Theoretical Study On Charge Transfer Of Amolecular Ssuprystems

Electron transfer processes is closely related to the deactivation dynamics ofelectronic excited-state of molecular systems. Following the certain components ofsuperamolecular systems are excited, the conformation relaxation as well as theelectronic coupling between the different components of the excited-state will takeplace, simultaneously. At this point, the external conditions (the hydrogen bondingeffect and the electric field, etc.) are believed to be particularly important for thesetwo excited-state dynamics processes. Therefore, researches on electron transfer ofsome applied superamolecular systems in the field of material science under theoutside interference conditions, by using quantum chemistry method, are morevaluable and in line with the actual situation in the application. For this purpose, twoaspects are studied in detail in this thesis.Firstly, the calculations of the excited-state properties of N,N-dimethyl andN,N-diphenyl substituted amino-stilbene-terpyridine (abbreviated as M1and M2,shown in Figure2.1) are performed using (time-dependent) density functional theorymethod. By analysis together with theoretical calculations and experimental results,the configurations of their charge transfer excited-state in protic and aprotic solventsare studied, and the effect of hydrogen bonding on their excited-state geometries isemphasized. Furthermore, the mechanism on the intensity change of theirexcited-state luminescence is discussed. Secondly, the quantum mechanicsperturbation method and nonadiabatic transition theory are employed to theorize anovel model for describing the electronic coupling under external field. The externalelectric field dependent excited-state dynamics of fullerene-polymer solar cellsystems based on different conjugated polymer, spatial distance and charge transportmode are calculated by using the quantum chemical theory and finite electric dipolefield method, and the influences of external field on exciton dissociation and chargerecombination are also visualized by2D/3D real space method. Moreover, thedependence between the strength of electric coupling and the scalar product of theexternal field has been studied quantitatively and the parameters and conditions for improving the power conversion efficiencies of solar cell can be obtained.