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<p>Lead-free perovskite CsEuBr<sub>3</sub> has recently attracted attention for its potential in blue-light applications, yet its specific electronic and excitonic behaviors have lacked detailed theoretical exploration. To address this, we investigated the material’s spin-polarized electronic structure and optical properties using Density Functional Theory plus U (DFT + U, U = 6.1&#xa0;eV) combined with the GW approximation and Bethe-Salpeter equation (BSE). Our calculations for the Pnma phase yielded lattice constants (a = 8.33 Å, b = 8.44 Å, c = 11.94 Å) that align closely with experimental benchmarks. The DFT + U analysis indicates a direct spin-up band gap of 2.87&#xa0;eV at the Γ-point, originating from Eu 4f-5d transitions, whereas the spin-down channel exhibits a much wider gap of 4.54&#xa0;eV. Furthermore, many-body GW + BSE calculations reveal a strong exciton peak at 2.7&#xa0;eV with a binding energy near 100 meV, which is consistent with the experimentally reported blue emission at ~ 2.77&#xa0;eV. Additionally, a computationally spurious sub-gap feature at ~ 0.5&#xa0;eV is critically evaluated and attributed to the over-binding effect of the static BSE kernel on highly localized 4f states. Overall, these results underscore the importance of electron-hole correlations and localized Eu-4f states in driving strong excitonic emission, confirming CsEuBr<sub>3</sub> as a viable, eco-friendly candidate for optoelectronics.</p>

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Spin-polarized electronic structure and excitonic properties of lead-free orthorhombic CsEuBr3: a combined DFT + U and GW-BSE study

  • 期刊论文

  • 发表日期：

    2026年6月25日

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  • Yuxi Bi,
  • Junxiang Hong,
  • Longbo Yang,
  • Lihong Han,
  • Gang Liu,
  • Bohao Cui

摘要

Lead-free perovskite CsEuBr3 has recently attracted attention for its potential in blue-light applications, yet its specific electronic and excitonic behaviors have lacked detailed theoretical exploration. To address this, we investigated the material’s spin-polarized electronic structure and optical properties using Density Functional Theory plus U (DFT + U, U = 6.1 eV) combined with the GW approximation and Bethe-Salpeter equation (BSE). Our calculations for the Pnma phase yielded lattice constants (a = 8.33 Å, b = 8.44 Å, c = 11.94 Å) that align closely with experimental benchmarks. The DFT + U analysis indicates a direct spin-up band gap of 2.87 eV at the Γ-point, originating from Eu 4f-5d transitions, whereas the spin-down channel exhibits a much wider gap of 4.54 eV. Furthermore, many-body GW + BSE calculations reveal a strong exciton peak at 2.7 eV with a binding energy near 100 meV, which is consistent with the experimentally reported blue emission at ~ 2.77 eV. Additionally, a computationally spurious sub-gap feature at ~ 0.5 eV is critically evaluated and attributed to the over-binding effect of the static BSE kernel on highly localized 4f states. Overall, these results underscore the importance of electron-hole correlations and localized Eu-4f states in driving strong excitonic emission, confirming CsEuBr3 as a viable, eco-friendly candidate for optoelectronics.