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排序方式: 共有216条查询结果,搜索用时 656 毫秒
51.
Li Hong Dr. Jovana V. Milić Paramvir Ahlawat Dr. Marko Mladenović Dr. Dominik J. Kubicki Farzaneh Jahanabkhshi Dr. Dan Ren María C. Gélvez-Rueda Dr. Marco A. Ruiz-Preciado Dr. Amita Ummadisingu Dr. Yuhang Liu Chengbo Tian Linfeng Pan Dr. Shaik M. Zakeeruddin Prof. Anders Hagfeldt Prof. Ferdinand C. Grozema Prof. Ursula Rothlisberger Prof. Lyndon Emsley Prof. Hongwei Han Prof. Michael Graetzel 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(12):4721-4727
Formamidinium (FA) lead iodide perovskite materials feature promising photovoltaic performances and superior thermal stabilities. However, conversion of the perovskite α-FAPbI3 phase to the thermodynamically stable yet photovoltaically inactive δ-FAPbI3 phase compromises the photovoltaic performance. A strategy is presented to address this challenge by using low-dimensional hybrid perovskite materials comprising guaninium (G) organic spacer layers that act as stabilizers of the three-dimensional α-FAPbI3 phase. The underlying mode of interaction at the atomic level is unraveled by means of solid-state nuclear magnetic resonance spectroscopy, X-ray crystallography, transmission electron microscopy, molecular dynamics simulations, and DFT calculations. Low-dimensional-phase-containing hybrid FAPbI3 perovskite solar cells are obtained with improved performance and enhanced long-term stability. 相似文献
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To explore the origin of low conversion efficiency for novel β-FeSi2/c-Si heterojunction solar cells, the effect of surface recombination and interface states on the cell performance has been investigated by numerical simulation. The present results show that surface recombination of β-FeSi2 film plays an important role in limiting the cell property since the photovoltaic behavior of β-FeSi2 is quite sensitive to surface recombination due to its especial characteristic of very high optical absorption coefficient. Surface quality of β-FeSi2 film should be much improved for better cell performance. In addition, it is shown that interface states between β-FeSi2 film and crystalline silicon are critical to device characterization. Interface states should be minimized to obtain higher conversion efficiency. If surface recombination and interface states can be best suppressed, potential conversion efficiency for the cell may be up to 28.12% at 300 K under illumination of AM 1.5, 100 mW/cm2. 相似文献
54.
The complexation of curium(III) with nitrate was studied at different temperatures (10-85 °C) by luminescence spectroscopy. The stability constants of CmNO(3)(2+) were calculated from the luminescence emission spectra. The specific ion interaction approach (SIT) was used to obtain the stability constants of CmNO(3)(2+) at infinite dilution and variable temperatures. The complexation is weak and little effect of temperature on the complexation was observed over the temperature range 10-85 °C. Data on the luminescence lifetime indicate that each nitrate ligand replaces two water molecules from the inner coordination sphere of Cm(3+), forming a bidentate inner-sphere complex with Cm(3+) in aqueous solutions. 相似文献
55.
