Investigations of structure-property relationships in some A2BX4-type organic-inorganic halide hybrids

Abstract

The “organic-inorganic halide hybrids”, as the name suggests, are the class of materials which incorporates both organic ammonium and inorganic metal halides in single phase and exhibits different component-dependent interesting physical properties. Originally known since the start of 20th century, the organic-inorganic halide hybrid materials have emerged over last two decades with ample promises by featuring pronounced structural diversity coupled with exciting range of remarkable dielectric, ferroelectric, magnetic and optoelectronic properties.1–8 To mention, recent years have seen unparalleled progress being achieved in photovoltaic properties of the perovskite based materials CH3NH3MX3 (M = Pb, Sn; X = Br, I).7–11 With modern day materialsbased research continuously focused on design and fabrication of multifunctional materials, the hybrid halides with their broad range of exciting properties and application can be claimed as truly multifunctional and are worthy to be focused on. Such diversity in physical properties arises from the different components that these materials contain. To describe, the organic ammonium cation with its own shape, size and dipole moment influence the structural symmetry largely, often giving rise to ferroelectric or piezoelectric states. The inorganic ions are seen to form various types of metal-halide complexes and influence the optoelectronic and magnetic properties of the material. Interestingly, as there are vast numbers of different ammonium ions, metal ions and halides which can play role of possible components, permuting them can lead to innumerable number of hybrids which can be studied. To mention, Cheetham et al. have modified the traditional tolerance factor equation and predicted that over 400 hybrid halides can have perovskite structures.