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To achieve the high charge carrier mobility of small molecular organic semiconductors, a molecular design strategy for controlling the packing structure of two-dimensional (2D) $\pi$-extended organic semiconductors in single crystal is essential. Although tetrabenzoporphyrin (BP) is one of the promising organic semiconductors, the control of the packing structure is still challenging. To improve the low solubility of 5,15-bis(trimethylsilylethynyl)-tetrabenzoporphyrin (TMS-BP) and the crystal polymorph of 5,15-bis(triisopropylsilylethynyl)-tetrabenzoporphyrin (TIPS-BP), 5-triisopropylsilylethynyl-15-trimethylsilylethynyl-tetrabenzoporphyrin (TIPS-TMS-BP) with different substituents at meso-positions was synthesized. TIPS-TMS-BP gave a herringbone structure of antiparallel slipped-stack dimers in single crystals. The single crystal field effect transistors exhibit a high hole mobility of 1.65 cm² V${}^{-1}$ s${}^{-1}$ in parallel to $\pi$–$\pi$ stacking direction and moderate 0.37 cm² V${}^{-1}$ s${}^{-1}$ in perpendicular to $\pi$–$\pi$ stacking direction.

The capacitance and loss tangent of thermally evaporated zinc phthalocyanine, ZnPc, semiconducting thin films were measured in the temperature range of 180–430 K and frequency between 0.1 and 20 kHz. Aluminum and gold electrical contact electrodes were employed to sandwich ZnPc films. For both electrode types, the capacitance and loss tangent showed strong dependence on both temperature and frequency. Such dependence is related to the relevant temperature and frequency range under consideration. The capacitance has strong temperature dependence for T>240 K and frequency below 3 kHz, while it becomes a constant at higher frequencies and all temperatures. The loss tangent dependence on temperature is more evident at low frequencies and a minimum or an indication of a minimum was observed in tan δ versus f curves. Loss tangent variation with temperature was not monotonic for all frequencies. An anomaly (maximum) in tan δ was observed approximately between 300 and 360 K. This maximum was attributed to the presence of oxygen molecules in the sample and their subsequent exhaustion as the temperature is increased. The behavior of capacitance and loss tangent (for both Al and Au-electrodes) may be explained qualitatively and successfully in terms of an equivalent circuit model.

The electrical properties of alizarin doped anthraquinone were investigated using a complex impedance spectroscopy technique. Dielectric study revealed a phase transition from the semiconducting to the conducting state at 53°C. The dielectric relaxation was found to be of non-Debye type. Evidence of temperature-dependent electrical relaxation phenomena as well as a positive temperature coefficient of conductivity character were observed in the sample. The frequency dependence of AC conductivity data followed a power law. Electric modulus as well as AC conductivity analyses indicated the possibility of a hopping mechanism for electrical conduction in the system. The activation energy and minimum hopping distance were estimated from the AC conductivity data.

Poly(aniline-co-o-bromoaniline) (p(an-co-o-BrAn)) copolymer has been synthesized using chemical oxidation method in the hydrochloric acid medium. Copolymerization of aniline with o-bromoaniline of different compositions, such as 1:1, 1:2, 2:1, 1:3 and 3:1 molar ratios were prepared. The synthesized copolymer is soluble in polar solvents like dimethyl sulphoxide (DMSO), dimethyl formamide (DMF), Tetrahydrofuran (THF) and 1-methyl 2-pyrrolidone (NMP). The copolymer is analyzed by various characterization techniques, such as FTIR, UV–Visible (UV–Vis) spectroscopy, X-ray diffraction (XRD), conductivity, Differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). FTIR spectrum confirms the characteristic peaks of the copolymer containing benzenoid and quinoid ring stretching. UV spectrum reveals the formation of $\pi$–${\pi }^{\ast }$ transition and $n$–${\pi }^{\ast }$ transition between the energy levels. XRD peaks reveal that the copolymer possesses amorphous nature. Morphological study reveals that the agglomerated particles form globular structure and size of the each particle is about 100 nm. The electrical conductivity of the copolymers is found in the range of $10^{-5}\mathrm{\text{S}}{\mathrm{\text{cm}}}^{-1}$. These organic semiconductor materials can be used to fabricate thinner and cheaper environmental friendly optoelectronic devices that will replace the conventional inorganic semiconductors.

By using the extended Hubbard model under the Hartree–Fock approximation, we theoretically investigate the effect of electron–electron interaction on the polarization of the single-photon excited state of the charged $\pi$-conjugated oligomer. In the framework of one-dimensional tight-binding model, a uniform weak electric field is applied for polarization. The results show that the polarization property will vary with the electron–electron interaction. For example, with the increase of on-site Coulomb interaction strength, the value of the induced dipole moment is decreased. Its physical origin is revealed by analyzing the wavefunction of the localized energy level. In addition, the relation between the critical electric field for the dissociation of the single-photon excited state of the charged oligomer and the electron–electron interaction strength is also discussed.

