Photonics / Fotonik
Permanent URI for this collectionhttps://hdl.handle.net/11147/2590
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Article Citation - WoS: 4Citation - Scopus: 4Color-Tunable All-Inorganic Cspbbr3 Perovskites Nanoplatelet Films for Photovoltaic Devices(American Chemical Society, 2019) Özcan, Mehmet; Demir, Mustafa Muammer; Özen, Sercan; Şahin, Hasan; Topçu, Gökhan; Demir, Mustafa Muammer; Şahin, Hasan; 04.04. Department of Photonics; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyHerein, 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: 72Citation - Scopus: 77Gd3+-Doped Alpha-Cspbi3 Nanocrystals With Better Phase Stability and Optical Properties(American Chemical Society, 2019) Güvenç, Çetin Meriç; Şahin, Hasan; Yalçınkaya, Yenal; Demir, Mustafa Muammer; Özen, Sercan; Şahin, Hasan; Demir, Mustafa Muammer; 04.04. Department of Photonics; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyBlack alpha-CsPbI3 perovskites are unable to maintain their phase stability under room conditions; hence, the alpha-CsPbI3 phase transforms into a thermodynamically stable yellow delta-CsPbI3 phase within a few days, which has a nonperovskite structure and high band gap for optoelectronic applications. This phase transformation should be prevented or at least retarded to make use of superior properties of alpha-CsPbI3 in optoelectronic applications. In this study, Gd3+ doping was employed with the aim of increasing the stability of alpha-CsPbI3. All doped alpha-CsPbI3 nanocrystals with various levels of Gd3+, between 5 and 15 mol %, have shown greater phase stability than that of the pure alpha-CsPbI3 phase from 5 days up to 11 days under ambient conditions. This prolonged phase stability can be attributed to three potential reasons: increased tolerance factor of the perovskite structure, distorted cubic symmetry, and decreased defect density in nanocrystals. Urbach energy values suggest the reduction of defect density in the doped nanocrystals. Also, use of 10 mol % Gd3+ as a dopant material increases the photoluminescence quantum yield from 70 to 80% and fluorescence lifetime of alpha-CsPbI3 from 47.4 to 64.4 ns. Further, density functional theory calculations are in a good agreement with the experimental results.Article Citation - WoS: 17Citation - Scopus: 17Monitoring the Doping and Diffusion Characteristics of Mn Dopants in Cesium Lead Halide Perovskites(American Chemical Society, 2018) Güner, Tuğrul; Şahin, Hasan; Akbalı, Barış; Demir, Mustafa Muammer; Özcan, Mehmet; Topçu, Gökhan; Demir, Mustafa Muammer; Şahin, Hasan; 04.04. Department of Photonics; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyCesium lead perovskites, in the form of CsPbX3 or Cs4PbX6, have been widely used for various optoelectronic applications due to their exceptionally good optical properties. In this study, the effect of Mn doping on the structural and optical properties of cesium lead halide perovskite crystals are investigated from both experimental and theoretical points of view. It is found that adding MnCl2 during the synthesis not only leads to a Mn-driven structural phase transition from Cs4PbBr6 to CsPbCl3 but also triggers the Br- to Cl- halide exchange. On the other hand, it is observed that, under UV illumination, the color of Mn-doped crystals changes from orange to blue in approximately 195 h. While the intensity of Mn-originated photoluminescence emission exponentially decays in time, the intensity of CsPbCl3-originated emission remains unchanged. In addition, diffusive motion of Mn ions results in both a growing population of MnO2 at the surface and transition of the host into a cesium-rich Cs4PbCl6 phase.Article Citation - WoS: 15Citation - Scopus: 21Triboluminescent Electrospun Mats With Blue-Green Emission Under Mechanical Force(American Chemical Society, 2017) İncel, Anıl; Varlıklı, Canan; Demir, Mustafa Muammer; Demir, Mustafa Muammer; Varlıklı, Canan; 04.04. Department of Photonics; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyFibrous mechanosensing elements can provide information about the direction of crack propagation and the mechanism of material failure when they are homogeneously dispersed into the bulk volume of materials. A fabrication strategy of fibrous systems showing triboluminescent (TL) responses is in high demand for such applications. In this work, micrometer-sized Cu(NCS)(py)2(PPh3) crystals were synthesized, and polymeric fibrous mats containing the TL crystals were obtained via electrospinning as a stress probe for the determination of mechanical impact. Four different polymeric systems have been employed (PMMA, PS, PU, and PVDF), and the mechano-optical sensing performance of electrospun mats of the polymer-crystal composites was measured. Photophysical properties (quantum yield, band gap, and broadness of the emission) of the TL crystal/electrospun mat composites were also studied. TL and PL emission maxima of the PU-based composite mat show identical behavior due to the chemical affinity between the two structures and the smallest fiber diameter. Moreover, the PU fiber mats exhibit long-lived bluish-green emission persisting over a large number of drops.