Yazar "Ciris, Ali" seçeneğine göre listele
Listeleniyor 1 - 16 / 16
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe An Investigation on CdSeTe/CdTe Stacks Deposited by Evaporation: Impact of Halide Treatment Depending on the Applied Surface(Wiley-V C H Verlag Gmbh, 2024) Ciris, Ali; Atasoy, Yavuz; Tomakin, Murat; Bacaksiz, EminAmong the methods applied to modify the characteristics of CdSeTe/CdTe stacks, one of the most well-known and widely used procedures is the CdCl2 halide treatment. In this connection, the influence of CdCl2 on microstructural properties, phase distribution, and optical properties of CdSeTe/CdTe stack depending on location of the employed surface is investigated. In CdSeTe/CdTe stacks deposited by evaporation in vacuum, CdCl2 halide treatment is applied to the interface of CdSeTe and CdTe, the upper surface of CdTe, and both surface regions of the stack. CdCl2 treatment applied depending on the region has a definite effect on the phase structure, interlayer CdSexTe1-x alloying rate, and crystallization quality of the stack structure. Regardless of the applied region, all CdCl2-treated stacks exhibit a granular and compact surface morphology. On the other hand, CdCl2 treated only on single surface results in a shift of the absorption edge to the shorter wavelength, but rather to the long spectral region for both surfaces. The photoluminescence spectra reveal the presence of band emissions of the CdTe layer and CdSeTe alloys. Overall, the findings of the study indicate that only the upper-surface application of CdCl2 has more promising features for potential solar cell applications.Öğe Application of locational CdCl2 treatment to CdS thin films grown on an ultra-thin MgZnO for CdTe solar cells(Springer Heidelberg, 2023) Ciris, AliIn this study, the impact of locational CdCl2 treatment on the MgZnO/CdS stacks was investigated. In the stack structure with an ultra-thin MgZnO layer, the samples with CdCl2 applied to the inter-face, the top-surface, and both the inter-face and top-surface were grown by chemical bath deposition. The application of CdCl2 to the inter-face and to the inter-face and top-surface caused the CdS to change from cubic to hexagonal phase and the formation a cubic CdO phase. However, the MgZnO phase disappeared in the stacks, due to the applied experimental conditions. CdCl2 treatment only to the inter-face or only to the top-surface improved the grain structure of the stacks, but CdCl2 applied to both surfaces led to a porous structure. In addition, it was observed the presence of CdS and MgZnO absorption edges in all stacks. Besides, similar emission bands revealed for defect transitions relating to the MgZnO and CdS layers in all samples. The refractive index values decreased with the effect of CdCl2 treatment. In addition, the application of CdCl2 only to the top-surface appeared the inter-band transition of both MgZnO and CdS, while CdCl2 treatment to both surfaces caused the sharp band transition to disappear. According to the analysis results, it can be said that local CdCl2 treatment has a clear effect on the structural and optical properties of MgZnO/CdS stacks, and that CdTe can potentially improve cell performance with optimization processes.Öğe Comparison of the impact of different chlorination treatments to ZnS and CdS thin films(Academic Press Ltd- Elsevier Science Ltd, 2022) Ciris, Ali; Atasoy, Yavuz; Tomakin, Murat; Bacaksiz, EminIn this study, the effect of ZnCl2 and CdCl2 treatments on the structural, optical and electrical properties of ZnS and CdS thin films grown by chemical bath deposition method was examined. Employing CdCl2 or ZnCl2 treatment to CdS caused a change from cubic to hexagonal structure. After treating ZnS with CdCl2, ZnS phase disappeared and a highly crystalline hexagonal CdS phase formed. CdCl2 treatment on CdS showed an improving effect on surface morphology, but ZnCl2 led to an unfavorable effect. CdCl2 treatment to ZnS was transformed it into a fused structure in which individual grains were disappeared. Treatment of ZnCl2 to ZnS and CdCl2 to CdS induced a slight increase in the amount of Zn and Cd, respectively. However, processing of CdCl2 to ZnS (or ZnCl2 to CdS) resulted in significant quantity of Cd (or Zn) elements in the samples. The transmittance of CdS decreased