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<p>Hybrid materials have garnered significant attention due to their versatile properties and broad applicability. This study explores in detail the structural, optical, electrical, and dielectric characteristics of two hybrid compounds, [(C<sub>4</sub>H<sub>9</sub>)<sub>4</sub>N]<sub>2</sub>CoBr<sub>4</sub> and [(C<sub>4</sub>H<sub>9</sub>)<sub>4</sub>N]<sub>2</sub>ZnBr<sub>4</sub>, prepared via a solvent evaporation method. Rietveld refinement of the XRD data confirmed the successful formation of phase-pure [TBA]<sub>2</sub>CoBr<sub>4</sub> and [TBA]<sub>2</sub>ZnBr<sub>4</sub> with monoclinic P2<sub>1</sub>/c and P2<sub>1</sub>/n space groups, respectively. UV–Vis spectrophotometry was employed to investigate the optical properties of the samples. Analysis of absorbance using Tauc’s method revealed a direct band gap of 3.49&#xa0;eV for [TBA]<sub>2</sub>CoBr<sub>4</sub> and 4.88&#xa0;eV for [TBA]<sub>2</sub>ZnBr<sub>4</sub>, reflecting their semiconducting nature. The zinc compound exhibits a higher Urbach energy compared to its cobalt analogue, indicating greater structural disorder and confirming that the central metal cation strongly influences lattice defects and optical properties. The dielectric and electrical behaviors were systematically examined as functions of the frequency using impedance and electric modulus approaches. This allowed a clear distinction between grain and grain boundary contributions, relaxation processes, and charge transport mechanisms. The impedance data were successfully fitted using an equivalent circuit, and the variation in resistance further confirmed the Negative Temperature Coefficient of Resistance (NTCR) behavior for both samples. The compound [TBA]<sub>2</sub>CoBr<sub>4</sub> demonstrates greater conductivity than [TBA]<sub>2</sub>ZnBr<sub>4</sub> within the low-frequency range, which implies either a higher density of mobile carriers or a more favorable activation energy within the cobalt-containing lattice. Furthermore, the cobalt compound displays a notably high dielectric constant (ε' ~ 2.5 × 10<sup>4</sup>), reflecting effective polarization processes and thermally activated charge carrier motion. Analysis of resistance–temperature characteristics (RTCs), fitted using the thermistor equation, underscores the decisive role of the metal cation in tuning the NTCR parameters. Ultimately, these findings highlight the potential of these hybrid halides for next-generation optoelectronic and thermistor applications.</p>

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Impact of metal substitution on the structural, optical and electrical properties of [N(C4H9)4]2XBr4 (X = Zn, Co) for optoelectronic device applications

  • 期刊论文

  • 发表日期：

    2026年5月19日

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  • Ridha Briki,
  • Leila Miladi,
  • Malika Ben Gzaiel,
  • Souad Chkoundali,
  • Mohamed Tliha,
  • Walid Oueslati,
  • Abderrazek Oueslati

摘要

Hybrid materials have garnered significant attention due to their versatile properties and broad applicability. This study explores in detail the structural, optical, electrical, and dielectric characteristics of two hybrid compounds, [(C4H9)4N]2CoBr4 and [(C4H9)4N]2ZnBr4, prepared via a solvent evaporation method. Rietveld refinement of the XRD data confirmed the successful formation of phase-pure [TBA]2CoBr4 and [TBA]2ZnBr4 with monoclinic P21/c and P21/n space groups, respectively. UV–Vis spectrophotometry was employed to investigate the optical properties of the samples. Analysis of absorbance using Tauc’s method revealed a direct band gap of 3.49 eV for [TBA]2CoBr4 and 4.88 eV for [TBA]2ZnBr4, reflecting their semiconducting nature. The zinc compound exhibits a higher Urbach energy compared to its cobalt analogue, indicating greater structural disorder and confirming that the central metal cation strongly influences lattice defects and optical properties. The dielectric and electrical behaviors were systematically examined as functions of the frequency using impedance and electric modulus approaches. This allowed a clear distinction between grain and grain boundary contributions, relaxation processes, and charge transport mechanisms. The impedance data were successfully fitted using an equivalent circuit, and the variation in resistance further confirmed the Negative Temperature Coefficient of Resistance (NTCR) behavior for both samples. The compound [TBA]2CoBr4 demonstrates greater conductivity than [TBA]2ZnBr4 within the low-frequency range, which implies either a higher density of mobile carriers or a more favorable activation energy within the cobalt-containing lattice. Furthermore, the cobalt compound displays a notably high dielectric constant (ε' ~ 2.5 × 104), reflecting effective polarization processes and thermally activated charge carrier motion. Analysis of resistance–temperature characteristics (RTCs), fitted using the thermistor equation, underscores the decisive role of the metal cation in tuning the NTCR parameters. Ultimately, these findings highlight the potential of these hybrid halides for next-generation optoelectronic and thermistor applications.