation motion manifests as a broad central peak in the Raman spectrum, which increases in intensity with temperature. A comparison of the experimental Raman spectrum of hybrid organometallic MAPbBr3 and fully inorganic CsPbBr3 suggests that structural fluctuations in lead-halide perovskites is more general than rotation of polar organic cations and is intimately coupled to the inorganic framework.

  2. 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.

  3. Shape-Controlled Synthesis of All-Inorganic CsPbBr3 Perovskite Nanocrystals with Bright Blue Emission.

    Science.gov (United States)

    Liang, Zhiqin; Zhao, Suling; Xu, Zheng; Qiao, Bo; Song, Pengjie; Gao, Di; Xu, Xurong

    2016-10-26

    We developed a colloidal synthesis of CsPbBr 3 perovskite nanocrystals (NCs) at a relative low temperature (90 °C) for the bright blue emission which differs from the original green emission (∼510 nm) of CsPbBr 3 nanocubes as reported previously. Shapes of the obtained CsPbBr 3 NCs can be systematically engineered into single and lamellar-structured 0D quantum dots, as well as face-to-face stacking 2D nanoplatelets and flat-lying 2D nanosheets via tuning the amounts of oleic acid (OA) and oleylamine (OM). They exhibit sharp excitonic PL emissions at 453, 472, 449, and 452 nm, respectively. The large blue shift relative to the emission of CsPbBr 3 bulk crystal can be ascribed to the strong quantum confinement effects of these various nanoshapes. PL decay lifetimes are measured, ranging from several to tens of nanoseconds, which infers the higher ratio of exciton radiative recombination to the nonradiative trappers in the obtained CsPbBr 3 NCs. These shape-controlled CsPbBr 3 perovskite NCs with the bright blue emission will be widely used in optoelectronic applications, especially in blue LEDs which still lag behind compared to the better developed red and green LEDs.

  4. Development of the electric utility dispersed use PAFC stack

    Energy Technology Data Exchange (ETDEWEB)

    Horiuchi, Hiroshi; Kotani, Ikuo [Mitsubishi Electric Co., Kobe (Japan); Morotomi, Isamu [Kansai Electric Power Co., Hyogo (Japan)] [and others

    1996-12-31

    Kansai Electric Power Co. and Mitsubishi Electric Co. have been developing the electric utility dispersed use PAFC stack operated under the ambient pressure. The new cell design have been developed, so that the large scale cell (1 m{sup 2} size) was adopted for the stack. To confirm the performance and the stability of the 1 m{sup 2} scale cell design, the short stack study had been performed.

  5. Stacked Heterogeneous Neural Networks for Time Series Forecasting

    Directory of Open Access Journals (Sweden)

    Florin Leon

    2010-01-01

    Full Text Available A hybrid model for time series forecasting is proposed. It is a stacked neural network, containing one normal multilayer perceptron with bipolar sigmoid activation functions, and the other with an exponential activation function in the output layer. As shown by the case studies, the proposed stacked hybrid neural model performs well on a variety of benchmark time series. The combination of weights of the two stack components that leads to optimal performance is also studied.

  6. Turbostratic stacked CVD graphene for high-performance devices

    Science.gov (United States)

    Uemura, Kohei; Ikuta, Takashi; Maehashi, Kenzo

    2018-03-01

    We have fabricated turbostratic stacked graphene with high-transport properties by the repeated transfer of CVD monolayer graphene. The turbostratic stacked CVD graphene exhibited higher carrier mobility and conductivity than CVD monolayer graphene. The electron mobility for the three-layer turbostratic stacked CVD graphene surpassed 10,000 cm2 V-1 s-1 at room temperature, which is five times greater than that for CVD monolayer graphene. The results indicate that the high performance is derived from maintenance of the linear band dispersion, suppression of the carrier scattering, and parallel conduction. Therefore, turbostratic stacked CVD graphene is a superior material for high-performance devices.

  7. Method for monitoring stack gases for uranium activity

    International Nuclear Information System (INIS)

    Beverly, C.R.; Ernstberger, H.G.

    1988-01-01

    A method for sampling stack gases emanating from the purge cascade of a gaseous diffusion cascade system utilized to enrich uranium for determining the presence and extent of uranium in the stack gases in the form of gaseous uranium hexafluoride, is described comprising the steps of removing a side stream of gases from the stack gases, contacting the side stream of the stack gases with a stream of air sufficiently saturated with moisture for reacting with and converting any gaseous uranium hexafluroide contracted thereby in the side stream of stack gases to particulate uranyl fluoride. Thereafter contacting the side stream of stack gases containing the particulate uranyl fluoride with moving filter means for continuously intercepting and conveying the intercepted particulate uranyl fluoride away from the side stream of stack gases, and continually scanning the moving filter means with radiation monitoring means for sensing the presence and extent of particulate uranyl fluoride on the moving filter means which is indicative of the extent of particulate uranyl fluoride in the side stream of stack gases which in turn is indicative of the presence and extent of uranium hexafluoride in the stack gases

  8. Highly Efficient, Durable Regenerative Solid Oxide Stack, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Precision Combustion, Inc. (PCI) proposes to develop a highly efficient regenerative solid oxide stack design. Novel structural elements allow direct internal...

  9. All-inorganic inverse perovskite solar cells using zinc oxide nanocolloids on spin coated perovskite layer

    Science.gov (United States)

    Shibayama, Naoyuki; Kanda, Hiroyuki; Yusa, Shin-ichi; Fukumoto, Shota; Baranwal, Ajay K.; Segawa, Hiroshi; Miyasaka, Tsutomu; Ito, Seigo

    2017-07-01

    We confirmed the influence of ZnO nanoparticle size and residual water on performance of all inorganic perovskite solar cells. By decreasing the size of the ZnO nanoparticles, the short-circuit current density ( Jsc) and open circuit photovoltage ( Voc) values are increased and the conversion efficiency is improved. Although the Voc value is not affected by the influence of residual water in the solution for preparing the ZnO layer, the Jsc value drops greatly. As a result, it was found that it is important to use the oxide nanoparticles with a small particle diameter and to reduce the water content in the oxide forming material in order to manufacture a highly efficient all inorganic perovskite solar cells.

  10. 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.)

  11. Double Charged Surface Layers in Lead Halide Perovskite Crystals

    KAUST Repository

    Sarmah, Smritakshi P.

    2017-02-01

    Understanding defect chemistry, particularly ion migration, and its significant effect on the surface’s optical and electronic properties is one of the major challenges impeding the development of hybrid perovskite-based devices. Here, using both experimental and theoretical approaches, we demonstrated that the surface layers of the perovskite crystals may acquire a high concentration of positively charged vacancies with the complementary negatively charged halide ions pushed to the surface. This charge separation near the surface generates an electric field that can induce an increase of optical band gap in the surface layers relative to the bulk. We found that the charge separation, electric field, and the amplitude of shift in the bandgap strongly depend on the halides and organic moieties of perovskite crystals. Our findings reveal the peculiarity of surface effects that are currently limiting the applications of perovskite crystals and more importantly explain their origins, thus enabling viable surface passivation strategies to remediate them.

  12. The Surface of Hybrid Perovskite Crystals: A Boon or Bane

    KAUST Repository

    Banavoth, Murali; Yengel, Emre; Yang, Chen; Peng, Wei; Alarousu, Erkki; Bakr, Osman; Mohammed, Omar F.

