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<p>A thorough investigation of perovskite structures formed through doping is essential for advancing the efficiency and stability of perovskite solar cells. In this study, Bi-doped FAPbI<sub>3</sub> perovskite films with varying Bi concentrations (0.5–2%) were fabricated using a spin-coating technique on ITO glass substrates. Then the films’ phase structure, local structure, and optical characteristics were analyzed. X-ray diffraction (XRD) analysis revealed that the pristine FAPbI<sub>3</sub> film exhibited both hexagonal and cubic phases, indicating structural instability. In contrast, Bi-doped FAPbI<sub>3</sub> films predominantly displayed a cubic perovskite structure, with a notable reduction in the XRD peak intensity corresponding to the hexagonal phase. UV–Vis spectroscopy showed that the undoped FAPbI<sub>3</sub> film had an absorption edge in the visible-near infrared range, while Bi-doping caused a redshift, indicating a reduction in the optical band gap. The calculated results show that optical band gaps decrease with increasing Bi, from a value of 1.49 (pure) to 1.43 (2% Bi) eV. X-ray absorption near edge structure (XANES) analysis confirmed the oxidation states of Pb<sup>2+</sup> and Bi<sup>3+</sup> ions across all samples, with Bi ions replacing Pb in the local structure. Photoluminescence (PL) measurements revealed an increased PL intensity with 1% Bi doping (7 <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41598_2025_2226_Article_IEq1.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\(\times\)</EquationSource> </InlineEquation> 10<sup>5</sup>) compared with pristine FAPbI<sub>3</sub> (4.7 <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41598_2025_2226_Article_IEq1.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\(\times\)</EquationSource> </InlineEquation> 10<sup>5</sup>), suggesting a reduction in carrier recombination. These findings demonstrate the potential of Bi-doping to stabilize perovskite structures with improved optoelectronic properties.</p>

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Characterization of Bi-doped FAPbI3 perovskite films investigated by X-ray absorption spectroscopy

  • 期刊论文

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  • 发表日期：

    2025年5月26日

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  • Tirapat Wechprasit,
  • Atipong Bootchanont,
  • Yingyot Infahsaeng,
  • Poramed Wongjom,
  • Suttipong Wannapaiboon,
  • Anusit Kaewprajak,
  • Pisist Kumnorkaew,
  • Wutthigrai Sailuam,
  • Wittawat Saenrang,
  • Wisanu Pecharapa,
  • Wasan Maiaugree

摘要

A thorough investigation of perovskite structures formed through doping is essential for advancing the efficiency and stability of perovskite solar cells. In this study, Bi-doped FAPbI3 perovskite films with varying Bi concentrations (0.5–2%) were fabricated using a spin-coating technique on ITO glass substrates. Then the films’ phase structure, local structure, and optical characteristics were analyzed. X-ray diffraction (XRD) analysis revealed that the pristine FAPbI3 film exhibited both hexagonal and cubic phases, indicating structural instability. In contrast, Bi-doped FAPbI3 films predominantly displayed a cubic perovskite structure, with a notable reduction in the XRD peak intensity corresponding to the hexagonal phase. UV–Vis spectroscopy showed that the undoped FAPbI3 film had an absorption edge in the visible-near infrared range, while Bi-doping caused a redshift, indicating a reduction in the optical band gap. The calculated results show that optical band gaps decrease with increasing Bi, from a value of 1.49 (pure) to 1.43 (2% Bi) eV. X-ray absorption near edge structure (XANES) analysis confirmed the oxidation states of Pb2+ and Bi3+ ions across all samples, with Bi ions replacing Pb in the local structure. Photoluminescence (PL) measurements revealed an increased PL intensity with 1% Bi doping (7 \(\times\) 105) compared with pristine FAPbI3 (4.7 \(\times\) 105), suggesting a reduction in carrier recombination. These findings demonstrate the potential of Bi-doping to stabilize perovskite structures with improved optoelectronic properties.