Photoinduced Charge Transfer in Donor-Bridge-Acceptor in One-and Two-photon Absorption: Sequential and Superexchange Mechanisms

In this work, the one- (OPA) and two-photon absorption (TPA) and transition characteristics of the porphyrin and fullerene donor-acceptor systems linked by thiophene oligomers are investigated theoretically. In the study of the transition characteristics of OPA and TPA, a combination of 2D and 3D visualization methods is used. During the OPA and TPA transitions of this D-A system, there is both superexchange charge transfer without thiophene oligomers and sequential charge transfer through thiophene oligomers. On this basis, there exist also charge recombination TPA excitations of the previous two kinds of charge transfer into an intrinsic process. The degree of polymerization of the thiophene oligomer significantly affects the efficiency of superexchange charge transfer and participates in excitation in units of quarter-thiophene. Finally, a method to enhance the charge transfer efficiency during TPA excitation is proposed, which is local excitation enhanced charge transfer excitation.