الفهرس 
Cu2SnS3 thin films prepared for solar cell applications
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Abstract
Ternary compound Cu2SnS3 (CTS) thin film is a promising candidate as a
potential alternative to CIGS and CZTS absorbers in photovoltaic (PV) thinfilm technology as it obtained a wide stability range and strong optical
absorption. CTS has a similar crystal structure to CZTS with a favorable
absorber material for solar cells due to its p-type conductivity, direct band gap
range of 0.9–1.4 eV, and high absorption coefficient of 104
to105
cm−1
. Kuku
and Fakolujo fabricated the first CTS device with experimental efficiency of
0.11%, while the theoretical efficiency of CTS is significant at 30% according
to the Shockley-Queisser limit.
The current study sheds light on the formation of the pure Cu2SnS3 (CTS)
thin film that qualified as an absorber layer for solar cell applications. A
variety of chemical and physical deposition techniques were used to produce
CTS thin film, including spray pyrolysis and radio frequency (RF) sputtering
techniques. The effect of changing depositions parameters and sulfurization
process on the structural, morphological, and optical properties of the CTS
films were discussed.
Different spray pyrolysis temperatures and types of solvent illustrated a
clear effect on the physical properties of the CTS films. The film quality was
improved by optimizing the Cu ratio. Moreover, the impact of different
annealing atmospheres on sprayed films was studied. After annealing in a
nitrogen atmosphere using rapid thermal annealing (RTA), the crystal quality
of the CTS films was enhanced and the band tailing tended to vanish. However,
ethanol was obtained as a solvent in the sprayed process; the sprayed CTS
films were not contaminated by carbon and oxygen. While by sulfurization atmosphere, the bandgap of the sprayed CTS thin films was changed. The
merit of the RTA process influenced the composition of the film, modifying
the crystal quality, and improving the electrical properties of the material.
These results represent the initial step toward the experimental application of
CTS thin film solar cells using an inexpensive chemical fabrication technique.
On the other hand, Cu2SnS3 (CTS) thin films were synthesized onto soda
lime glass substrate coated with molybdenum by sulfurization of the Cu-Sn
stacks prepared using RF sputtering. The monoclinic Cu2SnS3 thin films were
optimized without secondary phase formation. After that, the influence of Nadoped CTS, Sb-doped CTS, and Sb+Na co-doped CTS films on their physical
properties has been studied. Larger grain size and improvement in the
photoluminescence sharpening were obtained in the existence of Na and/or Sb.
The power conversion efficiency was improved from 0.32% for un-doped
CTS to 1.54, 1.89, and 0.76 % for Na, Sb, and co-doping CTS, respectively.
In a more deep study, the effect of Na doping at different sulfur amounts
was studied. The optical direct bandgap and crystalline size increased with
the increasing amount of sulfur. It was due to enhancement in the film
crystallinity. The J-V measurements indicated that the cell efficiency with
Na-doped CTS increased to 2.01 % (10 mg of S) and 2.43% (100 mg of S).
Furthermore, the physical properties of the various Sb doping level with
different amounts of S in the sulfurization process were studied. CTS has a
monoclinic structure for both pure and doped films, with a larger grain size
under the influence of Sb doping. XRD, Raman, XPS, and Hall Effect
measurements concluded the optimum doping level of Sb was at a doping
time of 25 min. Because the high level of Sb doping showed some secondary
phases. The optimum conversion efficiency of the fabricated cells was 2.13%
at 25 min of Sb doping and 100 mg of sulfur.Therefore, many efforts to improve cell performance and understand its
physical properties are demanded. Whether obtaining high efficiencies in
CTS solar cells is dependent on the film crystal quality and the extra phase
contamination during the synthesis process.