Theoretical Investigation of Charge-Transfer Processes at Pentacene–C60 Interface: The Importance of Triplet Charge Separation and Marcus Electron Transfer Theory

Abstract

Photovoltaic devices have great potential in harvesting solar energy. In organic solar cells, the role of the donor–acceptor heterojunction is critically important; here optical excitation leads to charge separation (CS) and subsequently photocurrent generation. Charge recombination (CR) may also happen, which reduces the overall efficiency of the device. After light absorption, the singlet excitation of a pentacene can achieve CS at the interface, or it may also undergo singlet fission and produce two triplet excitons, which may further undergo CS at the interface. In this work, we study charge-transfer processes at the pentacene–C60 interface, including CS rates in both singlet and triplet surfaces, and the CR rate back to the ground state. We first constructed two different pentacene–C60 interfacial structures by force field optimization. With pentacene–C60 molecular pairs derived from the structures, we calculate the electronic couplings of CS and CR reactions. We found that the electron-transfer coup...