Abstract
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•Vibrationally resolved absorption/fluorescence spectra of hBN dots are investigated.•Vibronic transitions clarify the details of the ground-first state excitation.•The absorption and fluorescence spectra are asymmetric.•The absorption and fluorescence spectra show that the optical band gap equals ∼5 eV.•The optical gap can be smothely decreased to ∼0.5 eV by doping with C-atoms.
The vibrationally-resolved absorption and fluorescence spectra of square hexagonal boron nitride (shBN) quantum dot are studied using time dependent DFT calculations. The details of the first excited state in the UV–Vis absorption spectrum significantly clarified by the inclusion of vibronic transitions. The lowest vibronic transition in the absorption or fluorescence spectra shows that shBN has a wide optical energy gap of 4.93 eV. The absorption-fluorescence spectra indicate that doping with three C-atoms (doping percentage of 6%) decreases the optical energy gap to 0.46 eV. Doping also significantly enhances the interaction with the incident photon due to the boosted dipole strength.