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排序方式: 共有472条查询结果,搜索用时 78 毫秒
461.
Nico Leupold Philipp Ramming Irene Bauer Christina Witt Jennifer Jungklaus Prof. Dr. Ralf Moos Dr. Helen Grüninger Dr. Fabian Panzer 《欧洲无机化学杂志》2023,26(8):e202200736
Here, we investigate in detail the impact of the size of the methylammonium iodide (MAI) reactants in the mechanochemical powder synthesis of the halide perovskite methylammonium lead iodide (MAPbI3). Morphology and structural characterizations by scanning electron microscopy and X-ray diffraction reveal that with increasing MAI reactant size, the particle size of the perovskite powder increases, while its defect density decreases, as suggested by nuclear quadrupole resonance spectroscopy and photoluminescence investigations. The reason for this behavior seems to be associated to the sensitive influence of the MAI size on the time durations of MAPbI3 synthesis and delayed MAPbI3 crushing stage during ball milling. Thus, our results emphasize the high importance the reactant properties have on the mechanochemical synthesis of halide perovskites and will contribute to enhance the reproducibility and control of the fabrication of halide perovskites in powder form. 相似文献
462.
Enhanced stability of low temperature processed perovskite solar cells via augmented polaronic intensity of hole transporting layer 下载免费PDF全文
Md. Arafat Mahmud Naveen Kumar Elumalai Mushfika Baishakhi Upama Dian Wang Faiazul Haque Matthew Wright Kah Howe Chan Cheng Xu Ashraf Uddin 《固体物理学:研究快报》2016,10(12):882-889
The commercial mass production of perovskite solar cells requires full compatibility with roll‐to‐roll processing with enhanced device stability. In line with this, the present work addresses following issues simultaneously from multiple fronts: (i) low temperature processed (140 °C) ZnO is used as electron transport layer (ETL) for fabricating the mixed organic cation based perovskite solar cells, (ii) the expensive hole transporting layer (HTL) spiro‐OMeTAD is replaced with F4TCNQ doped P3HT and (iii) the fabrication method does not incorporate the dopant TBP which is known to induce degradation processes in perovskite layer. All the devices under study were fabricated in ambient conditions. The F4TCNQ doped P3HT (HTL) based devices exhibits 14 times higher device stability compared to the conventional Li‐TFSI/TBP doped P3HT devices. The underlying mechanism behind the enhanced device lifetime in F4TCNQ doped P3HT (HTL) based devices was investigated via in‐depth electronic, ionic and polaronic characterization. The enhanced polaronic property in F4TCNQ doped P3HT HTL device ascertains its superior hole extraction and electron blocking capability; and consequently higher stability retained even after a month of ageing.
463.
Exceptional elastic anisotropy of hybrid organic–inorganic perovskite CH3NH3PbBr3 measured by laser ultrasonic technique 下载免费PDF全文
Alexey M. Lomonosov Xiaoliang Yan Chuanxiang Sheng Vitalyi E. Gusev Chenyin Ni Zhonghua Shen 《固体物理学:研究快报》2016,10(8):606-612
The results of the direct experimental evaluation of all elastic constants of single crystal hybrid organic–inorganic perovskite (HOIP) methylammonium lead bromide, a material known due to its possible solar‐energy, optoelectronics, X‐ray detector and thermoelectricity applications, are reported. The measurements of anisotropic elasticity of CH3NH3PbBr3by the technique of laser ultrasonics demonstrate that properties of HOIPs can be even more remarkable than the theoretical expectations: the extracted shear modulus is more than twice smaller, the universal anisotropy is more than twice higher, while the Debye temperature is more than 50° lower. Thus HOIPs can exhibit extremely low shear rigidity and extremely high anisotropy, both strongly overrunning the parameters which have been expected based on earlier first principles theoretical predictions. A simple theoretical model of granular crystal indicates that these observations could be related to the contributions of rotations/tilts of PbBr6octahedra to elastic response of cubic CH3NH3PbBr3. Another experimental observation is strong stiffening of shear rigidity with temperature increase from its room value up to 120 °C. Discovered elastic properties of HOIPs characterize them as exceptionally ductile/flexible/adaptive materials which could be deposited on corrugated/structured surfaces. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
464.
