الفهرس 
Theoretical Background and Literature ReviewOnly 14 pages are availabe for public view
 |  | from | 379 |  |  |
| | | from | 379 | | |
Abstract
This thesis represents an experimental and theoretical study of the physical properties of organic compounds. This thesis consists of five chapters, a conclusion, and a list of references.
The thesis begins with a short theoretical background about the field of organic semiconductors, the electronic structure of organic semiconductors, and the optical properties of semiconductors. We also represent IR spectroscopy, the fundamentals of the light absorption process, the fundamentals of organic photovoltaic solar cells, and finally computational physics.
Then it represented a brief overview of the experimental techniques used in this thesis. It describes the basics of the conventional thermal evaporation (vacuum deposition) techniques, the configuration of sample preparation, the film thickness measurement methods, the techniques used to determine the molecular structure, i.e. Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, an X-ray diffraction pattern (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM) and Atomic force microscope (AFM) techniques, the techniques that used to determine the optical properties usually the Spectrophotometric measurement of transmittance (T) and reflectance (R) at normal incidence light, current-voltage (I-V) measurement, the γ-irradiation and heat treatment techniques and finally the computational program package.
The results of pristine, γ-irradiated, and heat-treated beta metal-free phthalocyanine (β-H2Pc) structural properties are also represented. X-ray diffraction results indicate that the powder of the investigated compound has a polycrystalline nature with a monoclinic structure. The deposited β-H2Pc thin film takes on the form of a distribution of nanoparticles, with an average particle size measuring approximately 150 nm. The β-H2Pc sample has high thermal stability from room temperature up to approximately 470 °C. The results of FT-IR confirm the formation of H2Pc in the β-form. The results of the computational study for the molecular structure of metal-free phthalocyanine are also represented. The equilibrium geometries, harmonic vibrational frequencies, thermo-chemical parameters, total dipole moment, HOMO-LUMO energies, ionization energy, electron affinity, global hardness, electronic chemical potential, global electrophilicity index, softness, and first-order hyperpolarizability are calculated by DFT/B3LYP utilizing 6-311G basis set. Comparison of the vibrational frequencies calculated at B3LYP utilizing a 6-311G basis set with experimental values reveals that B3LYP/6-311G gives reasonable deviations from the experimental values.
We also represent the optical properties of the as-deposited β-H2Pc thin films and the γ-irradiation and heat treatment films: transmittance (T), reflectance (R), optical constants (n,k), absorption coefficient (α), molar extinction coefficient (εmolar), oscillator strength (f), electric dipole strength (q2), HOMO- LUMO gap, single oscillator energy (Eo), dispersion energy (Ed) and dielectric constant (εL). The type of optical transition responsible for the optical absorption is indirect allowed transition. The refractive index showed an anomalous dispersion in the absorption region as well as a normal one in the transparent region. Some dispersion parameters, the real and imaginary parts of dielectric constant (ε1 and ε2), volume and surface energy loss functions (VELF and SELF), and real and imaginary parts of optical conductivity (σ1 and σ2) of β-H2Pc films are determined.
Finally, the thesis represents the electrical properties of β-H2Pc thin film by studying the dark and illumination (I-V) characterization of Au/β-H2Pc/p-Si/Al heterojunction. The transport mechanism of the electronic charges is determined for the heterojunction in the forward direction in Au/β-H2Pc/p-Si/Al heterojunction. At low forward voltages, the transport mechanism is the thermionic emission mechanism, and at high voltages is the space-charge-limited conduction (SCLC) mechanism. The junction shows a photovoltaic behavior with a power conversion efficiency, η, of 1.1%.