Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Selective Growth of Fapbbr3 Nanocrystals With Precisely Tailored Optical Properties for Advanced Optoelectronic Applications(Amer Chemical Soc, 2025) Guvenc, C. Meric; Polat, Nahit; Arica, Tugce A.; Balci, SinanUnderstanding the evolution of semiconductor nanocrystals (NCs) during their colloidal synthesis is essential for achieving improved control over their physical and chemical properties. The fast reaction kinetics and concurrent nucleation and growth periods of lead halide perovskite NCs pose significant challenges in controlling the synthesis. Here, we present the room-temperature colloidal synthesis of FAPbBr3 NCs with physically decoupled nucleation and growth periods by using the common oleylamine and oleic acid ligand pair for lead halide perovskite NCs. Importantly, in this method, the nucleation and growth phases are entirely decoupled by halting the reaction at a metastable state, where the FAPbBr3 nuclei are formed. Subsequently, preformed FAPbBr3 nuclei are selectively grown by increasing supersaturation. This is achieved by reducing the monomer solubility through the injection of oleic acid into the solution. Notably, two-dimensional perovskite nanostructures form as intermediate products during the synthesis. Furthermore, the size of the FAPbBr3 NCs is tuned from 5.7 to 13.5 nm by controlling the injected oleic acid amount. Photoluminescence quantum yields of the FAPbBr3 perovskite NCs synthesized by using this method reached up to 95%. These findings demonstrate a robust strategy for the controlled synthesis of FAPbBr3 perovskite NCs, providing precisely tailored optical properties for advanced applications such as solar cells, photodetectors, and light-emitting diodes.Article Citation - WoS: 7Citation - Scopus: 7Breaking the Boundaries of the Goldschmidt Tolerance Factor With Ethylammonium Lead Iodide Perovskite Nanocrystals(American Chemical Society, 2024) Güvenç, Çetin Meriç; Toso, Stefano; Ivanov, Yurii P.; Saleh, Gabriele; Balcı, Sinan; Divitini, Giorgio; Manna, LiberatoWe report the synthesis of ethylammonium lead iodide (EAPbI3) colloidal nanocrystals as another member of the lead halide perovskites family. The insertion of an unusually large A-cation (274 pm in diameter) in the perovskite structure, hitherto considered unlikely due to the unfavorable Goldschmidt tolerance factor, results in a significantly larger lattice parameter compared to the Cs-, methylammonium- and formamidinium-based lead halide perovskite homologues. As a consequence, EAPbI3 nanocrystals are highly unstable, evolving to a nonperovskite delta-EAPbI3 polymorph within 1 day. Also, EAPbI3 nanocrystals are very sensitive to electron irradiation and quickly degrade to PbI2 upon exposure to the electron beam, following a mechanism similar to that of other hybrid lead iodide perovskites (although degradation can be reduced by partially replacing the EA+ ions with Cs+ ions). Interestingly, in some cases during this degradation the formation of an epitaxial interface between (EA x Cs1-x )PbI3 and PbI2 is observed. The photoluminescence emission of the EAPbI3 perovskite nanocrystals, albeit being characterized by a low quantum yield (similar to 1%), can be tuned in the 664-690 nm range by regulating their size during the synthesis. The emission efficiency can be improved upon partial alloying at the A site with Cs+ or formamidinium cations. Furthermore, the morphology of the EAPbI3 nanocrystals can be chosen to be either nanocube or nanoplatelet, depending on the synthesis conditions.Article Citation - WoS: 10Citation - Scopus: 9Recyclability of Cspbbr3 Quantum Dot Glass Nanocomposites for Their Long-Standing Use in White Leds(2022) Vahedigharehchopogh, Naji; Erol, Erdinç; Kıbrıslı, Orhan; Genç, Aziz; Çelikbilek Ersundu, Miray; Ersundu, Ali ErçinThe embedding of CsPbBr3 perovskite quantum dots (PQDs) in an inorganic glass matrix not only protects them against chemical, thermal, and photodegradation but also provides an effective strategy to isolate toxic elements such as Pb from