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<p>In this work, we reported a systematic first-principles density functional theory (DFT) investigation of the structural, electronic, optical, real-space charge density, and thermoelectric properties of pristine CsSnCl₃ and three Eu/Bi co-doped configurations; Eu_Bi_CsSnCl₃ (5%), Eu_2Bi_CsSnCl₃ (7.5%), and 2Eu_Bi_CsSnCl₃ (7.5%), using the TB-mBJ and GGA + U + SOC approaches within the WIEN2k code. Eu_2Bi_CsSnCl₃ was identified as the most thermodynamically stable configuration with a formation energy of − 2.51&#xa0;eV/atom. Co-doping dramatically narrowed the band gap from 3.89&#xa0;eV in pristine CsSnCl₃ to near-metallic values of 0.031–0.057&#xa0;eV, driven by hybridization among Eu 4f, Bi 6p, and host Sn/Cl states. Real-space electron charge density maps revealed a systematic evolution from predominantly ionic bonding in the pristine system toward mixed ionic–covalent character with increasing dopant concentration, underpinning the observed modifications in optical response and band gap narrowing. CIE 1931 chromaticity analysis, derived from first-principles ε₂(ω) spectra, revealed a computationally predicted shift in spectral emission character from cool-white/bluish toward near-warm-white with increasing Eu:Bi ratio. However, these coordinates serve as theoretical screening metrics; the near-metallic band gaps (0.031–0.057&#xa0;eV) of the co-doped systems warrant caution when assessing their suitability for direct PC-LED applications. Thermoelectric analysis revealed a temperature-driven n-type to p-type carrier transition in Eu_Bi_CsSnCl₃, though calculated ZT values remained modest (10⁻<sup>4</sup>–10⁻<sup>3</sup>) as upper-bound estimates. These results establish Eu/Bi co-doped CsSnCl₃ as a computationally characterized narrow band gap perovskite system whose ε₂(ω) spectra encode compositionally tunable spectral power distributions, from which CIE chromaticity coordinates are extracted as first-order theoretical descriptors, demonstrating the utility of this screening approach for directing future experimental investigation toward targeted optoelectronic compositions.</p>

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Chromaticity-tunable white-light emission, real-space charge redistribution, and thermoelectric response in Eu/Bi Co-doped lead-free CsSnCl₃ perovskite: a comprehensive first-principles investigation for phosphor-converted LED applications

  • 期刊论文

  • 发表日期：

    2026年7月10日

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  • Asiya Zaman Khan,
  • Shahid Ali,
  • Habib Arshad,
  • Syed Muhammad Zia-ul-haq,
  • Salman Ahmad,
  • Amin Ur Rahman,
  • Muhammad Shoaib Hanif,
  • Faisal Alresheedi,
  • Muhammad Asif Hasham

摘要

In this work, we reported a systematic first-principles density functional theory (DFT) investigation of the structural, electronic, optical, real-space charge density, and thermoelectric properties of pristine CsSnCl₃ and three Eu/Bi co-doped configurations; Eu_Bi_CsSnCl₃ (5%), Eu_2Bi_CsSnCl₃ (7.5%), and 2Eu_Bi_CsSnCl₃ (7.5%), using the TB-mBJ and GGA + U + SOC approaches within the WIEN2k code. Eu_2Bi_CsSnCl₃ was identified as the most thermodynamically stable configuration with a formation energy of − 2.51 eV/atom. Co-doping dramatically narrowed the band gap from 3.89 eV in pristine CsSnCl₃ to near-metallic values of 0.031–0.057 eV, driven by hybridization among Eu 4f, Bi 6p, and host Sn/Cl states. Real-space electron charge density maps revealed a systematic evolution from predominantly ionic bonding in the pristine system toward mixed ionic–covalent character with increasing dopant concentration, underpinning the observed modifications in optical response and band gap narrowing. CIE 1931 chromaticity analysis, derived from first-principles ε₂(ω) spectra, revealed a computationally predicted shift in spectral emission character from cool-white/bluish toward near-warm-white with increasing Eu:Bi ratio. However, these coordinates serve as theoretical screening metrics; the near-metallic band gaps (0.031–0.057 eV) of the co-doped systems warrant caution when assessing their suitability for direct PC-LED applications. Thermoelectric analysis revealed a temperature-driven n-type to p-type carrier transition in Eu_Bi_CsSnCl₃, though calculated ZT values remained modest (10⁻4–10⁻3) as upper-bound estimates. These results establish Eu/Bi co-doped CsSnCl₃ as a computationally characterized narrow band gap perovskite system whose ε₂(ω) spectra encode compositionally tunable spectral power distributions, from which CIE chromaticity coordinates are extracted as first-order theoretical descriptors, demonstrating the utility of this screening approach for directing future experimental investigation toward targeted optoelectronic compositions.