Synthesis and Study of Pure and Nitrogen-Doped Graphene Quantum Dot Thin Films as a Transparent and Conducting Electrode
摘要
Pure and nitrogen-doped graphene quantum dots thin films were synthesized using hydrothermal and spin-coating techniques. The prepared thin films have been characterized by high-resolution transmission electronic spectroscopy (HR-TEM), atomic force microscopy, ultraviolet–visible spectroscopy, and two-probe resistivity measurement techniques. The formation of graphene quantum dots has been confirmed by HR-TEM analysis, depicting the particle size average of 4.738 ± 0.002 nm in pure graphene quantum dot film, which then increases to 7.385 ± 0.003 nm in 9% nitrogen-doped graphene quantum dots. The energy dispersive spectroscopy study has confirmed the substitutional doping of nitrogen in the graphene quantum dots structure. Further, the prepared samples exhibited a decrease in their energy bandgap value from 4.52 ± 0.01 eV for pure graphene quantum dots to 4.39 ± 0.02 eV with an increase in nitrogen concentration up to 9%. Also, the graphene quantum dot thin film showed a high optical transmittance of 91%, which then decreased to 87%, and for 9% graphene quantum dot thin film at 700 nm. In addition to this, the high temperature-dependent electrical study within the 303- to 573-K temperature region, and the 3 to 120 V voltage region showed increased conductivity up to 1.62 × 104 S cm−1 for the 9% nitrogen-doped graphene quantum dots from 1.05 × 10−5 S cm−1 for pure graphene quantum dot thin film. Moreover, the high optical transparency and increased conductivity up to 1.62 × 10−4 S cm−1 at 573 K for 9% nitrogen-doped graphene quantum dots make it an efficient transparent conducting material in various optoelectronic devices.
Graphical Abstract