the environment for a long period of time. Herein, the recyclability of glass is another important feature that contributes to environmental sustainability. Hence, effective and efficient recycling technologies are needed for the widespread use of PQD glass nanocomposites (GNCs) in many commercial applications. However, studies on the recyclability of CsPbBr3 PQD GNCs have not been conducted so far. Therefore, in this work, we investigate the structural, thermal, optical, and photoluminescence properties of recycled CsPbBr3 PQD GNCs to assess their suitability as long-standing and reusable luminescent materials. For this purpose, the recyclability of GNCs is checked by three repeated melt-quenching and subsequent heat-treatment processes. Although the color emission properties of GNCs under the same heat-treatment conditions show a slight variation after each recycling step, PQD GNCs almost retain their PLQY even after the last recycling step. Ultimately, a prototype white light-emitting diode is constructed by coupling recycled PQD GNCs and a commercial red phosphor on top of a blue LED chip showing high-performance with CIE color coordinates of x = 0.3228, y = 0.3470 and a CCT value of 5920 K. The findings of this work reveal that the recyclability of PQD GNCs holds great promise for a more sustainable technology.Article Citation - WoS: 9Citation - Scopus: 18Improvement of Photophysical Properties of Cspbbr3 and Mn2+:cspb(br,cl)(3) Perovskite Nanocrystals by Sr2+ Doping for White Light-Emitting Diodes(American Chemical Society, 2022) Yüce, Hürriyet; Mandal, Mukunda; Yalçınkaya, Yenal; Andrienko, Denis; Demir, Mustafa MuammerAll-inorganic metal halide perovskite nanocrystals (NCs) having the general formula ABX(3), where A is a monovalent cation, for example, Cs+, B is a divalent cation, typically Pb2+, and X is Cl-, Br-, I-, or their binary mixture, show potential in optoelectronic devices. In this work, we explore the effect of B-site doping on the optoelectronic properties of CsPbX3 NCs (X = Br, Cl). First, the Pb2+ ions in the pristine CsPbBr3 NC are partially substituted by Mn2+ ions. The alkaline earth metal strontium is then doped on both pristine and the Mn2+-substituted NCs. We found that a small percentage of Sr2+ doping remarkably improves the photoluminescence quantum yield of CsPbBr3 and Mn2+-state emission in Mn2+:CsPb(Br,Cl)(3) NCs. Perovskite NC film/ poly(methyl methacrylate) composites with all four NC variants were used in a white light-emitting diode (WLED), where Sr2+ doping increased the luminous efficiency of the WLED by similar to 4.7%. We attribute this performance enhancement to a reduced defect density and an attenuated microstrain in the local NC structure.Article Citation - WoS: 2Citation - Scopus: 2Highly Mobile Excitons in Single Crystal Methylammonium Lead Tribromide Perovskite Microribbons(American Chemical Society, 2022) McClintock, Luke; Song, Ziyi; Travaglini, H. Clark; Senger, Ramazan Tuğrul; Chandrasekaran, Vigneshwaran; Htoon, Han; Yarotski, Dmitry; Yu, DongExcitons are often given negative connotation in solar energy harvesting in part due to their presumed short diffusion lengths. We investigate exciton transport in single-crystal methylammonium lead tribromide (MAPbBr3) microribbons via spectrally, spatially, and temporally resolved photocurrent and photoluminescence measurements. Distinct peaks in the photocurrent spectra unambiguously confirm exciton formation and allow for accurate extraction of the low temperature exciton binding energy (39 meV). Photocurrent decays within a few μm at room temperature, while a gate-tunable long-range photocurrent component appears at lower temperatures (about 100 μm below 140 K). Carrier lifetimes of 1.2 μs or shorter exclude the possibility of the long decay length arising from slow trapped-carrier hopping. Free carrier diffusion is also an unlikely source of the highly nonlocal photocurrent, due to their small fraction at low temperatures. We attribute the long-distance transport to high-mobility excitons, which may open up new opportunities