Perovskite (structure)

About: Perovskite (structure) is a research topic. Over the lifetime, 51482 publications have been published within this topic receiving 1541750 citations.

Oxygen ion conductors and their technological applications

Abstract: The magnitudes of the oxygen fluxes through ceramic oxides incorporated in a variety of technological devices and systems are briefly surveyed, and attention is drawn to the importance of the kinetics of the associated surface exchange process. For most applications, oxygen ion conductivities greater than 10 −1 S cm −1 are required at intermediate temperatures (600–800 °C). The strategies adopted to design materials with appropriate oxygen ion conductivity values are summarized with special reference to the fluorite, perovskite and related oxide structures. Finally oxygen ion order-disorder processes in highly defective perovskite (ABO 3 ) and brownmillerite (ABO 2.5 ) mixed conducting oxides are briefly reviewed, with emphasis upon the role of isotopic exchange-diffusion profile techniques to separate the contributions of the various charge carriers to the total conductivity.

Hybrid Improper Ferroelectricity in a Multiferroic and Magnetoelectric Metal‐Organic Framework

Abstract: There is great interest in hybrid organic-inorganic materials such as metal-organic frameworks (MOFs). The compounds [C(NH$_{2}$)$_{3}$]M(HCOO)$_{3}$, where M=Cu$^{2+}$ or Cr$^{2+}$ are Jahn-Teller (JT) active ions, are MOF with perovskite topology which crystallizes in polar space group Pna2$_{1}$. In inorganic compounds, octahedral tilting and Jahn-Teller structural distortions are usually non-polar distortions. However, in this MOF cooperative interactions between the antiferro-distortive distortions of the framework and the C(NH2)$_{3}$ organic cation via hydrogen bonding breaks the inversion symmetry and induces a ferroelectric polarization.[Angew. Chem. Int. Ed. 50, 5847, 2011] Our ab-initio study supports the picture of an orbital-order-induced ferroelectricity, a rare example of dipolar ordering caused by electronic degrees of freedom. The switching of polarization direction implies the reversal of the weak ferromagnetic component. The microscopic mechanism in this JT-based MOF with ABX$_{3}$ perovskite structure displays a Hybrid Improper Ferroelectric (HIF) state, arising from a trilinear coupling between different structural deformations that comprise tilting, rotations and Jahn-Teller distortions of both the BX$_{3}$ framework and the organic cation at the A sites. Since these distortion modes in perovskite-inorganic compounds usually freeze-in at elevated temperatures, the trilinear coupling in MOF compounds may provide an interesting route towards high-temperature multiferroicity. These results offer an important starting point for tailoring multiferroic properties in this emerging class of materials for various technological applications. In particular, the high tunability of the ferroelectric polarization by means of the modification of the organic A cation has been recently shown[J. Am. Chem. Soc. 135 18126 (2013)]

Aluminum-Doped Cesium Lead Bromide Perovskite Nanocrystals with Stable Blue Photoluminescence Used for Display Backlight.

Abstract: Bright and stable blue emitters with narrow full-width at half-maxima are particularly desirable for applications in television displays and related technologies. Here, this study shows that doping aluminum (Al3+) ion into CsPbBr3 nanocrystals (NCs) using AlBr3 can afford lead-halide perovskites NCs with stable blue photoluminescence. First, theoretical and experimental analyses reveal that the extended band gap and quantum confinement effect of elongated shape give rise to the desirable blueshifted emission. Second, the aluminum ion incorporation path is rationalized qualitatively by invoking fundamental considerations about binding relations in AlBr3 and its dimer. Finally, the absence of anion-exchange effect is corroborated when green CsPbBr3 and blue Al:CsPbBr3 NCs are mixed. Combinations of the above two NCs with red-emitting CdSe@ZnS NCs result in UV-pumped white light-emitting diodes (LED) with an National Television System Committee (NTSC) value of 116% and ITU-R Recommendation B.T. 2020 (Rec. 2020) of 87%. The color coordinates of the white LED are optimized at (0.32, 0.34) in CIE 1931. The results suggest that low-cost, earth-abundant, solution-processable Al-doped perovskite NCs can be promising candidate materials for blue down-conversion layer in backlit displays.

Defect Passivation of Organic–Inorganic Hybrid Perovskites by Diammonium Iodide toward High-Performance Photovoltaic Devices

Abstract: The polycrystalline feature of solution-processed perovskite film and its ionic nature inevitably incur substantial crystallographic defects, especially at the film surface and the grain boundaries (GBs). Here, a simple defect passivation method was exploited by post-treating CH3NH3PbI3 (MAPbI3) film with a rationally selected diammonium iodide. The molecular structure of the used diammonium iodide was discovered to play a critical role in affecting the phase purity of treated MAPbI3. Both NH3I(CH2)4NH3I and NH3I(CH2)2O(CH2)2NH3I (EDBE) induce three-dimensional (3D) to two-dimensional (2D) perovskite phase transformation during the treatment while only NH3I(CH2)8NH3I (C8) successfully passivates perovskite surface and GBs without forming 2D perovskite because of the elevated activation energy arising from its unique anti–gauche isomerization. Defect passivation of MAPbI3 was clearly confirmed by scanning Kelvin probe microscopy (SKPM) and time-resolved photoluminescence (TRPL) studies, which results in th...