with CdCl2 and ZnCl2 treatments. However, the highest transmittance in ZnS thin films was achieved after ZnCl2 treatment. According to PL spectra, different emission types increased partially in CdS/CdCl2, but decreased in CdS/ZnCl2. After applying ZnCl2 treatment to ZnS, the emission type appears similar to the as deposited sample, while CdCl2 treatment caused the emission type to change. Electrical measurements showed that the resistivity and carrier concentrations of the samples were in the order of 10(3) Omega cm and 10(13) cm(-3), respectively. The carrier concentrations of the CdS/ZnCl2 and ZnS/CdCl2 sample increased slightly compared the as deposited samples.Öğe Deposition of CdSeTe alloys using CdTe-CdSe mixed powder source material in a close-space sublimation process(Springer, 2021) Ciris, Ali; Basol, Bulent M.; Atasoy, Yavuz; Karaca, Abdullah; Kuckomeroglu, Tayfur; Tomakin, Murat; Bacaksiz, EminCdSexTe1-x films were deposited using a close-space sublimation (CSS) method and CdSe + CdTe mixed powders as the source material. Composition of the source was changed to obtain films with varying x values, and the resulting films were characterized by XRD, SEM, photoluminescence, Raman and optical transmission measurements. All data agreed with the fact that as the Se content of the source material was increased, the composition parameter x also increased. GI-XRD measurements showed the films to be graded in composition, the surface region being more Se-rich. Band gap values obtained from optical measurements showed a minimum band gap of about 1.4 eV for the material that had the highest Se content of about 45% near its top surface. Energy gap vs composition data demonstrated the expected bowing effect in band gap values and a bowing parameter of 0.678 was determined.Öğe Determination of radioactivity level of water supply network in Trabzon province, Turkey(Taylor & Francis Ltd, 2021) Kucukomeroglu, Belgin; Sen, Aysegul; Duran, Selcen Uzun; Ciris, Ali; Taskin, Halim; Ersoy, HakanIn the present study, the radioactivity levels of water samples collected from the main water supply network in Trabzon province and districts and soil samples taken from the vicinity of the water network were measured. An Alphaguard-PQ2000 radon gas detector was used to determine the seasonal radon gas level in the water samples. An HPGe detector was used to determine the level of radioactivity in soil and water samples. The average concentration of Rn-222 in drinking water ranges from 0.56 +/- 0.51 to 13.3 +/- 5 Bq L-1. In water samples, average gross alpha and gross beta values were measured as 8 +/- 1 and 43 +/- 1 mBq L-1, respectively. The average concentrations of U-238, Th-232, Cs-137, K-40 radionuclides in soil were measured as 51 +/- 2, 21 +/- 2, 16 +/- 1, 28 +/- 7 Bq m(-3), respectively. The average concentrations of U-238, Th-232, Cs-137, K-40 radionuclides in drinking water were measured as 147 +/- 5, 25 +/- 2, 77 +/- 2, 12 +/- 2 mBq L-1, respectively. When the radon concentrations for drinking water were examined, it was found that the radon concentration of the three samples was above the limit value (11 Bq L-1) allowed by the US-EPA for drinking water. All other results are below the limit values.Öğe Effect of CdS and CdSe pre-treatment on interdiffusion with CdTe in CdS/CdTe and CdSe/CdTe heterostructures(Elsevier Sci Ltd, 2021) Ciris, Ali; Basol, Bulent M.; Atasoy, Yavuz; Kucukomeroglu, Tayfur; Karaca, Abdullah; Tomakin, Murat; Bacaksiz, EminHigh efficiency CdTe solar cell structure has the configuration of CdS/CdSe/CdTe. Depending on the deposition and post deposition techniques employed, this stack is often subjected to high temperatures, often in presence of CdCl2, which leads to various degrees of interdiffusion at the CdS/CdSe and CdSe/CdTe interfaces. Such interdiffusion greatly influences device performance. Therefore, understanding and controlling these interdiffusion processes are important. In this contribution, interdiffusion between CdS-CdTe and CdSe-CdTe pairs were studied using CdS/CdTe and CdSe/CdTe stacks annealed at 673 K. Effect of pre-treating the CdS and CdSe layers with CdCl2 before the CdTe deposition on this interdiffusion was investigated. CdS films were grown by CBD and CdSe and CdTe films were vacuum evaporated. CdTe thickness was intentionally kept at the low 150?200 nm range to more easily identify alloy phases formed. GA-XRD measurements demonstrated that in absence of any CdCl2 pretreatment, there was more interdiffusion between CdSe and CdTe compared to CdS and CdTe. In all cases CdCl2 pre-treatment of CdS or CdSe before the deposition of the CdTe film was found to reduce diffusion of S and Se into CdTe.