The electronic structure of cobalt phthalocyanine (CoPc) on Pt(111), graphene/Pt (111), and Au-intercalated graphene/Ni(111) is investigated by photoexcited electron spectroscopies: photoemission (XPS and UPS) and X-ray absorption spectroscopy (XAS or NEXAFS). For CoPc on Pt(111), significant changes of the shape of XPS and XAS spectra indicate a charge transfer from the metal substrate to the Co ion of CoPc. The strong interaction between CoPc and Pt(111) can be completely prevented by the insertion of a graphene buffer layer. For CoPc on graphene/ Ni(111), the charge transfer is only prevented if the graphene on Ni(111) is intercalated by gold. Therefore, the disturbance of the graphene electronic structure by the interaction with underlying substrate and the corresponding charge doping of graphene has been found to affect the electronic properties of adsorbed CoPc considerably.

Although hexacene was first synthesized in 1939, the thin film properties, which are interesting for future applications and fundamental research, have never been investigated. Therefore, we synthesized hexacene by reduction of 6,15-hexacenequinone, evaporated hexacene, and grew films of variable thicknesses on Au(110). This allowed us to study the electronic properties and molecular orientations in the bulk as well as at the molecule–metal interface by X-ray absorption spectroscopy (XAS) and photoelectron spectroscopy. Valence band spectra of a multilayer hexacene film are compared to those of electronic states obtained from density functional theory calculations. C 1s core-level spectra show typical satellite structures of the extended aromatic π-system, similar to pentacene. XAS shows that anisotropy rises with decreasing film thickness and indicates that hexacene is almost flat lying on the Au(110) substrate. The different peak shapes of XAS spectra as a function of the film thickness, as well as changes in valence band spectra and C 1s satellite structures, indicate a strong electronic coupling of the molecular states with the states of the Au(110) substrate at the interface.

The electronic structure of the interface between cobalt phthalocyanine (CoPc) and epitaxially grown manganese oxide (MnO) thin films is studied by means of photoemission (PES) and X-ray absorption spectroscopy (XAS). Our results reveal a flat-lying adsorption geometry of the molecules on the oxide surface which allows a maximal interaction between the π-system and the substrate. A charge transfer from MnO, in particular, to the central metal atom of CoPc is observed by both PES and XAS. The change of the shape of N-K XAS spectra at the interface points, however, to the involvement of the Pc macrocycle in the charge transfer process. As a consequence of the charge transfer, energetic shifts of MnO related core levels were observed, which are discussed in terms of a Fermi level shift in the semiconducting MnO films due to interface charge redistribution.

Compounds containing the [Mo6I8L6]2– ion in which L is an inorganic or organic ligand show remarkable photophysical properties. Similar properties were observed for the corresponding compounds based on octahedral tungsten clusters. The properties of these photosensitizers are significantly impacted by the six outer iodide ligands of [W6I8I6]2–. To analyze the role of the outer ligands, we prepared and structurally characterized octahedral tungsten cluster compounds with [W6I8I6]2– and [M6I8L6]2– ions (M = W, Mo; L = para‐toluenesulfonate). The distinct photophysical properties of the clusters were analyzed with respect to their photoluminescence (i.e., phosphorescence) and luminescence quenching in the presence of molecular oxygen. The electronic structures were analyzed through photoelectron spectroscopy to expose differences in the electronic situations of the compounds.

Charge separation efficiency is a crucial parameter for photovoltaic devicespolymers consisting of alternating electron-rich and electron-deficient parts can achieve high such efficiencies, for instance, together with a fullerene electron acceptor. This offers a viable path toward solar cells with organic bulk heterojunctions. Here, we measured the charge-transfer times in the femtosecond and attosecond regimes via the decay of sulfur 1s X-ray core-excited states (with the core-hole clock method) in blends of a low-band gap polymer {PCPDTBT [poly­[2,6-(4,4-bis­(2-ethylhexyl)-4H-cyclopenta­[2,1-b;3,4-b′]­dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)]]} consisting of a cyclopentadithiophene electron-rich part and a benzothiadiazole electron-deficient part. The constituting parts of the bulk heterojunction were varied by adding the fullerene derivative PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) (weight ratio of polymer/PCBM as 1:0, 1:1, 1:2, and 1:3). For low-energy excitations, the charge-transfer time varies to the largest extent for the thiophene donor part. The charge-transfer time in the 1:2 blend is reduced by 86% compared to that of pristine PCPDTBT. At higher energy excitations, the charge-transfer time does not vary with the chemical environment, as this regime is dominated by intramolecular conduction that yields ultrafast charge-transfer times for all blends, approaching 170 as. We thus demonstrate that the core-hole clock method applied to a series with changing composition can give information about local electron dynamics (with chemical specificity) at interfaces between the constituting partsthe crucial part of a bulk heterojunction where the initial charge separation occurs.