Ionization Energy and Energy Gap Structure of MoSI Molecular Wires: Kelvin Probe, Ultraviolet Photoelectron Spectroscopy, and Cyclic Voltammetry Measurements

The work function W of Mo6S3I6 molecular nanowires is determined by Kelvin probe (KP) measurements, UV photoelectron spectroscopy (UPS), and cyclic voltammetry (CV). The values obtained by all three methods agree well, giving W = 4.8 +/- 0.1 eV. CV measurements also give a gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of Eg = 1.2 +/- 0.1 eV, in agreement with recent optical measurements, but in disagreement with theoretical calculations, which predictict the materials to be a metal. The electronic structure of Mo6S3I6 suggests use of the material in applications such as bulk heterostructure photovoltaics and transparent electrodes and for molecular electronics devices.