Öğe Effect of ultra-thin CdSexTe1-x interface layer on parameters of CdTe solar cells(Pergamon-Elsevier Science Ltd, 2022) Ciris, Ali; Basol, Bulent M.; Atasoy, Yavuz; Karaca, Abdullah; Tomakin, Murat; Kucukomeroglu, Tayfur; Bacaksiz, EminEffects of an ultra-thin CdSexTe1-x junction interface layer on CdTe solar cell parameters were investigated employing a CdSexTe1-x/CdTe absorber structure. CdSexTe1-x thin films with varying composition were grown by vacuum evaporation and CdTe films were produced by the close spaced sublimation (CSS) method. XRD analysis showed that while the CdSexTe1-x layers with x values less than 0.39 crystallized in cubic structure, films that were richer in Se displayed a (cubic + hexagonal) mixed phase. SEM analysis demonstrated a morphology with compact grains for all films. However, the grain size decreased appreciably with increasing Se content. Optical measurements showed that the band gaps of the alloys reached the minimum value of 1.40 eV at x similar to 0.32. CdS/CdSexTe1-x/CdTe solar cells were fabricated employing 100 nm thick CdSexTe1-x interlayers. The Grazing Incidence (GI)-XRD spectra of CdSexTe1-x used in the device structure showed that these inter-layers had graded alloy composition. The average Se-concentration within the graded alloy films were found to agree with the values obtained by EDS. Conversion efficiencies of 9.59% 11.69% and 10.13%, were obtained for x values of 0.24, 0.32 and 0.39, respectively. Spectral response showed enhanced long wavelength response for all devices due to the presence of the CdSexTe1-x interlayer. It was concluded that using an ultra-thin CdSexTe1-x inter-layer with optimum properties between CdS (junction partner) and CdTe improves the cell performance by increasing the current density of the device.Öğe Employing pre-annealing as a control tool for alloying in CdSeTe/ CdTe stacks produced by evaporation in vacuum(Academic Press Ltd- Elsevier Science Ltd, 2024) Ciris, Ali; Atasoy, Yavuz; Bacaksiz, EminAlloying plays a critical role in CdSeTe/CdTe stacks used as absorber structure in high efficiency solar cells. In this study, the effect of pre-annealing between CdSeTe and CdTe on the structural and optical properties of stacks was examined in detail. After the CdSeTe layers (before CdTe) were grown by vacuum evaporation, pre-annealing was applied at moderate temperatures in the range of 200 degrees C-300 degrees C. According to both XRD patterns and Raman spectra, a clear effect of preannealing temperature on alloying ratios and phase formations between CdSeTe and CdTe was ascertained. It was observed from the surface images that the change in pre-annealing temperature affected the grain sizes and morphology, depending on the Se ratios in the alloying. It was found that the transmission spectrum shifted to the long wavelength region with the change in crystallization as a result of pre-annealing. In the PL spectra, the presence of transitions related to the phase structures revealed by the XRD results was detected. In consequence, pre-annealing at 250 degrees C presented more promising results for potential CdTe cell applications.Öğe Gamma-ray absorbing characteristic of obsidian rocks as a potential material for radiation protection(Pergamon-Elsevier Science Ltd, 2022) Duran, Selcen Uzun; Kucukomeroglu, Belgin; Ciris, Ali; Ersoy, HakanIn this study, natural radionuclide levels and mass absorption coefficients of obsidian samples were examined to determine their gamma radiation properties. Fourteen obsidian samples were collected from 7 different locations in Rize province, Ikizdere region, Turkey. X-ray fluorescence measurements of the samples revealed the silica structure and comparable elemental structure with slight differences in atomic ratios. Radionuclide analysis showed that the Cs-137 activity was below the detection limit, and the mean activities of U-238, Th-232 and K-40 were 93 +/- 9, 67 +/- 7, 