  This work demonstrates the unique approach of introducing divacancy
imperfections in topological Stone-Wales type defected graphene quantum dots
for harvesting both singlet and triplet excitons, essential for fabricating
fluorescent organic light-emitting diodes. Here, we first reveal that
structural relaxation of these systems establishes the high-spin triplet state
as the stable ground state at room temperature, thereby significantly
increasing their potential in designing spintronic devices. Our extensive
electron-correlated computations then demonstrate that the energetic ordering
of the singlet and triplet states in these relaxed structures can trigger both
prompt and delayed fluorescence of different wavelengths through various decay
channels. Particularly, the position of divacancy determines the tunability
range of the emission wavelengths. In addition, our results obtained from both
multi-reference singles-doubles configurationinteraction (MRSDCI) and
first-principles time-dependent density functional theory (TDDFT) methodologies
highlight that the synergetic effects of divacancy-position,structural
relaxation and spin multiplicity critically govern the nature and magnitude of
shift exhibited by the most intense peak of the absorption profile, crucial for
designing optoelectronic devices.
