perovskite


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perovskite

[pə′rävz‚kīt]
(mineralogy)
Ca[TiO3] A natural, yellow, brownish-yellow, reddish, brown, or black mineral and a structure type which includes no less than 150 synthetic compounds; the crystal structure is ideally cubic, it occurs as rounded cubes modified by the octahedral and dodecahedral forms, luster is subadamantine to submetallic, hardness is 5.5 on Mohs scale, and specific gravity is 4.0.

Perovskite

 

(named for L. A. Perovskii). (1) A mineral of the oxide class. The chemical formula of perovskite is CaTiO3, with CaO accounting for 41.24 percent of the composition, and TiO2 for 58.76 percent. Perovskite that contains admixtures of Ce is called knopite; of Ni, Ce, and Fe, dysanalite; and of Na, Ce, Ti, and Nb, loparite.

Perovskite crystallizes in the pseudoisometric system. Each calcium atom is surrounded by 12 oxygen atoms, which are located at the apexes of a cuboctahedron; the coordination number of Ti is eight. Characteristic striations appear on the cubic faces parallel to the edges. Cleavage is cubic, hardness is 5.5–6 on Mohs’ scale, and the density ranges from 3,950 to 4,040 kg/m3. The color may be black, grayish black, or brownish.

Perovskite frequently occurs in ultrabasic alkaline rocks, including olivinites, pyroxenes, and kimberlites, as well as in associated ore segregations and carbonatites. It fills the interstices at the point of contact of basic rocks with limestone; it also is interstitially distributed in chloritic shale and in nephelinic, leu-citic, and melilitic basalts.

Knopite is used as a source of rare-earth elements of the cerium group, and loparite is a source of niobium and titanium.

(2) A group of chemical compounds whose crystal structure resembles that of perovskite [in English usage “perovskite” is the adjectival noun that denotes the structure type of these compounds and not the compounds themselves]. Perovskites have the general formula ABX3, where A is a tetravalent cation, B is a heptavalent cation, and X is an anion—usually oxygen, as in NaNbO3 and BaTiO3. Many of these compounds are ferroelectric, including BaTiO3 and LiNbO3; the group also includes some superconductors (for example, SrTiO3), semiconductors, and compounds that display magnetic ordering.

perovskite

An oxide mineral made up of calcium titanate that is expected to be commercialized in higher-efficiency solar cells in the 2020-2021 time frame. Named after Russian mineralogist Lev Perovski, who discovered it in the 1800s, perovskite may also be employed as quantum dots in future screen technologies due to its high color purity. See quantum dot.

Automatic Solar Cell Window Shades
In 2018, using perovskite and carbon nanotube technologies, the National Renewable Energy Lab in Golden, Colorado developed clear window glass that emits electricity and darkens with sunshine. When the sun fades, the window becomes transparent again. The transparency range is 3% to 68%.
References in periodicals archive ?
The experiments revealed benzylamine enters into the surface of the crystal to create a new, two-dimensional material -- 2D perovskite -- on the surface of the three-dimensional crystal.
Perovskites are semiconductor materials that have many applications.
The company develops devices exploiting the promising new PV material class known as perovskites, exploiting research from Jinsong Huang's team at the University of North Carolina, Chapel Hill.
Previous attempts to improve the thermal stability of these solar cells have included enhancing the perovskite layer by introducing compounds such as dimethyl sulfoxide, but researchers have struggled to boost the cells' efficiency and long-term stability.
They (https://www.sciencedaily.com/releases/2019/04/190425115639.htm) added caffeine to the perovskite of 40 solar cells and used spectroscopy to make sure that the caffeine has successfully bonded with the material.
The first perovskite found to be good at carrying photons, methylammonium lead tri-iodide, degrades in air or moisture.
For a double cubic perovskite of the formula [A.sub.2]BB'[O.sub.6] the intensity, in particular, the (111) superstructure reflection is proportional to the dilference in the scattering power of the B and B' atoms, when all the atoms are situated in the ideal position (Howard, et al., 2003).
It is worth noting that the p[O.sub.2] dependence of oxygen content measured at this temperature and shown in Figure 5 exhibits inflection when oxygen content of the double perovskite reaches the value of 5.
Its electron-donating alkoxy peripheral substituents have been chosen to accomplish two main tasks: (i) tuning the [(n-BuO).sub.4]ZnPc electronic properties, thus optimizing the alignment of HOMO-LUMO levels to the perovskite band edges, and (ii) assuring the [(n-BuO).sub.4]ZnPc processability within a device by formation of spin-coated homogeneous films with favorable molecular packing.
We have reported the scaling behavior and related physical growth dynamics of [MAPbI.sub.3] perovskite thin films on smooth Si substrates [11].
In recent years, the emerging organic-inorganic hybrid perovskite material has been regarded as the promising candidate for the next-generation solar cells due to its strong optical absorption, long diffusion length, tunable bandgap, solution processability, low cost, and so on [1-5].