Synthesis and investigation of optical and high-temperature conduction mechanism of pure and S-GQDs thin films as a transparent conducting material
摘要
Nowadays, carbon-based materials, especially graphene quantum dots, are one of the most promising transparent and conducting materials in optoelectronic devices. The doping of heteroatoms, such as sulfur, nitrogen, boron, phosphorus, and oxygen, into the carbon lattice structure has a significant impact on its structural, optical, and electrical properties. In this context, the study of sulfur-doped graphene quantum dot thin films is important due to their applications in various technological fields, owing to their tunable optical, electronic, and chemical properties. Therefore, this study investigates the structural, morphological, optical, and temperature-dependent electrical properties of pure and sulfur-doped graphene quantum dots thin films synthesized using hydrothermal and spin-coating techniques. The formation of graphene quantum dots has been confirmed by HR-TEM analysis, depicting an average particle size of 4.5 nm for the pure graphene quantum dots, which then increases to 7.7 nm on 9% sulfur doping. The atomic force microscopy study reveals that the average surface roughness value increases as sulfur atoms are incorporated into graphene quantum dot thin films. Further, the prepared samples exhibit a decrease in energy bandgap value from 4.51 eV for pure graphene quantum dots to 4.37 eV in the 9% sulfur-doped sample. Also, the pure graphene quantum dots thin film depicts high optical transparency of 87%, which decreases to 81% in a 9% sulfur-doped graphene quantum dots thin film at 700 nm. In addition, the graphene quantum dots thin film exhibits temperature-dependent electrical characteristics over the temperature range of 295 K to 573 K and the voltage range of 2 to 60 V. The electrical resistivity was found to decrease to 3.06 × 104 Ohm⋅cm for a 9% sulfur-doped graphene quantum dots thin film from 6.07 × 105 Ohm⋅cm in the case of the graphene quantum dots thin film. Moreover, the high optical transparency and decreased resistivity up to 3.06 × 104 Ohm⋅cm at 573 K for the 9% sulfur-doped graphene quantum dots may suggest its utilization as a transparent conducting material in optoelectronic devices.