الفهرس 
Chapter 1 Introduction and Literature ReviewOnly 14 pages are availabe for public view
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Abstract
Great intense studies have been made in recent years to understand the physical properties of organic semiconductors. They exhibit different properties compared to inorganic semiconductors. Many classes of compounds such as organic photochromic compounds which undergo color changes due to heat, light, electrical current. The color change phenomena can be classified into photochromism, thermochromism and electrochromism according to the affecting stimulus such as light irradiation, heat and electrical current respectively. One of these compounds is 1’,3 ’-dihydro-1’,3’,3’-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2’-[2H] indole] denoted as DTNBI. which is the focus of our study.
Thin films of DTNBI were prepared by thermal evaporation technique. Differential Thermal Analysis (DTA), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) technique and scanning electron microscope (SEM) used to achieve structural characterizations. It was found that DTNBI compound in powder form has a monoclinic structure with space group (P2) and the lattice constants, a = 29.912 Å, b = 18.815 Å, and c = 13.062 Å.
X-ray diffraction patterns of DTNBI for the as deposited (thickness 1343 nm) and annealed (at 273 K for 1 hour) thin films. , the as deposited film have a semi polycrystalline form which improved for the annealed film with a diffraction peak (1 ̅31), around 2θo = 16.05 o which has a crystallite size 11.21 nm from Scherrer equation.
The temperature and frequency dependence of the AC conductivity σac(ω), the dielectric constant ε1(ω) and the dielectric loss ε2(ω) are studied for DTNBI compound with ohmic Au electrodes in the temperature range 303-363K and in the frequency range 40 Hz -5 Mhz. Regarding to the values of S and its variation against temperature and the suitable model is the correlated barrier hopping (CBH).
The optical properties of the as-deposited DTNBI films are investigated by spectrophotometric measurements of transmittance and reflectance at normal incidence of light in the wavelength range 200–2500 nm. The values of direct and indirect energy bandgaps were found to be 2.88 and 2.6 eV respectively and decreased with annealing. The dispersion of the refractive index, n, is discussed according to Cauchy relation and the single oscillator model. The polarizability, the dispersion parameters, the ratio of free carrier concentration to the free carrier effective mass are estimated.
The J-V characteristics of the Au/ DTNBI/p-Si/Al heterojunction, where exhibits rectifying behavior in the dark which can be explained due to the formation of Schottky barrier at Au electrode and the typical junction parameters were estimated in temperatures from 303 to 363 K.
Hybrid organic-inorganic solar cell (Au/ DTNBI/p-Si/Al) exhibited photovoltaic characteristics with a short circuit current (J_sc) of 0.0074 mA/cm2 and an open-circuit voltage (〖 V〗_oc) of 0.737 V, a fill factor FF = 0.64. and a power conversion efficiency η of 0.01 %.
Composite films based on poly (methyl methacrylate) (PMMA) and 1’,3-dihydro-1’,3’,3’-trimethyl-6-nitrospiro[2H-1-benrzopyran-2,2’-[2H] indole](DTNBI) were prepared using casting technique with different concentrations of DTNBI (0, 1, 3 and 5wt %). Fourier Transformation (FTIR) spectroscopy was performed in the range (4000 –500 cm-1) to investigate the chemical structural characterizations of the prepared composite films. The characteristic of linear and non-linear optical properties of composite films were indexed in the spectral range of wavelength (200-1800) nm. The calculated refractive index of DTNBI – PMMA films decrease by increasing DTNBI concentration at constant wave length. The detected optical band gap was found to be depend on DTNBI doping where the lower value at 5 wt % of DTNBI concentration. The third order nonlinear susceptibility and nonlinear refractive index decreased by rise concentration of DTNBI doped.