Visible light activated SnO2:Dy thin films for the photocatalytic degradation of methylene blue

Abstract

This paper explores the impact of dysprosium (Dy) doping on structural, optical, and photocatalytic properties of tin oxide (SnO₂) thin films fabricated via spray pyrolysis. Dysprosium doping levels ranged from 0 to 7 at%, and films were grown on glass substrates at 350 °C. X-ray diffraction (XRD) analysis revealed an increase in crystallite size with Dy doping, signifying improved crystalline quality. Simultaneously, dislocation density and strain decreased, indicating enhanced film quality. Texture coefficient (T_chkl) results showed a predominant crystal orientation along the (110) plane due to Dy doping. Optical band gap energy (E_g) decreased with Dy doping up to 5%. Urbach energy increased with Dy doping, suggesting atomic structural flaws and defects. Scanning electron microscopy (SEM) analysis revealed the presence of numerous micro-aggregates on the film's surface. Notably, the density of these micro-aggregates increased proportionally with higher Dy doping levels, particularly emphasizing the pronounced effect observed in SnO₂:Dy 5% thin films. These findings underscore the potential of Dy-doped SnO₂ thin films for advanced photocatalytic applications, with SnO₂:Dy 5% exhibiting favorable properties and demonstrating a 90.99% degradation efficiency in three hours under solar irradiation.