(CNH)SbI and (CNH)BiI: ferroelastic lead-free hybrid perovskite-like materials as potential semiconducting absorbers.

We have synthesised and characterised novel organic-inorganic hybrid crystals: and ( and ). The thermal DSC and TG analyses indicate four structural phase transitions (PTs) at 366.2/366.8, 274.6/275.4, 233.3/233.3 and 142.8/143.1 K (on cooling/heating) for and two reversible PTs at 365.2/370.8 and 252.6/257.9 K for . Both analogues crystallize at room temperature in the orthorhombic structure, which transforms, in the case of , to monoclinic 2/ at low temperature. According to the X-ray diffraction results, the anionic component is discrete and built of face-sharing bioctahedra, [MI], in both compounds, whereas cations exhibit distinct dynamical disorder over high temperature phases. Dielectric spectroscopy and H NMR spectroscopy have been used to characterise the dynamical state of the cations. The ferroelastic domain structure has been characterised by observations under a polarized optical microscope. Both compounds are semiconductors with narrow bandgaps of 1.97 eV () and 2.10 eV ().