PubMed İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/397
Browse
3 results
Search Results
Article Performance Boost in QLEDs Using Octanethiol-Capped Core/Shell Quantum Dots(IOP Publishing Ltd, 2026-01-07) Yazici, Ahmet F.; Yuruc, Adnan M.; Kelestemur, Yusuf; Serin, Ramis Berkay; Kacar, Rifat; Ulku, Alper; Mutlugun, EvrenQuantum dots attract significant attention as one of the most promising colloidal nanocrystals with unique optical properties and potential applications for the next generation of display technology. In this paper, we evaluate the performance of CdZnSeS-based alloyed-shell quantum dots (QDs) for electroluminescence devices upon additional shell growth and ligand exchange. This includes core/shell (C/S) and core/shell/shell (C/S/S) QDs, whose latter includes an additional ZnS shell and octanethiol (OT) ligands. We present detailed characterizations of QDs using transmission electron microscopy, XRD, and various spectroscopic techniques and demonstrate their QD light emitting (QLEDs). We find the photoluminescence quantum yield of C/S/S QDs increased from 68.8% to 88.7% compared to C/S QDs whereas the emission linewidth narrows from 22.2 nm to 20.8 nm. QLEDs fabricated with C/S/S QDs exhibit a higher peak external quantum efficiency (EQE) of 4.1% and maximum luminance of 85 000 cd m-2, compared to 2.3% EQE and 67 000 cd m-2 for C/S QLEDs. In this respect, the OT-assisted shell growth significantly improves the optical property of QDs and performance of QLEDs, likely attributed to the enhanced charge balance and increased radiative recombination rate.Article Citation - WoS: 1Citation - Scopus: 1Osmotic-Pressure Nematic Ordering in Suspensions of Laponite and Carboxy Methyl Cellulose(Amer Chemical Soc, 2020-10-12) Xu, Peicheng; Yazici, Ahmet F.; Erdem, Talha; Lekkerkerker, Henk N. W.; Mutlugun, Evren; Eiser, ErikaLaponite is a synthetic clay that is known to form gels in aqueous suspensions at low concentrations (0.01 g/cm(3)) Although it is expected to form lyotropic liquid crystals, such phases usually do not form, as a consequence of laponite's tendency to form gels at concentrations below the threshold for liquid crystal formation. Here we show that macroscopic, birefringent phases of laponite can be prepared through osmotic compression of a laponite solution by an aqueous solution of carboxy methyl cellulose (CMC). We present polarization imaging studies showing how the initially dilute, isotropic laponite phase shrinks while developing typical birefringence colors between crossed polarizers. Using the MichelLevy interference charts, we were able to extract the refractive index and orientation of the laponite nanodisks in the compressed region. Our observations allow us to propose a tentative state diagram, indicating the concentration regions for which we obtain optically anisotropic gels.Article Citation - WoS: 51Citation - Scopus: 53CdSe/ZnS Quantum Dot Films for High Performance Flexible Lighting and Display Applications(IOP Publishing Ltd, 2016-06-10) Altintas, Yemliha; Genc, Sinan; Talpur, Mohammad Younis; Mutlugun, EvrenColloidal quantum dots have attracted significant interest in recent years for lighting and display applications and have recently appeared in high-end market products. The integration of quantum dots with light emitting diodes has made them promising candidates for superior lighting applications with tunable optical characteristics. In this work we propose and demonstrate high quality colloidal quantum dots in their novel free-standing film forms to allow high quality white light generation to address flexible lighting and display applications. High quality quantum dots have been characterized using transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, steady state and time resolved photoluminescence and dynamic light scattering methods. The engineering of colloidal quantum dot composition and its optical properties in stand-alone film form has led to the experimentally high NTSC color gamut of 122.5 (CIE-1931) for display applications, color rendering index of 88.6, luminous efficacy of optical radiation value of 290 lm/W-opt and color temperature of 2763 K for lighting applications.