‘Perovskite’ originates from the mineral name of calcium titanate (CaTiO3) and the compounds with formula of ABO3 generally belong to a perovskite-type compound, where the A is a divalent and B is a tetravalent metal ion. A perovskite with cubic or orthorhombic phases shows ferroelectricity, for instance, barium titanate (BaTiO3) is a ferroelectric or piezoelectric material.1) High temperature superconductive oxides with unit of a copper oxide are obtained from all perovskite compounds.2) These perovskite compounds consist of metal ions and oxygen atoms, and are manufactured by a physical procedure (eg. sintering method).3) Modification of the metal ion and a changing ratio of the metal ion components can drastically control physical properties of the perovskite. In addition to the oxide perovskites, halide-based perovskites are also well known.
On the other hand, one can replace the cationic component with an organic ammonium. In this case, a chemical method can provide a perovskite compound. This perovskite compound is called an ‘organic-inorganic perovskite compound’, because it contains an organic component. A metal ion component usually involves tin or lead.4,5) This perovskite compound has the general formula [(RNH3)mMXn], in which modifications of metal (M), halide (X) and organic groups (R) precisely control physical properties. Among them, the tin perovskite is relatively better for electrical conduction,6) and the lead one is better for optical properties.7) A chemical modification of the halide controls band gap.8) Selection of organic ammonium halide, metal halide and their mixing ratio changes the component ratio of the halide. The organic groups are selected from methyl, long alkyls, phenyl, benzyl, phenethyl and so on. Diversity of these organic groups allows controlling the structure of a perovskite compound. For instance, a perovskite compound with R = methyl provides [(MeNH3)MX3] having a three-dimensional cubic perovskite structure.9) A perovskite compound with R = CnH2n+1 (n ≥ 2) provides a two-dimensional perovskite layer and the length of alkyl group can control the inter-layer distance.10)
An application of organic-inorganic perovskite is a perovskite solar cell (PSC).11) This solar cell can be usually fabricated by the three-dimensional cubic perovskite [(MeNH3)MX3]. Research on the perovskite solar cell recently received much attention. Power conversion efficiency of this solar cell is more than those of organic photovoltaics (OPV) and dye-sensitized solar cells (DSSC), and the device can be fabricated by solution-process at low cost.
Three Advantages of TCI's Perovskite-Related Products
- High Purity
We can provide high purity PbX2 (X = I, Br, Cl) as well as organic onium salts with low water content (eg. MAI, FAI, etc). High purity and low water materials can enhance the perovskite solar cell performance such as efficiency and stability. Highly pure PbX2 shows good solubility in polar organic solvents to be appropriate for solution processable device fabrication of the perovskite solar cell.
- Product Variety
We can provide various PbX2 (X = I, Br, Cl) and organic onium salts. A mixed cation perovskite where the A site includes some cations, enables the perovskite solar cell to be efficient and stable. A DMF complex of MAPbI3 (P2415) is already prepared in 1:1 of lead iodide (PbI2) and MAI (i.e. ready-to-use), and it is highly soluble in DMF and DMSO.
We can provide various PbX2 (X = I, Br, Cl), the MAPbI3/DMF complex (P2415) and some dominant organic onium salts in bulk scale. Our bulk production enables the perovskite solar cell to be low cost and large area.