Investigation of the structural, optical, and electrical properties of the (CH₃NH₃)₃(SbCl₅)·Cl compound

Single crystals of (CH₃NH₃)₃(SbCl₅)·Cl were synthesized via slow evaporation. X-ray diffraction revealed a monoclinic structure (space group P2₁/m) with lattice parameters a = 13.0073 Å, b = 8.0388 Å, c = 15.1149 Å, and β = 95.669°. Optical studies indicated a direct band gap of 2.34 eV. Photoluminescence studies showed a broad emission centered at 600-610 nm with a full width at half-maximum of 100-150 nm, suggesting self-trapped excitons. Impedance spectroscopy from 313 to 363 K and 0.1 to 10⁶ Hz showed that the direct current conductivity increased from 5.26 × 10^-7 Ω^-1 cm^-1 at 313 K to 7.20 × 10^-5 Ω^-1 cm^-1 at 363 K, following Arrhenius behavior with an activation energy of 0.27 eV. Relaxation frequency exhibited thermally activated behavior with an activation energy of 0.49 eV. Alternating current conductivity obeyed Jonscher's universal power law, with the exponent ranging from 0.53 to 0.76 and increasing with temperature. Charge transport was governed by non-overlapping small polaron tunneling. The temperature evolution of the imaginary modulus peak revealed a stretching exponent varying between 0.47 and 0.48, confirming a thermally activated non-Debye relaxation mechanism. A correlation between the ionic conductivity and crystallographic channels along the 101 direction was established, highlighting the potential for fabricating optoelectronic and ionic devices.