for novel exciton-based photovoltaic applications.Article Citation - WoS: 8Citation - Scopus: 9Cesium Manganese Chloride: Stable Lead-Free Perovskite From Bulk To Single Layer(Elsevier, 2021) Sözen, Yiğit; Özen, Sercan; Şahin, HasanMotivated by the recent advances in perovskite-based solar cells, here we investigate stability, electronic properties and vibrational characteristics of lead-free perovskite, CsMnCl3, and its low dimensional forms by means of first-principles calculations. Structural optimizations reveal that, regardless of whether it is bulk or ultra-thin single layer cubic perovskite structure, CsMnCl3 crystal exhibit robust antiferromagnetism in its ground state due to oppositely aligned magnetic moments of Mn atoms. In addition to total energy calculations, phonon band dispersions indicate that CsMnCl3 structure sustains its dynamical stability down to its thinnest single layer crystal structures. The calculated Raman spectrums state that while the first-order Raman scattering is forbidden for bulk CsMnCl3 due to the cubic symmetry; dimensional-reduction-driven symmetry breaking leads to emergence of experimentally-observable distinctive Raman active modes in bilayer and single-layer crystal structures. Moreover, the electronic band dispersions reveal that from its bulk to ultra-thin single layer structures CsMnCl3 crystals are robust antiferromagnetic insulators. Multiple valid features like controllable dimensionality, robust antiferromagnetism and wide electronic band gap make cubic CsMnCl3 crystal as a potential candidate for nano-scale optoelectronic applications.Article Citation - WoS: 21Citation - Scopus: 21Graphene-Supported Lafeo3 for Photocatalytic Hydrogen Energy Production(Wiley, 2021) Orak, Ceren; Yüksel, AslıHydrogen is a green, environmentally benign and sustainable energy source with no harmful combustion products to fulfil the increasing energy demand. Photocatalytic oxidation has various advantageous to produce hydrogen from different sources such as wastewater, alcohol solutions using different types of catalysts. Sucrose solution was chosen as a model solution to evolve hydrogen using LFO and GLFO catalysts under solar light irradiation, and graphene was used as a catalyst support to enhance the amount of produced hydrogen amount. A characterization study, which consists of SEM-EDX, BET, XRD, PL, TEM, XPS and FT-IR analyses, was carried out. A full factorial design was created via Minitab 18 to analyse the factors affecting the produced hydrogen amount, which are pH, catalyst loading, H2O2 concentration and graphene content statistically. Based on the results, graphene content is an important parameter and pH and H2O2 concentration have a synergetic effect over hydrogen production. Additionally, the effects of calcination temperature, pH, H2O2 concentration and catalyst loading over produced gases were investigated. The best promising result was obtained as 3388 mu mol/g(cat) at the following reaction conditions: 7.5 of pH, 0.1 g L-1 catalyst loading (GLFO, which is calcined at 700 degrees C) and using 15 mM H2O2 under solar light irradiation. Novelty Statement Hydrogen is produced from sucrose solution with low cost process requiring no special equipment, high pressure or temperature. First study that uses perovskite catalysts for the production of hydrogen from sucrose solution by photo-Fenton like oxidation GLFO is a promising photocatalyst for H-2 production by solar-Fenton like oxidation with the highest H-2 evaluation at 3388.34 mu mol/g(cat).Article Citation - WoS: 3Citation - Scopus: 5Plasmon-Induced Spectral Tunability of Perovskite Nanowires(Elsevier, 2021) Gökbulut, Belkıs; Topçu, Gökhan; Demir, Mustafa Muammer; İnci, Mehmet NaciIn this paper, plasmon-assisted spectral tunability in random media, composed of Perovskite (CsPbBr3) nanowires surrounded by Au nanoparticle clusters in polystyrene matrix, is achieved. The interaction between the surface plasmons and the quantum sources is observed to generate photoluminescence from the higher excited state energy levels of