Transition-Metal Doped Armchair Hexagonal SiC Quantum Dots: Insights into Stability, Electronic Structure, and Optoelectronic Properties from First-Principles Calculations

The rational design of stable, earth-abundant quantum dots with tunable electronic and optical properties is crucial for advancing sustainable optoelectronic and photocatalytic technologies. In this work, density functional theory (DFT) is employed to investigate pristine and 3d transition-metal (TM)-doped armchair hexagonal silicon carbide quantum dots (AH-SiC-QDs, Si₅₇C₅₇H₃₀). Structural analysis reveals that pristine AH-SiC-QDs exhibit high stability (5.612 eV), surpassing previously reported SiC- and AlN-based QDs. Upon TM incorporation, stability remains robust, with Ni-doping providing the strongest binding and Sc-doping the weakest. Electronic structure calculations show significant dopant-induced modifications in HOMO–LUMO distributions and bandgaps, where Ti- and Sc-doped systems achieve remarkable bandgap narrowing (1.056 and 0.919 eV), enhancing electronic coupling with the host lattice. Optical absorption studies demonstrate pronounced red-shifts into the visible and near-infrared regions, with Sc- and V-doped systems offering extended light-harvesting potential. Mulliken charge and natural bond orbital (NBO) analyses confirm strong donor–acceptor interactions, orbital rehybridization, and enhanced charge transfer, directly linking dopant chemistry to improved catalytic and optoelectronic behavior. These findings establish TM-doped AH-SiC-QDs as versatile and highly tunable platforms for next-generation photocatalysis and energy conversion applications.