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    Annealing time effect on CIGS thin films
    (Emerald Group Publishing Ltd, 2020) Matur, Utku Canci; Baydogan, Nilgun
    Chalcopyrite copper indium gallium (di)selenide (Cu(In, Ga)Se-2 (CIGS)) thin film has been examined as an absorber layer for solar cells because of its suitable absorption value, stability and economy in manufacture. CIGS thin films belong to the I-III-VI2 group of the periodic table with the appropriate direct bandgap (1.5 eV). In this study, CIGS thin films were annealed at similar to 200 degrees C for four different annealing times (15, 30, 45 and 60 min) to investigate the effect of the annealing time on the crystalline structure and optical properties of CIGS thin films prepared by using the sol-gel dip-coating technique. CIGS thin films annealed at similar to psi 200 degrees C for 60 min were found to have the best structural and optical properties in this study. As the crystallite size increased with the rise in the annealing time, the lattice strain decreased, indicating the elimination of crystallite defects in the CIGS thin-film structure. Hence, the structural changes affected the optical properties slightly and the rise in the optical absorbance (A%) resulted in a decrease in the optical transmittance (T%).
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    Changes in gamma attenuation behaviour of sol-gel derived CIGS thin film irradiated using Co-60 radioisotope
    (Elsevier Science Sa, 2017) Matur, Utku Canci; Baydogan, Nilgun
    Copper indium gallium (di) selenide-Cu(In, Ga)Se-2 (CIGS) thin films were fabricated on soda-lime silicate glass substrates using a layer-by-layer sol-gel dip-coating method. The irradiation procedure was handled using a certified Co-60 radioisotope at two different absorbed dose levels (at 0,03 and 0,05 Gray (Gy)) to examine the enhancements of optical and electrical properties of the CIGS thin films. Cs-137 (with 0,662 MeV) and Co-60 (with similar to 1,25 MeV) radioisotopes were used to evaluate the effect of the absorbed dose on CIGS thin films with different thicknesses by the gamma transmission technique. The irradiated CIGS thin films exhibited an improved optical band gap and electrical resistivity at the optimal layer thickness. This improvement occurs due to the enhancement of crystalline properties in comparison with those of non-irradiated CIGS thin films. The CIGS thin film of similar to 300 nm (11 layers) thickness was suitable for comparing changes in the linear attenuation coefficient after the irradiation process at two different absorbed dose levels. In the experiments, the gamma transmission technique was utilized to investigate the gamma attenuation properties of non-irradiated and irradiated CIGS thin films at different thicknesses against Cs-137 (with 0,662 MeV) and Co-60 (with similar to 1,25 MeV) gamma radioisotope sources. The irradiation process and the increase of thickness of CIGS thin films caused a higher linear attenuation coefficient, higher absorption and improvement in electrical conductivity. These results demonstrate the suitability of these materials for solar cell applications in aerospace technology, especially for high-altitude flight operations. (C) 2016 Elsevier B.V. All rights reserved.
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    Effects of Production Parameters on Characteristic Properties of Cu(In,Ga)Se2 Thin Film Derived by Solgel Process
    (Springer International Publishing Ag, 2015) Akyol, Sengul; Matur, Utku Canci; Baydogan, Nilgun; Cimenoglu, Huseyin
    Cu(In,Ga)Se-2 (CIGS) thin films were obtained by solgel method on sodalime glass substrates, economically. The optimum optical properties of CIGS thin films are obtained by varying the film layers. Besides, the solgel-derived CIGS thin films were thermally treated at different temperatures from 135 degrees C up to 200 degrees C. These results indicate that the transparent CIGS thin films derived by solgel process can be good candidates for the applications in optoelectronic devices.
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    I-V Characterization of the Irradiated ZnO:Al Thin Film on P-Si Wafers By Reactor Neutrons
    (Springer Int Publishing Ag, 2015) Gunaydin, Emrah; Matur, Utku Canci; Baydogan, Nilgun; Tugrul, A. Beril; Cimenoglu, Huseyin; Yesilkaya, Serco Serkis
    ZnO:Al/p-Si heterojunctions were fabricated by solgel dip coating technique onto p-type Si wafer substrates. Al-doped zinc oxide (ZnO:Al) thin film on p-Si wafer was irradiated by reactor neutrons at ITU TRIGA Mark-II nuclear reactor. Neutron irradiation was performed with neutron/gamma ratio at 1.44 x 10(4) (n cm(-2) s(-1) mR(-1)). The effect of neutron irradiation on the electrical characteristics of the ZnO: Al thin film was evaluated by means of current-voltage (I-V) characteristics for the unirradiated and the irradiated states. For this purpose, the changes of I-V characteristics of the unirradiated ZnO: Al thin films were compared with the irradiated ZnO: Al by reactor neutrons. The irradiated thin ZnO: Al film cell structure is appropriate for the usage of solar cell material which is promising energy material.
