| Summary: | Electronic and optical properties of the graphene nanoflakes (GNFs) are investigated with and without various concentrations of S impurities in different locations via a time-dependent density-functional theory (TDDFT) calculation. Results showed very fascinating results. Results showed up that the pristine GNFs have a semiconductor behavior. S-doped GNFs also have a semiconductor behavior with reducing electronic band gap value. The band gap of the GNFs is reduced by altering the location of the S impurity. Correspondingly, it is decreased by increasing the concentration of the S impurity. Also, when the concentration of S goes up, the total and formation energies are increased with negative sign, which means the structures became more stable and exothermic process. Our findings show λ max also depends on the site and concentrations of S impurity, which is taken value from 474.54 to 12514.22 nm for pristine and 3S-PNG (a) cases, respectively. Correspondingly, we observed that the sturdy absorption peaks (pristine, 1S-PNG (a), 4S-PNG (b)) cases are in the visible light and near-infrared region. In brief, the optoelectronics properties of the GNFs are dependent on the position and concentrations of S impurities.
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