الفهرس 
Theoretical Background and Literature ReviewOnly 14 pages are availabe for public view
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Abstract
Organic semiconducting materials are of particular interest, since they
possess a prosperous optoelectronic, electrical and processing properties for
designing and fabrication of electronic devices [1]. Among these materials, a
series of phthalocyanines represent a large family of heterocyclic conjugated
molecules with high chemical stability. Phthalocyanines as a class of organic
materials are generally thermally stable and can easily be deposited as thin
films with high quality by thermal evaporation without dissociation. Metal
phthalocyanines (MPc’s) have gained considerable attention in recent years
because they have been successfully applied in many applications such as gas
sensors [2, 3], solar cells [4– 6] and light emitting diodes [7, 8]. Optical
absorption studies of MPc’s thin films have attracted the researchers over the
last few years [9, 10]. Relatively few studies have focused on the halogenated
MPc’s although there is evidence that they may exhibit properties suitable for
gas sensing applications [11]. It has also been shown that the halogenated Pc’s
exhibit remarkable morphological and thermal stability over a larger
temperature range compared to unhalogenated Pc’s [12].
One of the most halogenated MPc’s derivatives is aluminum
phthalocyanine chloride (AlPcCl), which is the focus of our study. It has a
chemical formula of (C32H16AlClN8).
Thin films of aluminum phthalocyanine chloride (AlPcCl) were
fabricated, with different thicknesses (109–518 nm) using thermal evaporation
technique. Structural and optical properties of AlPcCl thin films were
investigated. The material in powder form showed a polycrystalline nature
with monoclinic structure. Miller indices, hkl, values for each diffraction line
in X-ray diffraction (XRD) spectrum were calculated. The field emission scanning electron microscope (FESEM) showed the nanostructure property of
the as- deposited thin films. The optical properties of the thin films were
studied by the spectrophotometric measurements of the transmittance, T, and
the reflectance, R, at the normal incidence of the light in the spectral range
200–2500 nm. The refractive and absorption indices of the thin films were
calculated and were found to be independent on film thickness in the range
109-518 nm. The films exhibited indirect allowed inter-band transitions. The
optical band gaps transitions were calculated as 1.42, 2.87 and 3.69 eV,
respectively. Also, different dispersion and absorption parameters were
determined for thin films of AlPcCl.
AC conductivity and dielectric behavior for bulk aluminum
phthalocyanine chloride (AlPcCl) have been studied over a temperature range
(303– 403K) and frequency range (42–106 Hz). The frequency dependence of
ac-conductivity (ω) has been investigated by the universal power law
(ω) = Aωs. The variation of the frequency exponent (s) with temperature
was analyzed in terms of different conduction mechanisms, and it was found
that the correlated barrier hopping (CBH) model is the predominant
conduction mechanism. The barrier height was calculated by using (CBH)
model, and was found to be 1.41 eV.
The temperature dependence of (ω) showed a linear increase with
the increase in temperature at different frequencies. The density of states N
( ) was calculated to be equal 4.11 x 1019 cm-3 using Elliott model. The acactivation
energy was determined at different frequencies. Dielectric values
were analyzed using complex permittivity and complex electric modulus for
bulk AlPcCl at various temperatures Analysis of electrical properties Au/AlPcCl /p-Si/Al as p–p+
heterojunction was studied. The dark forward current–voltage characteristics
showed a thermionic emission mechanism at low voltage region (V≤ 0.26
volt), while at high voltage region (V≥ 0.32 volt); the operating conduction
mechanism was found to be space charge limited current. from (I-V) curves,
the junction parameters such as series resistance (Rs), ideality factor (n) and
effective barrier height (Φb) were determined at temperatures range (308–378
K). The series resistance and barrier height values of AlPcCl /p-Si
heterojunction estimated from Cheung’s and Norde’s methods are strongly
temperature dependent especially towards the lower temperatures.
The capacitance–voltage (C–V) characteristics of AlPcCl/p-Si devices
were also investigated. The built-in potential obtained from the (C–V)
measurements was found to be 0.49 eV. Solar cell parameters were evaluated
under illumination of mW/cm2 and the power conversion efficiency was
estimated as 2.6 %.