| Thin film synthesis methods were used to modify the surface of indium tin oxide (ITO). Films both of discrete small molecules and self-assembled monolayers (SAMs) were formed on the ITO surface. Loadings of discrete complexes and of the SAMs were measured by quartz crystal microgravimetry (QCM). Work function changes induced by surface modifications were measured using a home-built Kelvin probe. Dipole moments of surface complexes were calculated, which correlated well with measured work function changes. Simple diode devices were built using modified ITO substrates, and a linear correlation between logarithms of current densities and substrate work functions was measured, which agrees well with a thermionic emission model for hole injection. Similar observations were made for devices built on SAM-modified ITO. Surface modification using complexes with restricted ligand conformations was also accomplished, but devices built on these surfaces did not perform as expected. Explanations for these latter results were suggested. |
