Durmuş Ali Aldemir

Bu çalışmada, kurşun içermeyen ve çevre dostu bir perovskit malzeme olan MA₂CuCl₄’ün sentezi gerçekleştirilmiş ve optoelektronik özellikleri incelenmiştir. MACl ve susuz CuCl₂’nin etanol içinde çözdürülmesi ile sarı renkte MA₂CuCl₄ kristalleri elde edilmiştir. Elde edilen malzemenin X-ışını kırınımı (XRD) ölçümleriyle yapısal özellikleri ortaya konmuştur. Scherrer denklemi yardımıyla kristal boyutu 65 nm olarak hesaplanmıştır. Toz numunenin EDS analizi sonucunda Cl/Cu oranı 3.6 bulunmuştur. Toz numenin ve FTO/TiO2 üzerine biriktirilmiş ince filmin Tauc eğrilerinden optik bant aralığı değerleri sırasıyla 2.38 eV ve 2.67 eV olarak belirlenmiştir.

Bu çalışmada SnS2 ince filmler cam alttaşlar üzerine ultrasonik sprey piroliz yöntemi (USP) ile biriktirildi. Kalay öncüsü olarak kalay (IV) klorür pentahidrat (SnCl4.5H2O) ve sülfür öncüsü olarak da tiyoüre (CH4N2S) kullanıldı. Filmlerin yapısal, morfolojik, elektriksel ve elektro-optik karakterizasyonları gerçekleştirildi. Tauc metodu yardımıyla SnS2 ince filmler için doğrudan ve dolaylı bant aralıkları sırasıyla 2.35 eV ve 2.10 eV olarak belirlendi. Sıcak prob yöntemi ile filmlerin n-tipi olduğu tespit edildi ve özdirenci 285 cm hesaplandı.

The morphological, structural, and optical characterization of the SnS thin film deposited by the ultrasonic spray pyrolysis (USP) method was carried out. Simple and inexpensive commercial ultrasonic nano‐mist device was used to deposit SnS thin film. The solution procedure was developed to obtain highly oriented SnS thin film. The SnS thin film exhibited an orthorhombic crystal structure with a strong (111) preferred orientation. The crystallite size was calculated as 56 nm. A direct band gap of 1.21 eV was determined from the Tauc plot. Raman spectroscopy was performed to identify the phases present in the films. The FTO/TiO ₂ /SnS/Au solar cells were fabricated. The ideality factor and saturation current of the device were calculated as 3.02 and 2.59 × 10 ⁻⁶ A, respectively. The series resistance of 370 Ω was obtained using Cheung’s method. The photovoltaic parameters of the champion cell with a power conversion efficiency (PCE) of 0.388% were found to be J _sc = 6.50 mA/cm ² , V _oc = 0.207 V, and FF = 28.9%. In addition, the photodiode performance of the cell was evaluated.

The Yb/p-Cu(In $_{{\textit{x}}}$ Ga $_{{\textit{x}-\text{1}}}$ )Se $_{{\text{2}}}$ (CIGS) Schottky photodiodes were fabricated on Mo-coated glass substrates. Structural and morphological characterizations of the CIGS on the Mo layer were investigated. The current–voltage ( $\textit{I}$ – $\textit{V}$ ) characteristics of the produced devices were performed for dark and solar light (100 mW/cm $^{{\text{2}}}$ ) in the temperature range of 40–300 K. The activation energy ( $\textit{E}_{{\textit{a}}}$ ) was found to be 0.645 eV from the temperature dependence of the open circuit voltage. It was determined that this value is very close to half of the bandgap of CIGS thin films ( $\textit{E}_{{\textit{g}}}$ , 1.35 eV for this study). The responsivity and detectivity values were calculated for a wide temperature range. The responsivity value decreased and the detectivity value increased with the decrease in temperature. The highest responsivity value was found as 14.3 mA/W at 280 K. The highest detectivity value was calculated as $\text{4.97} \times \text{10}^{{\text{9}}}$ Jones at 60 K. The suitability of the produced devices for photodetector applications at low temperatures has been investigated.