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    Sol-Gel Derived Cu(In,Ga)Se2 Thin Film Solar Cell
    (Amer Scientific Publishers, 2017) Matur, Utku Canci; Baydogan, Nilgun
    Well crystallized copper indium gallium (di) selenide-Cu(In, Ga) Se-2 (CIGS) thin films were deposited on conducting substrates (molybdenum coated soda-lime glass) by sol-gel dip coating technique. The n-type cadmium sulfide (CdS) buffer layer was produced by chemical bath deposition (CBD) technique and the n-type ZnO: Al thin film has been used as transparent conductive layer was deposited by sol-gel dip coating technique. The selenium powder was dissolved in trioctylphosphine (TOP, 90%, technical grade) solution during the experiment process to make some progress on scientific innovation of CIGS thin films derived by sol-gel dip coating technique. Hence, the heterojunction at Mo/CIGS/CdS/ZnO: Al/Al configuration was produced on a soda-lime silicate glass substrate (SLSG). SLSG/Mo/CIGS/CdS/ZnO: Al/Al heterojunction was fabricated by using a practical economical and more eco-friendly technique. The structural, optical and current-voltage (I-V) characteristics of the CIGS based heterojunction was analysed by using the SLSG/Mo/CIGS/CdS/ZnO: Al/Al device configuration. The optoelectronic properties such as the open-circuit voltage (V-oc), the short-circuit current (I-sc), the fill factor (FF), the ideality factor (n) etc. of the CIGS thin film solar cells were examined depending on the annealing temperature at 500 degrees C for 45 minutes in air. The CIGS thin film heterojunctions which has been obtained present diode like rectifying behaviour besides photovoltaic behaviour under UV illumination.
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    The Characteristic Behaviors of Solgel-Derived CIGS Thin Films Exposed to the Specific Environmental Conditions
    (Springer Int Publishing Ag, 2015) Matur, Utku Canci; Akyol, Sengul; Baydogan, Nilgun; Cimenoglu, Huseyin
    This study was performed to determine the time effect on optical properties of solgel-derived Cu(In, Ga)Se-2 (CIGS) thin films at the specific environmental conditions. For this purpose, solgel-derived CIGS thin films were exposed to a variety of environmental conditions at different steps of the production process from the preparation of solution to deposition of substrate. The optical properties of the CIGS thin films changed with the rise of time at the specific environmental conditions such as the increase of the aging time of solgel solution (from 18 to 35 days) and the rise of the annealing time of the thin film (from 15 to 60 min). The CIGS solution was aged with the rise of time to investigate the effect of the aging time on optical properties of the thin film. The films were deposited by aged colloidal solution which kept at -5 degrees C in a dark environment in order to extend the useful life of solution. The color of the colloidal solution changed slightly with the increase in the elapsed time after the preparation of the solution. The increase of the annealing time has affected the optical behaviors of the CIGS thin films with the changes of the surface morphology.
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    Thermal neutrons effect on improvement of electrical properties at CIGS thin film derived by sol-gel dip coating technique
    (Elsevier, 2022) Matur, Utku Canci; Baydogan, Nilgun
    The thermal neutron effect on the copper indium gallium (di)selenide thin film synthesized by the sol-gel dip -coating technique has explained the novel use of this film under extreme conditions (such as neutron irradiation fields). The thin film samples were treated by using the reactor neutrons to obtain the optimum neutron treat-ment for the determination of the variations in the structural characteristics. The gamma filter system has provided the evaluation of the high thermal neutron flux effect on the thin film samples by using the tangential beam tube of ITU TRIGA Mark-II reactor. The influence of the neutron effect on the electrical and optical features was explained by the rise of selenium amount in the thin film. The neutron-treated thin film samples (at 50 at. % Se) had a significant effect on the lowest electrical resistivity depending on the increase of the film density. The equivalent gamma dose of the neutron-treated thin film was determined as a 0.024 Gy dose level for neutron irradiation. The neutron treatment was significant to evaluate the decrease in the sheet resistivity of the thin film at this dose level. The neutron dose has led to a slight decrease in the optical band gap as the result of the thermal and epithermal neutrons' effects on the thin film.