To gain further insight into the nature of the deuterated and non-deuterated compounds, the density functional theory (DFT) calculations were performed (Supplementary Fig. ). The highest occupied molecular orbitals (HOMOs) of electron donors were predominantly localized on the bi-carbazoles, while the lowest unoccupied molecular orbitals (LUMOs) of electron acceptors were mainly distributed on the triazine and adjacent phenyl moiety. This demonstrated that the deuteration had no direct effect on the orbital distribution owing to the Born-Oppenheimer approximation. The HOMO and LUMO distributions in the ionic state were also presented in order to facilitate intuitive understanding of the chemical activity. As illustrated in Supplementary Fig. and Supplementary Fig. , the HOMOs of the electron donors were primarily distributed on the carbazoles, indicating that the carbazole moieties participate in the charge transfer process in cationic state. Conversely, in anionic state, neither the HOMOs nor the LUMOs of the electron acceptors were distributed on the carbazole moieties. This verified that the carbazoles in acceptors serve solely as spatial functional groups and do not contribute to the interaction of electron orbitals, which becomes one of the reasons for the subsequent difference in performance.