B/N-doping-induced non-radiative relaxation dynamics in graphene quantum dots

Doping graphene quantum dots (GQDs) with heteroatoms is a typical approach to tailoring their electrical structure to different applications. The effect of the doping atoms on the photoluminescence properties of GQDs, especially the non-radiative decay dynamics, is poorly understood. This study investigates the optoelectronic properties of undoped and B/N-doped GQDs using density functional theory (DFT). In addition, the role of B/N-doping in the non-radiative decay dynamics of GQDs has been investigated. Both B- and N-doping break the integrity of the π-conjugated system, leading to midgap states within the bandgaps of GQDs. Electron trapping and hole trapping are two phases of the non-radiative relaxation dynamics in B/N-doped GQDs. For N-doped GQDs, electron trapping is the rate-limiting step, while for B-doped GQDs, hole trapping is the rate-limiting step. These computational results contribute to a better understanding of the role of heteroatom doping in the quantum yield of GQDs.