C60ThSe2/ITO interface formation: photoemission-based charge-transfer recognition for organic electronics applications

Within the presented work, we propose a complex photoemission-based approach for the investigation of the C60ThSe2 dyad (C60ThSe2)/indium-tin oxide (ITO) interface formation. For surface topography and basic morphology determination, atomic force microscopy was utilized, and the results showed that C60ThSe2 agglomerated into close-to-spherical crystallites and the island-like growth was the dominant type for fullerene growth on the ITO substrate. Further, detailed X-ray and UV-photoelectron spectroscopies (XPS, UPS) were used for thorough characterization of the chemical and electronic properties of the investigated structures. Experiments were conducted by means of cyclic voltammetry and UV-VIS techniques for both deposition purposes and for determination of the basic electronic structure. As a result, we present the detailed characterization of the chemical and energy structures with a clear designation of the mutual influence of both materials on their counterparts. Among others, the accurate photoemission signal decomposition of the overlapping signals was done with respect to obtaining the energy-related information depth. The obtained data clearly showed that an interface dipole (0.56 eV) was created between the ITO substrate and organic overlayer at the ultrathin coverage stage. Since our results point out the most probable charge-carrier relocation in the vicinity of the interface, this together with the dipole existence should be taken into account while creating energy-level cascades for various (e.g., photovoltaic or organic electronic) applications. The work may also provide insights for engineers working with a vast range of organic-based electronics while designing devices based on fullerene/ITO hybrid structures.