    2017-01-01

    Hybrid perovskite single crystals have garnered tremendous research attention and are expected to be next-generation materials for high-efficiency photoactive devices. Therefore, it is fundamentally important to understand the 8 relationship between

  13. Single Crystals of Organolead Halide Perovskites: Growth, Characterization, and Applications

    KAUST Repository

    Peng, Wei

    2017-01-01

    Despite their outstanding charge transport characteristics, organolead halide perovskite single crystals grown by hitherto reported crystallization methods are not suitable for most optoelectronic devices due to their small aspect ratios

  14. Present status and future prospects of perovskite photovoltaics

    Science.gov (United States)

    Snaith, Henry J.

    2018-05-01

    Solar cells based on metal halide perovskites continue to approach their theoretical performance limits thanks to worldwide research efforts. Mastering the materials properties and addressing stability may allow this technology to bring profound transformations to the electric power generation industry.

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

    KAUST Repository

    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

    2015-01-01

    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

  16. Manganites in Perovskite Superlattices: Structural and Electronic Properties

    KAUST Repository

    Jiwuer, Jilili

    2016-01-01

    Perovskite manganites are widely investigated compounds due to the discovery of the colossal magnetoresistance effect in 1994. They have a broad range of structural, electronic, magnetic properties and potential device applications in sensors

  17. Chemically Addressable Perovskite Nanocrystals for Light-Emitting Applications

    KAUST Repository

    Sun, Haizhu; Yang, Zhenyu; Wei, Mingyang; Sun, Wei; Li, Xiyan; Ye, Shuyang; Zhao, Yongbiao; Tan, Hairen; Kynaston, Emily L.; Schon, Tyler B.; Yan, Han; Lu, Zheng-Hong; Ozin, Geoffrey A.; Sargent, Edward H.; Seferos, Dwight S.

    2017-01-01

    Whereas organic–inorganic hybrid perovskite nanocrystals (PNCs) have remarkable potential in the development of optoelectronic materials, their relatively poor chemical and colloidal stability undermines their performance in optoelectronic devices

  18. Pyridine-induced Dimensionality Change in Hybrid Perovskite Nanocrystals

    KAUST Repository

    Ahmed, Ghada H.; Yin, Jun; Bose, Riya; Sinatra, Lutfan; Alarousu, Erkki; Yengel, Emre; AlYami, Noktan; Saidaminov, Makhsud I.; Zhang, Yuhai; Hedhili, Mohamed N.; Bakr, Osman; Bredas, Jean-Luc; Mohammed, Omar F.

    2017-01-01

    of pyridine during the synthesis of methylammonium lead bromide (MAPbBr) perovskite nanocrystals can transform three-dimensional (3D) cubes into two-dimensional (2D) nanostructures. Density functional theory (DFT) calculations show that pyridine preferentially

  19. 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.

  20. Metal Halide Perovskite Single Crystals: From Growth Process to Application

    Directory of Open Access Journals (Sweden)

    Shuigen Li

    2018-05-01

    Full Text Available As a strong competitor in the field of optoelectronic applications, organic-inorganic metal hybrid perovskites have been paid much attention because of their superior characteristics, which include broad absorption from visible to near-infrared region, tunable optical and electronic properties, high charge mobility, long exciton diffusion length and carrier recombination lifetime, etc. It is noted that perovskite single crystals show remarkably low trap-state densities and long carrier diffusion lengths, which are even comparable with the best photovoltaic-quality silicon, and thus are expected to provide better optoelectronic performance. This paper reviews the recent development of crystal growth in single-, mixed-organic-cation and fully inorganic halide perovskite single crystals, in particular the solution approach. Furthermore, the application of metal hybrid perovskite single crystals and future perspectives are also highlighted.

  1. Preparation of manganese-based perovskite nanoparticles using a ...

    Indian Academy of Sciences (India)

    Preparation of manganese-based perovskite nanoparticles using a reverse microemulsion method: ... ted much attention in various fields of medicine and pharma- cology such as .... In addition, the SAR value of sample was calculated through ...

  2. Working Mechanism for Flexible Perovskite Solar Cells with Simplified Architecture.

    Science.gov (United States)

    Xu, Xiaobao; Chen, Qi; Hong, Ziruo; Zhou, Huanping; Liu, Zonghao; Chang, Wei-Hsuan; Sun, Pengyu; Chen, Huajun; De Marco, Nicholas; Wang, Mingkui; Yang, Yang

    2015-10-14

    In this communication, we report an efficient and flexible perovskite solar cell based on formamidinium lead trihalide (FAPbI3) with simplified configuration. The device achieved a champion efficiency of 12.70%, utilizing direct contact between metallic indium tin oxide (ITO) electrode and perovskite absorber. The underlying working mechanism is proposed subsequently, via a systematic investigation focusing on the heterojunction within this device. A significant charge storage has been observed in the perovskite, which is believed to generate photovoltage and serves as the driving force for charge transferring from the absorber to ITO electrode as well. More importantly, this simplified device structure on flexible substrates suggests its compatibility for scale-up fabrication, which paves the way for commercialization of perovskite photovoltaic technology.

  3. A general approach for monodisperse colloidal perovskites, Chemistry of Materials

    NARCIS (Netherlands)

    Demirors, A.F.; Imhof, A.

    2009-01-01

    We describe a novel general method for synthesizing monodisperse colloidal perovskite particles at room temperature by postsynthesis addition of metal hydroxides to amorphous titania colloids. In previous work, we used titania particles to synthesize homogenously mixed silica-titania composite

  4. 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.)

  5. 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.

  6. Durable solid oxide electrolysis cells and stacks

    Energy Technology Data Exchange (ETDEWEB)

    Ming Chen

    2010-08-15

    The purpose of this project was to make a substantial contribution to development of a cost competitive electrolysis technology based on solid oxide cells. The strategy was to address what had been identified as the key issues in previous research projects. Accordingly five lines of work were carried out in the here reported project: 1) Cell and stack element testing and post test characterization to identify major degradation mechanisms under electrolysis operation. 2) Development of interconnects and coatings to allow stable electrolysis operation at approx850 deg. C or above. 3) Development of seals with reduced Si emission. 4) Development of durable SOEC cathodes. 5) Modeling. Good progress has been made on several of the planned activities. The outcome and most important achievements of the current project are listed for the five lines of the work. (LN)

  7. ATLAS software stack on ARM64

    CERN Document Server

    AUTHOR|(INSPIRE)INSPIRE-00529764; The ATLAS collaboration; Stewart, Graeme; Seuster, Rolf; Quadt, Arnulf

    2017-01-01

    This paper reports on the port of the ATLAS software stack onto new prototype ARM64 servers. This included building the “external” packages that the ATLAS software relies on. Patches were needed to introduce this new architecture into the build as well as patches that correct for platform specific code that caused failures on non-x86 architectures. These patches were applied such that porting to further platforms will need no or only very little adjustments. A few additional modifications were needed to account for the different operating system, Ubuntu instead of Scientific Linux 6 / CentOS7. Selected results from the validation of the physics outputs on these ARM 64-bit servers will be shown. CPU, memory and IO intensive benchmarks using ATLAS specific environment and infrastructure have been performed, with a particular emphasis on the performance vs. energy consumption.

  8. ATLAS software stack on ARM64

    Science.gov (United States)

    Smith, Joshua Wyatt; Stewart, Graeme A.; Seuster, Rolf; Quadt, Arnulf; ATLAS Collaboration

    2017-10-01

    This paper reports on the port of the ATLAS software stack onto new prototype ARM64 servers. This included building the “external” packages that the ATLAS software relies on. Patches were needed to introduce this new architecture into the build as well as patches that correct for platform specific code that caused failures on non-x86 architectures. These patches were applied such that porting to further platforms will need no or only very little adjustments. A few additional modifications were needed to account for the different operating system, Ubuntu instead of Scientific Linux 6 / CentOS7. Selected results from the validation of the physics outputs on these ARM 64-bit servers will be shown. CPU, memory and IO intensive benchmarks using ATLAS specific environment and infrastructure have been performed, with a particular emphasis on the performance vs. energy consumption.

