الفهرس 
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Abstract
During the recent years a Great intense studies have been made to understand the optical, electrical and photovoltaic properties of the organic semiconductors. They exhibit different properties compared to inorganic semiconductors, and present many advantages such as unlimited potential to be synthesized in new molecular structures, and capability of being processed inexpensively. Among these groups of materials, organic molecules with conjugated π-electron systems, such as porphyrin molecules, have created a new class of materials that offer the possibility of implementing innovative applications in many modern applications. One of these materials is 5,10,15, 20-tetraphenyl -21H, 23H- porphine nickel (II) (NiTPP). The present thesis is devoted to study some structural, optical and electrical transport properties of 5,10,15, 20-tetraphenyl -21H, 23H- porphine nickel (II) (NiTPP) in thin film form.
Thin films of NiTPP were prepared by thermal evaporation technique. It was found that NiTPP compound in powder form is thermally stable up to 770 K. The infrared transmission spectra of the powder, the as-deposited, annealed and irradiated thin films revealed that the main chemical composition of NiTPP has been preserved by thermal evaporation technique. Structural investigation using X-ray powder diffractograms confirmed that the powder of NiTPP has a monoclinic form with lattice constants of a = 14.622 Å, b = 7.566 Å, c = 11.785 Å and β=104.11º. Also, the as-deposited and annealed films were polycrystalline like structure. The X-ray film diffractograms of the gamma-irradiated NiTPP thin films showed that the gamma radiation of dose 150 kGy converted the polycrystalline nature to amorphous structure of wide range of nano-granular particles.
The analysis of scanning electron microscope, SEM, and the contact mode atomic force microscopy, AFM, topographs for as-deposited NiTPP thin films showed a wide range of nano-sized particles of granular shape. The effect of annealing and (gamma and neutron) radiation showed a large impact effect where it modificate the size and the shape of the prepared film structure.
The morphology of the prepared NiTPP films were studied by the transmission electron microscopy, TEM, with the aid of the diffraction pattern NiTPP thin films confirmed the nano-size and the polycrystalline nature of the prepared NiTPP films. The analysis of the transmission electron microscopy, TEM, showed with the aid of the diffraction pattern that the gamma and neutron radiation modificate the structure of the prepared NiTPP films.
The optical properties of the as-deposited NiTPP films are investigated by spectrophotometric measurements of transmittance and reflectance at normal incidence of light in the wavelength range 200-2500 nm. Absorption spectra of NiTPP thin films showed the absorption peaks and shoulder of Q-band in the wavelength region 500–640 nm and extend with longer wavelengths in red and IR region. The other three closed bands labeled (N, M and L) appear in the UV region. The peaks of Q and B bands are assigned π-π* transition between bonding and anti-bonding molecular orbitals. The mean value of the first transition is the onset optical gap, = 1.92 eV, or excitonic gap and the mean value of last one is = 2.58 eV. Between them there are one or two transitions corresponding to the trap transitions. The dispersion of the refractive index, n, is discussed according to the single oscillator model. The polarizability, the dispersion parameters, the ratio of free carrier concentration to the free carrier effective mass are also estimated.
It was found that the values of and decrease by increasing the annealing temperature from 298 to 573 K. Also, it was found that the gamma-ray irradiation (150 kGy) has an effect on the excitonic and impurities levels while no effect was observed on the fundamental gap. On the other hand, it was found that the refractive index of the as-deposited film decreases by gamma-ray irradiation and by increasing the annealing temperature. Neutron irradiation decreases the refractive index at low energy but it was found to increasing at high energy.
The effects of film thickness ranges from138 to 227 nm and annealing temperature at 423 K on the dark DC conductivity of the planer NiTPP films were studied. The planer NiTPP films showed high resistivity in dark at room temperature. The temperature dependence of electrical conductivity in NiTPP films indicate that; the conduction is through a thermally activated process having two conduction mechanisms in two different regions. The activation energy of the prepared planer NiTPP films of different thickness has nearly the same values which generally equal the half of the onset optical gap.
The electrical conductivity and dielectric properties of the NiTPP has been investigated in the frequency range from 42 Hz to 5MHz and in the temperature range 303–373 K. The frequency dependence of σ(ω, T) follows the Jonscher’s universal dynamic law. The correlated barrier hopping (CBH) model has been applied to the interpretation of the a.c. electrical conductivity. The real and imaginary parts of the electric modulus were used to determine the static and dynamic dielectric constants and it was found that as the temperature increases the values of the static and dynamic dielectric constants decreases. The effect of grain and grain boundary was discussed by using the Cole-Cole diagram by using the real and imaginary parts of the impedance.
Organic/inorganic heterojunction cell based on thermally evaporated NiTPP as the organic semiconductor and p-Si wafer as the inorganic semiconductor have been investigated. This device showed rectification behaviour like diode in dark and photoconducting bulk behaviour under illumination. A short–circuit current of 1.097 mA, an open–circuit voltage of 0.46 V and a fill factor of 42 % were extracted from (I-V) characteristics under illumination of ≈20 mW/cm2 and the obtained power conversion efficiency have the value of 4.03 %.