N. Kalanda S. Demyanov W. Masselink A. Mogilatenko M. Chashnikova N. Sobolev O. Fedosenko 《Crystal Research and Technology》2011,46(5):463-469
Double perovskites with the structural formula A2BB′O6±δ, especially the strontium ferromolybdate Sr2FeMoO6–δ, have attracted a lot of attention due to their unique magnetic and electrical properties and a possible application in spintronic devices. However, a strict correlation between the functional characteristics of Sr2FeMoO6–δ and its synthesis technology has been lacking up to date. Thus, we have studied in the present work the crystallization kinetics of Sr2FeMoO6–δ using reagents with different pre‐history as well as the structural and magnetic properties of the obtained compounds. Differences in the crystallization kinetics as well as higher magnetic inhomogeneity of Sr2FeMoO6–δ synthesised from a mixture of MoO3, Fe2O3, SrCO3 in comparison with the compound synthesised from the SrFeO2.5 and SrMoO4–y precursors have been found and interpreted. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
465.
The electrical properties of Pb(Zn1/3 Nb2/3)0.91Ti0.09O3 single crystals over a wide range of frequencies (20 Hz to 2 MHz) and temperature (30 to 490 °C) were studied using impedance spectroscopic technique. A strongly frequency dependant Debye type relaxation process in crystals was observed. The activation energy for relaxation was found to be 1.72 eV. The nature of Cole‐Cole plot reveals the contribution of only grain (bulk) effect in the sample. The temperature dependant conductivity was found to different in different temperature regions, which shows the presence of different carrier for conduction. The activation energy for conduction in the order of 1.69 eV suggested that the conduction process in higher temperature region is governed by the presence of lead vacancy defect in the sample. Further, the negative temperature thermistor behaviour of the system was explored and various associated parameters were calculated. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
466.
I. E. Animitsa 《Russian Journal of Electrochemistry》2009,45(6):668-676
Data on the thermogravimetry, spectroscopy, and electrical charge transfer as functions of T, aH2O, and aO2 for niobates and tantalates of alkali-earth metals with structure disordering of the oxygen sublattice, which can show high-temperature proton conduction, are summarized. It is shown that in the solid solution series with decreasing x (that is, with the increasing of the oxygen vacancies concentration) the proton conductivity increase, which is caused by the increasing of both the concentration of proton defects formed in the structure (in compliance with the formula Sr6 ? 2x M 2 + 2x +5 O10(OH)2?6x and their mobility. The proton transfer dominates for the compositions with x < 0.15 at temperatures below 550°C. In the solid solutions (Ba1?y Ca y )6Nb2O11 (0.23 ≤ y ≤ 0.47) characterized by equal concentration of oxygen vacancies, with the increasing of barium content (correspondingly, with the increasing of the lattice parameter) the oxygen-ion conductivity (at aH2O = 3 × 10?5) grows monotonically, which is caused by the decreasing of the oxygen atom migration energy and increasing of their mobility. In this series, the proton conductivity (at aH2O = 2 × 10?2) increased. It was shown, by using IR-spectroscopy and the 1H NMR method, that the protons exist in the complex oxide structure mainly as energy-wise nonequivalent OH? groups: isolated, closely set, and paired, whose quantitative ratios are determined by the coordination preference of the B-sublattice elements. 相似文献
467.
