Graphene Quantum Dot with Divacancy and Topological Defects: A Novel Material for Promoting Prompt and Delayed Fluorescence of Tunable Wavelengths

Abstract: 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.