Synthesis, Structure, and Properties of Organic-Inorganic Perovskites and Related Materials

With guidance from retro-crystal engineering, iodometalate structures based on MI6 octahedra of group 14 (M = Sn(II), Pb(II)) and group 15 (M = Sb(III) and Bi(III)) are analysed. The criterion of I/M ratio, with the function of indicating the degree of condensation of octahedra in inorganic networks and the average charge density at the organic–inorganic interface, is introduced to classify all of the iodometalate networks, resulting in an easy and clear way to identify isomers with different dimensionalities. Of all iodometalates, the 2D M(II)I4 anion derived from the perovskite network is special since it can be easily stabilized by a range of common organic cations. We provide here the up-to-date progress in this extensively studied field, focusing on crystal engineering of hybrids in the aim of getting materials with a reduced band gap. Relationships between the molecular layouts of cationic entities and the structures of several non-perovskite anionic networks, focusing on the organic–inorganic interface, are highlighted. Distinct dependences between different types of cations and different types of anions are revealed, although it is still unfeasible to apply them in the actual control, design, or prediction of specific hybrid structures.

Structural diversity and retro-crystal engineering analysis of iodometalate hybrids

Undistorted perovskite layers are formed in PbI4-based hybrid perovskites incorporating X−(CH2)2−NH3+ (X = Br, Cl) cations. The outstanding structural feature of these compounds is the result of halogen and hydrogen bonding at the organic−inorganic interface, leading to the absence of hydrogen bonds between equatorial iodine atoms of the perovskite layer and ammonium parts, these last being located out of perovskite layers. As a consequence, these red salts display a reduced band gap (2.2 eV) which is assigned to a more disperse HOMO band compared to other salts such as (I−(CH2)2−NH3)2PbI4.

Reduced Band Gap Hybrid Perovskites Resulting from Combined Hydrogen and Halogen Bonding at the Organic−Inorganic Interface

Thermochromic phase transitions in transition metal salts

In the organic−inorganic perovskites family, the 〈100〉-oriented type has been extensively investigated as a result of its unique magnetic, optical, and electrical properties, and only one type of 〈110〉-oriented hybrid perovskite stabilized by methylammonium and iodoformamidinium cations or the latter themselves has been known so far. In this paper, another novel 〈110〉-oriented organic−inorganic perovskite (C6H13N3)PbBr4 (compound 1) has been prepared by reacting N-(3-aminopropyl)imidazole (API) with PbBr2 in hydrobromic acid. The crystal structure is determined, which indicates that the perovskite is stabilized by API. The introduction of the optically active organic ligand API into the hybrid perovskite results in a red shift and a great enhancement of photoluminescence in the perovskite with respect to organic ligand API itself. These results have been explained according to calculation based on density-functional theory. Moreover, the excellent film processing ability for the perovskite (C6H13N3)PbBr4 ...

R. D. Willett

Papers

Thermochromism in copper(II) chlorides. Coordination geometry changes in tetrachlorocuprate(2-)anions

Thermochromism in copper(ii) chlorides, coordination geometry changes in cucl4(2-) anions