Mixed Stack Organic Semiconductors: The Anomalous Case of the BTBT-TCNQF_<i>x</i> Series

We present a detailed characterization of three mixed stack organic semiconductors, where benzothieno-benzothiophene electron donor is associated with fluorine-substituted TCNQ of increasing electron affinity. BTBT-TCNQ and BTBT-TCNQF₂ are isomorphous, whereas the three-dimensional packing of BTBT-TCNQF₄ is different. Rather surprisingly, we found that the degree of charge transfer is almost constant along the series, at variance with what has been found in analogous cocrystal series in which TCNQF_<i>x</i> are involved. We explain this finding in terms of the Madelung energy resulting from interstack packing of the cocrystals, and of the fact that both the HOMO and HOMO–1 of BTBT are involved in the charge transfer mechanism. We also propose that the difference in interstack packing resulting from increasing F substitution is a consequence of electrostatic interactions

Interlayer Sliding Phonon Drives Phase Transition in the Ph‑BTBT-10 Organic Semiconductor

In the field of organic electronics, the semiconductor 7-decyl-2-phenyl[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10) has become a benchmark due to its high charge mobility and chemical stability in thin film devices. Its phase diagram is characterized by a crystal phase with a bilayer structure that at high temperature transforms into a Smectic E liquid crystal with monolayer structure. As the charge transport properties appear to depend on the phase present in the thin film, the transition has been the subject of structural and computational studies. Here such a process has been investigated by polarized low frequency Raman spectroscopy, selectively probing the intermolecular dynamics of the two phases. The spectroscopic observations demonstrate the key role played by a displacive component of the transition, with the interpenetration of the crystal bilayers driven by lattice phonon mode softening followed by the intralayer rearrangement of the molecule rigid cores into the herringbone motif of the liquid crystal. The mechanism can be related to the effectiveness of thermal annealing to restore the crystal phase in films

Two New Polymorphs of the Organic Semiconductor 9,10-Diphenylanthracene: Raman and X‑ray Analysis

Raman microscopy in the lattice phonon region coupled with X-ray diffraction have been used to study the polymorphism in crystals and microcrystals of the organic semiconductor 9,10-diphenylanthracene (DPA) obtained by various methods. While solution grown specimens all display the well-known monoclinic structure widely reported in the literature, by varying the growth conditions two more polymorphs have been obtained, either from the melt or by sublimation. By injecting water as a nonsolvent in a DPA solution, one of the two new polymorphs was predominantly obtained in the shape of microribbons. Lattice energy calculations allow us to assess the relative thermodynamic stability of the polymorphs and verify that the energies of the different phases are very sensitive to the details of the molecular geometry adopted in the solid state. The mobility channels of DPA polymorphs are shortly investigated

An Alternative Strategy to Polymorph Recognition at Work: The Emblematic Case of Coronene

We show that the development of highly accurate density functional theory calculations coupled to low-frequency Raman spectroscopy constitutes a valid method for polymorph characterization alternative/complementary to X-ray. The method is applied here to the temperature-induced, first-order phase transition of coronene, known for a long time, but has remained structurally uncharacterized due to crystal breaking during the process. The astonishing fidelity of the Raman calculated spectra to the experiments allows us to unambiguously identify the low-temperature phase with the β-coronene polymorph, recently reported as new and obtained in the presence of a magnetic field. We also suggest that additional measurements are needed to confirm that a magnetic field can actually drive the growth of a β-polymorph surviving indefinitely at ambient temperature

An Alternative Strategy to Polymorph Recognition at Work: The Emblematic Case of Coronene

We show that the development of highly accurate density functional theory calculations coupled to low-frequency Raman spectroscopy constitutes a valid method for polymorph characterization alternative/complementary to X-ray. The method is applied here to the temperature-induced, first-order phase transition of coronene, known for a long time, but has remained structurally uncharacterized due to crystal breaking during the process. The astonishing fidelity of the Raman calculated spectra to the experiments allows us to unambiguously identify the low-temperature phase with the β-coronene polymorph, recently reported as new and obtained in the presence of a magnetic field. We also suggest that additional measurements are needed to confirm that a magnetic field can actually drive the growth of a β-polymorph surviving indefinitely at ambient temperature

