Insight into the Adsorption Structure of TIPS-Pentacene on Noble Metal Surfaces

Organic-metal interfaces are of vital importance for regulating the optoelectronic properties of devices in molecular electronics. Interactions within the metal-adsorbate system influence the photonic performance through perturbations of the electronic structure. Such changes and associated interfacial charge transfer are directly influenced by how the organic molecule structurally adsorbs to the substrate. Herein, we use a combination of surface-enhanced Raman scattering (SERS) spectroscopy and dispersion-corrected density functional theory (DFT-D) to show that 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-Pc) adsorbs through both physisorption and chemisorption on a gold surface with the TIPS-Pc adopting an adsorption geometry with the pentacene backbone oriented parallel to the substrate. When chemisorbed, our results provide direct evidence of Au-C bond formation within the ethynyl moieties. Most importantly, we demonstrate that the electronic structure of the resulting TIPS-Pc surface system is distinctly dependent on the adsorption mechanism. These results show new evidence of chemisorption routes for TIPS-Pc on metal surfaces and illustrate the importance of understanding the interfacial structure at the molecular level for dictating and assessing the performance of molecular optoelectronic devices.