1027 +/- 19 Bq.kg(-1), respectively. The average experimental mass absorption coefficients at 81.0 keV, 302.9 keV, 356.0 keV and 661.7 keV were found to be 0.216, 0.108, 0.098 and 0.080 cm(2) g(-1), respectively. In the <100 keV region which the photoelectric effect is dominant, differences among the absorption coefficients were more pronounced, while it was relatively much smaller in the intermediate energy region. Also, it was seen that the absorption coefficients of the samples were higher than many materials, especially in the low energy region. The average half-value thicknesses showed that obsidian between 1.43 cm and 3.84 cm depending on the photon energy should be used to halve the radiation intensity. In addition, it was determined that the thicknesses in the range of 4.75 cm-12.76 cm were sufficient to reduce the intensity to one tenth. Considering all the analysis results, it can be said that obsidian is a potential material in radiation protection and its absorption properties can be improved by processes such as elemental doping.Öğe Impact of CdSeTe and CdSe film deposition parameter on the properties of CdSeTe/CdTe absorber structure for solar cell applications(Iop Publishing Ltd, 2024) Ciris, Ali; Atasoy, Yavuz; Tomakin, Murat; Karaca, Abdullah; Kucukomeroglu, Tayfur; Bacaksiz, EminIn this study, the effect of depositing CdSeTe and CdTe layers at different substrate temperatures (STs) by evaporation in vacuum on the properties of the CdSeTe/CdTe stacks was investigated. First, CdSeTe layers in stack structure were grown at STs of 150 degrees C, 200 degrees C and 250 degrees C and then CdTe layers on the CdSeTe produced with the optimum temperature were coated at STs of 150 degrees C, 200 degrees C and 250 degrees C. The employing of STs up to 150 degrees C on both CdSeTe and CdTe films in CdSeTe/CdTe stacks demonstrated the presence of Te and/or oxide phases as well as the alloying, while more stable phase structures at higher temperatures. In the CdSeTe/CdTe stack, the increase in ST of CdSeTe promoted the alloying, while it weakened the alloy in which was applied in CdTe. It was concluded that under the applied experimental conditions, STs of 250 degrees C and 200 degrees C with the graded alloying structure, suitable absorption sites, more homogeneous surface morphology for potential solar cell applications would be more suitable for CdSeTe and CdTe, respectively. As a result, the application of ST to CdSeTe or CdTe in the stacks can be used as a tool to control the properties of the stack structure.Öğe Improved CZTSe solar cell efficiency via silver and germanium alloying(Pergamon-Elsevier Science Ltd, 2024) Atasoy, Yavuz; Bacaksiz, Emin; Ciris, Ali; Olgar, Mehmet Ali; Zan, Recep; Ali, Ahmed M. J. Al-dala; Kucukomeroglu, TayfurIn this study, we report systematic investigation of the effects of Ag and Ge alloying on properties of CZTSe layers, as well as, on the performance of solar cells fabricated using these films. In this context, Ag-Ge doped CZTSe layers were produced by selenization of Cu/Sn/Zn/Cu/(Ag,Ge)/Se precursor stack structures using rapid thermal processing. All precursor stacks and the Ag-Ge doped CZTSe films obtained after selenization exhibited (Cu + Ag)-poor and Zn-rich chemical composition. XRD studies demonstrated pure kesterite phase for all reacted films. Raman spectra confirmed this finding. Cross-sectional SEMs showed large grain structure, which resulted from Ag-Se and Ge-Se liquid phase formation that assisted crystal growth during high temperature annealing. While a slight Ag-front-gradient was achieved in Ag-doped CZTSe film, the Ag gradient disappeared with incorporation of Ge into the lattice. Addition of Ge formed a gradient within the material such that near-contact region was more Ge-rich. Solar cells fabricated using films with various compositions demonstrated that double doping CZTSe with both Ag and Ge improved the device efficiency from about 5 % to over 8 %.