Methylammonium iodide (MAI) and methylammonium bromide (MABr) reactants were synthesized in powder form. Tin-based perovskites (MASnI_xBr_3−x (x = 3, 2, 1, 0)) were deposited as a thin film on glass substrates using the ultrasonic spray pyrolysis (USP) method. X-ray diffraction (XRD) was used to examine the crystallographic characteristics of the synthesized MAI/MABr powders and perovskite thin films. A shift occurred in the XRD peaks by changing the I/Br ratios. Morphological analysis of the MAI and MABr were carried out by scanning electron microscopy (SEM). While the average particle size was calculated a ~ 94 μm for MAI, it was obtained as ~ 188 μm for MABr. The Fourier transform infrared (FTIR) spectroscopy peaks observed for synthesized MAI and MABr were found to be compatible with commercial MAI and MABr FTIR peaks. Elemental analysis of MASnI_xBr_3−x (x = 3, 2, 1, 0) perovskite thin films was performed energy dispersive spectroscopy (EDS). Forbidden band gap (E_g) values of perovskite thin films were obtained from Tauc curves. The E_g value increased with an increasing I/Br ratio. The deposition of highly stoichiometric MASnI_xBr_3–x perovskites thin films was achieved by the USP method. This method has many parameters need to be optimized. This study gives optimum parameters that are difficult to determine.

All layers of MASnI₂Br-based perovskite solar cells (PSCs) were deposited by ultrasonic spray pyrolysis method. The depositions of the layers were carried out in a large area. The perovskite thin film deposited on FTO/TiO₂ had large grains. The crystallite size of the film was calculated as 90[ ]nm from the XRD pattern. The bandgap of 1.54[ ]eV was determined from the UV-visible measurement of MASnI₂Br thin film. The PSCs with the different active areas (0.3[ ]cm² and 3.18[ ]cm²) were fabricated. The champion cells’ power conversion efficiencies were recorded at 0.181% and 0.120% for 0.3[ ]cm² and 3.18[ ]cm², respectively.

Lead-free all-inorganic Cs₂TiBr₆ perovskite solar cells have attracted attention with their 3.3% efficiency and stability. However, instability in air ambiance has been reported for Cs₂TiBr₆ synthesized in powder form. In this work, Cs₂TiBr₆ perovskite is synthesized using a solution-based method. Time-dependent x-ray diffraction patterns are analyzed for air ambience. Cs₂TiBr₆ perovskite quickly deteriorates and decomposes in the air. Morphology and optical properties are obtained using a scanning electron microscope and the ultraviolet region, respectively. The average particle size is ∼2.4 μm. The forbidden band gap is found to be 1.82 eV from the Tauc plot. The Hall Effect measurement of the perovskite pellet is taken at room temperature and under vacuum. The pellet has high resistivity (1.1 × 10⁴ ohm·cm) and high Hall mobility (502 cm²V⁻¹s⁻¹). Cs₂TiBr₆ shows p-type conductivity. Low stability to air and high resistivity are handicaps for the Cs₂TiBr₆ perovskite absorber layer in solar cell applications.

Bu çalışmada ultrasonik sprey piroliz yöntemi ile cam alttaşlar üzerine CH3NH3PbI3-xClx perovskit ince filmler kaplanmıştır. Alttaş sıcaklığının perovskit filmlerin yapısal, morfolojik ve optik özellikleri üzerine etkisi, X-ışını kırınım (XRD) cihazı, taramalı elektron mikroskobu (SEM), atomik kuvvet mikroskobu (AFM) ve Uv-Vis spektrofotometresi kullanılarak araştırılmıştır. XRD spektrumları incelendiğinde, tüm filmlerin tetragonal perovskit örgü yapısında olduğu ancak 75 °C ve 100 °C alttaş sıcaklığı uygulanan ince filmlerde farklı kristal yapılara ait fazladan piklerinde olduğu görülmüştür. Filmlere sonradan herhangi bir tavlama işlemi uygulanmadığı halde, 125 °C alttaş sıcaklığında kaplanan filmlerin literatür ile birebir uyumlu saf perovskit kristali formunda olduğu tespit edilmiştir. XRD spektrum verileri ve Debye-Scherrer formülü kullanılarak ince filmlerin kristal boyutları belirlenmiştir. En yüksek kristal boyutu 743 Å ile 125 °C alttaş sıcaklığında kaplanan filmlerde elde edilmiştir. SEM görüntüleri incelendiğinde film yüzeylerinin sadece 125 °C alttaş sıcaklığında homojen kaplandığı ve kristal tanecikler arasında boşlukların oluşmadığı saptanmıştır. Filmlerin yüzey pürüzlülüğü atomik kuvvet mikroskobu ile incelenmiş, en düşük yüzey pürüzlülüğü 41.32 nm ile 125 °C alttaş sıcaklığına sahip olan ince filmde elde edilmiştir. Optik soğurma ölçümleri, oda sıcaklığında çalıştırılan Uv-Vis spektrofotometre kullanılarak gerçekleştirilmiştir. Filmler kaplanırken uygulanan alttaş sıcaklığı artıkça filme ait yasak bant aralığının 1.20’ eV tan teorik analizler ile de uyuşan 1.56 eV’ a çıktığı görülmüştür.