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: 6Citation - Scopus: 6Polar Solvent-Free Room Temperature Synthesis of Cspbx3 (x = Br, Cl) Perovskite Nanocubes(Royal Society of Chemistry, 2023) Güvenç, Çetin Meriç; Kocabaş, Aşkın; Balcı, SinanConventionally, colloidal lead halide perovskite nanocubes have been synthesized by the hot-injection or ligand-assisted reprecipitation (LARP) methods. We herein demonstrate a polar solvent-free room temperature method for the synthesis of CsPbX3 (X = Br, Cl) nanocubes. In addition to the commonly used ligand pair of oleylamine and oleic acid, guanidinium (GA) has been used to passivate the surface of the nanocrystals. Our study demonstrates that GA inhibits the formation of low dimensional structures such as nanowires and nanoplatelets and further supports the formation of perovskite nanocubes. In fact, GA diminishes the restricted monomer-addition effect of long-chain oleylammonium (OLAM) ions to the nanocrystal. We show that above a critical GA/OLAM molar ratio, the synthesis yields homogeneous CsPbX3 (X = Br, Cl) nanocubes. Importantly, we observe the nucleation and growth kinetics of the GA-assisted CsPbBr3 nanocube formation by using in situ absorption and photoluminescence (PL) measurements. Small nanocrystals with an excitonic absorption peak at around 435 nm and photoluminescence (PL) maxima at 447 nm were nucleated and continuously shifted to longer wavelengths during the growth period. Crucially, our method allows the synthesis of CsPbCl3 nanocubes at room temperature without using polar organic solvents. The synthesized CsPbBr3, CsPb(Cl0.5Br0.5)3, and CsPbCl3 nanocubes have PL peaks at 508 nm, 443 nm, and 405 nm, photoluminescence quantum yields (PLQY) of 85%, 58% and 5%, and lifetimes of 18.98 ns, 18.97 ns, and 14.74 ns, respectively.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: 9Citation - Scopus: 11Synthesis, Bottom Up Assembly and Thermoelectric Properties of Sb-Doped Pbs Nanocrystal Building Blocks(MDPI, 2021) Cadavid, Doris; Wei, Kaya; Liu, Yu; Zhang, Yu; Li, Mengyao; Genc, Aziz; Berestok, TaisiiaThe precise engineering of thermoelectric materials using nanocrystals as their building blocks has proven to be an excellent strategy to increase energy conversion efficiency. Here we present a synthetic route to produce Sb-doped PbS colloidal nanoparticles. These nanoparticles are then consolidated into nanocrystalline PbS:Sb using spark plasma sintering. We demonstrate that the introduction of Sb significantly influences the size, geometry, crystal lattice and especially the carrier concentration of PbS. The increase of charge carrier concentration achieved with the introduction of Sb translates into an increase of the electrical and thermal conductivities and a decrease of the Seebeck coefficient. Overall, PbS:Sb nanomaterial were characterized by two-fold higher thermoelectric figures of merit than undoped PbS.Article Citation - WoS: 2Citation - Scopus: 31-Octanol Is a Functional Impurity Modifying Particle Size and Photophysical Properties of Colloidal Zncdsse/Zns Nanocrystals(American Chemical Society, 2021) Sevim Ünlütürk, Seçil; Çağır, Ali; Varlıklı, Canan; Özçelik, SerdarImpurities in trioctylphophine (TOP) strongly affect nanocrystal synthesis. 1-Octanol among other contaminants in TOP is identified for the first time as a functional impurity by H-1 NMR. The deliberate addition of 1-octanol into trioctylphosphine reduced particle size and modified photophysical properties of ZnCdSSe/ZnS colloidal nanocrystals. NMR analysis furthermore revealed that 1-octanol is bonded to the nanocrystal surfaces. The ratio of integrals for the O-CH2 protons of 1-octanol, which is the lowest compared to the other ligands, suggests that 1-octanol plays a critical role to tune the particle size of nanocrystals. The increased amount of 1-octanol added into TOP reduces the particle size from 9.8 to 7.2 nm, causing a progressive blue shift in the UV-vis and PL spectra but leaving the alloy composition unaffected. The rate of nonradiative processes is enhanced with the amount of 1-octanol added into TOP, correlating with higher dislocation density observed in the nanocrystals. As a conclusion, 1-octanol is proposed as a functional impurity that varies particle size and nonradiative photophysical processes in the ZnCdSSe/ZnS colloidal nanocrystals.Article Citation - WoS: 12Citation - Scopus: 12Ge Nanocrystals Embedded in Sio2 in Mos Based Radiation Sensors(Elsevier Ltd., 2010) Aktağ, Aliekber; Yılmaz, Ercan; Mogaddam, Nader A.P.; Aygün, Gülnur; Cantaş, Ayten; Turan, RaşitIn this work, the effects of gamma radiation on the Raman spectra of Ge nanocrystals embedded in SiO2 have been investigated. SiO2 films containing nanoparticles of Ge were grown using the r.f.-magnetron sputtering technique. Formation of Ge nanocrystals was observed after high temperature annealing in an inert atmosphere and confirmed by Raman measurements. The intensity of the Raman signal originating from Ge nanocrystals was found to decrease with increasing gamma radiation. The study also includes the gamma radiation effects on MOS structure with Ge nanocrystals embedded in SiO2. The gamma radiation effects from 500 up to 4000 Gray were investigated. Capacitance-voltage measurements were performed and analyzed. Oxide traps and interface trap charges were calculated. Results show that MOS structure with Ge nanocrystals embedded in SiO2 is a good candidate to be used in radiation sensors, especially at high radiation doses. © 2010 Elsevier B.V. All rights reserved.