Abstract
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)2GeI4(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)2GeI4 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.
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