A density functional theory investigation of the symmetry, size and edge morphology of hexagonal boron nitride quantum dots as topological regulators for tunable optoelectronic devices

This work extensively investigates the distinctive signatures of the various topological parameters (symmetry, size and edge termination nature) on the electronic and optical attributes of hexagonal boron nitride quantum dots (BNQDs). Our time-dependent density functional theory based studies highlight that the electronic bandgap and optical absorption range of highly-symmetric diamond shaped BNQDs exhibit higher sensitivity to size enhancement in comparison to low-symmetric triangular or asymmetric shaped BNQDs. The computed spectral profile reveals that variation in symmetry and size modulates the energy of the most intense (MI) absorption peak more conspicuously than the first optical peak. The edge termination nature predominantly governs the energy bandgap and nature of shift of the entire absorption spectrum. The transition dipole moment density identifies the relation between the degree of electron-hole delocalization and the unique direction of energy-shift exhibited by the MI peak due to symmetry variation of BNQDs. Also, these topological factors regulate exclusively the charge-transfer character of the excited states, essential for photoluminescence applications. This comprehensive theoretical analysis opens up new horizons for the applicability of morphologically flexible BNQDs in fabricating new-generation optoelectronic devices.