الفهرس 
Theoretical background and literature review.
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Abstract
Because of the designable materials properties,
compatibility with conventional Si fabrication and thin film
processes, and unique physical and chemical properties, PS is
a versatile material with potential in a number of different
application areas. Optical and optoelectronic applications are
based on the tunable optical properties of the porous layer,
such as the index of refraction and layer thickness (solar cells,
PDs, reflectors), and on the various luminescence phenomena
linked to PS (LEDs).
Fabrication of PS layers (PSLs) was performed by
electrochemical etching process on the front side of textured n+
p Si junctions. The formed porosity was determined
gravimetrically within a good range of 88.27 - 97%. The effect
of porosity on the structure, electrical, and photoelectrical
properties was investigated. Surface morphology and the
crystallites size of PS were characterized by using scanning
electron microscope (SEM) and X-ray diffraction (XRD) respectively. Scanning electron microscope (SEM) shows the
evolution of PSLs morphology through the increase in surface
area due to the regular increase in porosity. The broadening of
the FWHM obtained from the XRD spectra provided the
reduction in the crystallite size.
The optical properties of the fabricated PSLs have been
characterized by using a UV–Vis spectrophotometer equipped
with an integrating sphere attachment. The reflection
measurements showed an excellent light trapping at
wavelengths ranging from 200 to 1000 nm at 30 mA/cm2
etching current density. The optical absorption coefficient was
calculated from the reflection spectra and the optical band gap
was determined. The value of the energy gap (Eg) was also
determined by applying the Kubelka–Munk (K–M or F(R))
method. The optical band gaps have been found to tunable with
the variation of particle size, which attributed to quantum
confinement effect. from the photoluminescence (PL)
measurements, the PL peak intensity increases upon increasingthe porosity and also shows slight blue shifts at 629 nm and
640 nm as the porosity increases. The band gaps of PSLs
obtained from the photoluminescence measurements and from
the reflection data were compared. It is found that the band
gap increases in a range between 1.84 eV and 2.23 eV, which
is higher than the band gap of silicon (1.12 eV).
The current-voltage (I-V) characteristics of Al/PS /n+ p
/Al junction fabricated at etching current density of 30 mA/cm2
were investigated and compared with the reference Al/n+ p/Al
junction. The junction parameters such as series resistance
(RS), ideality factor (n) and effective barrier height ( ) were
determined by using different methods. It was shown that the
values of the series resistance RS and barrier height values
using Cheung’s and Norde’s functions are dependent on
temperature for the junctions under investigation.
Under illumination, the short-circuit current density (JSC) and
the open-circuit voltage (VOC) increased from 0.35 mA/cm2 to
5.3 mA/cm2 and from 0.39 V to 0.62 V, respectively. Thephotosensitivity of PSLs solar cells showed a noticeable
enhancement in quantum efficiency of the PS cells by
increasing the porosity.
In this thesis, the structural, optical and electrical
properties of the treated textured cells was investigated and
compared with the untreated textured cell under the variation
of etching current densities. The results confirm that PS layers
formed on textured surface can be used as both broadband
antireflection coatings and passivation layers for the
application in solar cells.