Photoelectron Spectra of Phthalocyanine Thin Films: A Valence Band Theoretical Interpretation

A theoretical investigation of the photoelectron valence band spectra of metal-free phthalocyanine (H₂Pc) thin films is performed using the nonempirical valence effective Hamiltonian (VEH) quantum-chemical method. The results of the VEH band structure calculations are presented in the form of theoretical UPS and XPS simulations and are analyzed by comparison to the electronic structure of the H₂Pc molecule. The theoretical spectra are found to be fully consistent with experimental solid-state synchrotron (hν = 100 eV) and XPS spectra. An excellent quantitative agreement between theory and experiment is achieved when comparing the energies of the main peaks. A detailed interpretation of all the photoemission bands constituting the experimental spectra is reported in the light of the VEH predictions.