(Benzimidazolium)_(2)GeI_(4):A layered two-dimensional perovskite with dielectric switching and broadband near-infrared photoluminescence

Two-dimensional(2D)lead halide perovskites have attracted tremendous attention due to their outstanding physical properties.However,the presence of toxic lead is a major problem for large-scale applications.Here,we report the synthesis,phase transition,dielectric and photoluminescence(PL)properties of a lead-free 2D Ge-based perovskite(BIM)_(2)GeI_(4)(BIM=benzimidazolium)which experiences a phase transition at 405 K accompanied by an order-disorder change of organic spacer.Moreover,the step-like dielectric transition near the phase transition temperature makes it suitable for dielectric switching.Meanwhile,(BIM)_(2)GeI_(4)has a direct bandgap of 2.23 eV and broadband emission from 550 to 1000 nm,implying its unique optical property for potential near-infrared lighting and displaying.This work provides a fresh example for the development of lead-free 2D Ge-based perovskite with potential applications in the fields of optoelectronics and high temperature dielectric switching.