Structural Elucidation of Electrical and Optical Properties in Lead‐free Organic‐Inorganic Copper Bromide [(CH₃)₄N]₂CuBr₄ Single Crystals

Abstract

Organic‐inorganic metal halide single crystals have attracted a lot of attention due to their flexible structural design and excellent optoelectronic applications. This study details the synthesis of copper‐based [(CH3)4N]2CuBr4 hybrid metal halide single crystals via a slow evaporation method. The crystal structure, crystal habit, chemical groups, intermolecular interactions, electrical properties of the sample were studied via single crystal x‐ray diffraction, scanning electron microscopy, Raman and Fourier transform infrared spectrometer, Hirshfeld surface analysis, impedance spectroscopy, and modulus spectroscopy, respectively. An orthorhombic crystal system with the non‐centrosymmetric space group Pna21 was identified at room temperature. The deformation in the tetrahedra was calculated by the bond angle and bond length deformation index. The Cole‐Cole plot displayed the existence of depressed semicircles, which indicated the predominant distribution of grains, further confirmed by the SEM image. The deformed semi‐circular arcs on the electric modulus curve undeniably prove that the bulk effect dominates the material‘s electrical properties. Significantly, the compound presents a phase transition at ~240 K and excellent thermal stability up to a temperature of 400 K. Therefore, our research sheds light on the temperature dependence of electrical responses in these hybrid crystals and gives inspiration for the development of single crystal‐based efficient energy devices.