  9. Stacked generalization: an introduction to super learning.

    Science.gov (United States)

    Naimi, Ashley I; Balzer, Laura B

    2018-04-10

    Stacked generalization is an ensemble method that allows researchers to combine several different prediction algorithms into one. Since its introduction in the early 1990s, the method has evolved several times into a host of methods among which is the "Super Learner". Super Learner uses V-fold cross-validation to build the optimal weighted combination of predictions from a library of candidate algorithms. Optimality is defined by a user-specified objective function, such as minimizing mean squared error or maximizing the area under the receiver operating characteristic curve. Although relatively simple in nature, use of Super Learner by epidemiologists has been hampered by limitations in understanding conceptual and technical details. We work step-by-step through two examples to illustrate concepts and address common concerns.

  10. Manifold seal structure for fuel cell stack

    Science.gov (United States)

    Collins, William P.

    1988-01-01

    The seal between the sides of a fuel cell stack and the gas manifolds is improved by adding a mechanical interlock between the adhesive sealing strip and the abutting surface of the manifolds. The adhesive is a material which can flow to some extent when under compression, and the mechanical interlock is formed providing small openings in the portion of the manifold which abuts the adhesive strip. When the manifolds are pressed against the adhesive strips, the latter will flow into and through the manifold openings to form buttons or ribs which mechanically interlock with the manifolds. These buttons or ribs increase the bond between the manifolds and adhesive, which previously relied solely on the adhesive nature of the adhesive.

  11. Actuators Using Piezoelectric Stacks and Displacement Enhancers

    Science.gov (United States)

    Bar-Cohen, Yoseph; Sherrit, Stewart; Bao, Xiaoqi; Badescu, Mircea; Lee, Hyeong Jae; Walkenmeyer, Phillip; Lih, Shyh-Shiuh

    2015-01-01

    Actuators are used to drive all active mechanisms including machines, robots, and manipulators to name a few. The actuators are responsible for moving, manipulating, displacing, pushing and executing any action that is needed by the mechanism. There are many types and principles of actuation that are responsible for these movements ranging from electromagnetic, electroactive, thermo-mechanic, piezoelectric, electrostrictive etc. Actuators are readily available from commercial producers but there is a great need for reducing their size, increasing their efficiency and reducing their weight. Studies at JPL’s Non Destructive Evaluation and Advanced Actuators (NDEAA) Laboratory have been focused on the use of piezoelectric stacks and novel designs taking advantage of piezoelectric’s potential to provide high torque/force density actuation and high electromechanical conversion efficiency. The actuators/motors that have been developed and reviewed in this paper are operated by various horn configurations as well as the use of pre-stress flexures that make them thermally stable and increases their coupling efficiency. The use of monolithic designs that pre-stress the piezoelectric stack eliminates the use of compression stress bolt. These designs enable the embedding of developed solid-state motors/actuators in any structure with the only macroscopically moving parts are the rotor or the linear translator. Finite element modeling and design tools were used to determine the requirements and operation parameters and the results were used to simulate, design and fabricate novel actuators/motors. The developed actuators and performance will be described and discussed in this paper.

  12. Enhanced Charge Collection with Passivation Layers in Perovskite Solar Cells.

    Science.gov (United States)

    Lee, Yong Hui; Luo, Jingshan; Son, Min-Kyu; Gao, Peng; Cho, Kyung Taek; Seo, Jiyoun; Zakeeruddin, Shaik M; Grätzel, Michael; Nazeeruddin, Mohammad Khaja

    2016-05-01

    The Al2 O3 passivation layer is beneficial for mesoporous TiO2 -based perovskite solar cells when it is deposited selectively on the compact TiO2 surface. Such a passivation layer suppressing surface recombination can be formed by thermal decomposition of the perovskite layer during post-annealing. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Topological Crystalline Insulators and Dirac Octets in Anti-perovskites

    OpenAIRE

    Hsieh, Timothy H.; Liu, Junwei; Fu, Liang

    2014-01-01

    We predict a new class of topological crystalline insulators (TCI) in the anti-perovskite material family with the chemical formula A$_3$BX. Here the nontrivial topology arises from band inversion between two $J=3/2$ quartets, which is described by a generalized Dirac equation for a "Dirac octet". Our work suggests that anti-perovskites are a promising new venue for exploring the cooperative interplay between band topology, crystal symmetry and electron correlation.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Thermodynamic stability and kinetic dissolution of perovskite in natural waters

    International Nuclear Information System (INIS)

    Nesbitt, H.W.; Bancroft, G.M.; Fyfe, W.S.; Karkhanis, S.; Melling, P.; Nishijima, A.

    1981-01-01

    Ringwood and coworkers have recently proposed using titanates and zirconates as hosts for nuclear waste in the Synroc B process. Three minerals are used as hosts: perovskite (CaTiO 3 ), Ba-hollandite (BaAl 2 Ti 6 O 16 ), and zirconolite (CaZrTi 2 O 7 ). The Synroc philosophy relies heavily on geological and geochemical observations in selecting stable host minerals. Although it has been recognized that the Synroc minerals are not thermodynamically compatible with siliceous rocks, the minerals are considered to be thermodynamically stable in the presence of water, and it has been reported that these minerals are kinetically stable under high-temperature (up to 900 0 C) hydrothermal conditions. Detailed thermodynamic calculations and leach tests have been performed which demonstrate: first, that perovskite is thermodynamically unstable in all known natural waters; and second, that pervoskite leaches at a significant rate even at 100 0 C. Hydrothermal leach tests have been made on natural and synthetic perovskite and perovskite analogues between 100 0 C and 300 0 C. Weight losses and solution concentrations were monitored. The results reported previously in the literature also show that perovskite is kinetically unstable in the presence of common silicates. Our results show that perovskite may be no more stable than siliceous glasses, such as rhyolite, which have been studied previously. Geologic evidence from common alkaline rocks also indicates that hollandite and zirconolite probably will not survive in common rock matrices

  2. 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.

  3. 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

  4. 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

  5. A dual shared stack for FSLM in Erika Enterprise

    NARCIS (Netherlands)

    Balasubramanian, S.M.N.; Afshar, S.; Gai, P.; Behnam, M.; Bril, R.J.

    2017-01-01

    Recently, the flexible spin-lock model (FSLM) has been introduced, unifying spin-based and suspension-based resource sharing protocols for real-time multi-core platforms. Unlike the multiprocessor stack resource policy (MSRP), FSLM doesn’t allow tasks on a core to share a single stack, however. In

  6. Long Josephson Junction Stack Coupled to a Cavity

    DEFF Research Database (Denmark)

    Madsen, Søren Peder; Pedersen, Niels Falsig; Groenbech-Jensen, N.

    2007-01-01

    A stack of inductively coupled long Josephson junctions are modeled as a system of coupled sine-Gordon equations. One boundary of the stack is coupled electrically to a resonant cavity. With one fluxon in each Josephson junction, the inter-junction fluxon forces are repulsive. We look at a possible...... transition, induced by the cavity, to a bunched state....

  7. Efficient Context Switching for the Stack Cache: Implementation and Analysis

    DEFF Research Database (Denmark)

    Abbaspourseyedi, Sahar; Brandner, Florian; Naji, Amine

    2015-01-01

    , the analysis of the stack cache was limited to individual tasks, ignoring aspects related to multitasking. A major drawback of the original stack cache design is that, due to its simplicity, it cannot hold the data of multiple tasks at the same time. Consequently, the entire cache content needs to be saved...