The optical absorption, fluorescence excitation, and emission spectra of the Cm(III) aqua ion in 0.001 M perchloric acid were studied in pure H(2)O, pure D(2)O, and in mixtures of H(2)O-D(2)O at temperatures from 10 to 85 °C. The quantum yield of the fluorescence of the Cm(III) aqua ion in pure H(2)O and D(2)O was also measured in this temperature range and the radiative decay rate constant was obtained from these data. The results indicate that, from 10 to 85 °C, the effect of temperature on the absorption, excitation, and emission spectra is very small. By correcting the observed decay rate constant for the radiative rate constant, a set of correlations between the observed fluorescence decay rate constant and the hydration number of Cm(3+) in H(2)O at temperatures from 10 to 85 °C was developed. A weak temperature dependence was observed for the nonradiative decay rate constant for the (6)D'(7/2)-(8)S'(7/2) transition and described by the Arrhenius equation. The activation energy of the nonradiative decay was measured to be 0.9 kJ mol(-1), approximately matching the energy gap between the first and the second (A(1) and A(2)) levels of the metastable (6)D'(7/2) multiplet of the Cm(III) aqua ion. On the basis of these observations, it is postulated that the slight increase in the observed fluorescence decay rate constant as the temperature increases from 10 to 85 °C is due to the effect of thermal population of the A(2) level. 相似文献
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The pK of p-(methylamino)biphenyl, 1, on our Li scale, pK(Li) = 22.09, compared to the cesium scale, pK(Cs) = 28.60. For hexamethyldisilazane, HMDS, pK(Li) = 23.05, pK(Cs) = 29.26. These results are those for the monomers in THF; corrections were made for dimers present in some cases. The pK(Li) of these two amines fit well the previously found correlation with Hartree-Fock calculations at 6-31+g(d) using RLi coordinated with three dimethyl ethers as a computational model for RLi in THF. The results are also compared with earlier pK(Li)s reported from equilibria with lithium amides in which aggregation was not considered. 相似文献
58.
Optical spectroscopy study of organic-phase lanthanide complexes in the TALSPEAK separations process
Time-resolved fluorescence spectroscopy and Fourier transform IR spectroscopy have been applied to characterize the coordination environment of lipophilic complexes of Eu(3+) with bis(2-ethylhexyl)phosphoric acid (HDEHP) and (2-ethylhexyl)phosphonic acid mono(2-ethylhexyl) ester (HEH[EHP]) in 1,4-diisopropylbenzene (DIPB). The primary focus is on understanding the role of lactate (HL) in lanthanide partitioning into DIPB solutions of HDEHP or HEH[EHP] as it is employed in the TALSPEAK solvent extraction process for lanthanide separations from trivalent actinides. The broader purpose of this study is to characterize the changes that can occur in the coordination environment of lanthanide ions as metal-ion concentrations increase in nonpolar media. The optical spectroscopy studies reported here complement an earlier investigation of similar solutions using NMR spectroscopy and electrospray ionization mass spectrometry. Emission spectra of Eu(3+) complexes with HDEHP/HEH[EHP] demonstrate that, as long as the Eu(3+) concentration is maintained well below saturation of the organic extractant solution, the Eu(3+) coordination environment remains constant as both [HL](org) and [H(2)O](org) are increased. If the total organic-phase lanthanide concentration is increased (by extraction of moderate amounts of La(3+)), the (5)D(0) → (7)F(1) transition singlet splits into a doublet with a notable increase in the intensity of both (5)D(0) → (7)F(1) and (5)D(0) → (7)F(2) electronic transitions. The increased multiplicity in the emission spectra indicates that Eu(3+) ions are present in multiple coordination environments. The increased emission intensity of the 614 nm band implies an overall reduction in symmetry of the extracted Eu(3+) complex in the presence of macroscopic La(3+). Although [H(2)O](org) increases to above 1 M at high [HL](tot), this water is not associated with the Eu(3+) metal center. IR spectroscopy results confirm a direct Ln(3+)-lactate interaction at high concentrations of lanthanide and lactate in the extractant phase. At low organic-phase lanthanide concentrations, the predominant complex is almost certainly the well-known Ln(DEHP·HDEHP)(3). As lanthanide concentrations in the organic phase increase, mixed-ligand complexes with the general stoichiometry Ln(L)(n)(DEHP)(3-n) or Ln(L)(n)(DEHP·HDEHP)(3-n) become the dominant species. 相似文献
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60.
Linfeng Zhou 《Geometriae Dedicata》2012,158(1):353-364
We investigate projective spherically symmetric Finsler metrics with constant flag curvature in R n and give the complete classification theorems. Furthermore, a new class of Finsler metrics with two parameters on n-dimensional disk is found to have constant negative flag curvature. 相似文献