Transparent conductive oxides (TCOs) are common contact materials in optoelectronic devices such as organic light emitting diodes, photovoltaic cells and liquid crystal displays. The interface between TCO and an organic film largely defines charge transport and light emission, and thus it is important to determine the interfacial structure and properties, and understand how it forms. Studies of adsorption on metal surfaces have revealed much diversity in molecular orientation and alignment in the first monolayer resulting from a competition between intermolecular and molecule-substrate interactions. Studies of relevant molecules on TCO surfaces are scarce, partly because obtaining a clean and sufficiently well-ordered TCO surface for surface science investigations is challenging, and partly because the communities studying organic and metal oxide surfaces are largely distinct, with little overlap. In this project, I aim to combine my experiences with organic overlayers and metal oxides surfaces and begin to bridge this divide.
The project will involve some of the first studies of the adsorption of prototypical, industrially relevant conjugated organic molecules on model TCO surfaces. The key to this work is the use of rare In2O3 single crystals, which I have learned to prepare reliably and reproducibly during my postdoctoral studies. The well-defined substrate is crucial if we are to understand the atomic-scale structure of the TCO/organic interface, and is a vital prerequisite for theoretical calculations aimed at elucidating the atomic scale mechanisms in play. It will be fascinating to discover the extent to which the highly corrugated surface potential of the metal oxide influences the geometric and electronic properties. State-of-the-art surface science techniques such as low temperature scanning tunneling microscopy, low energy electron diffraction and photoemission electron microscopy will be used to understand the morphological properties, and photoelectron spectroscopies will be used to elucidate the molecular frontier orbitals and the band alignment, distinguish inter- and intra-molecular interactions, and determine the character of the interaction with the substrate. Organic films ranging from sub monolayer to several nanometers thickness will be compared to investigate the difference between the interface and the organic bulk.
Granting this proposal would provide the springboard I need to launch my own independent research program that combines the skills acquired during my career to date. The research will be conducted in groups specializing in metal-oxide and organic surface science, in collaboration with my mentor Prof. Ulrike Diebold, and Prof. Georg Koller and Prof. Hans-Peter Steinrück, respectively. Theoretical calculations will be provided through the collaboration with Prof. Bernd Meyer. With the advice and support of four leading players in their respective fields, I am confident I can make a real and lasting contribution in an important technological area.