  8. Analysis of preemption costs for the stack cache

    DEFF Research Database (Denmark)

    Naji, Amine; Abbaspour, Sahar; Brandner, Florian

    2018-01-01

    , the analysis of the stack cache was limited to individual tasks, ignoring aspects related to multitasking. A major drawback of the original stack cache design is that, due to its simplicity, it cannot hold the data of multiple tasks at the same time. Consequently, the entire cache content needs to be saved...

  9. Simultaneous stack-gas scrubbing and waste water treatment

    Science.gov (United States)

    Poradek, J. C.; Collins, D. D.

    1980-01-01

    Simultaneous treatment of wastewater and S02-laden stack gas make both treatments more efficient and economical. According to results of preliminary tests, solution generated by stack gas scrubbing cycle reduces bacterial content of wastewater. Both processess benefit by sharing concentrations of iron.

  10. A Software Managed Stack Cache for Real-Time Systems

    DEFF Research Database (Denmark)

    Jordan, Alexander; Abbaspourseyedi, Sahar; Schoeberl, Martin

    2016-01-01

    In a real-time system, the use of a scratchpad memory can mitigate the difficulties related to analyzing data caches, whose behavior is inherently hard to predict. We propose to use a scratchpad memory for stack allocated data. While statically allocating stack frames for individual functions...

  11. Designing pseudocubic perovskites with enhanced nanoscale polarization

    Energy Technology Data Exchange (ETDEWEB)

    Levin, I. [Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA; Laws, W. J. [Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA; Wang, D. [Department of Materials Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom; Reaney, I. M. [Department of Materials Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom

    2017-11-20

    A crystal-chemical framework has been proposed for the design of pseudocubic perovskites with nanoscale ferroelectric order, and its applicability has been demonstrated using a series of representative solid solutions that combined ferroelectric (K0.5Bi0.5TiO3, BaTiO3, and PbTiO3) and antiferroelectric (Nd-substituted BiFeO3) end members. The pseudocubic structures obtained in these systems exhibited distortions that were coherent on a scale ranging from sub-nanometer to tens of nanometers, but, in all cases, the macroscopic distortion remained unresolvable even if using high-resolution X-ray powder diffraction. Different coherence lengths for the local atomic displacements account for the distinctly different dielectric, ferroelectric, and electromechanical properties exhibited by the samples. The guidelines identified provide a rationale for chemically tuning the coherence length to obtain the desired functional response.

  12. Ferroelastic Fingerprints in Methylammonium Lead Iodide Perovskite

    KAUST Repository

    Hermes, Ilka M.

    2016-02-12

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

  13. 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.

  14. Properties and applications of perovskite proton conductors

    Directory of Open Access Journals (Sweden)

    Eduardo Caetano Camilo de Souza

    2010-09-01

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

  15. 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.

  16. 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.

  17. New lithium-ion conducting perovskite oxides related to (Li, La)TiO3

    Indian Academy of Sciences (India)

    Unknown

    We describe the synthesis and lithium-ion conductivity of new perovskite-related oxides ... work on lithium-ion conducting perovskite oxides containing d0 cations. Keywords. ..... On the other hand, Nb/Ta compounds show a higher conductivity.

  18. 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.

  19. Solar cells, structures including organometallic halide perovskite monocrystalline films, and methods of preparation thereof

    KAUST Repository

    Bakr, Osman; Peng, Wei; Wang, Lingfei

    2017-01-01

    Embodiments of the present disclosure provide for solar cells including an organometallic halide perovskite monocrystalline film (see fig. 1.1B), other devices including the organometallic halide perovskite monocrystalline film, methods of making

  20. Light-Responsive Ion-Redistribution-Induced Resistive Switching in Hybrid Perovskite Schottky Junctions

    KAUST Repository

    Guan, Xinwei; Hu, Weijin; Haque, Mohammed; Wei, Nini; Liu, Zhixiong; Chen, Aitian; Wu, Tao

    2017-01-01

    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

  1. Growth and Characterization of PDMS-Stamped Halide Perovskite Single Microcrystals

    NARCIS (Netherlands)

    Khoram, P.; Brittman, S.; Dzik, W.I.; Reek, J.N.H.; Garneett, E.C.

    2016-01-01

    Recently, halide perovskites have attracted considerable attention for optoelectronic applications, but further progress in this field requires a thorough understanding of the fundamental properties of these materials. Studying perovskites in their single-crystalline form provides a model system for

  2. Routes to a commercially viable PEM fuel cell stack

    Energy Technology Data Exchange (ETDEWEB)

    Newton, J.; Foster, S.E.; Hodgson, D.; Marrett, A.

    2002-07-01

    This report describes the results of a project to design and build a 10 kW{sub e} proton exchange membrane fuel cell (PEMFC) stack, including membrane electrode assemblies (MEAs), bipolar plates and stack hardware. The aim was to prove the design concept and to demonstrate functionality by operating the stack at >1 kW{sub e}/L and 500 W/kg for 200 hours operation. The project was extended to include the assembly and testing of two additional 1 kW{sub e} PEMFC stacks based on coated metal components. Low equivalent weight perfluorinated ionomer ion exchange membranes were prepared and were found to give a superior electrochemical performance to commercial materials. A technique to etch various stainless steel grades and control processes was successfully developed and optimised. Coatings for stainless steel and titanium were successfully developed and met the required performance criteria. All PEMFC stack components were selected and designed to enable subsequent commercial manufacture.

  3. High-Density Stacked Ru Nanocrystals for Nonvolatile Memory Application

    International Nuclear Information System (INIS)

    Ping, Mao; Zhi-Gang, Zhang; Li-Yang, Pan; Jun, Xu; Pei-Yi, Chen

    2009-01-01

    Stacked ruthenium (Ru) nanocrystals (NCs) are formed by rapid thermal annealing for the whole gate stacks and embedded in memory structure, which is compatible with conventional CMOS technology. Ru NCs with high density (3 × 10 12 cm −2 ), small size (2–4 nm) and good uniformity both in aerial distribution and morphology are formed. Attributed to the higher surface trap density, a memory window of 5.2 V is obtained with stacked Ru NCs in comparison to that of 3.5 V with single-layer samples. The stacked Ru NCs device also exhibits much better retention performance because of Coulomb blockade and vertical uniformity between stacked Ru NCs

  4. Effects of hydrostatic pressure on the thermoelectric properties of the ɛ-polytype of InSe, GaSe, and InGaSe2 semiconductor compounds: an ab initio study

    Science.gov (United States)

    Elsayed, H.; Olguín, D.; Cantarero, A.

    2017-12-01

    This work presents an ab initio study of the effects of hydrostatic pressure on the Seebeck coefficients and thermoelectric power factors of the ɛ-polytype of InSe, GaSe, and InGaSe2 semiconductor compounds. Our study is performed using the semi-classical Boltzmann theory and the rigid band approach. The electronic band structures of these materials are calculated using the full-potential linearized augmented plane-wave method. The obtained thermoelectric properties are discussed in terms of the results of the electronic structure calculations. As we will show, our calculated Seebeck coefficient values indicate that these materials are good alternatives to other well-studied thermoelectric systems.

  5. 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

  6. Ferromagnetism in 4H-GaN polytype doped by non-magnetic light elements Li, Be, B, C, O, F, Ne, Na, and Mg: Ab-initio study

    International Nuclear Information System (INIS)

    Torrichi, M.; Ferhat, M.; Bouhafs, B.

