Role of Mg doping in the structural, optical, and electrical characteristics of ZnO-based DSSCs

ZnO- and Mg-doped ZnO samples are prepared by spray pyrolysis on conducting glass substrates to fabricate ZnO-based dye-sensitized solar cells (DSSCs). In uences of Mg-doping content on the power conversion efficiencies of ZnO-based DSSCs are investigated. X-ray diffraction results show that all the samples exhibit a hexagonal wurtzite structure. Scanning electron microscopy data indicate that the ZnO sample has uniform rods with 1 ? m diameter. With respect to ZnO, the band gap value of 4 at.% Mg-doped ZnO samples improves to the value of 3.27 eV and a further increase in Mg level up to 6 at.% gives rise to a decline in the band gap value of 3.22 eV. Photoluminescence measurements illustrate that intensities of the ultraviolet peak and a red luminescence peak take their maximum values for 4 at.% Mg doping. From solar cell performance measurements, the best power conversion efficiency of 0.08% is obtained for the doping amount of 4 at.% Mg

Yüzey modifikasyonu yardımıyla CdS toz bazlı hibrit güneş pillerinde performans artışı

The effects of surface modification of CdS through organic Eosin-Y, indoline D205, and Ru-based complex N719 and N3 dyes on CdS-based hybrid solar cells were studied. Chemical bath deposition (CBD) and doctor blade methods were in turn employed to fabricate the CdS specimens on Indium-Tin Oxide (ITO) covered glass substrates. P3HT material with and without dye coatings was covered through a spin-coater on the surface of CdS specimens. Ag paste was then deposited on the surface of P3HT to obtain hybrid solar cells. Structural analysis indicated that CdS powders showed a cubic growth with the preferred orientation of (111). Morphological analysis demonstrated that CdS powders exhibited hierarchical morphology and the morphology turned to granular structure with some porosity upon deposition of both N3 dye and P3HT layers. Absorption plots indicated that Eosin-Y dye loading led to a rise in the absorbance values of CdS specimens. After dye loading, photoluminescence data of CdS-based heterostructure illustrated a decrement in the luminescence intensity, implying that effective exciton dissociation was obtained. Current density-voltage (J-V) characteristics of the hybrid solar cells depicted that the best overall efficiency was observed for Eosin-Y-modified cell as 0.135%. This proved that surface modification by Eosin-Y dye led to a better interfacial contact between CdS and P3HT bilayer due to the enhancement in the charge separation.CdS-tabanlı hibrit güneş pillerinde, CdS'nin yüzey modifikasyon etkileri organik Eosin-Y, indolin D205 ve Ru bazlı N719 ve N3 boyaları vasıtasıyla incelendi. CdS örneklerini İndiyum-Kalay Oksit (ITO) kaplı cam altlıklar üzerinde büyütmek için, sırasıyla kimyasal banyo çökeltme (CBD) ve doktor bıçak yöntemleri kullanıldı. Boya kaplamaları olan ve olmayan CdS örneklerinin yüzeyine P3HT materyali, spin kaplama (spin-coater) cihazı yardımıyla kaplandı. Devamında Ag pasta, hibrit güneş pillerini tamamlamak için P3HT yüzeyine çökeltildi. Yapısal analiz, CdS tozlarının kübik yapıda ve (111) tercihli yönelime sahip olduğunu gösterdi. Morfolojik analiz, CdS tozlarının hiyerarşik morfolojide olduğunu ve morfolojinin hem N3 boyası hem de P3HT tabakasının çökeltilmesiyle birlikte taneli ve gözenekli yapıya döndüğünü gösterdi. Soğurma (absorbsiyon) grafikleri, Eosin-Y boya kaplamasının CdS örneklerinin soğurma değerinde bir artışa yol açtığını gösterdi. Boya kaplamasının, CdS tabanlı heteroyapının fotolüminesans şiddetinde azalma oluşturması, etkin bir eksiton ayrışması elde edildiğini ortaya koymaktadır. Hibrit güneş pillerinin akım yoğunluğu-voltaj (J-V) karakteristiklerinden, Eosin-Y modifikasyonlu güneş pilinin veriminin % 0,135 olarak en yüksek değerde olduğu tespit edildi. Bu durum, Eosin-Y boyası ile yapılan yüzey modifikasyonunun, yük ayrışmasında oluşturduğu iyileşmeden dolayı, CdS ve P3HT ikili yapısının arasında daha iyi bir ara yüzey teması sağladığını ispatlamaktadır

Comparison of the impact of different chlorination treatments to ZnS and CdS thin films

In 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

Phase transformation in Cu2SnS3 (CTS) thin films through pre-treatment in sulfur atmosphere

