Diphenoquinone as a Prototype of Singlet Fission Chromophores

Singlet fission (SF) is attracting attention due to its potential applications in organic photovoltaics, quantum computing, and dynamic nuclear polarization. In this paper, we have theoretically investigated the potential of 4,4’-diphenoquinone (1a) as a promising backbone for efficient SF chromophores. Single-reference ab initio correlated methods were employed to investigate the excited states of 1a. A strong photo-absorption is predicted for the S0-S3 transition, which is described by the HOMO-LUMO excitation. Although the excitation energies of the S3 and T1 states satisfy the exothermic energy matching condition of SF, internal conversion from the S3 to a low-lying nπ* singlet excited state may suppress the efficient generation of 1(T1T1) in the condensed phase. We have demonstrated that the obstacle of 1a can be overcome by introducing typical donors or halogen atoms and fusing aromatic six-membered ring(s), while retaining the advantages of the diphenoquinone backbone.