    2016-01-01

    Using density-functional theory within the generalized-gradient approximation, we explore the magnetic behavior induced by nonmagnetic impurity X atoms, such as Li, Be, B, C, O, F, Ne, Na, and Mg on cation site in 4H-GaN polytype. The results reveal that Ne doped 4H-GaN has the highest magnetic moment of 3µ B , whereas Mg doped 4H-GaN has the lowest magnetic moment of 0.75µ B . Among the systems studied 4H-GaN doped Ne has been found to be half-metallic, whereas 4H-GaN doped F and Na are found to be nearly half-metallic. The partial density of states evidence that magnetism is achieved through a p-p like coupling between the impurity and the host 2p states. Furthermore, we inspect whether there exists a relationship between the spin-polarization and the local structure around the doping X atoms. It is found that for all the compounds studied, the total magnetic moment increases with increasing the X–N bond lengths. Interestingly, 4H-GaN:Be becomes ferromagnetic with increasing the Be–N bond length, whereas 4H-GaN:Na and 4H-GaN:F become half-metallic with increasing Na–N and F–N bond lengths. - Highlights: • The partial densities of states of 4H-GaN polytype doped light nonmagnetic elements have been investigated. • We found that 4H-GaN:Ne is half metallic. • We found that N atoms induced strong local magnetic. • We found that doping with half-filled X-s impurity states promotes ferromagnetism. • We found that doping with full-filled X-s impurity annihilates ferromagnetism.

  7. Reflector imaging by diffraction stacking with stacking velocity analysis; Jugo sokudo kaiseki wo tomonau sanran jugoho ni yoru hanshamen imaging

    Energy Technology Data Exchange (ETDEWEB)

    Matsushima, J; Rokugawa, S; Kato, Y [The University of Tokyo, Tokyo (Japan). Faculty of Engineering; Yokota, T [Japan National Oil Corp., Tokyo (Japan); Miyazaki, T [Geological Survey of Japan, Tsukuba (Japan)

    1997-10-22

    Concerning seismic reflection survey for geometrical arrangement between pits, the scattering stacking method with stacking velocity analysis is compared with the CDP (common depth point horizontal stacking method). The advantages of the CDP supposedly include the following. Since it presumes an average velocity field, it can determine velocities having stacking effects. The method presumes stratification and, since such enables the division of huge quantities of observed data into smaller groups, more data can be calculated in a shorter time period. The method has disadvantages, attributable to its presuming an average velocity field, that accuracy in processing is lower when the velocity field contrast is higher, that accuracy in processing is low unless stratification is employed, and that velocities obtained from stacking velocity analysis are affected by dipped structures. Such shortcomings may be remedied in the scattering stacking method with stacking velocity analysis. Possibilities are that, as far as the horizontal reflection plane is concerned, it may yield stack records higher in S/N ratio than the CDP. Findings relative to dipped reflection planes will be introduced at the presentation. 6 refs., 12 figs.

  8. 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.

  9. Solar cells, structures including organometallic halide perovskite monocrystalline films, and methods of preparation thereof

    KAUST Repository

    Bakr, Osman M.

    2017-03-02

    Embodiments of the present disclosure provide for solar cells including an organometallic halide perovskite monocrystalline film (see fig. 1.1B), other devices including the organometallic halide perovskite monocrystalline film, methods of making organometallic halide perovskite monocrystalline film, and the like.

  10. 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.

  11. Overcoming the Photovoltage Plateau in Large Bandgap Perovskite Photovoltaics.

    Science.gov (United States)

    Rajagopal, Adharsh; Stoddard, Ryan J; Jo, Sae Byeok; Hillhouse, Hugh W; Jen, Alex K-Y

    2018-05-09

    Development of large bandgap (1.80-1.85 eV E g ) perovskite is crucial for perovskite-perovskite tandem solar cells. However, the performance of 1.80-1.85 eV E g perovskite solar cells (PVKSCs) are significantly lagging their counterparts in the 1.60-1.75 eV E g range. This is because the photovoltage ( V oc ) does not proportionally increase with E g due to lower optoelectronic quality of conventional (MA,FA,Cs)Pb(I,Br) 3 and results in a photovoltage plateau ( V oc limited to 80% of the theoretical limit for ∼1.8 eV E g ). Here, we incorporate phenylethylammonium (PEA) in a mixed-halide perovskite composition to solve the inherent material-level challenges in 1.80-1.85 eV E g perovskites. The amount of PEA incorporation governs the topography and optoelectronic properties of resultant films. Detailed structural and spectroscopic characterization reveal the characteristic trends in crystalline size, orientation, and charge carrier recombination dynamics and rationalize the origin of improved material quality with higher luminescence. With careful interface optimization, the improved material characteristics were translated to devices and V oc values of 1.30-1.35 V were achieved, which correspond to 85-87% of the theoretical limit. Using an optimal amount of PEA incorporation to balance the increase in V oc and the decrease in charge collection, a highest power conversion efficiency of 12.2% was realized. Our results clearly overcome the photovoltage plateau in the 1.80-1.85 eV E g range and represent the highest V oc achieved for mixed-halide PVKSCs. This study provides widely translatable insights, an important breakthrough, and a promising platform for next-generation perovskite tandems.

  12. Long Duration Balloon Charge Controller Stack Integration

    Science.gov (United States)

    Clifford, Kyle

    NASA and the Columbia Scientific Balloon Facility are interested in updating the design of the charge controller on their long duration balloon (LDB) in order to enable the charge controllers to be directly interfaced via RS232 serial communication by a ground testing computers and the balloon's flight computer without the need to have an external electronics stack. The design involves creating a board that will interface with the existing boards in the charge controller in order to receive telemetry from and send commands to those boards, and interface with a computer through serial communication. The inputs to the board are digital status inputs indicating things like whether the photovoltaic panels are connected or disconnected; and analog inputs with information such as the battery voltage and temperature. The outputs of the board are 100ms duration command pulses that will switch relays that do things like connect the photovoltaic panels. The main component of this design is a PIC microcontroller which translates the outputs of the existing charge controller into serial data when interrogated by a ground testing or flight computer. Other components involved in the design are an AD7888 12-bit analog to digital converter, a MAX3232 serial transceiver, various other ICs, capacitors, resistors, and connectors.

  13. Black Hole Spectroscopy with Coherent Mode Stacking.

    Science.gov (United States)

    Yang, Huan; Yagi, Kent; Blackman, Jonathan; Lehner, Luis; Paschalidis, Vasileios; Pretorius, Frans; Yunes, Nicolás

    2017-04-21

    The measurement of multiple ringdown modes in gravitational waves from binary black hole mergers will allow for testing the fundamental properties of black holes in general relativity and to constrain modified theories of gravity. To enhance the ability of Advanced LIGO/Virgo to perform such tasks, we propose a coherent mode stacking method to search for a chosen target mode within a collection of multiple merger events. We first rescale each signal so that the target mode in each of them has the same frequency and then sum the waveforms constructively. A crucial element to realize this coherent superposition is to make use of a priori information extracted from the inspiral-merger phase of each event. To illustrate the method, we perform a study with simulated events targeting the ℓ=m=3 ringdown mode of the remnant black holes. We show that this method can significantly boost the signal-to-noise ratio of the collective target mode compared to that of the single loudest event. Using current estimates of merger rates, we show that it is likely that advanced-era detectors can measure this collective ringdown mode with one year of coincident data gathered at design sensitivity.

  14. ATLAS software stack on ARM64

    CERN Document Server

    Smith, Joshua Wyatt; The ATLAS collaboration

    2016-01-01

    The ATLAS experiment explores new hardware and software platforms that, in the future, may be more suited to its data intensive workloads. One such alternative hardware platform is the ARM architecture, which is designed to be extremely power efficient and is found in most smartphones and tablets. CERN openlab recently installed a small cluster of ARM 64-bit evaluation prototype servers. Each server is based on a single-socket ARM 64-bit system on a chip, with 32 Cortex-A57 cores. In total, each server has 128 GB RAM connected with four fast memory channels. This paper reports on the port of the ATLAS software stack onto these new prototype ARM64 servers. This included building the "external" packages that the ATLAS software relies on. Patches were needed to introduce this new architecture into the build as well as patches that correct for platform specific code that caused failures on non-x86 architectures. These patches were applied such that porting to further platforms will need no or only very little adj...

