Explore the Structural and Electronic Properties at the Organic/Organic Interfaces of Thiophene-Based Supramolecular Architectures

The structural and electronic properties at organic/organic interfaces determine the functionality of organic electronics. Here, we investigated the structural and electronic properties at interfaces between methyl-substituted dicyanovinyl-quinquethiophenes (DCV5T-Me₂) and other electron acceptor molecules, namely fullerene (C₆₀) and tetracyanoquinodimethane (TCNQ), by using low-temperature scanning tunneling microscopy/spectroscopy (STM/STS). Upon adsorption on Au(111), DCV5T-Me₂ molecules self-assemble into compact islands at sub-monolayer coverage through hydrogen bonding and electrostatic interactions. A similar bonding configuration dominates in the second layer of a bilayer film, where DCV5T-Me₂ possesses higher-lying LUMO (lowest unoccupied molecular orbital) and LUMO+1 in energy due to a decoupling effect. The co-deposition of DCV5T-Me₂ and C₆₀ does not result in ordered hybrid assemblies at the sub-monolayer coverage on Au(111). On the other hand, C₆₀ molecules can self-assemble into ordered islands on top of the DCV5T-Me₂ monolayer. The dI/dV spectra reveal that the LUMO of decoupled C₆₀ is 400 mV lower in energy than the LUMO of decoupled DCV5T-Me₂. This energy difference facilitates electron transfer from DCV5T-Me₂ to C₆₀. The co-deposition of DCV5T-Me₂ and TCNQ leads to the formation of hybrid nanostructures. A tip-induced electric field can manipulate the charging and discharging of TCNQ by surrounding DCV5T-Me₂, manifested as sharp peaks and dips in dI/dV spectra recorded over TCNQ.