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<p>Germanium-based materials are attracting growing attention as environmentally friendly alternatives for optoelectronic and energy-related applications. In this work, lead-free Na<sub>2</sub>GeO<sub>3</sub> was successfully synthesized via a conventional solid-state reaction and structurally confirmed by x-ray diffraction to crystallize in an orthorhombic system (space group Cmc2<sub>1</sub>). Optical investigations reveal an indirect bandgap of approximately 3.03&#xa0;eV, indicating semiconducting behavior suitable for UV-region applications. The optical response was further analyzed through the determination of the Urbach energy, extinction coefficient, and penetration depth, providing insight into the degree of structural disorder and electron–phonon interactions. Impedance spectroscopy measurements performed over 453–673&#xa0;K and 10&#xa0;Hz–3&#xa0;MHz demonstrate thermally activated conduction behavior. The AC conductivity follows Jonscher's single and double power laws depending on temperature, confirming the dominance of the correlated barrier hopping (CBH) mechanism at lower temperatures and the combined contribution of CBH and non-overlapping small-polaron tunneling (NSPT) at higher frequencies. Dielectric analysis reveals a pronounced non-Debye relaxation behavior governed by Maxwell–Wagner interfacial polarization effects. Notably, the compound exhibits a high dielectric permittivity reaching ~1.4 × 10<sup>5</sup> at low frequencies. These results highlight Na<sub>2</sub>GeO<sub>3</sub> as a promising lead-free material with attractive optical and dielectric properties for energy storage and optoelectronic device applications.</p>

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Electronic Behavior, Charge-Carrier Transport Properties, and Dielectric Polarization of Lead-Free Sodium Metagermanate (Na2GeO3) Perovskite: Insights into Its Optoelectronic Potential

  • 期刊论文

  • 发表日期：

    2026年3月27日

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  • Iheb Garoui,
  • Sourour Ben Yahya,
  • Saber Nasri,
  • Mona A. Alamri,
  • Mohamed Tliha,
  • Abderrazek Oueslati,
  • Bassem Louati

摘要

Germanium-based materials are attracting growing attention as environmentally friendly alternatives for optoelectronic and energy-related applications. In this work, lead-free Na2GeO3 was successfully synthesized via a conventional solid-state reaction and structurally confirmed by x-ray diffraction to crystallize in an orthorhombic system (space group Cmc21). Optical investigations reveal an indirect bandgap of approximately 3.03 eV, indicating semiconducting behavior suitable for UV-region applications. The optical response was further analyzed through the determination of the Urbach energy, extinction coefficient, and penetration depth, providing insight into the degree of structural disorder and electron–phonon interactions. Impedance spectroscopy measurements performed over 453–673 K and 10 Hz–3 MHz demonstrate thermally activated conduction behavior. The AC conductivity follows Jonscher's single and double power laws depending on temperature, confirming the dominance of the correlated barrier hopping (CBH) mechanism at lower temperatures and the combined contribution of CBH and non-overlapping small-polaron tunneling (NSPT) at higher frequencies. Dielectric analysis reveals a pronounced non-Debye relaxation behavior governed by Maxwell–Wagner interfacial polarization effects. Notably, the compound exhibits a high dielectric permittivity reaching ~1.4 × 105 at low frequencies. These results highlight Na2GeO3 as a promising lead-free material with attractive optical and dielectric properties for energy storage and optoelectronic device applications.