ACS Appl Mater Interfaces
February 2024
Donor-acceptor (D-A) structured molecules are essential components of organic electronics. The respective molecular structures of these molecules and their synthesis are primarily determined by the intended area of application. Typically, D-A molecules promote charge separation and transport in organic photovoltaics or organic field-effect transistors.
View Article and Find Full Text PDFUltrathin films of tetracyanoethylene (TCNE) on Co(100) were investigated by means of spin-integrated and spin-resolved photoemission spectroscopy ((sp-)UPS), X-ray photoemission spectroscopy (XPS), near edge X-ray absorption fine-structure spectroscopy (NEXAFS), and X-ray magnetic circular dichroism (XMCD). We found a coverage-dependent modulation of the interface dipole and a switching between a metallic and a resistive spin filtering at the interface triggered by two distinct adsorption geometries of TCNE. The strongest hybridization and spin structure modifications are found at low coverage with a face-on adsorption geometry indicating changes in the distance between the surface Co atoms beneath.
View Article and Find Full Text PDFDithienylated phenothiazines (DTPTs) with different functional groups attached to the central nitrogen atom are presented as a class of versatile metal-free chromophores for the design of dye-sensitized solar cells (DSSCs) and organic light-emitting diodes (OLEDs). The electronic characteristics of spin-coated thin films on polycrystalline gold were studied using photoelectron spectroscopy assisted by theoretical calculations, scanning force microscopy, and UV/Vis spectroscopy. Complementary fluorescence spectra show light emission in the blue region (465 nm).
View Article and Find Full Text PDFThe valence band structure of different metal-phthalocyanines was investigated by comparing ultraviolet photoelectron spectra at different excitation energies with simulated spectra that take the different photoionization cross-sections at these energies into account. The Kohn-Sham eigenvalue spectra, derived from density functional theory calculations, using hybrid exchange-correlation functionals, were weighted with the photoionization coefficients in accordance with the used excitation energy. By applying these techniques, the differences in the photoelectron spectra using He I and He II radiation can be reproduced and investigated.
View Article and Find Full Text PDFThe electronic structure of the interface between ferromagnetic cobalt and the organic semiconductors copper- (CuPc) and iron-phthalocyanine (FePc) was investigated by means of photoemission spectroscopy (UPS, IPES, and XPS). These metal-phthalocyanine (MePc) molecules have an open shell structure and are known to show promising properties for their use in organic spintronics. In spintronic devices, the interface between ferromagnetic electrode and the organic layer determines the spin injection properties and is hence important for the quality of, e.
View Article and Find Full Text PDFA fundamental prerequisite for the implementation of organic semiconductors (OSCs) in spintronics devices is the still missing basic knowledge about spin injection and transport in OSCs. Here, we consider a model system consisting of a high-quality interface between the ferromagnet cobalt and the OSC copper phthalocyanine (CuPc). We focus on interfacial effects on spin injection and on the spin transport properties of CuPc.
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