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<p>This study investigates the structural, morphological, optical, thermoelectric, photodetector, and photocatalytic properties of ZnO, and W-doped ZnO [2, 5, and 10%] thin films deposited via spray pyrolysis at 450&#xa0;°C. The X-ray diffraction (XRD) analysis confirms the hexagonal wurtzite structure, with improved crystallinity and reduced lattice parameters (a, c) due to W incorporation. Crystallite size increases from 32.4&#xa0;nm (pure ZnO) to 39.2&#xa0;nm (5% W-ZnO), while lattice strain decreases from 0.189 to 0.162%. Optical studies reveal a bandgap narrowing from 3.30&#xa0;eV (ZnO) to 3.24&#xa0;eV (10% W-ZnO), attributed to defect states and band tailing. The refractive index at 598&#xa0;nm decreases from 1.78 (ZnO) to 1.68 (2% W-ZnO) but increases to 1.76 for 10% W-ZnO. Seebeck coefficient measurements show an initial decrease from − 321.9&#xa0;μV/K (ZnO) to − 273.9&#xa0;μV/K (5% W-ZnO), followed by an increase to − 348.7&#xa0;μV/K (10% W-ZnO), indicating optimized carrier concentration. Photocurrent response analysis demonstrates that both 2 and 5% W-ZnO exhibit enhanced UV photoresponse, with 2% W-ZnO reaching the highest stable response of 140&#xa0;mA, while 5% W-ZnO also delivers a significantly improved response compared to pure ZnO. Photocatalytic degradation of methylene blue (MB) reaches nearly 100% efficiency within 120&#xa0;min for 2% W-ZnO, with a reaction rate constant of 0.02759&#xa0;min⁻<sup>1</sup> and an R<sup>2</sup> value of 0.9987, confirming its superior photocatalytic activity. Notably, 5% W-ZnO also demonstrates high photocatalytic efficiency, slightly lower than 2% W-ZnO, which highlights that both 2 and 5% W doping levels are optimal depending on the targeted property. These findings indicate that W doping at optimal concentrations (2 and 5%) significantly enhances ZnO’s multifunctional performance for optoelectronic and environmental applications. The photocatalytic degradation behavior of pure ZnO, 2% W-ZnO, and 5% W-ZnO thin films under UV light was further investigated using scavenger experiments, which revealed that W doping enhances degradation efficiency, with hydroxyl and superoxide radicals playing dominant roles in the photodegradation mechanism.</p>

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Enhanced structural, optical, thermoelectric, photodetector, and photocatalytic properties of ZnO and W-doped ZnO thin films synthesized via spray pyrolysis: insights into active species involved in the photocatalytic degradation of methylene blue via scavenger-assisted studies

  • 期刊论文

  • 发表日期：

    2025年10月2日

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  • Sabrina Roguai

摘要

This study investigates the structural, morphological, optical, thermoelectric, photodetector, and photocatalytic properties of ZnO, and W-doped ZnO [2, 5, and 10%] thin films deposited via spray pyrolysis at 450 °C. The X-ray diffraction (XRD) analysis confirms the hexagonal wurtzite structure, with improved crystallinity and reduced lattice parameters (a, c) due to W incorporation. Crystallite size increases from 32.4 nm (pure ZnO) to 39.2 nm (5% W-ZnO), while lattice strain decreases from 0.189 to 0.162%. Optical studies reveal a bandgap narrowing from 3.30 eV (ZnO) to 3.24 eV (10% W-ZnO), attributed to defect states and band tailing. The refractive index at 598 nm decreases from 1.78 (ZnO) to 1.68 (2% W-ZnO) but increases to 1.76 for 10% W-ZnO. Seebeck coefficient measurements show an initial decrease from − 321.9 μV/K (ZnO) to − 273.9 μV/K (5% W-ZnO), followed by an increase to − 348.7 μV/K (10% W-ZnO), indicating optimized carrier concentration. Photocurrent response analysis demonstrates that both 2 and 5% W-ZnO exhibit enhanced UV photoresponse, with 2% W-ZnO reaching the highest stable response of 140 mA, while 5% W-ZnO also delivers a significantly improved response compared to pure ZnO. Photocatalytic degradation of methylene blue (MB) reaches nearly 100% efficiency within 120 min for 2% W-ZnO, with a reaction rate constant of 0.02759 min⁻1 and an R2 value of 0.9987, confirming its superior photocatalytic activity. Notably, 5% W-ZnO also demonstrates high photocatalytic efficiency, slightly lower than 2% W-ZnO, which highlights that both 2 and 5% W doping levels are optimal depending on the targeted property. These findings indicate that W doping at optimal concentrations (2 and 5%) significantly enhances ZnO’s multifunctional performance for optoelectronic and environmental applications. The photocatalytic degradation behavior of pure ZnO, 2% W-ZnO, and 5% W-ZnO thin films under UV light was further investigated using scavenger experiments, which revealed that W doping enhances degradation efficiency, with hydroxyl and superoxide radicals playing dominant roles in the photodegradation mechanism.