Synthesis and trigonal structure of a new lead-free zero-dimensional perovskite (CH3NH3)2[SnBr6] with multifunctional optical and electrical properties

Abstract

Tin-halide perovskites have recently gained attention as a promising alternative to lead-halide perovskites for optoelectronic and photovoltaic applications. This study focuses on synthesizing and characterizing the zero-dimensional perovskite-type halide (CH₃NH₃)₂[SnBr₆]. The compound was successfully synthesized through the slow evaporation technique at ambient temperature. The crystal structure was determined using diffraction data from a single crystal, confirming that the compound crystallizes in the R-3m trigonal space group. Furthermore, X-ray diffraction analysis of the powdered sample, obtained by grinding multiple crystals, demonstrated that all crystals share an identical chemical composition. Raman spectroscopy provided comprehensive insights into the vibrational properties of the material. Optical absorption analysis revealed a direct band gap of approximately 3.21 eV, indicating the semiconductor nature of the material. The complex impedance spectroscopy (CIS) method is employed to investigate the material's electrical and dielectric behaviors, with an emphasis on carrier dynamics, grain boundaries influence, dielectric relaxation (localized relaxation), and long-range conduction (non-localized relaxation). Analyzing the complex impedance and electric modulus allows identifying the grain boundary's contribution to the material's conductive and dielectric properties, revealing a non-Debye relaxation behavior. The compound demonstrates low dielectric loss and a high permittivity value (ε ∼ 10³). By addressing the scientific challenge of improving material performance for microelectronics, this research advances the field and paves the way for further exploration and application of organic-inorganic hybrid materials.