Perovskites have stood out as excellent photoactive materials with high efficiencies and stabilities, achieved via cation mixing techniques. Overcoming challenges to the stabilization of Perovskite solar cells calls for the development of design principles of large cation incorporation in halide perovskite to accelerate the discovery of optimal stable compositions. Large fluorinated organic cations incorporation is an attractive method for enhancing the intrinsic stability of halide perovskites due to their high dipole moment and moisture-resistant nature. However, a fluorinated cation has a larger ionic size than its non-fluorinated counterpart, falling within the upper boundary of the mixed-cation incorporation. Here, we report on the intrinsic stability of mixed Methylammonium (MA) lead halides at different concentrations of large cation incorporation, namely, ehtylammonium (EA; [CH3CH2NH3]+) and 2-fluoroethylammonium (FEA; [CH2FCH2NH3]+). Density functional theory (DFT) calculations of the enthalpy of the mixing and analysis of the perovskite structural features enable us to narrow down the compositional search domain for EA and FEA cations around concentrations that preserve the perovskite structure while pointing towards the maximal stability. This work paves the way to developing design principles of a large cation mixture guided by data analysis of DFT data. Finally, we present the automated search of the minimum enthalpy of mixing by implementing Bayesian optimization over the compositional search domain. We introduce and validate an automated workflow designed to accelerate the compositional search, enabling researchers to cut down the computational expense and bias to search for optimal compositions. 相似文献
468.
Dr. Gonzalo García-Espejo Dr. Konstantis F. Konidaris Dr. Pietro Anzini Prof. Stefano Brenna Dr. Antonietta Guagliardi Prof. Norberto Masciocchi 《欧洲无机化学杂志》2023,26(23):e202300282
The discovery of new 3D perovskites and their 2D and 1D analogues continues to attract the interest of the scientific community and therefore the understanding of their structural, optical, and physicochemical properties is of fundamental importance. Here, we report the one-pot synthesis and the full characterization of 1D and 2D lead halide polycrystalline solids containing the rather rigid 1,4-xylylenediammonium (pXDA) organic cation as spacer. We isolated 2D Dion-Jacobson (DJ) perovskites, namely (pXDA)PbX4 (X=Cl, Br) and the mixed halide (pXDA)Pb(Br1–xIx)4 species (all based on 2D monolayers of corner-sharing lead halide octahedra), and, for iodine, the (pXDA)Pb2I6 . 2H2O phase, which contains 1D ribbons. The latter species can be reversibly dehydrated by gentle heating, forming the isomorphous (pXDA)Pb2I6. crystal phase. These species, some of which have recently been studied in the frame of broad light emitters and for photovoltaic applications, have been characterized by variable-temperature X-ray diffraction methods, shedding light onto their anisotropic thermal responses, of utmost importance for day-night cycling in functional devices. Spin-coated thin films were also prepared and studied by means of synchrotron radiation grazing incidence X-ray diffraction, SEM imaging and fluorescence spectroscopy experiments. 相似文献
469.
470.
Dr. Supriya Ghosh Dr. Debkumar Rana Dr. Bapi Pradhan Dr. Patrice Donfack Prof. Dr. Johan Hofkens Prof. Dr. Dr. Arnulf Materny 《Chemphyschem》2023,24(21):e202300303
In recent years, there has been an impressively fast technological progress in the development of highly efficient lead halide perovskite solar cells. Nonetheless, the stability of perovskite films and associated solar cells remains a source of uncertainty and necessitates sophisticated characterization techniques. Here, we report low- to mid-frequency resonant Raman spectra of formamidinium-based lead mixed-halide perovskites. The assignment of the different Raman lines in the measured spectra is assisted by DFT simulations of the Raman spectra of suitable periodic model systems. An important result of this work is that both experiment and theory point to an increase of the stability of the perovskite structure with increasing chloride doping concentration. In the Raman spectra, this is reflected by the appearance of new lines due to the formation of hydrogen bonds. Thus, higher chloride doping results in less torsional motion and lower asymmetric bending contributing to higher stability. This study yields a solid basis for the interpretation of the Raman spectra of formamidinium-based mixed-halide perovskites, furthering the understanding of the properties of these materials, which is essential for their full exploitation in solar cells. 相似文献