  15. Testing system for a fuel cells stack

    International Nuclear Information System (INIS)

    Culcer, Mihai; Iliescu, Mariana; Stefanescu, Ioan; Raceanu, Mircea; Enache, Adrian; Lazar, Roxana Elena

    2006-01-01

    Hydrogen and electricity together represent one of the most promising ways to realize sustainable energy, whilst fuel cells provide the most efficient conversion devices for converting hydrogen and possibly other fuels into electricity. Thus, the development of fuel cell technology is currently being actively pursued worldwide. Due to its simple operation and other fair characteristics, the Proton Exchange Membrane Fuel Cell (PEMFC) is especially suitable as a replacement for the internal combustion engine. The PEMFC is also being developed for decentralized electricity and heat generation in buildings and mobile applications. Starting with 2001 the Institute of Research - Development for Cryogenics and Isotopic Technologies - ICIT - Rm. Valcea developed research activities supported by the Romanian Ministry of Education and Research within the National Research Program in order to bridge the gap to European competencies in the area of hydrogen and fuel cells. The paper deals with the testing system designed and developed in ICIT Rm. Valcea as a flexible and versatile tool allowing a large scale of parameter settings and measurements on a single cell or on a fuel cells stack onto a wind range of output power values. (authors)

  16. Weyl magnons in noncoplanar stacked kagome antiferromagnets

    Science.gov (United States)

    Owerre, S. A.

    2018-03-01

    Weyl nodes have been experimentally realized in photonic, electronic, and phononic crystals. However, magnonic Weyl nodes are yet to be seen experimentally. In this paper, we propose Weyl magnon nodes in noncoplanar stacked frustrated kagome antiferromagnets, naturally available in various real materials. Most crucially, the Weyl nodes in the current system occur at the lowest excitation and possess a topological thermal Hall effect, therefore they are experimentally accessible at low temperatures due to the population effect of bosonic quasiparticles. In stark contrast to other magnetic systems, the current Weyl nodes do not rely on time-reversal symmetry breaking by the magnetic order. Rather, they result from explicit macroscopically broken time reversal symmetry by the scalar spin chirality of noncoplanar spin textures and can be generalized to chiral spin liquid states. Moreover, the scalar spin chirality gives a real space Berry curvature which is not available in previously studied magnetic Weyl systems. We show the existence of magnon arc surface states connecting projected Weyl magnon nodes on the surface Brillouin zone. We also uncover the first realization of triply-degenerate nodal magnon point in the noncollinear regime with zero scalar spin chirality.

  17. Lithiation-induced shuffling of atomic stacks

    KAUST Repository

    Nie, Anmin

    2014-09-10

    In rechargeable lithium-ion batteries, understanding the atomic-scale mechanism of Li-induced structural evolution occurring at the host electrode materials provides essential knowledge for design of new high performance electrodes. Here, we report a new crystalline-crystalline phase transition mechanism in single-crystal Zn-Sb intermetallic nanowires upon lithiation. Using in situ transmission electron microscopy, we observed that stacks of atomic planes in an intermediate hexagonal (h-)LiZnSb phase are "shuffled" to accommodate the geometrical confinement stress arising from lamellar nanodomains intercalated by lithium ions. Such atomic rearrangement arises from the anisotropic lithium diffusion and is accompanied by appearance of partial dislocations. This transient structure mediates further phase transition from h-LiZnSb to cubic (c-)Li2ZnSb, which is associated with a nearly "zero-strain" coherent interface viewed along the [001]h/[111]c directions. This study provides new mechanistic insights into complex electrochemically driven crystalline-crystalline phase transitions in lithium-ion battery electrodes and represents a noble example of atomic-level structural and interfacial rearrangements.

  18. Captioning Transformer with Stacked Attention Modules

    Directory of Open Access Journals (Sweden)

    Xinxin Zhu

    2018-05-01

    Full Text Available Image captioning is a challenging task. Meanwhile, it is important for the machine to understand the meaning of an image better. In recent years, the image captioning usually use the long-short-term-memory (LSTM as the decoder to generate the sentence, and these models show excellent performance. Although the LSTM can memorize dependencies, the LSTM structure has complicated and inherently sequential across time problems. To address these issues, recent works have shown benefits of the Transformer for machine translation. Inspired by their success, we develop a Captioning Transformer (CT model with stacked attention modules. We attempt to introduce the Transformer to the image captioning task. The CT model contains only attention modules without the dependencies of the time. It not only can memorize dependencies between the sequence but also can be trained in parallel. Moreover, we propose the multi-level supervision to make the Transformer achieve better performance. Extensive experiments are carried out on the challenging MSCOCO dataset and the proposed Captioning Transformer achieves competitive performance compared with some state-of-the-art methods.

  19. Efficiency of Polymer Electrolyte Membrane Fuel Cell Stack

    Directory of Open Access Journals (Sweden)

    Hans Bosma

    2011-08-01

    Full Text Available This paper applies a feedforward control of optimal oxygen excess ratio that maximize net power (improve efficiency of a NedStack P8.0-64 PEM fuel cell stack (FCS system. Net powers profile as a function of oxygen excess ratio for some points of operation are analyzed by using FCS model. The relationships between stack current and the corresponding control input voltage that gives an optimal oxygen excess ratio are used to design a feedforward control scheme. The results of this scheme are compared to the results of a feedforward control using a constant oxygen excess ratio. Simulation results show that optimal oxygen excess ratio improves fuel cell performance compared to the results of constant oxygen excess ratio. The same procedures are performed experimentally for the FCS system. The behaviour of the net power of the fuel cell stack with respect to the variation of oxygen excess ratio is analyzed to obtain optimal values. Data of stack current and the corresponding voltage input to the compressor that gives optimal values of oxygen excess ratio are used to develop a feedforward control. Feedforward control based on constant and optimal oxygen excess ratio control, are implemented in the NedStack P8.0-64 PEM fuel cell stack system by using LabVIEW. Implementation results shows that optimal oxygen excess ratio control improves the fuel cell performance compared to the constant oxygen excess ratio control.

  20. Reliability analysis and initial requirements for FC systems and stacks

    Science.gov (United States)

    Åström, K.; Fontell, E.; Virtanen, S.

    In the year 2000 Wärtsilä Corporation started an R&D program to develop SOFC systems for CHP applications. The program aims to bring to the market highly efficient, clean and cost competitive fuel cell systems with rated power output in the range of 50-250 kW for distributed generation and marine applications. In the program Wärtsilä focuses on system integration and development. System reliability and availability are key issues determining the competitiveness of the SOFC technology. In Wärtsilä, methods have been implemented for analysing the system in respect to reliability and safety as well as for defining reliability requirements for system components. A fault tree representation is used as the basis for reliability prediction analysis. A dynamic simulation technique has been developed to allow for non-static properties in the fault tree logic modelling. Special emphasis has been placed on reliability analysis of the fuel cell stacks in the system. A method for assessing reliability and critical failure predictability requirements for fuel cell stacks in a system consisting of several stacks has been developed. The method is based on a qualitative model of the stack configuration where each stack can be in a functional, partially failed or critically failed state, each of the states having different failure rates and effects on the system behaviour. The main purpose of the method is to understand the effect of stack reliability, critical failure predictability and operating strategy on the system reliability and availability. An example configuration, consisting of 5 × 5 stacks (series of 5 sets of 5 parallel stacks) is analysed in respect to stack reliability requirements as a function of predictability of critical failures and Weibull shape factor of failure rate distributions.

