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<p>Earth-abundant iron chalcogenides have attracted increasing attention as photoactive semiconductors because of their tunable electronic structures and favorable light-absorption properties. In this study, cubic pyrite FeS<sub>2</sub> and orthorhombic marcasite FeSe<sub>2</sub> were synthesized by a solvothermal method and systematically investigated through experimental characterization combined with density functional theory (DFT) calculations. X-ray diffraction (XRD) and Rietveld refinement confirmed the successful formation of pyrite FeS<sub>2</sub> and marcasite FeSe<sub>2</sub> and provided reliable crystal structure models. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and selected-area electron diffraction (SAED) analyses revealed clear morphological and crystallographic differences: FeS<sub>2</sub> particles were approximately spherical and polycrystalline, whereas FeSe<sub>2</sub> exhibited a block-like morphology with single-crystal-like characteristics. Vibrating sample magnetometry (VSM) measurements showed that both crystals are essentially non-magnetic at room temperature. Optical measurements gave band gaps of 1.02 eV for FeS<sub>2</sub> and 0.70 eV for FeSe<sub>2</sub>, while DFT calculations yielded corresponding values of 0.94 and 0.52 eV, respectively. Both materials were identified as indirect-band-gap semiconductors, with band-edge states mainly arising from strong hybridization between Fe 3<i>d</i> and chalcogen <i>p</i> orbitals. Optical calculations further revealed high absorption coefficients on the order of 10<sup>5</sup> cm<sup>−1</sup> for both compounds, while FeSe<sub>2</sub> showed a broader long-wavelength response due to its narrower band gap. Based on these results, pyrite FeS<sub>2</sub> appears more suitable for photovoltaic applications because of its favorable band gap range and strong UV–visible absorption, whereas marcasite FeSe<sub>2</sub> appears more suitable for near-infrared photodetection. This study provides insight into the structure–property relationships of Fe-based chalcogenides and offers guidance for their rational application in optoelectronic devices.</p>

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Solvothermal synthesis of FeS2 and FeSe2: electronic structure and optical properties

  • 期刊论文

  • 发表日期：

    2026年5月9日

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  • Dong Zhang,
  • Dingming Cao,
  • Yuqi Gao,
  • Xiangyu Li,
  • Haodong Yan,
  • Yalong Chen,
  • He Zhang,
  • Jing Bai,
  • Haonan Yang

摘要

Earth-abundant iron chalcogenides have attracted increasing attention as photoactive semiconductors because of their tunable electronic structures and favorable light-absorption properties. In this study, cubic pyrite FeS2 and orthorhombic marcasite FeSe2 were synthesized by a solvothermal method and systematically investigated through experimental characterization combined with density functional theory (DFT) calculations. X-ray diffraction (XRD) and Rietveld refinement confirmed the successful formation of pyrite FeS2 and marcasite FeSe2 and provided reliable crystal structure models. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and selected-area electron diffraction (SAED) analyses revealed clear morphological and crystallographic differences: FeS2 particles were approximately spherical and polycrystalline, whereas FeSe2 exhibited a block-like morphology with single-crystal-like characteristics. Vibrating sample magnetometry (VSM) measurements showed that both crystals are essentially non-magnetic at room temperature. Optical measurements gave band gaps of 1.02 eV for FeS2 and 0.70 eV for FeSe2, while DFT calculations yielded corresponding values of 0.94 and 0.52 eV, respectively. Both materials were identified as indirect-band-gap semiconductors, with band-edge states mainly arising from strong hybridization between Fe 3d and chalcogen p orbitals. Optical calculations further revealed high absorption coefficients on the order of 105 cm−1 for both compounds, while FeSe2 showed a broader long-wavelength response due to its narrower band gap. Based on these results, pyrite FeS2 appears more suitable for photovoltaic applications because of its favorable band gap range and strong UV–visible absorption, whereas marcasite FeSe2 appears more suitable for near-infrared photodetection. This study provides insight into the structure–property relationships of Fe-based chalcogenides and offers guidance for their rational application in optoelectronic devices.