Polarization at the gold/pentacene interface

Direct and inverse photoemission spectroscopy are used to investigate the electronic polarization P = P+ + P− induced by the pentacene anion and cation at the Au/pentacene interface. Based on the spectroscopic measurements and on previously published calculations, we determine that the total polarization at the metal interface is approximately 0.67 eV larger than at the surface of the pentacene film, leading to a corresponding decrease of the interface transport gap. This reduced interface gap leads to hole and electron injection barriers of 0.47 eV and 1.17 eV, respectively.