Organic–inorganic copper( <scp>ii</scp> )-based perovskite: a low-toxic, highly stable light absorber for optoelectronic applications

Organic-inorganic hybrid perovskites have emerged as promising next-generation materials for high-performance optoelectronic devices due to their structural tunability and versatile physical properties. In this work, bis(triethylammonium) chlorocuprate(ii), [(C₂H₅)₃NH]₂CuCl₄ was successfully synthesized <i>via</i> a slow evaporation method. The crystal structure, morphology, and optical and electrical properties of [(C₂H₅)₃NH]₂CuCl₄ were systematically investigated using powder X-ray diffraction (PXRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), Raman spectroscopy, UV-visible spectroscopy, and complex impedance spectroscopy. PXRD analysis reveals that the compound crystallizes in a monoclinic system with a centrosymmetric <i>P</i>2₁/<i>c</i> space group at room temperature. SEM observations show uniformly distributed grains with an average size of approximately 17.5 µm, separated by well-defined grain boundaries, while EDS analysis confirms the expected elemental composition, indicating successful synthesis of the hybrid material. Raman spectroscopy confirms the coexistence of vibrational modes characteristic of both the organic and inorganic components. Optical absorption measurements recorded in the 200-800 nm range reveal a wide direct band gap of approximately 2.36 ± 0.004 eV, characteristic of semiconducting hybrid perovskites. Electrical investigations demonstrate that the AC conductivity follows Jonscher's universal power law, indicating a thermally activated charge transport process over the investigated frequency range. Moreover, the temperature dependence of the frequency exponent <i>s</i> reveals that the correlated barrier hopping (CBH) model governs the electrical conduction mechanism in the studied material. Furthermore, complex modulus analysis provides additional insight into the relaxation behavior and the dominant electrical transport mechanisms.