  1. Planar-Structure Perovskite Solar Cells with Efficiency beyond 21.

    Science.gov (United States)

    Jiang, Qi; Chu, Zema; Wang, Pengyang; Yang, Xiaolei; Liu, Heng; Wang, Ye; Yin, Zhigang; Wu, Jinliang; Zhang, Xingwang; You, Jingbi

    2017-12-01

    Low temperature solution processed planar-structure perovskite solar cells gain great attention recently, while their power conversions are still lower than that of high temperature mesoporous counterpart. Previous reports are mainly focused on perovskite morphology control and interface engineering to improve performance. Here, this study systematically investigates the effect of precise stoichiometry, especially the PbI 2 contents on device performance including efficiency, hysteresis and stability. This study finds that a moderate residual of PbI 2 can deliver stable and high efficiency of solar cells without hysteresis, while too much residual PbI 2 will lead to serious hysteresis and poor transit stability. Solar cells with the efficiencies of 21.6% in small size (0.0737 cm 2 ) and 20.1% in large size (1 cm 2 ) with moderate residual PbI 2 in perovskite layer are obtained. The certificated efficiency for small size shows the efficiency of 20.9%, which is the highest efficiency ever recorded in planar-structure perovskite solar cells, showing the planar-structure perovskite solar cells are very promising. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. 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.

  3. Decreasing the electronic confinement in layered perovskites through intercalation.

    Science.gov (United States)

    Smith, Matthew D; Pedesseau, Laurent; Kepenekian, Mikaël; Smith, Ian C; Katan, Claudine; Even, Jacky; Karunadasa, Hemamala I

    2017-03-01

    We show that post-synthetic small-molecule intercalation can significantly reduce the electronic confinement of 2D hybrid perovskites. Using a combined experimental and theoretical approach, we explain structural, optical, and electronic effects of intercalating highly polarizable molecules in layered perovskites designed to stabilize the intercalants. Polarizable molecules in the organic layers substantially alter the optical and electronic properties of the inorganic layers. By calculating the spatially resolved dielectric profiles of the organic and inorganic layers within the hybrid structure, we show that the intercalants afford organic layers that are more polarizable than the inorganic layers. This strategy reduces the confinement of excitons generated in the inorganic layers and affords the lowest exciton binding energy for an n = 1 perovskite of which we are aware. We also demonstrate a method for computationally evaluating the exciton's binding energy by solving the Bethe-Salpeter equation for the exciton, which includes an ab initio determination of the material's dielectric profile across organic and inorganic layers. This new semi-empirical method goes beyond the imprecise phenomenological approximation of abrupt dielectric-constant changes at the organic-inorganic interfaces. This work shows that incorporation of polarizable molecules in the organic layers, through intercalation or covalent attachment, is a viable strategy for tuning 2D perovskites towards mimicking the reduced electronic confinement and isotropic light absorption of 3D perovskites while maintaining the greater synthetic tunability of the layered architecture.

  4. 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).

  5. 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....

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

    Directory of Open Access Journals (Sweden)

    Yaxian Pei

    2016-01-01

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

  7. Magnetoresistance and magnetic properties of the double perovskites

    International Nuclear Information System (INIS)

    Philipp, J.B.; Majewski, P.; Resinger, D.; Gepraegs, S; Opel, M.; Reb, A.; Alff, L.; Gross, R.

    2004-01-01

    The magnetic double perovskite materials of composition A 2 BB'O 6 with A an alkaline earth ion and B and B' a magnetic and non-magnetic transition metal or lanthanide ions, respectively, have attracted considerable attention due to their interesting magnetic properties ranging from antiferromagnetism to geometrically frustrated spin systems and ferromagnetism. With respect to application in spin electronics, the ferromagnetic double perovskites with BB' = CrW, CrRe, FeMo or FeRe and A = Ca, Ba, Sr are highly interesting due to their in most cases high Curie temperatures well above room temperature and their half-magnetic behaviour. Here, we summarize the structural, magnetotransport, magnetic and optical properties of the ferromagnetic double perovskites and discuss the underlying physics. In particular, we discuss the impact of the steric effects resulting in a distorted perovskite structure, doping effects obtained by a partial replacing of the divalent alkaline earth ions on the A site by a trivalent lanthanide as well as B/B' cationic disorder on the Curie temperature T C , the saturation magnetization and the magnetotransport properties. Our results support the presence of a kinetic energy driven mechanism in the ferromagnetic double perovskites, where ferromagnetism is stabilised by a hybridization of states of the non-magnetic B'- site positioned in between the high spin B-sites. (author)

  8. Mixed Mechanism of Lubrication by Lipid Bilayer Stacks.

    Science.gov (United States)

    Boţan, Alexandru; Joly, Laurent; Fillot, Nicolas; Loison, Claire

    2015-11-10

    Although the key role of lipid bilayer stacks in biological lubrication is generally accepted, the mechanisms underlying their extreme efficiency remain elusive. In this article, we report molecular dynamics simulations of lipid bilayer stacks undergoing load and shear. When the hydration level is reduced, the velocity accommodation mechanism changes from viscous shear in hydration water to interlayer sliding in the bilayers. This enables stacks of hydrated lipid bilayers to act as efficient boundary lubricants for various hydration conditions, structures, and mechanical loads. We also propose an estimation for the friction coefficient; thanks to the strong hydration forces between lipid bilayers, the high local viscosity is not in contradiction with low friction coefficients.

  9. Fabrication of high gradient insulators by stack compression

    Science.gov (United States)

    Harris, John Richardson; Sanders, Dave; Hawkins, Steven Anthony; Norona, Marcelo

    2014-04-29

    Individual layers of a high gradient insulator (HGI) are first pre-cut to their final dimensions. The pre-cut layers are then stacked to form an assembly that is subsequently pressed into an HGI unit with the desired dimension. The individual layers are stacked, and alignment is maintained, using a sacrificial alignment tube that is removed after the stack is hot pressed. The HGI's are used as high voltage vacuum insulators in energy storage and transmission structures or devices, e.g. in particle accelerators and pulsed power systems.

  10. Study and Development of an OpenStack solution

    OpenAIRE

    Jorba Brosa, Maria

    2014-01-01

    Estudi i desenvolupament d'una solució de virtualització amb Openstack. Es farà un especial èmfasi en la part de seguretat. Deployment of a solution based in OpenStack for the creation of an Infrastructure service cloud. Implementación de una solución basada en OpenStack para la creación de una infrastructura de servicios cloud. Implementació d'una solució basada en OpenStack per la creació d'una infrastructura de serveis cloud.

  11. Loop Entropy Assists Tertiary Order: Loopy Stabilization of Stacking Motifs

    Directory of Open Access Journals (Sweden)

    Daniel P. Aalberts

    2011-11-01

    Full Text Available The free energy of an RNA fold is a combination of favorable base pairing and stacking interactions competing with entropic costs of forming loops. Here we show how loop entropy, surprisingly, can promote tertiary order. A general formula for the free energy of forming multibranch and other RNA loops is derived with a polymer-physics based theory. We also derive a formula for the free energy of coaxial stacking in the context of a loop. Simulations support the analytic formulas. The effects of stacking of unpaired bases are also studied with simulations.

