The interface between chlorogallium phthalocyanine (GaClPc) and ferroelectric polymer: a photoelectron spectroscopy (PES) study

Understanding the organic/organic interfaces is crucial for truly flexible electronic devices, as the device functionality depends on interface electronic properties. In this study, the electronic properties of the GaClPc/P(VDF-TrFE) dielectric interface have been studied systematically using photoemission spectroscopy. A clear thickness-dependent evolution of vacuum-level (VL) shift is evident from the UPS results. Two distinct scenarios were observed; for thin film (5 Å), a negative VL shift of 0.35 eV was observed, reducing substrate work function. On the contrary, 50 Å thick film showed an opposite VL shift of 0.44 eV, increasing the work function. Results suggest different dipole formations occur for different thicknesses of GaClPc molecules. A significant increase in the binding energy in the Cl2p and N1s XPS spectra of the 5 Å film, compared to thick layers (50 Å), suggests that the interaction between GaClPc and substrate primarily occurs through Cl- and N-atoms in the thin films. Such site-specific interaction possibly results in two possible orientations, Cl-up or Cl-down, of the GaClPc molecules on the substrate. The broadening of the HOMO feature observed in the 5 Å film further supports the possibility of these two dipole orientations. Other important parameters like energy-level alignment, dipole formation, ionisation potentials, etc., were also addressed and summarised to understand GaClPc/P(VDF-TrFE) dielectric interface electronic properties. (author)