▎ 摘　　要

In this paper, a brand new structure based on graphene quantum dots (GQDs) is introduced which is doped with two selenium atoms and functionalized with amino groups simultaneously. The purpose of the structure is to achieve a photoluminescence (PL) spectrum which peaks at free-space communication wavelengths range. Hence, using density functional theory (DFT), time-dependent DFT (TD-DFT) calculations and analyzing charge density distribution, the density and the energy of molecular orbitals and dominant electronic transitions, the energy and the wavelength for dominant excited states and also the density of states (DOS) diagram for pure GQD, selenium-doped GQD and simultaneously doped and functionalized GQD is discussed. PL spectrum of the device is obtained for each three structures. Studying precisely all the mechanisms which affect PL spectrum, it is understood that selenium doping with graphitic configuration by inducing an electrical dipole moment to the structure leads to increasing charge density in pi and pi* orbitals at doped regions. Moreover, by decreasing the gap between dominant transitions, it shifts the PL spectrum peak from 484.4 to 520 nm. After functionalizing the doped structure with NH2 groups with a configuration which is close to the structure that will be obtained at real synthesis conditions and also analyzing the dominant states and DOS diagram, it can be figured out that not only a large electrical dipole moment is induced, but also some new inter-band states are formed within the band gap and these new states improve the interactions between charge carrier transitions in the structure just like the inter band trap levels in optical electronics. In addition, they increase the hybridization between the orbitals and also decrease the gap between dominant transitions and thus the PL spectrum peak will shift to 760 nm.