A number of hexaarylbenzene compounds were studied theoretically, in order to compare energy changes as a result of the toroidal delocalization effect that is characteristic of all these species. The energy was studied taking advantage of locally designed isodesmic reactions. Results indicate that the amount of aromaticity manifested by each substituent is a factor that should be considered when assessing the quantity of energy dissipated from each aromatic center. The influence of different substituents on electronic delocalization is also analyzed, as well as the role played by their frontier molecular orbitals.

The structure formed by cobalt phthalocyanine (CoPc) and cobalt octaethylporphyrin (CoOEP) with electron-acceptor tetracyano-π-quinodimethane (TCNQ), was studied by Density Functional Theory (DFT) methods. According to theoretical calculations, both cobalt systems can establish dispersion forces related to TCNQ and also in both cases the link between them is built by means of hydrogen bonds. Based on the results of these DFT calculations, we developed experimental work: the organic semiconductors were doped, and the thermal evaporation technique was used to prepare semiconductor thin films of such compounds. The structure of the films was studied by FTIR and Raman spectroscopy. The optical properties of the CoPc-TCNQ and CoOEP-TCNQ films were investigated by means of UV-Vis measurements. The results obtained were used to estimate the type of transitions and the optical bandgap. The results were compared to the previously calculated theoretical bandgap. The CoOEP-TCNQ film presented the smallest theoretical and experimental bandgap. Finally, the electrical properties of the organic semiconductors were evaluated from a PET (polyethylene terephthalate)/indium tin oxide (ITO)/cobalt macrocycle-TCNQ/silver (Ag) device we prepared. The CoOEP-TCNQ-based device showed an ohmic behavior. The device manufactured from CoPc-TCNQ also showed an ohmic behavior at low voltages, but significantly changed to SCLC (space-charge limited conductivity) at high voltage values.

In this work, we investigated an organic semiconductor based on zinc 8-hydroxyquinoline (ZnQ₂) and tetracyanoquinodimethane (TCNQ), which can be used as a photoactive layer in organic devices. The semiconductor was optimized by applying density-functional theory (DFT) methods, and four hydrogen bridges were formed between ZnQ₂ and TCNQ. Later, thin films of ZnQ₂-TCNQ were successfully deposited. The films were structurally and morphologically characterized, and the optical characteristics of the photoactive layer were investigated using ultraviolet–visible spectroscopy and time-dependent density-functional theory (TDDFT) calculations. The comparison and analysis of the experimental and theoretical absorption spectra indicate that the optical bandgap of the photoactive layer is 2.4 eV. Additionally, a flexible photo device was manufactured with the active layer ZnQ₂-TCNQ, and its electrical behavior was evaluated under dark and light conditions. The results show a significant change in the behavior of the device when radiation is eliminated; the layer is light sensitive. The electrical resistance in the flexible photo device is associated with the optical behavior of the materials that constitute the active layer.

A raspberry-like SiO₂@TiO₂ new material supported on functionalized graphene oxide was prepared to reduce titania’s band gap value. The material was characterized through different analytical methods such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HR-TEM). The band gap value was studied via UV-Vis absorption spectra and determined through the Kubelka–Munk equation. A theoretical study was also carried out to analyze the interaction between the species.

In the present work, we have investigated an organic semiconductor based on tris(8-hydroxyquinoline) aluminum (AlQ₃) doped with tetracyanoquinodimethane (TCNQ), which can be used as an organic photoconductor. DFT calculations were carried out to optimize the structure of semiconductor species and to obtain related constants in order to compare experimental and theoretical results. Subsequently, AlQ₃-TCNQ films with polypyrrole (Ppy) matrix were fabricated, and they were morphologically and mechanically characterized by Scanning Electron Microscopy, X-ray diffraction and Atomic Force Microscopy techniques. The maximum stress for the film is 8.66 MPa, and the Knoop hardness is 0.0311. The optical behavior of the film was also analyzed, and the optical properties were found to exhibit two indirect transitions at 2.58 and 3.06 eV. Additionally, photoluminescence measurements were carried out and the film showed an intense visible emission in the visible region. Finally, a photoconductor was fabricated and electrically characterized. Applying a cubic spline approximation to fit cubic polynomials to the J-V curves, the ohmic to SCLC transition voltage $V_{\mathrm{ON}}$ and the trap-filled-limit voltage $V_{\mathrm{TFL}}$ for the device were obtained. Then, the free carrier density and trap density for the device were approximated to $n_0=4.4586\times {10}^{19}\frac{1}{{\mathrm{m}}^3}$ and $N_t=3.1333\times {10}^{31}\frac{1}{{\mathrm{m}}^3}$, respectively.