An Alternative Strategy to Polymorph Recognition at Work: The Emblematic Case of Coronene

We show that the development of highly accurate density functional theory calculations coupled to low-frequency Raman spectroscopy constitutes a valid method for polymorph characterization alternative/complementary to X-ray. The method is applied here to the temperature-induced, first-order phase transition of coronene, known for a long time, but has remained structurally uncharacterized due to crystal breaking during the process. The astonishing fidelity of the Raman calculated spectra to the experiments allows us to unambiguously identify the low-temperature phase with the β-coronene polymorph, recently reported as new and obtained in the presence of a magnetic field. We also suggest that additional measurements are needed to confirm that a magnetic field can actually drive the growth of a β-polymorph surviving indefinitely at ambient temperature

An Alternative Strategy to Polymorph Recognition at Work: The Emblematic Case of Coronene

We show that the development of highly accurate density functional theory calculations coupled to low-frequency Raman spectroscopy constitutes a valid method for polymorph characterization alternative/complementary to X-ray. The method is applied here to the temperature-induced, first-order phase transition of coronene, known for a long time, but has remained structurally uncharacterized due to crystal breaking during the process. The astonishing fidelity of the Raman calculated spectra to the experiments allows us to unambiguously identify the low-temperature phase with the β-coronene polymorph, recently reported as new and obtained in the presence of a magnetic field. We also suggest that additional measurements are needed to confirm that a magnetic field can actually drive the growth of a β-polymorph surviving indefinitely at ambient temperature

An Alternative Strategy to Polymorph Recognition at Work: The Emblematic Case of Coronene

We show that the development of highly accurate density functional theory calculations coupled to low-frequency Raman spectroscopy constitutes a valid method for polymorph characterization alternative/complementary to X-ray. The method is applied here to the temperature-induced, first-order phase transition of coronene, known for a long time, but has remained structurally uncharacterized due to crystal breaking during the process. The astonishing fidelity of the Raman calculated spectra to the experiments allows us to unambiguously identify the low-temperature phase with the β-coronene polymorph, recently reported as new and obtained in the presence of a magnetic field. We also suggest that additional measurements are needed to confirm that a magnetic field can actually drive the growth of a β-polymorph surviving indefinitely at ambient temperature

An Alternative Strategy to Polymorph Recognition at Work: The Emblematic Case of Coronene

We show that the development of highly accurate density functional theory calculations coupled to low-frequency Raman spectroscopy constitutes a valid method for polymorph characterization alternative/complementary to X-ray. The method is applied here to the temperature-induced, first-order phase transition of coronene, known for a long time, but has remained structurally uncharacterized due to crystal breaking during the process. The astonishing fidelity of the Raman calculated spectra to the experiments allows us to unambiguously identify the low-temperature phase with the β-coronene polymorph, recently reported as new and obtained in the presence of a magnetic field. We also suggest that additional measurements are needed to confirm that a magnetic field can actually drive the growth of a β-polymorph surviving indefinitely at ambient temperature

An Alternative Strategy to Polymorph Recognition at Work: The Emblematic Case of Coronene

We show that the development of highly accurate density functional theory calculations coupled to low-frequency Raman spectroscopy constitutes a valid method for polymorph characterization alternative/complementary to X-ray. The method is applied here to the temperature-induced, first-order phase transition of coronene, known for a long time, but has remained structurally uncharacterized due to crystal breaking during the process. The astonishing fidelity of the Raman calculated spectra to the experiments allows us to unambiguously identify the low-temperature phase with the β-coronene polymorph, recently reported as new and obtained in the presence of a magnetic field. We also suggest that additional measurements are needed to confirm that a magnetic field can actually drive the growth of a β-polymorph surviving indefinitely at ambient temperature