Charge-Separated States Determined Photoinduced Electron Transfer Efficiency in a D-D-A System in an External Electric Field

Abstract

Focusing on the photoinduced electron transfer properties of the D-D-A molecule ((TPA-TT)-BODIPY-C60) in an external electric field (Fext), the excited-state properties in which the double-donor molecule is excited to form three charge-separated states were simulated. The charge-transfer processes of these three charge-separated states were investigated by considering the two donors as a whole ((TPA-TT-BODIPY)·+-C60·–) as a comparison object. The electronic coupling (VDA), reorganization energy (λ), and free energy (ΔG) of the different charge-separated states in Fext were calculated and simulated. The calculated results show that the λ of (TPA-TT-BODIPY)·+-C60·– ranges from 0.576 to 0.51 eV, and the calculated ΔG of exciton dissociation ranges from −1.402 to −1.143 eV, indicating that exciton dissociation occurs in the Marcus inverted region. In the range of Fext = −10 × 10–5 to 10 × 10–5 au, the trend of the charge-transfer rate is gradually increasing, and the rate increase is mainly from the VDA and ΔG changes. Moreover, the rapid formation of the (TPA-TT)-BODIPY·+-C60·– charge-separated state and the formation of the long-lived (TPA-TT)·+ -BODIPY-C60·– are indicated by the exciton dissociation rate. By studying the charge-transfer parameters under different electric field directions, it is found that the regulation of electric field strength on the charge-transfer rate is consistent. These results provide a feasible method for the rational design of a new type of electron transfer process with high efficiency of the D-D-A system.