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<p>As global energy demands intensify and environmental concerns over lead-based materials grow, lead-free halide double perovskites (HDPs) have emerged as promising alternatives for clean energy applications. This study offers a detailed first-principles investigation into the structural, elastic, optoelectronic, and thermoelectric properties of Na<sub>2</sub>LiTlZ<sub>6</sub> (Z = Br, Cl). Both compounds crystallize in a stable cubic structure, with favorable formation energies, tolerance factors, and phonon spectra confirming their structural and dynamical stability. Elastic analysis reveals that while both materials exhibit ductility and mechanical anisotropy, Na<sub>2</sub>LiTlCl<sub>6</sub> demonstrates higher stiffness and thermal resistance. Electronic band structure calculations using the TB-mBJ potential indicate direct band gaps of 1.541&#xa0;eV (Br) and 2.910&#xa0;eV (Cl), making them suitable for solar energy applications. Optical evaluations highlight strong visible-light absorption, low reflectivity, and efficient exciton dissociation, which are key traits for photovoltaic performance. Na<sub>2</sub>LiTlBr<sub>6</sub> achieves a high spectroscopic limited maximum efficiency (SLME) of 31.60%, nearing the Shockley–Queisser limit and outperforming several traditional PV absorbers. Thermoelectric assessments show both materials exhibit high Seebeck coefficients (~ 207&#xa0;μV/K), moderate electrical conductivity, and near-unity ZT values (0.99 for Br, 0.98 for Cl) at 300&#xa0;K, with excellent stability at elevated temperatures. These results position Na<sub>2</sub>LiTlZ<sub>6</sub>, particularly the Br variant, as a versatile, lead-free candidate for next-generation solar and thermoelectric technologies.</p>

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Exploring the multifunctional potential of lead-free Na2LiTlZ6 (Z = Br, Cl) perovskites: a first-principles study of their photovoltaic and thermoelectric behavior

  • 期刊论文

  • 发表日期：

    2025年11月10日

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  • T. R. Hammad,
  • Samah Al-Qaisi,
  • Norah Algethami,
  • Abderrazak Boutramine,
  • Hind Saeed Alzahrani,
  • Amani H. Alfaifi,
  • Malak Azmat Ali,
  • Javed Rehman,
  • Abid Zaman,
  • Habib Rached

摘要

As global energy demands intensify and environmental concerns over lead-based materials grow, lead-free halide double perovskites (HDPs) have emerged as promising alternatives for clean energy applications. This study offers a detailed first-principles investigation into the structural, elastic, optoelectronic, and thermoelectric properties of Na2LiTlZ6 (Z = Br, Cl). Both compounds crystallize in a stable cubic structure, with favorable formation energies, tolerance factors, and phonon spectra confirming their structural and dynamical stability. Elastic analysis reveals that while both materials exhibit ductility and mechanical anisotropy, Na2LiTlCl6 demonstrates higher stiffness and thermal resistance. Electronic band structure calculations using the TB-mBJ potential indicate direct band gaps of 1.541 eV (Br) and 2.910 eV (Cl), making them suitable for solar energy applications. Optical evaluations highlight strong visible-light absorption, low reflectivity, and efficient exciton dissociation, which are key traits for photovoltaic performance. Na2LiTlBr6 achieves a high spectroscopic limited maximum efficiency (SLME) of 31.60%, nearing the Shockley–Queisser limit and outperforming several traditional PV absorbers. Thermoelectric assessments show both materials exhibit high Seebeck coefficients (~ 207 μV/K), moderate electrical conductivity, and near-unity ZT values (0.99 for Br, 0.98 for Cl) at 300 K, with excellent stability at elevated temperatures. These results position Na2LiTlZ6, particularly the Br variant, as a versatile, lead-free candidate for next-generation solar and thermoelectric technologies.