Electronic Structures of the Highest Occupied Molecular Orbital Bands of a Pentacene Ultrathin Film

Abstract

We report the energy dispersions of the highest occupied molecular orbitals (HOMO)-derived bands of a pentacene (Pn) thin film, whose in-plane structure resembles closely that of the $ab$ plane of a low-density bulk Pn phase. Our present photoemission result indicates that the overlap of the $\pi$-orbitals of adjacent Pn molecules is larger than what was expected from theoretical calculations. Further, of the two HOMO-derived bands, the large dispersion width of the band with higher binding energy suggests that this one mainly contributes to the bandlike charge transport in a Pn crystal.