Unveiling the role of external electric field on the charge transport and excited-state properties of high T1 host for blue OLED devices

Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations were performed to understand the effect of the external electric field (EEF) on the reorganization (λ) and the lowest triplet excited-state (T₁) energies of high T₁ blue host materials. Depending on the direction and the strength of the external electric field (EEF), the positive and negative changes of hole and electron λ(_h and λ _e) values were found in these materials. More importantly, λ _e seems to be more sensitive than λ _h values under the EEF. It is also noticed that the calculated T₁ energies are meaningfully changed in the application of EEF_x and EEF_y. In contrast, the effect of EEF_z on the T₁ energies can be negligible. From the results of theoretical investigation, the obvious evidence related to the influence of EEF on the charge transport and excited-state properties of high T₁ blue host materials were obtained. In the present work, we expect that our theoretical study will provide new insight into understanding the influence of EEF as a key player in manipulating essential properties of the high T₁ blue host material during the electrical operation.