In physical chemistry and engineering, passivation is coating a material so that it becomes "passive", that is, less readily affected or corroded by the environment. Passivation involves creation of an outer layer of shield material that is applied as a microcoating, created by chemical reaction with the base material, or allowed to build by spontaneous oxidation in the air. As a technique, passivation is the use of a light coat of a protective material, such as metal oxide, to create a shield against corrosion. Passivation of silicon is used during fabrication of microelectronic devices. Undesired passivation of electrodes, called "fouling", increases the circuit resistance so it interferes with some electrochemical applications such as electrocoagulation for wastewater treatment, amperometric chemical sensing, and electrochemical synthesis.
A perovskite is any material of formula ABX3 with a crystal structure similar to that of the mineral perovskite, which consists of calcium titanium oxide (CaTiO3). The mineral was first discovered in the Ural mountains of Russia by Gustav Rose in 1839 and named after Russian mineralogist L. A. Perovski (1792–1856). 'A' and 'B' are two positively charged ions (i.e. cations), often of very different sizes, and X is a negatively charged ion (an anion, frequently oxide) that bonds to both cations. The 'A' atoms are generally larger than the 'B' atoms. The ideal cubic structure has the B cation in 6-fold coordination, surrounded by an octahedron of anions, and the A cation in 12-fold cuboctahedral coordination. Additional perovskite forms may exist where both/either the A and B sites have a configuration of A1x-1A2x and/or B1y-1B2y and the X may deviate from the ideal coordination configuration as ions within the A and B sites undergo changes in their oxidation states.
Amidines are organic compounds with the functional group RC(NR)NR2, where the R groups can be the same or different. They are the imine derivatives of amides (RC(O)NR2). The simplest amidine is formamidine, HC(=NH)NH2.
Piezochromism, from the Greek piezô "to squeeze, to press" and chromos "color", describes the tendency of certain materials to change color with the application of pressure. This effect is closely related to the electronic band gap change, which can be found in plastics, semiconductors and hydrocarbons. One simple molecule displaying this property is 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile, also known as ROY owing to its red, orange and yellow crystalline forms. Individual yellow and pale orange versions transform reversibly to red at high pressure.
Perovskite (pronunciation: ) is a calcium titanium oxide mineral composed of calcium titanate (chemical formula CaTiO3). Its name is also applied to the class of compounds which have the same type of crystal structure as CaTiO3, known as the perovskite structure, which has a general chemical formula A2+B4+(X2−)3. Many different cations can be embedded in this structure, allowing the development of diverse engineered materials.
Ruddlesden-Popper (RP) phases are a type of perovskite structure that consists of two-dimensional perovskite-like slabs interleaved with cations. The general formula of an RP phase is An+1BnX3n+1, where A and B are cations, X is an anion, and n is the number of octahedral layers in the perovskite-like stack. Generally, it has a phase structure that results from the intergrowth of perovskite-type and NaCl-type structures.
A perovskite solar cell (PSC) is a type of solar cell that includes a perovskite-structured compound, most commonly a hybrid organic–inorganic lead or tin halide-based material as the light-harvesting active layer. Perovskite materials, such as methylammonium lead halides and all-inorganic cesium lead halide, are cheap to produce and simple to manufacture.
Methylammonium halides are organic halides with a formula of [CH3NH3]+X−, where X is F for methylammonium fluoride, Cl for methylammonium chloride, Br for methylammonium bromide, or I for methylammonium iodide. Generally they are white or light colored powders.
Methylammonium bromide in an organic halide with the formula of CH3NH3Br. It is the salt of methylammonium and bromide. It is a colorless, water-soluble solid.
Methylammonium iodide in an organic halide with a formula of CH3NH3I. It is an ammonium salt composed of methylamine and hydrogen iodide. The primary application for methylammonium iodide, sometimes in combination with other methylammonium halides, is as a component of perovskite (structure) crystalline solar cells.
Henry James Snaith is a professor in physics in the Clarendon Laboratory at the University of Oxford. Research from his group has led to the creation of a new research field, based on halide perovskites for use as solar absorbers. Many individuals who were PhD students and postdoctoral researchers in Snaith's group have now established research groups, independent research portfolios and commercial enterprises. He co-founded Oxford Photovoltaics in 2010 to commercialise perovskite based tandem solar cells.
Methylammonium lead halides (MALHs) are solid compounds with perovskite structure and a chemical formula of [CH3NH3]+Pb2+(X−)3, where X = Cl, Br or I. They have potential applications in solar cells, lasers, light-emitting diodes, photodetectors, radiation detectors, scintillator, magneto-optical data storage and hydrogen production.
A tin-based perovskite solar cell is a special type of perovskite solar cell, based on a tin perovskite structure (ASnX3, where 'A' is a monovalent cation, tin is in its Sn (II) oxidation state and 'X' is a monovalent halogen anion). As a technology, tin-based perovskite solar cells are still in the research phase, and are even less-studied than their counterpart, lead-based perovskite solar cells. The main advantages of tin-based perovskite solar cells are that they are lead-free. There are environmental concerns with using lead-based perovskite solar cells in large-scale applications; one such concern is that since the material is soluble in water, and lead is highly toxic, any contamination from damaged solar cells could cause major health and environmental problems.
Tsutomu Miyasaka, is a Japanese engineer in electrochemistry best known as the inventor of the perovskite solar cell.
Perovskite nanocrystals are a class of semiconductor nanocrystals, which exhibit unique characteristics that separate them from traditional quantum dots. Perovskite nanocrystals have an ABX3 composition where A = cesium, methylammonium (MA), or formamidinium (FA); B = lead or tin; and X = chloride, bromide, or iodide.
Hemamala Indivari Karunadasa is an assistant professor of chemistry at Stanford University. She works on hybrid organic – inorganic materials, such as perovskites, for clean energy and large area lighting.
Mohammad Khaja Nazeeruddin is an Indian-Swiss chemist and materials scientist who conducts research on Perovskite solar cells, dye-sensitized solar cells, and light-emitting diodes. He is a professor at EPFL and the director of the Laboratory for Molecular Engineering of Functional Materials at School of Basic Sciences.
Timeline of sustainable energy research 2020– documents increases in renewable energy, solar energy, and nuclear energy, particularly for ways that are sustainable within the Solar System.
Methylammonium tin halides are solid compounds with perovskite structure and a chemical formula of CH3NH3SnX3, where X = I, Br or Cl. They are promising lead-free alternatives to lead perovskites as photoactive semiconductor materials. Tin-based perovskites have shown excellent mobility in transistors which gives them an opportunity to be explored more for solar cell applications.
Ana Flávia Nogueira is a Brazilian chemist who is a Full Professor at the State University of Campinas (Unicamp) since 2004. Her research considers nanostructured materials for solar energy conversion. She was elected to the Brazilian Academy of Science in 2022.
