Critical evaluation of band bending determination in organic films from photoemission measurements

Electronic properties of conjugated films, namely, the band bending as derived from photoemission spectroscopy, are critically discussed. The study demonstrates that conclusions on the presence of the band bending deduced from the shift of electronic energy levels with the organic film thickness may be erroneous if the analysis does not consider the evolution of the film’s work function. The work function change—besides that being induced by the interfacial dipole—may occur due to the change in the molecular orientation from the lying down toward upright, as it often occurs with the increased thickness of molecular films.