Öğe Influence of deposition pressure of elemental Sn on structural, optical, electrical and schottky diode properties of SnS thin films grown by two-stage method(Springer, 2023) Ciris, Ali; Atasoy, Yavuz; Tomakin, Murat; Olgar, Mehmet AliIn the present study, SnS thin films were grown by two-stage method including sputtering deposition of elemental Sn films at various deposition pressures (6, 9, 12 ,15 and 18 mTorr) followed by sulfurization process carried out by Rapid Thermal Processing method at 350 degrees C for 1 min. The fabricated SnS thin films were characterized by several techniques. The energy dispersive X-ray spectroscopy measurements showed that deviation from stoichiometry in chemical composition of SnS samples deposited at above 9 mTorr was observed. X-ray diffraction and Raman spectroscopy measurements confirmed formation of orthorhombic SnS phase and SnS2 secondary phase. Furthermore, both characterization method also revealed that the preferential orientation of orthorhombic SnS phase altered from (111) to (040) by increasing the deposition pressure at above 9 mTorr. Scanning electron microscope images displayed formation of polycrystalline surface morphology. While lower deposition pressure (6 mTorr) gave rise to form small grains, the high deposition pressure (above 12 mTorr) caused some agglomerations. Optical bandgap of the films varied between 1.02 eV and 1.08 eV by varying the deposition pressure. SnS samples prepared at 9 and 12 mTorr deposition pressures presented lower resistivity and higher carrier concentration values. Due to more promising results of SnS samples fabricated utilizing 9 and 12 mTorr deposition pressures regarding structural and electrical properties, Schottky diode properties of both samples were investigated. The current-voltage characteristic of Mo/SnS/Al diode structure showed that SnS samples prepared at 12 mTorr has more ideal diode characteristic, comparatively.Öğe Investigation of growth temperature effects on SnSe-based photodetector performance(Springer, 2023) Yilmaz, Salih; Basol, Bulent M.; Polat, Ismail; Ciris, Ali; Kucukomeroglu, Tayfur; Bacaksiz, EminSnSe thin films were synthesized by thermal evaporation on glass slides at elevated growth temperatures. The grown films were investigated in terms of structural, morphological and optical properties. Furthermore, electrical characteristics and time-dependent photoresponses of SnSe-based photodetectors were studied in depth. SnSe thin films showed orthorhombic crystal structure with a preferred orientation of (400) for the growth temperature of 150 & DEG;C. However, the preferential orientation changed from (400) to (111) with increasing of growth temperature to 200 & DEG;C. Top view SEM data displayed a porous morphology for the samples grown at 200 & DEG;C and 250 & DEG;C temperatures. More transparent SnSe films were obtained when the growth temperature was increased to 200 & DEG;C. The band gaps of SnSe sample deposited at 150 & DEG;C and 200 & DEG;C were determined to be 1.22 eV. However, band gap reduces to 1.06 eV with the increase of the substrate temperature to 250 & DEG;C. Raman data demonstrated the shift in the general peak positions to higher frequencies as the growth temperature is increased due to the variation in bond lengths between Sn and Se atoms. Photocurrent-time data showed that SnSe sample grown at a growth temperature of 200 & DEG;C possessed the highest photocurrents because of the formation of porous structure. Rise and fall times of SnSe-based photodetector decay systematically with increasing growth temperature and the maximum responsivity and detectivity were found to be 3.33 x 10-1 A/W and 2.03 x 107 Jones, respectively for the device employing the film deposited at 200 & DEG;C.Öğe Processing CdS- and CdSe-containing window layers for CdTe solar cells(Iop Publishing Ltd, 2021) Ciris, Ali; Basol, Bulent M.; Atasoy, Yavuz; Karaca, Abdullah; Tomakin, Murat; Kucukomeroglu, Tayfur; Bacaksiz, EminThe influence of heat treatment steps on the characteristics of (CdS, CdSe) junction partners and on solar cell performance was studied. CdS films were obtained by chemical bath deposition, and CdSe layers were evaporated. Structural and compositional properties of CdS/CdSe bilayer stacks did not change upon heat treatment at 400 degrees C up to 10 min, whereas heat treatment in the presence of CdCl2 for 10 min caused formation of a CdSSe alloy with a bandgap value of about 2.05 eV. Originally, the cubic structure of the stack was also transformed into a hexagonal structure during this treatment. CdSe-CdTe interdiffusion was also studied using CdS/CdSe/CdTe triple layer stacks. CdTe