the excited semiconductor nanowires, which results in a blueshifted fluorescence emission of 50 nm. The localized surface plasmon properties are also determined to be tuned by plasmonic pumping of the quantum sources at different resonant frequencies. Thus, the first observation of the tunable blueshifted fluorescence emission of the semiconductor nanocrystals surrounded by plasmonic nanoparticle aggregates is achieved. The dramatic changes in the spectral profiles of the fluorescent nanowires are attributed to be due to the fast dynamics surface enhanced fluorescence mechanism.Article Citation - WoS: 4Citation - Scopus: 4Color-Tunable All-Inorganic Cspbbr3 Perovskites Nanoplatelet Films for Photovoltaic Devices(American Chemical Society, 2019) Özcan, Mehmet; Özen, Sercan; Topçu, Gökhan; Demir, Mustafa Muammer; Şahin, HasanHerein, we demonstrate a novel coating approach to fabricate CsPbBr3 perovskite nanoplatelet film with heat-free process via electrospraying from precursor solution. A detailed study is carried out to determine the effect of various parameters such as ligand concentration, electric field, flow rate, etc. on the optical properties. By controlling the volume ratios of the oleylamine (OAm) and oleic acid (OA), the coalescing and thickness of the resulting nanoplatelets can be readily tuned that results in control over emission in the range of 100 nm without any antisolvent crystallization or heating processes. The varying electrical field and flow rate was found as inefficient on the emission characteristics of the films. In addition, the crystal films were obtained under ambient conditions on the ITO coated glass surfaces as in the desired pattern. As a result, we demonstrated a facile and reproducible way of synthesizing and coating of CsPbBr3 perovskite nanoplatelets which is suitable for large-scale production. In this method, the ability of tuning the degree of quantum confinement for perovskite nanoplatelets is promising approach for the one-step fabrication of crystal films that may enable the use in optoelectronics.Article Citation - WoS: 89Citation - Scopus: 85Cspbbr3 Perovskites: Theoretical and Experimental Investigation on Water-Assisted Transition From Nanowire Formation To Degradation(American Physical Society, 2018) Akbalı, Barış; Topçu, Gökhan; Güner, Tuğrul; Özcan, Mehmet; Demir, Mustafa Muammer; Şahin, HasanRecent advances in colloidal synthesis methods have led to an increased research focus on halide perovskites. Due to the highly ionic crystal structure of perovskite materials, a stability issue pops up, especially against polar solvents such as water. In this study, we investigate water-driven structural evolution of CsPbBr3 by performing experiments and state-of-the-art first-principles calculations. It is seen that while an optical image shows the gradual degradation of the yellowish CsPbBr3 structure under daylight, UV illumination reveals that the degradation of crystals takes place in two steps: transition from a blue-emitting to green-emitting structure and and then a transition from a green-emitting phase to complete degradation. We found that as-synthesized CsPbBr3 nanowires (NWs) emit blue light under a 254 nm UV source. Before the degradation, first, CsPbBr3 NWs undergo a water-driven structural transition to form large bundles. It is also seen that formation of such bundles provides longer-term environmental stability. In addition theoretical calculations revealed the strength of the interaction of water molecules with ligands and surfaces of CsPbBr3 and provide an atomistic-level explanation to a transition from ligand-covered NWs to bundle formation. Further interaction of green-light-emitting bundles with water causes complete degradation of CsPbBr3 and the photoluminescence signal is entirely quenched. Moreover, Raman and x-ray-diffraction measurements revealed that completely degraded regions are decomposed to PbBr2 and CsBr precursors. We believe that the findings of this study may provide further insight into the degradation mechanism of CsPbBr3 perovskite by water.