| 초록 |
In organic light-emitting diodes (OLEDs), high internal quantum efficiency can be achieved using TADF molecule, by the reverse intersystem crossing which is accelerated from the triplet excited state to the singlet excited state. The ∆EST known as difference between S1 and T1 energies, determines rate of RISC but is not the sole parameter for TADF efficiency. It is noteworthy that the excitations may involve significant distortions of geometry, leading to change in photophysical behavior. By using density functional theory (DFT) calculations, we have investigated how excitations affect the distortion and thus the energy, of the different structural types. These differences are characterized by strong steric hindrance, large degrees of freedom and spiro union. Furthermore, the molecular structures with degenerate HOMOs become asymmetric as a result of Jahn–Teller effects. It is necessary for fully understand of geometric changes to better describe TADF processes. |
