Electronic properties of the F16CuPc molecule-gold interface: Spectroscopic signature of ultra-fast charge delocalization

Understanding the charge transfer process at organic/metal interfaces is crucial, as it affects the efficiencies of organic electronics and photovoltaic devices. To this aim, in situ, synchrotron radiation-based photoemission and near-edge X-ray absorption fine structure (NEXAFS) combined with resonant photoemission spectroscopies (RPES) spectra were used to study the interaction and alignment of the adsorbed F₁₆CuPc molecules on Au (111) substrate. The polarization-dependent NEXAFS reveals that F₁₆CuPc molecules were lying flat on the Au (111) surface at both the sub-monolayer and multilayer coverages. The core-level photoemission findings suggest that an interfacial layer was formed at the molecule-Au interface for an interfacial interaction. Moreover, the molecules remained nearly flat with a small deformation, staying in close contact with the substrate. In addition, employing the core-hole clock technique, the ultrafast interfacial charge transfer time was around 12 fs at the interface of the F₁₆CuPc thin film and the Au (111) substrate. Our results consequently provide valuable insights into the charge transfer process of a photo-excited n-type molecule on a metal surface, which will help open a new direction for the realization of the F₁₆CuPc for organic electronic devices.