Cs2ZnCl4: a lead-free all-inorganic perovskite with a large dielectric permittivity †

In recent years, inorganic perovskite materials based on metallic halides have attracted significant attention due to their non-toxicity and ease of synthesis, making them suitable for various applications. This article describes the slow evaporation approach at room temperature for the fabrication of a non-toxic inorganic perovskite based on metallic halide Cs₂ZnCl₄. This compound crystallizes in the orthorhombic phase of the Pnma space group, as confirmed by room temperature X-ray diffraction. Through SEM-EDX studies, the morphological distribution and grain size of the Cs₂ZnCl₄ crystal were determined. Optical investigations of our compound in the 200–800 nm wavelength range indicate that the direct band gap has a value of around 3.80 eV. The photoluminescence analysis reveals the highest emission peak at around 340 nm. By employing the Cauchy law in ellipsometry spectroscopy, the refractive index (n) and the extinction coefficient (k) were determined. Moreover, a fluorescence image of Cs₂ZnCl₄ powder was captured using a confocal microscope. The electrical properties, including the dielectric constant, the loss factor, and the electrical modulus, have been determined in the temperature range of 313 to 433 K. Utilizing the Maxwell–Wagner effect as proposed by the Koop theory, the thermal variation of permittivity has been interpreted. The Kohlrausch–Williams–Watts equation (KWW) was used to assess the asymmetric curves of the electrical modulus.