In this study, Cu2SnS3 (CTS) thin films prepared by a two-step sulfurization process were characterized. Cu and Sn metallic layers were first deposited on glass substrates by sputtering and then annealed in-situ while in the sputtering chamber to obtain CuSn (CT) alloys. This was followed by a pre-treatment step at temperatures between 200 and 350 degrees C in presence of S vapors. Finally, a full sulfurization step was performed at 525 degrees C to obtain the desired CTS phase. CTS films were characterized using EDX, XRD, Raman spectroscopy, SEM, optical transmission and Van der Pauw methods. It was found that all CTS samples had Cu-poor chemical composition. XRD data revealed only diffraction peaks belonging to CTS structure after the full sulfurization step. Raman spectra of the samples showed that except for the CTS sample pre-treated at 250 degrees C (CTS-250), which displayed the tetragonal crystal system, the films were dominated by the monoclinic structure. SEM surface images showed dense and polycrystalline microstructure, CTS-200 sample exhibiting a more uniform morphology. Optical band gap values were found to be ranging from 0.92 to 1.19 eV. All samples showed p-type conductivity but the sample pre-treated at 350 degrees C had higher resistivity and lower carrier concentration values. Overall, the CTS layer prepared using the pre-treatment step at 200 degrees C exhibited more promising structural and optical properties for potential photovoltaic applications. This work demonstrated that it is possible to change the crystal structure of sulfurized CTS thin films through a pre-treatment step

Effect of CdCI2CI_2/annealing on the crystalline transformation of CdTe thin films grown by evaporation at a low substrate temperature

The structural and optical properties of CdTe thin films prepared at a low substrate temperature were investigated before and after the Cd$CI _2$ /annealing. The crystal structure of CdTe film was cubic with a strong (111) preferential orientation. Annealing at 400 ◦C without Cd$CI _2$ treatment results in a decrease in the (111) peak intensity while the intensities of the (220), (311) and (331) peaks appeared, indicating that the texture is significantly changed. However, after the Cd$CI _2$ /annealing, the film exhibited a hexagonal phase as a dominant structure. The scanning electron microscopy patterns showed that the as-deposited and annealed samples had almost the same grain size. However, the grain size of the sample annealed after the Cd$CI _2$ treatment increased significantly. The optical band gap values for the as grown and Cd$CI _2$ /annealed films were determined to be ∼1.48 eV and ∼1.49 eV, respectively

Fabrication of CdS nanospheres-based hybrid solar cells having increased efficiency

The impact of surface modification through diverse dyes (Eosin-Y, D205, N719 and N3) on structural, morphological, optical, and electrical properties of CdS/P3HT hybrid solar cells is studied. X-ray diffraction (XRD) pattern shows that CdS nanospheres have a hexagonal structure with a preferential orientation of (002) with respect to indium tin oxide (ITO) coated glass slide. Scanning electron microscopy (SEM) results indicate that compact and dense spherical morphologies of CdS occurred, and the P3HT layer also consisted of small spherical grains. The bandgap of CdS is found to be 2.52 eV according to Tauc's plot analysis. Absorption spectra demonstrate that interfacial modification via each dye leads to an increase in the absorption in the wavelength range of 300-1000 nm. Photoluminescence (PL) data prove that surface modification of CdS nanospheres with diverse dyes causes a decrease in the spectral intensity of PL curve, implying that efficient exciton separation is taking place upon dye loadings. Fabricated devices with and without modification show photovoltaic effects that can be seen from current density-voltage (J-V) curves obviously, and the highest power conversion efficiency (PCE) is obtained as 0.881% for N719-modified (ITO/CdS/N719/P3HT/Ag) device (almost 70-fold of pristine one) with a short-circuit current density (J(sc)) of 2.878mA/cm(2) and open-circuit voltage (V-oc) of 0.92V, respectively. This enhancement can be attributed to a better surface area between CdS and P3HT after dye modification

27 Mayıs sonrasında 14'ler Olayı

Ankara : İhsan Doğramacı Bilkent Üniversitesi İktisadi, İdari ve Sosyal Bilimler Fakültesi, Tarih Bölümü, 2018.This work is a student project of the Department of History, Faculty of Economics, Administrative and Social Sciences, İhsan Doğramacı Bilkent University.The History of Turkey course (HIST200) is a requirement for all Bilkent undergraduates. It is designed to encourage students to work in groups on projects concerning any topic of their choice that relates to the history of Turkey. It is designed as an interactive course with an emphasis on research and the objective of investigating events, chronologically short historical periods, as well as historic representations. Students from all departments prepare and present final projects for examination by a committee, with 10 projects chosen to receive awards.Includes bibliographical references (pages 24-26).by Süha Ünsal

The effect of ZnCl2 and CdCl2 treatment on ZnS/CdS junction partner on CdTe cell performance

In 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