  12. Consolidity: Stack-based systems change pathway theory elaborated

    Directory of Open Access Journals (Sweden)

    Hassen Taher Dorrah

    2014-06-01

    Full Text Available This paper presents an elaborated analysis for investigating the stack-based layering processes during the systems change pathway. The system change pathway is defined as the path resulting from the combinations of all successive changes induced on the system when subjected to varying environments, activities, events, or any excessive internal or external influences and happenings “on and above” its normal stands, situations or set-points during its course of life. The analysis is essentially based on the important overall system paradigm of “Time driven-event driven-parameters change”. Based on this paradigm, it is considered that any affected activity, event or varying environment is intelligently self-recorded inside the system through an incremental consolidity-scaled change in system parameters of the stack-based layering types. Various joint stack-based mathematical and graphical approaches supported by representable case studies are suggested for the identification, extraction, and processing of various stack-based systems changes layering of different classifications and categorizations. Moreover, some selected real life illustrative applications are provided to demonstrate the (infinite stack-based identification and recognition of the change pathway process in the areas of geology, archeology, life sciences, ecology, environmental science, engineering, materials, medicine, biology, sociology, humanities, and other important fields. These case studies and selected applications revealed that there are general similarities of the stack-based layering structures and formations among all the various research fields. Such general similarities clearly demonstrate the global concept of the “fractals-general stacking behavior” of real life systems during their change pathways. Therefore, it is recommended that concentrated efforts should be expedited toward building generic modular stack-based systems or blocks for the mathematical

  13. Static analysis of worst-case stack cache behavior

    DEFF Research Database (Denmark)

    Jordan, Alexander; Brandner, Florian; Schoeberl, Martin

    2013-01-01

    Utilizing a stack cache in a real-time system can aid predictability by avoiding interference that heap memory traffic causes on the data cache. While loads and stores are guaranteed cache hits, explicit operations are responsible for managing the stack cache. The behavior of these operations can......-graph, the worst-case bounds can be efficiently yet precisely determined. Our evaluation using the MiBench benchmark suite shows that only 37% and 21% of potential stack cache operations actually store to and load from memory, respectively. Analysis times are modest, on average running between 0.46s and 1.30s per...

  14. Full Piezoelectric Multilayer-Stacked Hybrid Actuation/Transduction Systems

    Science.gov (United States)

    Su, Ji; Jiang, Xiaoning; Zu, Tian-Bing

    2011-01-01

    The Stacked HYBATS (Hybrid Actuation/Transduction system) demonstrates significantly enhanced electromechanical performance by using the cooperative contributions of the electromechanical responses of multilayer, stacked negative strain components and positive strain components. Both experimental and theoretical studies indicate that, for Stacked HYBATS, the displacement is over three times that of a same-sized conventional flextensional actuator/transducer. The coupled resonance mode between positive strain and negative strain components of Stacked HYBATS is much stronger than the resonance of a single element actuation only when the effective lengths of the two kinds of elements match each other. Compared with the previously invented hybrid actuation system (HYBAS), the multilayer Stacked HYBATS can be designed to provide high mechanical load capability, low voltage driving, and a highly effective piezoelectric constant. The negative strain component will contract, and the positive strain component will expand in the length directions when an electric field is applied on the device. The interaction between the two elements makes an enhanced motion along the Z direction for Stacked-HYBATS. In order to dominate the dynamic length of Stacked-HYBATS by the negative strain component, the area of the cross-section for the negative strain component will be much larger than the total cross-section areas of the two positive strain components. The transverse strain is negative and longitudinal strain positive in inorganic materials, such as ceramics/single crystals. Different piezoelectric multilayer stack configurations can make a piezoelectric ceramic/single-crystal multilayer stack exhibit negative strain or positive strain at a certain direction without increasing the applied voltage. The difference of this innovation from the HYBAS is that all the elements can be made from one-of-a-kind materials. Stacked HYBATS can provide an extremely effective piezoelectric

  15. Fuel flow distribution in SOFC stacks revealed by impedance spectroscopy

    DEFF Research Database (Denmark)

    Mosbæk, Rasmus Rode; Hjelm, Johan; Barfod, Rasmus

    2014-01-01

    As SOFC technology is moving closer to a commercial break through, methods to measure the “state-of-health” of operating stacks are becoming of increasing interest. This requires application of advanced methods for detailed electrical and electrochemical characterization during operation. An oper......As SOFC technology is moving closer to a commercial break through, methods to measure the “state-of-health” of operating stacks are becoming of increasing interest. This requires application of advanced methods for detailed electrical and electrochemical characterization during operation...... utilizations. The fuel flow distribution provides important information about the operating limits of the stack when high electrical efficiency is required....

  16. Stacking by electroinjection with discontinuous buffers in capillary zone electrophoresis.

    Science.gov (United States)

    Shihabi, Zak K

    2002-08-01

    The work presented here demonstrates that electroinjection can be performed using discontinuous buffers, which can result in better stacking than that obtained by hydrodynamic injection. The sample can be concentrated at the tip of the capillary leaving practically the whole capillary for sample separation. This results in several advantages, such as better sample concentration, higher plate number and shorter time of stacking. However, sample introduction by electromigration is suited for samples free or low in salt content. Samples, which are high in salt content, are better introduced by the hydrodynamic injection for stacking by the discontinuous buffers. Different simple methods to introduce the discontinuity in the buffer for electroinjection are discussed.

  17. Production and Reliability Oriented SOFC Cell and Stack Design

    DEFF Research Database (Denmark)

    Hauth, Martin; Lawlor, Vincent; Cartellieri, Peter

    2017-01-01

    The paper presents an innovative development methodology for a production and reliability oriented SOFC cell and stack design aiming at improving the stacks robustness, manufacturability, efficiency and cost. Multi-physics models allowed a probabilistic approach to consider statistical variations...... in production, material and operating parameters for the optimization phase. A methodology for 3D description of spatial distribution of material properties based on a random field models was developed and validated by experiments. Homogenized material models on multiple levels of the SOFC stack were...... and output parameters and to perform a sensitivity analysis were developed and implemented. The capabilities of the methodology is illustrated on two practical cases....

  18. Calculation of AC losses in large HTS stacks and coils

    DEFF Research Database (Denmark)

    Zermeno, Victor; Abrahamsen, Asger Bech; Mijatovic, Nenad

    2012-01-01

    In this work, we present a homogenization method to model a stack of HTS tapes under AC applied transport current or magnetic field. The idea is to find an anisotropic bulk equivalent for the stack of tapes, where the internal alternating structures of insulating, metallic, superconducting...... allowing for overcritical current densities to be considered. The method presented here allowed for a computational speedup factor of up to 2 orders of magnitude when compared to full 2-D simulations taking into account the actual structure of the stacks without compromising accuracy....

  19. Optimized stacked RADFETs for milli-rad dose measurement

    International Nuclear Information System (INIS)

    O'Connell, B.; Lane, B.; Mohammadzadeh, A.

    1999-01-01

    This paper details the improvements in the design of stacked RADFETs for increased radiation sensitivity. The issues of high read-out voltage has been shown to be a draw-back. It is the body (bulk)effect factor that is responsible for the increased overall stack Threshold voltage (V T ), which is greater than the sum of the individual devices V T . From extensive process and device simulation and resultant circuit simulation, modified stack structures have been proposed and designed. New and exciting result of lower initial (pre-irradiation) output voltage as well as increased radiation sensitivity will be presented. (author)

  20. Ablation of film stacks in solar cell fabrication processes

    Science.gov (United States)

    Harley, Gabriel; Kim, Taeseok; Cousins, Peter John

    2013-04-02

    A dielectric film stack of a solar cell is ablated using a laser. The dielectric film stack includes a layer that is absorptive in a wavelength of operation of the laser source. The laser source, which fires laser pulses at a pulse repetition rate, is configured to ablate the film stack to expose an underlying layer of material. The laser source may be configured to fire a burst of two laser pulses or a single temporally asymmetric laser pulse within a single pulse repetition to achieve complete ablation in a single step.