Self-assembly of the chiral donor-acceptor molecule DCzDCN on Cu(100) (2310.19534v1)

Abstract: Donor-acceptor (D-A) structured molecules are essential components in organic electronics. The respective molecular structure of these molecules and their synthesis are primarily determined by the intended area of application. Typically, D-A molecules promote charge separation and transport in organic photovoltaics (OPV) or organic field-effect transistors (OFET). D-A molecules showing a larger twist angle between D and A units are, e.g., extremely important for the development of high internal quantum efficiency in organic light-emitting diodes (OLEDs). A prototypical molecule of this D-A type is DCzDCN (5-(4,6-diphenyl-1,3,5-triazin-2-yl)benzene-1,3-dinitrile). In most cases, these molecules are only investigated regarding their electronic and structural interaction in bulk aggregates but not in ultra-thin films supported by a metallic substrate. Here, we present growth and electronic structure studies of DCzDCN on a Cu(100) surface. In a complementary approach, through the use of Scanning Tunneling Microscopy and Spectroscopy (STM and STS), we were able to view both the adsorption geometry and the local electronic states of the adsorbed molecules in direct comparison with the integral electronic structure of the DCzDCN/CU(100) interface using Ultraviolet and Inverse Photoemission Spectroscopy (UPS and IPS). The orientation of the molecules with the donor part towards the substrate results in a chiral resolution at the interface due to the molecular as well as the substrate symmetry and additional strong molecular electrostatic forces. Thus, the formation of various bulk-unlike homochiral structures and the appearance of hybrid interface states (HIS) modifies the molecular electronic properties of the DCzDCN/Cu(100) system significantly compared to that of a single DCzDCN molecule. This may be not only useful for optoelectronic applications but also in organic spintronics.