Synthesis and investigation of structural and high temperature conduction mechanism of TiO 2 /N-GQDs nanocomposite thin films as a transparent conducting material

Abstract

This study includes the synthesis and characterization of N-GQDs, pure TiO₂, and TiO₂/N-GQDs nanocomposites thin films prepared by spin-coating technique. The gel of TiO₂ nanoparticles and N-GQDs was prepared using sol-gel and hydrothermal techniques, respectively. Further, the TiO₂/N-GQDs nanocomposites were prepared by sol-gel method in the weight % ratio of 90 TiO₂/10 N-GQDs and 80 TiO₂/20 N-GQDs. The structural, optical and electrical behaviour of these thin film has been investigated using XRD, AFM, HR-TEM, UV-Visible spectroscopy and two probe methods. The XRD study had confirmed the tetragonal structure of TiO₂. The average crystallite size calculated using Debye-Scherrer’s equation has been found to be 13.56 nm for TiO₂ which decreases up to 11.31 nm for 80 TiO₂/20 N-GQDs. The HR-TEM analysis had confirmed the successful formation of N-GQDs having the average particle size about 8.63 nm. Further, the optical band gap was found to be 4.33 eV, 3.16 eV for N-GQDs, TiO₂ which increases up to 3.88 eV for 80 TiO₂/20 N-GQDs thin film. Also, it has been observed that the transparency of 80 TiO₂/20 N-GQDs thin film was increased up to 84.2% in contrast to 75.6% of pure TiO₂. Further, the temperature dependent I–V characteristics of prepared thin films within the temperature range of 293–513 K and voltage range of 0–60 V depicts the decreased resistivity up to 1.85 × 10⁴ Ω-cm at 513 K from 3.35 × 10⁴ Ω-cm at 293 K of 80 TiO₂/20 N-GQDs thin film. Moreover, the increase in the transparency of 80 TiO₂/20N-GQDs thin film and decreased resistivity up to 1.85 × 10⁴ Ω-cm at 513 K suggests its utilization as a transparent and conducting electrode in optoelectronic devices.