We show that the observation by photoemission spectroscopy of a finite density of occupied states at the Fermi-level on a film of a conjugated organic material (para-sexiphenyl) in which alkali metal atoms have been intercalated does not necessarily imply metallicity nor the presence of negative polarons (radical anions). The combination of ultraviolet photoemission spectroscopy and Kelvin probe measurements rules out the presence of surface photovoltage, and reveals that the substrate and the surface of the organic film are not in thermodynamic equilibrium.

• Received 24 January 2003

DOI:https://doi.org/10.1103/PhysRevB.67.195330