Theoretical Investigation of Singlet Fission Processes in Organic Photovoltaics

ABSTRACT Singlet fission (SF) is a down‐conversion photophysical process involving transforming a high‐energy singlet state into two lower‐energy triplet excitons. It has attracted extensive attention over the past two decades because of its potential to break the power conversion limit in photovoltaic devices. However, this material's complex, strongly correlated electronic properties and its various packing structures pose challenges to understanding its intrinsic mechanisms and limiting theory‐guided molecular design. In this review, we summarize our theoretical work by studying the electronic structure, exciton‐phonon structure and low‐excited state dynamics of several typical materials, clearly elucidating the microscopic mechanism of the SF process. Subsequently, based on an in‐depth understanding of the mechanism, we use the novel macrocyclic framework to design intramolecular SF candidates and hope to improve the energy conversion efficiency of SF‐based photovoltaic devices.