A combined experimental and theoretical approach, consisting of lattice phonon Raman spectroscopy and density functional theory (DFT) calculations, is proposed as a tool for lattice dynamics characterization and polymorph phase identification. To illustrate the reliability of the method, the lattice phonon Raman spectra of two polymorphs of the molecule 2,7-dioctyloxy[1]benzothieno[3,2-b]benzothiophene are investigated. We show that DFT calculations of the lattice vibrations based on the known crystal structures, including many-body dispersion van der Waals (MBD-vdW) corrections, predict experimental data within an accuracy of ≪5 cm–1 (≪0.6 meV). Due to the high accuracy of the simulations, they can be used to unambiguously identify different polymorphs and to characterize the nature of the lattice vibrations and their relationship to the structural properties. More generally, this work implies that DFT-MBD-vdW is a promising method to describe also other physical properties that depend on lattice dynamics like charge transport.
In this paper it is experimentally demonstrated that the electron‐spin/molecular‐handedness interaction plays a fundamental role in the chiral recognition process. This conclusion is inferred comparing current versus potential (I–V) curves recorded using chiral electrode surfaces, which are obtained via chemisorption of an enantiopure thiophene derivative: 3,3′‐bibenzothiophene core functionalized with 2,2′‐bithiophene wings (BT2T4). The chiral recognition capability of these chiral‐electrodes is probed via cyclic voltammetry measurements, where, Ag nanoparticles (AgNPs) capped with enantiopure BT2T4 (BT2T4@AgNP) are used as the chiral redox probe. Then, the interface handedness is explored by recording spin‐polarized I–V curves in spin‐dependent electrochemistry (SDE) and magnetic‐conductive atomic force microscopy (mc‐AFM) experiments. The quality of the interfaces is thoroughly cross‐checked using X‐ray photoemission spectroscopy, Raman, electrodesorption measurements, which further substantiate the metal(electrode)‐sulfur(thiophene) central role in the chemisorption process. Spin‐polarization values of about 15% and 30% are obtained in the case of SDE and mc‐AFM experiments, respectively.
Thin films of the organic semiconductor Ph-BTBT-10 and blends of this material with polystyrene have been deposited by a solution shearing technique at low (1 mm s−1) and high (10 mm s−1) coating velocities and implemented in organic field-effect transistors. Combined X-ray diffraction and electrical characterisation studies prove that the films coated at low speed are significantly anisotropic. The highest mobility is found along the coating direction, which corresponds to the crystallographic a-axis. In contrast, at high coating speed the films are crystallographically less ordered but with better thin film homogeneity and exhibit isotropic electrical characteristics. Best mobilities are found in films prepared at high coating speeds with the blended semiconductor. This work demonstrates the interplay between the crystal packing and thin film morphology and uniformity and their impact on the device performance.