Interaction between the Non-Fullerene Acceptor ITIC and Potassium

[Image: see text] Using density functional theory calculations and photoemission measurements, we have studied the interaction between the non-fullerene small-molecule acceptor ITIC and K atoms (a representative of reactive metals). It is found that the acceptor–donor–acceptor-type geometric structure and the electronic structure of ITIC largely decide the interaction process. One ITIC molecule can combine with more than 20 K atoms. For stoichiometries K(x≤6)ITIC, the K atoms are attracted to the acceptor units of the molecule and donate their 4s electrons to the unoccupied molecular orbitals. K–ITIC organometallic complexes, characterized by the breaking of some S–C bonds in the donor unit of ITIC and the formation of K–S bonds, are formed for stoichiometries K(x≥7)ITIC. The complexes are still conjugated despite the breaking of some S–C bonds.