films were deposited using a close-spaced sublimation method. Limited CdSe-CdTe interdiffusion was seen when CdTe was deposited over the as-deposited CdSe layer at 580 degrees C. However, such interdiffusion was not detected for samples where CdTe deposition was carried out on CdS/CdSe stacks pre-annealed in the presence of CdCl2. This suggests that partial crystallization of the CdS/CdSe bilayer stack by CdCl2 reduced such an interaction. Solar cells with CdSe/CdTe, CdS/CdTe and CdS/CdSe/CdTe structures with efficiencies of 8.39%, 10.12% and 11.47% were fabricated using 4.5-5 mu m thick CdTe layers and a final CdCl2 treatment. Quantum efficiency measurements demonstrated the benefit of CdSe-CdTe alloying during the final CdCl2 treatment in improving the short circuit current values.Öğe The effect of SbCl3 treatment on CdTe produced by close space sublimation method(Aip Publishing, 2023) Ciris, AliIn this study, influence of SbCl3 treatment on CdTe films deposited by the close space sublimation method was investigated. SbCl3 treatment was compared with conventional CdCl2 treated and untreated samples. It was determined that CdTe grew as Cd-rich and there was a slight decrease in Cd-amount after SbCl3 and CdCl2 treatments. In addition, a significant amount of Sb was detected in the SbCl3 treated sample. The samples crystallized in the cubic structure of CdTe. However, graded structures such as phase-I and phase-II with different structural parameters were formed. In the SbCl3 sample, it was revealed that the presence of Sb- caused a slight increase in the lattice parameter, compared to the other samples. Morphological analyses of the samples showed facet and large-small grain structures. CdCl2 treatment caused a slight decrease in grain size, while SbCl3 treatment resulted in a coarser and rougher grain structure. CdCl2 treatment increased transmittance, whereas SbCl3 treatment caused a decrease in transmittance (hence, an increase in absorbance). It was observed that the bandgaps were similar to 1.49 eV in all samples, and annealing, as well as CdCl2 and SbCl3 heat treatments did not cause a sharp change in the bandgaps. Photoluminescence spectra revealed the presence of band-edge and shallow-level defect transitions (except CdCl2 treated) in the samples. All results suggest that SbCl3 heat treatment has a significant effect on CdTe and may be an alternative to CdCl2.Öğe The effect of ZnCl2 and CdCl2 treatment on ZnS/CdS junction partner on CdTe cell performance(Elsevier Sci Ltd, 2022) Ciris, Ali; Atasoy, Yavuz; Karaca, Abdullah; Tomakin, Murat; Kucukomeroglu, Tayfur; Bacaksiz, EminIn this study, the impacts of ZnCl2 and CdCl2 treatments on the structural and optical properties of ZnS/CdS bilayers and on the parameters of CdTe solar cells with ZnS/CdS junction partners were investigated. CdS and ZnS thin films were grown by chemical bath deposition. In the as deposited ZnS/CdS sample, hexagonal CdS and Zn(S,O) phases were formed. After the application of CdCl2 treatment to the sample, ZnO and CdZnS alloys also appeared. In the ZnCl2 treated bilayer, it was observed that the crystal structure of the CdZnS alloy changed from hexagonal to cubic phase. While similar grain structure was observed in the as deposited and the ZnCl2 treated samples; it was seen that CdCl2 treatment significantly affected the grain form and size. CdCl2 treatment resulted in a large increase of Cd-ratio and a more balanced increase Zn-ratio in ZnCl2 treatment. It was determined that ZnCl2 and CdCl2 treatments caused a decrease in the transmittance of the samples. PL spectroscopy revealed the presence of many structural defects such as interstitial zinc, sulfur vacancies, surface states, cadmium vacancies in all bilayer samples. Solar cells with ZnS/CdS, ZnS/CdS (CdCl2-treated) and ZnS/CdS (ZnCl2-treated) junction partners achieved efficiencies of 4.56%, 5.64% and 5.20%, respectively. Solar cell parameters showed that ZnCl2 treatment increased the FF value, while CdCl2 treatment improved the Voc value. An efficiency of 6.01% was obtained from the ZnS/CdS (CdCl2-treated)/CdTe/CdCl2 cell produced by obtaining the highest efficiency with the ZnS/CdS/CdCl2 junction partner. This cell revealed that applying CdCl2 treatment on CdTe significantly increased Voc and Jsc while deteriorating FF.
