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<p>Inorganic CsPbI<sub>3</sub> perovskite has emerged as a promising light-absorbing material for photovoltaic applications, offering a suitable band gap for solar energy conversion and greater stability in ambient conditions compared to organic–inorganic halide perovskites. Nevertheless, the photoactive α-phase of CsPbI<sub>3</sub> remains stable only at higher temperatures, with a rapid phase transition to the inactive δ-phase occurring under room temperature conditions. Herein, we introduce a non-stoichiometric ratio of KI into CsPbI<sub>3</sub> film to stabilize the α-phase at room temperature. (XRD) analysis shows that the prepared CsPbI<sub>3</sub>:<i>x</i>%KI, <i>x</i> = 0.0, 0.3, 0.5, 0.7, 1.0%, films exhibit the α-phase, notably, with 0.7% KI enhancing stability under ambient conditions. Also, scanning electron microscopy (SEM) showed that the optimal morphology was achieved with 0.7% KI. Grain size decreased with 0.7%KI then slightly increased with the addition of 1%, suggesting a suitable ratio for photovoltaic applications. Additionally, UV–Vis spectroscopy was employed to analyze the optical properties, demonstrating enhanced light absorption in the doped films. In the visible region, the absorption reduced sharply to its lowest value for the CsPbI<sub>3</sub>:0.3%KI film and then increased as the KI ratio continued to rise. The optical energy gap (<i>E</i><sub>g</sub>) value of pristine CsPbI<sub>3</sub> film is 1.692&#xa0;eV, which is reduced slightly and irregularly as the amount of KI doping increased, with the 0.5% KI-doped film attaining the lowest <i>E</i><sub>g</sub> value of 1.681&#xa0;eV. Additionally, the photoluminescence (PL) spectroscopy showed higher intensity with 0.7%KI film, indicating fewer traps /defects and delayed recombination, improving the cell performance. These results suggest that KI doping significantly enhances the stability and optical properties of <i>CsPbI</i><sub><i>3</i></sub>, making it promising for perovskite solar cells.</p>

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Impact of non-stoichiometric ratios of the KI on the structure stability and optical properties of α-CsPbI3 perovskite thin films

  • 期刊论文

  • 发表日期：

    2025年5月10日

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  • Hadeer Mohamed Helal,
  • Sameh I. Ahmed,
  • Mohamed Bakr Mohamed,
  • Ahmed Mourtada Elseman,
  • Zein K. Heiba,
  • Hassan Elshimy

摘要

Inorganic CsPbI3 perovskite has emerged as a promising light-absorbing material for photovoltaic applications, offering a suitable band gap for solar energy conversion and greater stability in ambient conditions compared to organic–inorganic halide perovskites. Nevertheless, the photoactive α-phase of CsPbI3 remains stable only at higher temperatures, with a rapid phase transition to the inactive δ-phase occurring under room temperature conditions. Herein, we introduce a non-stoichiometric ratio of KI into CsPbI3 film to stabilize the α-phase at room temperature. (XRD) analysis shows that the prepared CsPbI3:x%KI, x = 0.0, 0.3, 0.5, 0.7, 1.0%, films exhibit the α-phase, notably, with 0.7% KI enhancing stability under ambient conditions. Also, scanning electron microscopy (SEM) showed that the optimal morphology was achieved with 0.7% KI. Grain size decreased with 0.7%KI then slightly increased with the addition of 1%, suggesting a suitable ratio for photovoltaic applications. Additionally, UV–Vis spectroscopy was employed to analyze the optical properties, demonstrating enhanced light absorption in the doped films. In the visible region, the absorption reduced sharply to its lowest value for the CsPbI3:0.3%KI film and then increased as the KI ratio continued to rise. The optical energy gap (Eg) value of pristine CsPbI3 film is 1.692 eV, which is reduced slightly and irregularly as the amount of KI doping increased, with the 0.5% KI-doped film attaining the lowest Eg value of 1.681 eV. Additionally, the photoluminescence (PL) spectroscopy showed higher intensity with 0.7%KI film, indicating fewer traps /defects and delayed recombination, improving the cell performance. These results suggest that KI doping significantly enhances the stability and optical properties of CsPbI3, making it promising for perovskite solar cells.