Two bilayer organic-inorganic hybrid perovskite compounds exhibiting reversible phase transition and dielectric anomalies

Abstract

Ruddlesden-Popper two-dimensional (2D) organic-inorganic hybrid perovskites have been explored for multiple applications, benefitting from their structural tunability, superior stability and congenital quantum-well effects. Herein, two bilayer hybrid perovskite-type compounds with the general formula [A2Bn-1PbnI3n+1] (n is the number of layer) [(C5H8NS)2(MA)Pb2I7] (1) and [(C5H8NS)2(FA)Pb2I7] (2) (C5H8NS: 2-thiophenemethylamine, MA: methylamine, FA: formamidine) are reported. The differential scanning calorimetry (DSC) measurements revealed both compounds 1 and 2 exhibit reversible phase transitions above the room temperature, accompanied by dielectric anomalies near the Curie temperature (Tc). The variable-temperature X-ray single-crystal diffraction disclosed the phase transitions derive from the order-disorder transformation of organic cations 2-thiophenemethylamine, methylamine and formamidine. Furthermore, compounds 1 and 2 exhibited strong emission peaks at about 600 ​nm when under an excitation wavelength of 475 ​nm.