Based on density functional theory (DFT) calculations, the electronic structures and magnetic properties of $3d$ transition-metal phthalocyanine (TMPc, TM = Ti, V, Cr, Mn, Fe, Co, Ni and Cu), as well as Li-adsorbed phthalocyanines have been studied. The results show that the pristine TMPcs all have a good $D_{4h}$ symmetry. When there is one Li atom adsorbed on TMPcs directly over (LiTMPc-$\alpha$) or slantly above (LiTMPc-$\beta$) the TM atoms, the geometries and electronic structures will be changed. For LiTMPc-$\alpha$ systems, the central TM atoms will deviate from the molecular plane and the molecules exhibit good $C_{4v}$ symmetry. LiTMPc-$\beta$ systems are more stable than LiTMPc-$\alpha$ systems but it do not possess $D_{4h}$ and $C_{4v}$ symmetries. The total and local magnetic moments and the charge transfer are also presented. Finally, by using the orbit mixing and splitting theory under $D_{4h}$ and $C_{4v}$ symmetry, we get the ordering of the energy levels of the central TM atoms.

The main objective of this paper is the realization and characterization of a new organic thin film semiconductor material through the use of an ideal mixture of Acetaminophen/Curcumin utilizing several characterization techniques. From optical analysis, we can conclude that our semiconductor material is comparable and shows good concurrency to the semiconductors applied in technologic applications. In fact, the analysis of the optical measurement (transmittance $T)$ conducting to the optical energy bandgap, $E_{\mathit{\text{g}}}$, it was found the optical bandgap is around to $2.6\pm 0.02$eV. In addition, by using the Wemple Didominico model it was found the dispersion energy E_D varied from 5eV to 7eV, the average bandgap $E_M$ separated the center of both bands occupied and unoccupied is around 4.5eV and the static refractive index $n_0$ varies from 1.3 to 2 and it dependent on the compactness and transparency of the material.

We have investigated the electronic structure of the interface formed by depositing Au on Cs-doped and Na-doped tris(8-hydroxyquinoline) aluminum (Alq) film using ultraviolet and X-ray photoemission spectroscopy (UPS and XPS). The initial Au deposition quenches the Alq gap state caused by the alkali metal doping. Further Au depositions shift gradually the energy levels opposite to that induced by Cs doping, especially the highest occupied molecular orbital (HOMO) that shows approximately full recovery to the pristine Alq position. However, the recovery is only partial for other levels, most noticeably the C 1s core level. The results indicate that the gap state and energy level positions can be decoupled in the organic semiconductors, and that it is possible to fine tune the electronic structure by selective doping in the interface region.

In order to probe the effects of substituents (F and CN) attached to benzo[1,2-b:3,4-$b^{\prime }$:5,6-$b^{\prime }{}^{\prime }$]tristhianaphthene (BTTP) on their charge carrier transport properties, we investigated the characteristics of molecular structures and charge transport properties of BTTP and its derivatives (BTTP1, BTTP2, BTTP3, BTTP4, and BTTP5). Six crystal structures were predicted by the Monte Carlo-simulated annealing method with the embedded electrostatic potential charges method. Even a subtle change of geometrical structures may result in a great change of the reorganization energy. With increasing numbers of substituted fluorine atoms, the reorganization energy of the BTTP derivative increases, which is disadvantageous to the electron transport. In contrast, the attachment of the electron-withdrawing cyano groups to BTTP decreases the reorganization energy and raises the electron affinity, which is beneficial to electron injection and charge carrier stabilization. The introduction of cyano groups also results in an enhancement of $\pi$–$\pi$ interaction and leads to an increase in the transfer integrals. Among the six compounds, the novel compound BTTP4 has the largest electron mobility (1.154cm${}^2\cdot {\mathrm{\text{V}}}^{-1}\cdot {\mathrm{\text{s}}}^{-1}$) on account of its larger transfer integral and smaller reorganization energy, indicating that BTTP4 is a promising high-performance n-type organic semiconductor and worth to synthesize. The analysis of angular-resolution anisotropic mobilities for the BTTP and BTTP4 shows that it is helpful to control the orientations of the conducting channels for a better charge transport efficiency. This work provides a rational strategy for the design of high-performance n-type organic semiconductors from molecule to crystal structure.

Films of organic polymers were prepared and investigated as insulating layers in contact with phthalocyanines as organic semiconductors for use in organic field effect transistors. The polymer films were obtained either by a high-vacuum technique based on the thermal decomposition of polymers and polymerization of the fragments on a substrate, by the spin-coating of polymer solutions or by the cross-linking of spin-coated precursors. Poly(vinylchloride), poly(vinylidenefluoride), poly(acrylonitrile), poly(methylmethacrylate), poly(N-vinylpyrrolidone), poly(styrene), poly(4-vinylpyridine), poly(N-vinylcarbazole) and a polyimide were used as polymers. The film growth was studied by mass spectrometry and infrared spectroscopy. Electrochemical measurements by cyclic voltammetry served to analyze the properties of the polymer films. The morphology was determined by atomic force microscopy. Interactions of the films with phthalocyaninatozinc (PcZn) was analyzed for co-evaporated PcZn in the polymer films, to probe the chemical compatibility of the methods. Subsequently, evaporated PcZn or hexadecafluorophthalocyaninato-oxo-vanadium (F₁₆PcVO) thin films were studied in detail by UV-vis spectroscopy and by electrical measurements to investigate interface formation, intermolecular coupling and electrical conduction in such films. The applicability of the different polymers as dielectric layers in organic field effect transistors, with phthalocyanines as the active semiconductor thin films, is discussed, based on their dielectric behavior and observed growth characteristics.

