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complexing agents added CuS, SnS and CuSnS thin films’ is elucidated in nine
chapters.
The first chapter comprises the growth of research in the field of
optoelectronics. Pure and complexing agents TEA / EDTA added Binary and
ternary compounds taken for our study is explained. Several thin film coating
techniques are discussed. Significances of SILAR and experimental techniques are
briefed. Various characterization techniques and the instruments used are discussed.
The review of literature on the area of research is discussed in detail.
Chapter 2 explains about the deposition of pure binary compound CuS
thin film on glass substrates using the SILAR method at room temperature in two
different ratios 1:1 & 1:2 and in five different molar concentrations. CuS thin films
reported by many researchers
previously.
by various methods and different chemicals
It was by Copper Iodide, Copper Chloride, Copper Acetate and
Sodium Sulphide, Thio urea. My source of material selection is copper Nitrate
[Cu(NO3)2·H2O], TEA, Sodium Sulphide [Na2S] and distilled water. It deals with
the absorbance, transmittance, band gap, morphological and topographical
properties. It reveals that, the band gap energy decreases from 2.26 to 2.05 eV for
1:1 ratio and from 2.21 to 1.86 eV for 1: 2 ratio when molar concentration increases
from 0.05 M to 0.25 M. The high absorbance of the films made them good materials
for conversion of solar energy. SEM and AFM images reveal the uniform and
homogeneous coating of CuS.
Chapter 3 deals with the deposition of binary compound CuS on glass
substrates with complex agent TEA - N(CH2CH2OH)3 using the SILAR method on
glass substrate at room temperature in five different molar concentrations. This
chapter aims to observe the absorbance, transmittance, band gap, morphological and
topographical properties of TEA added copper sulphide thin films. From the
analysis, it is concluded that, the TEA enables uniform coating throughout the glass
plate and TEA added copper sulphide (CuS) thin film’s band gap energy is suitable
for solar cell applications. X-ray diffraction (XRD) analysis was used to confirm the
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material and also to find the crystal size,
d-spacing, dislocation density and micro
strain. Optical band gap energy is found to decrease from 2.25 to 1.92 eV for the
increase in molar concentration. Also this chapter deals about the influence of
different molar concentration and determines the optimum condition for deposition
process.
Chapter 4 enumerates the deposition of binary compound CuS on glass
substrates with complex agent ethylene diamine tetra acetic acid (EDTA)
C10H16N2O8 using the SILAR method on glass substrate at room temperature in five
different molar concentrations. Multiple dipping of the substrate in an aqueous
solution of EDTA added copper nitrate, sodium sulphide and in deionised water is
achieved in SILAR technique. Various physico chemical properties such as
absorbance, transmittance, band gap, structural, morphological and topographical
properties of EDTA added copper sulphide thin films are analyzed. The structure,
crystal size, d-spacing, dislocation density and micro strain of the film are studied
by powder XRD studies. Scanning Electron Microscopy (SEM) and Atomic force
microscopy (AFM) measurements are performed to study the topographical and
morphological characteristics of the CuS thin films with EDTA and confirms the
uniform coating. It was also observed that the influence of molar concentration to
determine the optimum condition for deposition process was also observed. The
optical properties revealed that the EDTA added copper sulphide (CuS) thin film is
suitable for solar cell applications and solar panel fabrication.
Chapter 5 presents the deposition of thin films of binary compound Tin
Sulphide (SnS) with TEA on glass substrate at room temperature by SILAR method
for solar cell application. This chapter deals with the analysis of structural, optical,
morphological and topographical properties of TEA added Tin Sulphide thin films
by X-ray diffraction (XRD), FT-IR, UV-Vis spectrometer, SEM and AFM. Further,
the X-ray diffraction studies confirm that the deposited SnS films are amorphous
and polycrystalline structure and various functional groups present in the developed
thin films are analyzed by FT-IR spectrum. SEM is used to investigate the effect of
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the SnS thin film with addition of TEA for different molar concentration and the
phase morphology of the films. The SnS with TEA thin films are examined by AFM
for its surface roughness, particle height and for its grain size. It is observed that
the band gap energy (Eg= 2.31 eV, 2.27 eV, 2.16 eV, 2.09 eV) decreases with
increase in molar concentration 0.10 M, 0.15 M, 0.20 M and 0.25 M.
Chapter 6 elaborates the preparation of thin films of binary compound
SnS with EDTA on glass substrate at room temperature by SILAR method for solar
cell application as absorber layer to obtain wider energy band gap. Several coatings
of Tin Nitrate (Sn(NO3)2) as cationic precursor and Sodium Sulphide (Na2S) as
anionic precursor are made for the present investigation. The chapter deals with the
structural, optical, morphological and topographical properties of EDTA added tin
sulphide thin films. The XRD confirms that the deposited SnS films found as
amorphous nature and polycrystalline structure. The UV-Vis spectra of SnS films in
the wavelength range of 200-900 nm have been recorded to measure the direct band
gap. The band gap energy (Eg = 2.42 eV, 2.33 eV, 2.27 eV, 2.23 eV and 2.02 eV)
decreased as a function of molar concentration (0.05 M, 0.10 M 0.15 M and 0.20
M) and it was found that the band gap energy decreased with increasing particle
size. The FTIR measurements have been made in the wave number range 400 cm1
to 4000 cm-1. The SEM micrographs for the different concentration films are also
represented. SnS thin films with complexing agent EDTA are investigated by AFM
for its roughness average, particle height and for its grain size.
Chapter 7 articulates the influence of molar concentration on TEA added
nano CTS (CuxSn1-xSy) ternary compound (x=0.01 M to 0.10 M; y = 0.10 M)
deposited by SILAR technique. TEA added CTS films are coated on glass substrate
at room temperature. The structural, morphological and optical properties of the
nano thin films for different molar concentrations between 0.01 M and 0.10 M are
investigated and reported. The FTIR measurements have been made in the wave
number range 400 cm-1 to 4000 cm -1. The X-ray diffraction (XRD) pattern obtained
for CuxSn1-xSy thin films reveals amorphous nature. It is observed that the Cu xSn1-
x
xSy
films are nano crystalline in nature with mixed hexagonal phase of SnS and CuS
and the average grain size of the film material increases with the molar
concentration. Also the analyzes was focussed to investigate the influence of dopant
Cu2+ on the transmittance, absorbance, refractive index and band gap values of the
films. The analyzes revealed that the material is a direct band gap semiconductor
with band gap energy ranging from from 2.28 eV to 1.79 eV and the properties of
high absorbance in the visible region and wide band gap energy of the film makes it
may be suitable as window layers for solar cell application. SEM and AFM analysis
confirms the uniform coating.
Chapter 8 summarises and concludes the work. This chapter compares
the properties of CuS, SnS and CuSnS thin films.The band gap values of the
materials matches the expectation of solar cell.
Chapter 9 proposes the further extension of present work. The effect of
annealing the films will be studied. Also, planned to study some new binary, ternary
and quaternary compounds.
ACKNOWLEDGEMENT
First and foremost gratitude is to The Almighty for having given me the mental
and physical strength and dexterity to enter into this research in the field of Physics and
come out successfully.
I am greatly obliged to thank my Research supervisor, Dr. J. Joseph Prince,
Assistant Professor in Physics, Anna University - BIT Campus, Tiruchirappalli. His
guidance helped me to get a broader outlook of my work and raised my confidence level to