We have synthesized a series of novel phthalocyaninato copper(II) (abbreviated as PcCu) compounds, 1,4,8,11,15,18,22,25-octakisalkoxy-2,3,9,10,16,17,23,24-octachloro-phthalocyaninato copper(II) (abbreviated as ($\alpha$-C${}_{\mathrm{\text{n}}}$O)${}_{\mathrm{\text{8}}}(\beta$-Cl)${}_{\mathrm{\text{8}}}$PcCu (4a–4d): $n=$ 6 (a), 8 (b), 10 (c) and 12 (d)) and, for comparison, another series of PcCu compounds, 1,4,8,11,15,18,22,25-octakisalkoxyphthalocyaninato copper(II) (abbreviated as ($\alpha$-C${}_{\mathrm{\text{n}}}$O)${}_{\mathrm{\text{8}}}$PcCu (1a–1d)). The PcCu derivatives 1a–1d are substituted by alkoxy chains only at the $\alpha$ positions (1,4,8,11,15,18,22,25). On the other hand, the PcCu derivatives 4a–4d are substituted by alkoxy chains at the $\alpha$ positions and chlorine atoms at the $\beta$ positions (2,3,9,10,16,17,23,24). We have investigated the influence of chlorine atoms substituted at the $\beta$ positions of the Pc ring on mesomorphism, spectroscopic and electronic properties for these two series of PcCu derivatives 1 and 4 by using a polarizing optical microscope, DSC, temperature-variable small angle X-ray diffractometer, a UV-Vis spectrophotometer and cyclic voltammetry. Each of the derivatives 1a–1d is crystalline without showing mesomorphism. On the other hand, each of the chlorine-substituted PcCu derivatives 4a–4d shows plural phase transitions, and the longer chain-substituted PcCu derivatives 4c–4d show a rectangular ordered columnar [Col${}_{\mathrm{\text{ro}}}$(P2m)] mesophase. Furthermore, we have revealed that each of the PcCu derivatives 4a–4d shows a Q-band in the near-infrared region and a lower HOMO energy level than conventional phthalocyanine derivatives.

Global reactivity descriptors, Milliken’s charge distribution and molecular electrostatic potential based on Density Functional Theory (DFT), are used to understand the relationship between structure, stability and global chemical reactivity. In addition, these descriptors are used in the development of quantitative structure-activity and structure-property relationships. The study also shows the intense effect of the chlorine atom in the charge distribution. X-ray pattern reveals the crystalline structure along the (242) orientation of Aluminum Chloride phthalocyanine (AlCl-Pc) organic thin layer. Absorbance of such layer exhibits a high value within UV range and two consecutive peaks within visible range, spin coating is used to make an organic diode based on the AlCl-Pc cluster and the diode high rectifying facility is discovered. The height barrier is constant and saturation current is greatly reliant on light, the ideality factor of such a diode increases to 6.9 which confirms the non-ideality of such device.

The study of transport dynamics of charge carriers in homogeneous and inhomogeneous organic semiconductor using the variable order time-fractional drift-diffusion equation (VO-TFDDE) is presented in this paper. The fractional-time derivative operator and spatial derivative operator of the time-fractional drift-diffusion equation are discretized respectively using the implicit difference scheme and the centered difference scheme. Self-consistent Poisson solver was incorporated in the model to solve for the electric potential and the localized electric field that sweeps the charge carriers across the device. The homogeneity of the material is represented by the different values or functions of the fractional derivative order. Diffusion transport dynamics is observed when charge carriers are moving in homogeneous crystalline-like structure. In contrast, dispersive transport dynamics is observed when charge carriers are moving in homogeneous amorphous-like structure. For inhomogeneous amorphous-crystalline-mixed structure, pulse broadening effect is impeded as charge carriers are moving towards the crystalline-like region at the other end of the device. Conversely, pulse broadening effect is getting severe if charge carriers are moving across the device with inhomogeneous crystalline-amorphous-mixed structure. Therefore, in order to achieve diffusive-like transport dynamics that could reduce the pulse broadening effect, homogeneous crystalline-like structure or inhomogeneous amorphous-crystalline-mixed structure is recommended for device fabrication.

The frequency-dependent impedance of a series of ferromagnet (FM)/organic semiconductor (OSC)/FM tri-layered organic spin valves (OSV) is investigated in the frequency range of 10 Hz–1 MHz. An equivalent resistor–capacitor (RC) parallel network model is employed to analyze the magnetoresistance (MR) and magnetocapacitance (MC) effects. Fitting with the model yields field-dependent parameters and the resistive parameters agree with the experimental results. The analysis of the impedance spectra indicates an effective magnetotransport mechanism dominated by the charge accumulation at the organic–FM interfaces.